NAT + STUN Probes...

Co-Authored-By: brekotis <93345790+brekotis@users.noreply.github.com>

.github/workflows/codeql.yml

@@ -0,0 +1,45 @@
+name: "CodeQL Advanced"
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+  schedule:
+    - cron: '0 0 * * 0'
+
+jobs:
+  analyze:
+    name: Analyze (${{ matrix.language }})
+    runs-on: ${{ (matrix.language == 'swift' && 'macos-latest') || 'ubuntu-latest' }}
+
+    permissions:
+      security-events: write
+      packages: read
+      actions: read
+      contents: read
+
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - language: actions
+            build-mode: none
+          - language: rust
+            build-mode: none
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Initialize CodeQL
+        uses: github/codeql-action/init@v4
+        with:
+          languages: ${{ matrix.language }}
+          build-mode: ${{ matrix.build-mode }}
+          config-file: .github/codeql/codeql-config.yml
+
+      - name: Perform CodeQL Analysis
+        uses: github/codeql-action/analyze@v4
+        with:
+          category: "/language:${{ matrix.language }}"

.github/workflows/queries/common/ProductionOnly.qll

@@ -0,0 +1,20 @@
+import rust
+
+predicate isTestOnly(Item i) {
+  exists(ConditionalCompilation cc |
+    cc.getItem() = i and
+    cc.getCfg().toString() = "test"
+  )
+}
+
+predicate hasTestAttribute(Item i) {
+  exists(Attribute a |
+    a.getItem() = i and
+    a.getName() = "test"
+  )
+}
+
+predicate isProductionCode(Item i) {
+  not isTestOnly(i) and
+  not hasTestAttribute(i)
+}

.github/workflows/queries/qlpack.yml

@@ -0,0 +1,4 @@
+name: rust-production-only
+version: 0.0.1
+dependencies:
+  codeql/rust-all: "*"

.github/workflows/rust.yml

@@ -14,6 +14,11 @@ jobs:
     name: Build
     runs-on: ubuntu-latest
 
+    permissions:
+      contents: read
+      actions: write
+      checks: write
+
     steps:
     - name: Checkout repository
       uses: actions/checkout@v4

Cargo.toml

@@ -1,15 +1,14 @@
 [package]
 name = "telemt"
-version = "1.0.0"
+version = "1.2.0"
-edition = "2021"
+edition = "2024"
-rust-version = "1.75"
 
 [dependencies]
 # C
 libc = "0.2"
 
 # Async runtime
-tokio = { version = "1.35", features = ["full", "tracing"] }
+tokio = { version = "1.42", features = ["full", "tracing"] }
 tokio-util = { version = "0.7", features = ["codec"] }
 
 # Crypto
@@ -20,41 +19,41 @@ sha2 = "0.10"
 sha1 = "0.10"
 md-5 = "0.10"
 hmac = "0.12"
-crc32fast = "1.3"
+crc32fast = "1.4"
+zeroize = { version = "1.8", features = ["derive"] }
 
 # Network
 socket2 = { version = "0.5", features = ["all"] }
-rustls = "0.22"
 
-# Serial
+# Serialization
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 toml = "0.8"
 
 # Utils
-bytes = "1.5"
+bytes = "1.9"
-thiserror = "1.0"
+thiserror = "2.0"
 tracing = "0.1"
 tracing-subscriber = { version = "0.3", features = ["env-filter"] }
 parking_lot = "0.12"
 dashmap = "5.5"
 lru = "0.12"
-rand = "0.8"
+rand = "0.9"
 chrono = { version = "0.4", features = ["serde"] }
 hex = "0.4"
-base64 = "0.21"
+base64 = "0.22"
 url = "2.5"
-regex = "1.10"
+regex = "1.11"
-once_cell = "1.19"
 crossbeam-queue = "0.3"
 
 # HTTP
-reqwest = { version = "0.11", features = ["rustls-tls"], default-features = false }
+reqwest = { version = "0.12", features = ["rustls-tls"], default-features = false }
 
 [dev-dependencies]
 tokio-test = "0.4"
 criterion = "0.5"
 proptest = "1.4"
+futures = "0.3"
 
 [[bench]]
 name = "crypto_bench"

README.md

@@ -2,6 +2,26 @@
 
 **Telemt** is a fast, secure, and feature-rich server written in Rust: it fully implements the official Telegram proxy algo and adds many production-ready improvements such as connection pooling, replay protection, detailed statistics, masking from "prying" eyes
 
+## Emergency
+**Важное сообщение для пользователей из России**
+
+Мы работаем над проектом с Нового года и сейчас готовим новый релиз - 1.2
+
+В нём имплементируется поддержка Middle Proxy Protocol - основного терминатора для Ad Tag:
+работа над ним идёт с 6 ферваля, а уже 10 февраля произошли "громкие события"...
+
+Если у вас есть компетенции в асинхронных сетевых приложениях - мы открыты к предложениям и pull requests
+
+**Important message for users from Russia**
+
+We've been working on the project since December 30 and are currently preparing a new release – 1.2
+
+It implements support for the Middle Proxy Protocol – the primary point for the Ad Tag:
+development on it started on February 6th, and by February 10th, "big activity" in Russia had already "taken place"...
+
+If you have expertise in asynchronous network applications – we are open to ideas and pull requests!
+
+# Features
 💥 The configuration structure has changed since version 1.1.0.0, change it in your environment!
 
 ⚓ Our implementation of **TLS-fronting** is one of the most deeply debugged, focused, advanced and *almost* **"behaviorally consistent to real"**:  we are confident we have it right - [see evidence on our validation and traces](#recognizability-for-dpi-and-crawler) 
@@ -168,6 +188,7 @@ tls_domain = "petrovich.ru"
 mask = true
 mask_port = 443
 # mask_host = "petrovich.ru" # Defaults to tls_domain if not set
+# mask_unix_sock = "/var/run/nginx.sock" # Unix socket (mutually exclusive with mask_host)
 fake_cert_len = 2048
 
 # === Access Control & Users ===

config.toml

@@ -6,8 +6,13 @@ show_link = ["hello"]
 [general]
 prefer_ipv6 = false
 fast_mode = true
-use_middle_proxy = false
+use_middle_proxy = true
-# ad_tag = "..."
+ad_tag = "00000000000000000000000000000000"
+
+# Log level: debug | verbose | normal | silent
+# Can be overridden with --silent or --log-level CLI flags
+# RUST_LOG env var takes absolute priority over all of these
+log_level = "normal"
 
 [general.modes]
 classic = false
@@ -43,12 +48,13 @@ tls_domain = "petrovich.ru"
 mask = true
 mask_port = 443
 # mask_host = "petrovich.ru" # Defaults to tls_domain if not set
+# mask_unix_sock = "/var/run/nginx.sock" # Unix socket (mutually exclusive with mask_host)
 fake_cert_len = 2048
 
 # === Access Control & Users ===
-# username "hello" is used for example
 [access]
 replay_check_len = 65536
+replay_window_secs = 1800
 ignore_time_skew = false
 
 [access.users]
@@ -62,17 +68,13 @@ hello = "00000000000000000000000000000000"
 # hello = 1073741824 # 1 GB
 
 # === Upstreams & Routing ===
-# By default, direct connection is used, but you can add SOCKS proxy
-
-# Direct - Default
 [[upstreams]]
 type = "direct"
 enabled = true
 weight = 10
 
-# SOCKS5
 # [[upstreams]]
 # type = "socks5"
-# address = "127.0.0.1:9050"
+# address = "127.0.0.1:1080"
 # enabled = false
 # weight = 1

src/cli.rs

@@ -0,0 +1,300 @@
+//! CLI commands: --init (fire-and-forget setup)
+
+use std::fs;
+use std::path::{Path, PathBuf};
+use std::process::Command;
+use rand::Rng;
+
+/// Options for the init command
+pub struct InitOptions {
+    pub port: u16,
+    pub domain: String,
+    pub secret: Option<String>,
+    pub username: String,
+    pub config_dir: PathBuf,
+    pub no_start: bool,
+}
+
+impl Default for InitOptions {
+    fn default() -> Self {
+        Self {
+            port: 443,
+            domain: "www.google.com".to_string(),
+            secret: None,
+            username: "user".to_string(),
+            config_dir: PathBuf::from("/etc/telemt"),
+            no_start: false,
+        }
+    }
+}
+
+/// Parse --init subcommand options from CLI args.
+///
+/// Returns `Some(InitOptions)` if `--init` was found, `None` otherwise.
+pub fn parse_init_args(args: &[String]) -> Option<InitOptions> {
+    if !args.iter().any(|a| a == "--init") {
+        return None;
+    }
+    
+    let mut opts = InitOptions::default();
+    let mut i = 0;
+    
+    while i < args.len() {
+        match args[i].as_str() {
+            "--port" => {
+                i += 1;
+                if i < args.len() {
+                    opts.port = args[i].parse().unwrap_or(443);
+                }
+            }
+            "--domain" => {
+                i += 1;
+                if i < args.len() {
+                    opts.domain = args[i].clone();
+                }
+            }
+            "--secret" => {
+                i += 1;
+                if i < args.len() {
+                    opts.secret = Some(args[i].clone());
+                }
+            }
+            "--user" => {
+                i += 1;
+                if i < args.len() {
+                    opts.username = args[i].clone();
+                }
+            }
+            "--config-dir" => {
+                i += 1;
+                if i < args.len() {
+                    opts.config_dir = PathBuf::from(&args[i]);
+                }
+            }
+            "--no-start" => {
+                opts.no_start = true;
+            }
+            _ => {}
+        }
+        i += 1;
+    }
+    
+    Some(opts)
+}
+
+/// Run the fire-and-forget setup.
+pub fn run_init(opts: InitOptions) -> Result<(), Box<dyn std::error::Error>> {
+    eprintln!("[telemt] Fire-and-forget setup");
+    eprintln!();
+    
+    // 1. Generate or validate secret
+    let secret = match opts.secret {
+        Some(s) => {
+            if s.len() != 32 || !s.chars().all(|c| c.is_ascii_hexdigit()) {
+                eprintln!("[error] Secret must be exactly 32 hex characters");
+                std::process::exit(1);
+            }
+            s
+        }
+        None => generate_secret(),
+    };
+    
+    eprintln!("[+] Secret: {}", secret);
+    eprintln!("[+] User:   {}", opts.username);
+    eprintln!("[+] Port:   {}", opts.port);
+    eprintln!("[+] Domain: {}", opts.domain);
+    
+    // 2. Create config directory
+    fs::create_dir_all(&opts.config_dir)?;
+    let config_path = opts.config_dir.join("config.toml");
+    
+    // 3. Write config
+    let config_content = generate_config(&opts.username, &secret, opts.port, &opts.domain);
+    fs::write(&config_path, &config_content)?;
+    eprintln!("[+] Config written to {}", config_path.display());
+    
+    // 4. Write systemd unit
+    let exe_path = std::env::current_exe()
+        .unwrap_or_else(|_| PathBuf::from("/usr/local/bin/telemt"));
+    
+    let unit_path = Path::new("/etc/systemd/system/telemt.service");
+    let unit_content = generate_systemd_unit(&exe_path, &config_path);
+    
+    match fs::write(unit_path, &unit_content) {
+        Ok(()) => {
+            eprintln!("[+] Systemd unit written to {}", unit_path.display());
+        }
+        Err(e) => {
+            eprintln!("[!] Cannot write systemd unit (run as root?): {}", e);
+            eprintln!("[!] Manual unit file content:");
+            eprintln!("{}", unit_content);
+            
+            // Still print links and config
+            print_links(&opts.username, &secret, opts.port, &opts.domain);
+            return Ok(());
+        }
+    }
+    
+    // 5. Reload systemd
+    run_cmd("systemctl", &["daemon-reload"]);
+    
+    // 6. Enable service
+    run_cmd("systemctl", &["enable", "telemt.service"]);
+    eprintln!("[+] Service enabled");
+    
+    // 7. Start service (unless --no-start)
+    if !opts.no_start {
+        run_cmd("systemctl", &["start", "telemt.service"]);
+        eprintln!("[+] Service started");
+        
+        // Brief delay then check status
+        std::thread::sleep(std::time::Duration::from_secs(1));
+        let status = Command::new("systemctl")
+            .args(["is-active", "telemt.service"])
+            .output();
+        
+        match status {
+            Ok(out) if out.status.success() => {
+                eprintln!("[+] Service is running");
+            }
+            _ => {
+                eprintln!("[!] Service may not have started correctly");
+                eprintln!("[!] Check: journalctl -u telemt.service -n 20");
+            }
+        }
+    } else {
+        eprintln!("[+] Service not started (--no-start)");
+        eprintln!("[+] Start manually: systemctl start telemt.service");
+    }
+    
+    eprintln!();
+    
+    // 8. Print links
+    print_links(&opts.username, &secret, opts.port, &opts.domain);
+    
+    Ok(())
+}
+
+fn generate_secret() -> String {
+    let mut rng = rand::rng();
+    let bytes: Vec<u8> = (0..16).map(|_| rng.random::<u8>()).collect();
+    hex::encode(bytes)
+}
+
+fn generate_config(username: &str, secret: &str, port: u16, domain: &str) -> String {
+    format!(
+r#"# Telemt MTProxy — auto-generated config
+# Re-run `telemt --init` to regenerate
+
+show_link = ["{username}"]
+
+[general]
+prefer_ipv6 = false
+fast_mode = true
+use_middle_proxy = false
+log_level = "normal"
+
+[general.modes]
+classic = false
+secure = false
+tls = true
+
+[server]
+port = {port}
+listen_addr_ipv4 = "0.0.0.0"
+listen_addr_ipv6 = "::"
+
+[[server.listeners]]
+ip = "0.0.0.0"
+
+[[server.listeners]]
+ip = "::"
+
+[timeouts]
+client_handshake = 15
+tg_connect = 10
+client_keepalive = 60
+client_ack = 300
+
+[censorship]
+tls_domain = "{domain}"
+mask = true
+mask_port = 443
+fake_cert_len = 2048
+
+[access]
+replay_check_len = 65536
+replay_window_secs = 1800
+ignore_time_skew = false
+
+[access.users]
+{username} = "{secret}"
+
+[[upstreams]]
+type = "direct"
+enabled = true
+weight = 10
+"#,
+        username = username,
+        secret = secret,
+        port = port,
+        domain = domain,
+    )
+}
+
+fn generate_systemd_unit(exe_path: &Path, config_path: &Path) -> String {
+    format!(
+r#"[Unit]
+Description=Telemt MTProxy
+Documentation=https://github.com/nicepkg/telemt
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=simple
+ExecStart={exe} {config}
+Restart=always
+RestartSec=5
+LimitNOFILE=65535
+# Security hardening
+NoNewPrivileges=true
+ProtectSystem=strict
+ProtectHome=true
+ReadWritePaths=/etc/telemt
+PrivateTmp=true
+
+[Install]
+WantedBy=multi-user.target
+"#,
+        exe = exe_path.display(),
+        config = config_path.display(),
+    )
+}
+
+fn run_cmd(cmd: &str, args: &[&str]) {
+    match Command::new(cmd).args(args).output() {
+        Ok(output) => {
+            if !output.status.success() {
+                let stderr = String::from_utf8_lossy(&output.stderr);
+                eprintln!("[!] {} {} failed: {}", cmd, args.join(" "), stderr.trim());
+            }
+        }
+        Err(e) => {
+            eprintln!("[!] Failed to run {} {}: {}", cmd, args.join(" "), e);
+        }
+    }
+}
+
+fn print_links(username: &str, secret: &str, port: u16, domain: &str) {
+    let domain_hex = hex::encode(domain);
+    
+    println!("=== Proxy Links ===");
+    println!("[{}]", username);
+    println!("  EE-TLS:  tg://proxy?server=YOUR_SERVER_IP&port={}&secret=ee{}{}", 
+        port, secret, domain_hex);
+    println!();
+    println!("Replace YOUR_SERVER_IP with your server's public IP.");
+    println!("The proxy will auto-detect and display the correct link on startup.");
+    println!("Check: journalctl -u telemt.service | head -30");
+    println!("===================");
+}

src/config/mod.rs

@@ -1,31 +1,108 @@
 //! Configuration
 
-use std::collections::HashMap;
+use crate::error::{ProxyError, Result};
-use std::net::IpAddr;
-use std::path::Path;
 use chrono::{DateTime, Utc};
 use serde::{Deserialize, Serialize};
-use crate::error::{ProxyError, Result};
+use std::collections::HashMap;
+use std::net::{IpAddr, SocketAddr};
+use std::path::Path;
 
 // ============= Helper Defaults =============
 
-fn default_true() -> bool { true }
+fn default_true() -> bool {
-fn default_port() -> u16 { 443 }
+    true
-fn default_tls_domain() -> String { "www.google.com".to_string() }
+}
-fn default_mask_port() -> u16 { 443 }
+fn default_port() -> u16 {
-fn default_replay_check_len() -> usize { 65536 }
+    443
-fn default_handshake_timeout() -> u64 { 15 }
+}
-fn default_connect_timeout() -> u64 { 10 }
+fn default_tls_domain() -> String {
-fn default_keepalive() -> u64 { 60 }
+    "www.google.com".to_string()
-fn default_ack_timeout() -> u64 { 300 }
+}
-fn default_listen_addr() -> String { "0.0.0.0".to_string() }
+fn default_mask_port() -> u16 {
-fn default_fake_cert_len() -> usize { 2048 }
+    443
-fn default_weight() -> u16 { 1 }
+}
+fn default_replay_check_len() -> usize {
+    65536
+}
+fn default_replay_window_secs() -> u64 {
+    1800
+}
+fn default_handshake_timeout() -> u64 {
+    15
+}
+fn default_connect_timeout() -> u64 {
+    10
+}
+fn default_keepalive() -> u64 {
+    60
+}
+fn default_ack_timeout() -> u64 {
+    300
+}
+fn default_listen_addr() -> String {
+    "0.0.0.0".to_string()
+}
+fn default_fake_cert_len() -> usize {
+    2048
+}
+fn default_weight() -> u16 {
+    1
+}
 fn default_metrics_whitelist() -> Vec<IpAddr> {
-    vec![
+    vec!["127.0.0.1".parse().unwrap(), "::1".parse().unwrap()]
-        "127.0.0.1".parse().unwrap(),
+}
-        "::1".parse().unwrap(),
+
-    ]
+// ============= Log Level =============
+
+/// Logging verbosity level
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize, Default)]
+#[serde(rename_all = "lowercase")]
+pub enum LogLevel {
+    /// All messages including trace (trace + debug + info + warn + error)
+    Debug,
+    /// Detailed operational logs (debug + info + warn + error)
+    Verbose,
+    /// Standard operational logs (info + warn + error)
+    #[default]
+    Normal,
+    /// Minimal output: only warnings and errors (warn + error).
+    /// Startup messages (config, DC connectivity, proxy links) are always shown
+    /// via info! before the filter is applied.
+    Silent,
+}
+
+impl LogLevel {
+    /// Convert to tracing EnvFilter directive string
+    pub fn to_filter_str(&self) -> &'static str {
+        match self {
+            LogLevel::Debug => "trace",
+            LogLevel::Verbose => "debug",
+            LogLevel::Normal => "info",
+            LogLevel::Silent => "warn",
+        }
+    }
+
+    /// Parse from a loose string (CLI argument)
+    pub fn from_str_loose(s: &str) -> Self {
+        match s.to_lowercase().as_str() {
+            "debug" | "trace" => LogLevel::Debug,
+            "verbose" => LogLevel::Verbose,
+            "normal" | "info" => LogLevel::Normal,
+            "silent" | "quiet" | "error" | "warn" => LogLevel::Silent,
+            _ => LogLevel::Normal,
+        }
+    }
+}
+
+impl std::fmt::Display for LogLevel {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            LogLevel::Debug => write!(f, "debug"),
+            LogLevel::Verbose => write!(f, "verbose"),
+            LogLevel::Normal => write!(f, "normal"),
+            LogLevel::Silent => write!(f, "silent"),
+        }
+    }
 }
 
 // ============= Sub-Configs =============
@@ -42,7 +119,11 @@ pub struct ProxyModes {
 
 impl Default for ProxyModes {
     fn default() -> Self {
-        Self { classic: true, secure: true, tls: true }
+        Self {
+            classic: true,
+            secure: true,
+            tls: true,
+        }
     }
 }
 
@@ -62,6 +143,27 @@ pub struct GeneralConfig {
 
     #[serde(default)]
     pub ad_tag: Option<String>,
+
+    /// Path to proxy-secret binary file (auto-downloaded if absent).
+    /// Infrastructure secret from https://core.telegram.org/getProxySecret
+    #[serde(default)]
+    pub proxy_secret_path: Option<String>,
+
+    /// Public IP override for middle-proxy NAT environments.
+    /// When set, this IP is used in ME key derivation and RPC_PROXY_REQ "our_addr".
+    #[serde(default)]
+    pub middle_proxy_nat_ip: Option<IpAddr>,
+
+    /// Enable STUN-based NAT probing to discover public IP:port for ME KDF.
+    #[serde(default)]
+    pub middle_proxy_nat_probe: bool,
+
+    /// Optional STUN server address (host:port) for NAT probing.
+    #[serde(default)]
+    pub middle_proxy_nat_stun: Option<String>,
+
+    #[serde(default)]
+    pub log_level: LogLevel,
 }
 
 impl Default for GeneralConfig {
@@ -72,6 +174,11 @@ impl Default for GeneralConfig {
             fast_mode: true,
             use_middle_proxy: false,
             ad_tag: None,
+            proxy_secret_path: None,
+            middle_proxy_nat_ip: None,
+            middle_proxy_nat_probe: false,
+            middle_proxy_nat_stun: None,
+            log_level: LogLevel::Normal,
         }
     }
 }
@@ -154,6 +261,9 @@ pub struct AntiCensorshipConfig {
     #[serde(default = "default_mask_port")]
     pub mask_port: u16,
 
+    #[serde(default)]
+    pub mask_unix_sock: Option<String>,
+
     #[serde(default = "default_fake_cert_len")]
     pub fake_cert_len: usize,
 }
@@ -165,6 +275,7 @@ impl Default for AntiCensorshipConfig {
             mask: true,
             mask_host: None,
             mask_port: default_mask_port(),
+            mask_unix_sock: None,
             fake_cert_len: default_fake_cert_len(),
         }
     }
@@ -187,6 +298,9 @@ pub struct AccessConfig {
     #[serde(default = "default_replay_check_len")]
     pub replay_check_len: usize,
 
+    #[serde(default = "default_replay_window_secs")]
+    pub replay_window_secs: u64,
+
     #[serde(default)]
     pub ignore_time_skew: bool,
 }
@@ -194,13 +308,17 @@ pub struct AccessConfig {
 impl Default for AccessConfig {
     fn default() -> Self {
         let mut users = HashMap::new();
-        users.insert("default".to_string(), "00000000000000000000000000000000".to_string());
+        users.insert(
+            "default".to_string(),
+            "00000000000000000000000000000000".to_string(),
+        );
         Self {
             users,
             user_max_tcp_conns: HashMap::new(),
             user_expirations: HashMap::new(),
             user_data_quota: HashMap::new(),
             replay_check_len: default_replay_check_len(),
+            replay_window_secs: default_replay_window_secs(),
             ignore_time_skew: false,
         }
     }
@@ -274,15 +392,30 @@ pub struct ProxyConfig {
 
     #[serde(default)]
     pub show_link: Vec<String>,
+
+    /// DC address overrides for non-standard DCs (CDN, media, test, etc.)
+    /// Keys are DC indices as strings, values are "ip:port" addresses.
+    /// Matches the C implementation's `proxy_for <dc_id> <ip>:<port>` config directive.
+    /// Example in config.toml:
+    ///   [dc_overrides]
+    ///   "203" = "149.154.175.100:443"
+    #[serde(default)]
+    pub dc_overrides: HashMap<String, String>,
+
+    /// Default DC index (1-5) for unmapped non-standard DCs.
+    /// Matches the C implementation's `default <dc_id>` config directive.
+    /// If not set, defaults to 2 (matching Telegram's official `default 2;` in proxy-multi.conf).
+    #[serde(default)]
+    pub default_dc: Option<u8>,
 }
 
 impl ProxyConfig {
     pub fn load<P: AsRef<Path>>(path: P) -> Result<Self> {
-        let content = std::fs::read_to_string(path)
+        let content =
-            .map_err(|e| ProxyError::Config(e.to_string()))?;
+            std::fs::read_to_string(path).map_err(|e| ProxyError::Config(e.to_string()))?;
 
-        let mut config: ProxyConfig = toml::from_str(&content)
+        let mut config: ProxyConfig =
-            .map_err(|e| ProxyError::Config(e.to_string()))?;
+            toml::from_str(&content).map_err(|e| ProxyError::Config(e.to_string()))?;
 
         // Validate secrets
         for (user, secret) in &config.access.users {
@@ -299,20 +432,40 @@ impl ProxyConfig {
             return Err(ProxyError::Config("tls_domain cannot be empty".to_string()));
         }
 
-        // Warn if using default tls_domain
+        // Validate mask_unix_sock
-        if config.censorship.tls_domain == "www.google.com" {
+        if let Some(ref sock_path) = config.censorship.mask_unix_sock {
-            tracing::warn!("Using default tls_domain (www.google.com). Consider setting a custom domain in config.toml");
+            if sock_path.is_empty() {
+                return Err(ProxyError::Config(
+                    "mask_unix_sock cannot be empty".to_string(),
+                ));
+            }
+            #[cfg(unix)]
+            if sock_path.len() > 107 {
+                return Err(ProxyError::Config(format!(
+                    "mask_unix_sock path too long: {} bytes (max 107)",
+                    sock_path.len()
+                )));
+            }
+            #[cfg(not(unix))]
+            return Err(ProxyError::Config(
+                "mask_unix_sock is only supported on Unix platforms".to_string(),
+            ));
+
+            if config.censorship.mask_host.is_some() {
+                return Err(ProxyError::Config(
+                    "mask_unix_sock and mask_host are mutually exclusive".to_string(),
+                ));
+            }
         }
 
-        // Default mask_host to tls_domain if not set
+        // Default mask_host to tls_domain if not set and no unix socket configured
-        if config.censorship.mask_host.is_none() {
+        if config.censorship.mask_host.is_none() && config.censorship.mask_unix_sock.is_none() {
-            tracing::info!("mask_host not set, using tls_domain ({}) for masking", config.censorship.tls_domain);
             config.censorship.mask_host = Some(config.censorship.tls_domain.clone());
         }
 
         // Random fake_cert_len
         use rand::Rng;
-        config.censorship.fake_cert_len = rand::thread_rng().gen_range(1024..4096);
+        config.censorship.fake_cert_len = rand::rng().gen_range(1024..4096);
 
         // Migration: Populate listeners if empty
         if config.server.listeners.is_empty() {
@@ -353,11 +506,11 @@ impl ProxyConfig {
             return Err(ProxyError::Config("No modes enabled".to_string()));
         }
 
-        // Validate tls_domain format (basic check)
         if self.censorship.tls_domain.contains(' ') || self.censorship.tls_domain.contains('/') {
-            return Err(ProxyError::Config(
+            return Err(ProxyError::Config(format!(
-                format!("Invalid tls_domain: '{}'. Must be a valid domain name", self.censorship.tls_domain)
+                "Invalid tls_domain: '{}'. Must be a valid domain name",
-            ));
+                self.censorship.tls_domain
+            )));
         }
 
         Ok(())

src/crypto/aes.rs

@@ -1,9 +1,19 @@
 //! AES encryption implementations
 //!
 //! Provides AES-256-CTR and AES-256-CBC modes for MTProto encryption.
+//!
+//! ## Zeroize policy
+//!
+//! - `AesCbc` stores raw key/IV bytes and zeroizes them on drop.
+//! - `AesCtr` wraps an opaque `Aes256Ctr` cipher from the `ctr` crate.
+//!   The expanded key schedule lives inside that type and cannot be
+//!   zeroized from outside. Callers that hold raw key material (e.g.
+//!   `HandshakeSuccess`, `ObfuscationParams`) are responsible for
+//!   zeroizing their own copies.
 
 use aes::Aes256;
 use ctr::{Ctr128BE, cipher::{KeyIvInit, StreamCipher}};
+use zeroize::Zeroize;
 use crate::error::{ProxyError, Result};
 
 type Aes256Ctr = Ctr128BE<Aes256>;
@@ -12,7 +22,12 @@ type Aes256Ctr = Ctr128BE<Aes256>;
 
 /// AES-256-CTR encryptor/decryptor
 /// 
-/// CTR mode is symmetric - encryption and decryption are the same operation.
+/// CTR mode is symmetric — encryption and decryption are the same operation.
+///
+/// **Zeroize note:** The inner `Aes256Ctr` cipher state (expanded key schedule
+/// + counter) is opaque and cannot be zeroized. If you need to protect key
+/// material, zeroize the `[u8; 32]` key and `u128` IV at the call site
+/// before dropping them.
 pub struct AesCtr {
     cipher: Aes256Ctr,
 }
@@ -62,14 +77,23 @@ impl AesCtr {
 
 /// AES-256-CBC cipher with proper chaining
 ///
-/// Unlike CTR mode, CBC is NOT symmetric - encryption and decryption
+/// Unlike CTR mode, CBC is NOT symmetric — encryption and decryption
 /// are different operations. This implementation handles CBC chaining
 /// correctly across multiple blocks.
+///
+/// Key and IV are zeroized on drop.
 pub struct AesCbc {
     key: [u8; 32],
     iv: [u8; 16],
 }
 
+impl Drop for AesCbc {
+    fn drop(&mut self) {
+        self.key.zeroize();
+        self.iv.zeroize();
+    }
+}
+
 impl AesCbc {
     /// AES block size
     const BLOCK_SIZE: usize = 16;
@@ -141,17 +165,9 @@ impl AesCbc {
         
         for chunk in data.chunks(Self::BLOCK_SIZE) {
             let plaintext: [u8; 16] = chunk.try_into().unwrap();
-            
-            // XOR plaintext with previous ciphertext (or IV for first block)
             let xored = Self::xor_blocks(&plaintext, &prev_ciphertext);
-            
-            // Encrypt the XORed block
             let ciphertext = self.encrypt_block(&xored, &key_schedule);
-            
-            // Save for next iteration
             prev_ciphertext = ciphertext;
-            
-            // Append to result
             result.extend_from_slice(&ciphertext);
         }
         
@@ -180,17 +196,9 @@ impl AesCbc {
         
         for chunk in data.chunks(Self::BLOCK_SIZE) {
             let ciphertext: [u8; 16] = chunk.try_into().unwrap();
-            
-            // Decrypt the block
             let decrypted = self.decrypt_block(&ciphertext, &key_schedule);
-            
-            // XOR with previous ciphertext (or IV for first block)
             let plaintext = Self::xor_blocks(&decrypted, &prev_ciphertext);
-            
-            // Save current ciphertext for next iteration
             prev_ciphertext = ciphertext;
-            
-            // Append to result
             result.extend_from_slice(&plaintext);
         }
         
@@ -217,16 +225,13 @@ impl AesCbc {
         for i in (0..data.len()).step_by(Self::BLOCK_SIZE) {
             let block = &mut data[i..i + Self::BLOCK_SIZE];
             
-            // XOR with previous ciphertext
             for j in 0..Self::BLOCK_SIZE {
                 block[j] ^= prev_ciphertext[j];
             }
             
-            // Encrypt in-place
             let block_array: &mut [u8; 16] = block.try_into().unwrap();
             *block_array = self.encrypt_block(block_array, &key_schedule);
             
-            // Save for next iteration
             prev_ciphertext = *block_array;
         }
         
@@ -248,26 +253,20 @@ impl AesCbc {
         use aes::cipher::KeyInit;
         let key_schedule = aes::Aes256::new((&self.key).into());
         
-        // For in-place decryption, we need to save ciphertext blocks
-        // before we overwrite them
         let mut prev_ciphertext = self.iv;
         
         for i in (0..data.len()).step_by(Self::BLOCK_SIZE) {
             let block = &mut data[i..i + Self::BLOCK_SIZE];
             
-            // Save current ciphertext before modifying
             let current_ciphertext: [u8; 16] = block.try_into().unwrap();
             
-            // Decrypt in-place
             let block_array: &mut [u8; 16] = block.try_into().unwrap();
             *block_array = self.decrypt_block(block_array, &key_schedule);
             
-            // XOR with previous ciphertext
             for j in 0..Self::BLOCK_SIZE {
                 block[j] ^= prev_ciphertext[j];
             }
             
-            // Save for next iteration
             prev_ciphertext = current_ciphertext;
         }
         
@@ -347,10 +346,8 @@ mod tests {
         let mut cipher = AesCtr::new(&key, iv);
         cipher.apply(&mut data);
         
-        // Encrypted should be different
         assert_ne!(&data[..], original);
         
-        // Decrypt with fresh cipher
         let mut cipher = AesCtr::new(&key, iv);
         cipher.apply(&mut data);
         
@@ -364,7 +361,7 @@ mod tests {
         let key = [0u8; 32];
         let iv = [0u8; 16];
         
-        let original = [0u8; 32]; // 2 blocks
+        let original = [0u8; 32];
         
         let cipher = AesCbc::new(key, iv);
         let encrypted = cipher.encrypt(&original).unwrap();
@@ -375,31 +372,25 @@ mod tests {
     
     #[test]
     fn test_aes_cbc_chaining_works() {
-        // This is the key test - verify CBC chaining is correct
         let key = [0x42u8; 32];
         let iv = [0x00u8; 16];
         
-        // Two IDENTICAL plaintext blocks
         let plaintext = [0xAAu8; 32];
         
         let cipher = AesCbc::new(key, iv);
         let ciphertext = cipher.encrypt(&plaintext).unwrap();
         
-        // With proper CBC, identical plaintext blocks produce DIFFERENT ciphertext
         let block1 = &ciphertext[0..16];
         let block2 = &ciphertext[16..32];
         
         assert_ne!(
             block1, block2,
-            "CBC chaining broken: identical plaintext blocks produced identical ciphertext. \
+            "CBC chaining broken: identical plaintext blocks produced identical ciphertext"
-             This indicates ECB mode, not CBC!"
         );
     }
     
     #[test]
     fn test_aes_cbc_known_vector() {
-        // Test with known NIST test vector
-        // AES-256-CBC with zero key and zero IV
         let key = [0u8; 32];
         let iv = [0u8; 16];
         let plaintext = [0u8; 16];
@@ -407,11 +398,9 @@ mod tests {
         let cipher = AesCbc::new(key, iv);
         let ciphertext = cipher.encrypt(&plaintext).unwrap();
         
-        // Decrypt and verify roundtrip
         let decrypted = cipher.decrypt(&ciphertext).unwrap();
         assert_eq!(plaintext.as_slice(), decrypted.as_slice());
         
-        // Ciphertext should not be all zeros
         assert_ne!(ciphertext.as_slice(), plaintext.as_slice());
     }
     
@@ -420,7 +409,6 @@ mod tests {
         let key = [0x12u8; 32];
         let iv = [0x34u8; 16];
         
-        // 5 blocks = 80 bytes
         let plaintext: Vec<u8> = (0..80).collect();
         
         let cipher = AesCbc::new(key, iv);
@@ -435,7 +423,7 @@ mod tests {
         let key = [0x12u8; 32];
         let iv = [0x34u8; 16];
         
-        let original = [0x56u8; 48]; // 3 blocks
+        let original = [0x56u8; 48];
         let mut buffer = original;
         
         let cipher = AesCbc::new(key, iv);
@@ -462,41 +450,33 @@ mod tests {
     fn test_aes_cbc_unaligned_error() {
         let cipher = AesCbc::new([0u8; 32], [0u8; 16]);
         
-        // 15 bytes - not aligned to block size
         let result = cipher.encrypt(&[0u8; 15]);
         assert!(result.is_err());
         
-        // 17 bytes - not aligned
         let result = cipher.encrypt(&[0u8; 17]);
         assert!(result.is_err());
     }
     
     #[test]
     fn test_aes_cbc_avalanche_effect() {
-        // Changing one bit in plaintext should change entire ciphertext block
-        // and all subsequent blocks (due to chaining)
         let key = [0xAB; 32];
         let iv = [0xCD; 16];
         
-        let mut plaintext1 = [0u8; 32];
+        let plaintext1 = [0u8; 32];
         let mut plaintext2 = [0u8; 32];
-        plaintext2[0] = 0x01; // Single bit difference in first block
+        plaintext2[0] = 0x01;
         
         let cipher = AesCbc::new(key, iv);
         
         let ciphertext1 = cipher.encrypt(&plaintext1).unwrap();
         let ciphertext2 = cipher.encrypt(&plaintext2).unwrap();
         
-        // First blocks should be different
         assert_ne!(&ciphertext1[0..16], &ciphertext2[0..16]);
-        
-        // Second blocks should ALSO be different (chaining effect)
         assert_ne!(&ciphertext1[16..32], &ciphertext2[16..32]);
     }
     
     #[test]
     fn test_aes_cbc_iv_matters() {
-        // Same plaintext with different IVs should produce different ciphertext
         let key = [0x55; 32];
         let plaintext = [0x77u8; 16];
         
@@ -511,7 +491,6 @@ mod tests {
     
     #[test]
     fn test_aes_cbc_deterministic() {
-        // Same key, IV, plaintext should always produce same ciphertext
         let key = [0x99; 32];
         let iv = [0x88; 16];
         let plaintext = [0x77u8; 32];
@@ -524,6 +503,23 @@ mod tests {
         assert_eq!(ciphertext1, ciphertext2);
     }
     
+    // ============= Zeroize Tests =============
+    
+    #[test]
+    fn test_aes_cbc_zeroize_on_drop() {
+        let key = [0xAA; 32];
+        let iv = [0xBB; 16];
+        
+        let cipher = AesCbc::new(key, iv);
+        // Verify key/iv are set
+        assert_eq!(cipher.key, [0xAA; 32]);
+        assert_eq!(cipher.iv, [0xBB; 16]);
+        
+        drop(cipher);
+        // After drop, key/iv are zeroized (can't observe directly,
+        // but the Drop impl runs without panic)
+    }
+    
     // ============= Error Handling Tests =============
     
     #[test]

src/crypto/hash.rs

@@ -1,3 +1,16 @@
+//! Cryptographic hash functions
+//!
+//! ## Protocol-required algorithms
+//!
+//! This module exposes MD5 and SHA-1 alongside SHA-256. These weaker
+//! hash functions are **required by the Telegram Middle Proxy protocol**
+//! (`derive_middleproxy_keys`) and cannot be replaced without breaking
+//! compatibility. They are NOT used for any security-sensitive purpose
+//! outside of that specific key derivation scheme mandated by Telegram.
+//!
+//! Static analysis tools (CodeQL, cargo-audit) may flag them — the
+//! usages are intentional and protocol-mandated.
+
 use hmac::{Hmac, Mac};
 use sha2::Sha256;
 use md5::Md5;
@@ -21,14 +34,16 @@ pub fn sha256_hmac(key: &[u8], data: &[u8]) -> [u8; 32] {
     mac.finalize().into_bytes().into()
 }
 
-/// SHA-1
+/// SHA-1 — **protocol-required** by Telegram Middle Proxy key derivation.
+/// Not used for general-purpose hashing.
 pub fn sha1(data: &[u8]) -> [u8; 20] {
     let mut hasher = Sha1::new();
     hasher.update(data);
     hasher.finalize().into()
 }
 
-/// MD5
+/// MD5 — **protocol-required** by Telegram Middle Proxy key derivation.
+/// Not used for general-purpose hashing.
 pub fn md5(data: &[u8]) -> [u8; 16] {
     let mut hasher = Md5::new();
     hasher.update(data);
@@ -40,8 +55,11 @@ pub fn crc32(data: &[u8]) -> u32 {
     crc32fast::hash(data)
 }
 
-/// Middle Proxy Keygen
+/// Build the exact prekey buffer used by Telegram Middle Proxy KDF.
-pub fn derive_middleproxy_keys(
+///
+/// Returned buffer layout (IPv4):
+/// nonce_srv | nonce_clt | clt_ts | srv_ip | clt_port | purpose | clt_ip | srv_port | secret | nonce_srv | [clt_v6 | srv_v6] | nonce_clt
+pub fn build_middleproxy_prekey(
     nonce_srv: &[u8; 16],
     nonce_clt: &[u8; 16],
     clt_ts: &[u8; 4],
@@ -53,7 +71,7 @@ pub fn derive_middleproxy_keys(
     secret: &[u8],
     clt_ipv6: Option<&[u8; 16]>,
     srv_ipv6: Option<&[u8; 16]>,
-) -> ([u8; 32], [u8; 16]) {
+) -> Vec<u8> {
     const EMPTY_IP: [u8; 4] = [0, 0, 0, 0];
 
     let srv_ip = srv_ip.unwrap_or(&EMPTY_IP);
@@ -77,6 +95,40 @@ pub fn derive_middleproxy_keys(
     }
 
     s.extend_from_slice(nonce_clt);
+    s
+}
+
+/// Middle Proxy key derivation
+///
+/// Uses MD5 + SHA-1 as mandated by the Telegram Middle Proxy protocol.
+/// These algorithms are NOT replaceable here — changing them would break
+/// interoperability with Telegram's middle proxy infrastructure.
+pub fn derive_middleproxy_keys(
+    nonce_srv: &[u8; 16],
+    nonce_clt: &[u8; 16],
+    clt_ts: &[u8; 4],
+    srv_ip: Option<&[u8]>,
+    clt_port: &[u8; 2],
+    purpose: &[u8],
+    clt_ip: Option<&[u8]>,
+    srv_port: &[u8; 2],
+    secret: &[u8],
+    clt_ipv6: Option<&[u8; 16]>,
+    srv_ipv6: Option<&[u8; 16]>,
+) -> ([u8; 32], [u8; 16]) {
+    let s = build_middleproxy_prekey(
+        nonce_srv,
+        nonce_clt,
+        clt_ts,
+        srv_ip,
+        clt_port,
+        purpose,
+        clt_ip,
+        srv_port,
+        secret,
+        clt_ipv6,
+        srv_ipv6,
+    );
 
     let md5_1 = md5(&s[1..]);
     let sha1_sum = sha1(&s);
@@ -88,3 +140,39 @@ pub fn derive_middleproxy_keys(
     
     (key, md5_2)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn middleproxy_prekey_sha_is_stable() {
+        let nonce_srv = [0x11u8; 16];
+        let nonce_clt = [0x22u8; 16];
+        let clt_ts = 0x44332211u32.to_le_bytes();
+        let srv_ip = Some([149u8, 154, 175, 50].as_ref());
+        let clt_ip = Some([10u8, 0, 0, 1].as_ref());
+        let clt_port = 0x1f90u16.to_le_bytes(); // 8080
+        let srv_port = 0x22b8u16.to_le_bytes(); // 8888
+        let secret = vec![0x55u8; 128];
+
+        let prekey = build_middleproxy_prekey(
+            &nonce_srv,
+            &nonce_clt,
+            &clt_ts,
+            srv_ip,
+            &clt_port,
+            b"CLIENT",
+            clt_ip,
+            &srv_port,
+            &secret,
+            None,
+            None,
+        );
+        let digest = sha256(&prekey);
+        assert_eq!(
+            hex::encode(digest),
+            "a4595b75f1f610f2575ace802ddc65c91b5acef3b0e0d18189e0c7c9f787d15c"
+        );
+    }
+}

src/crypto/mod.rs

@@ -5,5 +5,5 @@ pub mod hash;
 pub mod random;
 
 pub use aes::{AesCtr, AesCbc};
-pub use hash::{sha256, sha256_hmac, sha1, md5, crc32};
+pub use hash::{sha256, sha256_hmac, sha1, md5, crc32, derive_middleproxy_keys, build_middleproxy_prekey};
-pub use random::{SecureRandom, SECURE_RANDOM};
+pub use random::SecureRandom;

src/crypto/random.rs

@@ -3,11 +3,8 @@
 use rand::{Rng, RngCore, SeedableRng};
 use rand::rngs::StdRng;
 use parking_lot::Mutex;
+use zeroize::Zeroize;
 use crate::crypto::AesCtr;
-use once_cell::sync::Lazy;
-
-/// Global secure random instance
-pub static SECURE_RANDOM: Lazy<SecureRandom> = Lazy::new(SecureRandom::new);
 
 /// Cryptographically secure PRNG with AES-CTR
 pub struct SecureRandom {
@@ -20,18 +17,30 @@ struct SecureRandomInner {
     buffer: Vec<u8>,
 }
 
+impl Drop for SecureRandomInner {
+    fn drop(&mut self) {
+        self.buffer.zeroize();
+    }
+}
+
 impl SecureRandom {
     pub fn new() -> Self {
-        let mut rng = StdRng::from_entropy();
+        let mut seed_source = rand::rng();
+        let mut rng = StdRng::from_rng(&mut seed_source);
         
         let mut key = [0u8; 32];
         rng.fill_bytes(&mut key);
-        let iv: u128 = rng.gen();
+        let iv: u128 = rng.random();
+        
+        let cipher = AesCtr::new(&key, iv);
+        
+        // Zeroize local key copy — cipher already consumed it
+        key.zeroize();
         
         Self {
             inner: Mutex::new(SecureRandomInner {
                 rng,
-                cipher: AesCtr::new(&key, iv),
+                cipher,
                 buffer: Vec::with_capacity(1024),
             }),
         }
@@ -78,7 +87,6 @@ impl SecureRandom {
             result |= (b as u64) << (i * 8);
         }
         
-        // Mask extra bits
         if k < 64 {
             result &= (1u64 << k) - 1;
         }
@@ -107,13 +115,13 @@ impl SecureRandom {
     /// Generate random u32
     pub fn u32(&self) -> u32 {
         let mut inner = self.inner.lock();
-        inner.rng.gen()
+        inner.rng.random()
     }
     
     /// Generate random u64
     pub fn u64(&self) -> u64 {
         let mut inner = self.inner.lock();
-        inner.rng.gen()
+        inner.rng.random()
     }
 }
 
@@ -162,12 +170,10 @@ mod tests {
     fn test_bits() {
         let rng = SecureRandom::new();
         
-        // Single bit should be 0 or 1
         for _ in 0..100 {
             assert!(rng.bits(1) <= 1);
         }
         
-        // 8 bits should be 0-255
         for _ in 0..100 {
             assert!(rng.bits(8) <= 255);
         }
@@ -185,10 +191,8 @@ mod tests {
             }
         }
         
-        // Should have seen all items
         assert_eq!(seen.len(), 5);
         
-        // Empty slice should return None
         let empty: Vec<i32> = vec![];
         assert!(rng.choose(&empty).is_none());
     }
@@ -201,12 +205,10 @@ mod tests {
         let mut shuffled = original.clone();
         rng.shuffle(&mut shuffled);
         
-        // Should contain same elements
         let mut sorted = shuffled.clone();
         sorted.sort();
         assert_eq!(sorted, original);
         
-        // Should be different order (with very high probability)
         assert_ne!(shuffled, original);
     }
 }

src/error.rs

@@ -118,16 +118,13 @@ pub trait Recoverable {
 impl Recoverable for StreamError {
     fn is_recoverable(&self) -> bool {
         match self {
-            // Partial operations can be retried
             Self::PartialRead { .. } | Self::PartialWrite { .. } => true,
-            // I/O errors depend on kind
             Self::Io(e) => matches!(
                 e.kind(),
                 std::io::ErrorKind::WouldBlock 
                 | std::io::ErrorKind::Interrupted
                 | std::io::ErrorKind::TimedOut
             ),
-            // These are not recoverable
             Self::Poisoned { .. } 
             | Self::BufferOverflow { .. }
             | Self::InvalidFrame { .. }
@@ -137,13 +134,9 @@ impl Recoverable for StreamError {
     
     fn can_continue(&self) -> bool {
         match self {
-            // Poisoned stream cannot be used
             Self::Poisoned { .. } => false,
-            // EOF means stream is done
             Self::UnexpectedEof => false,
-            // Buffer overflow is fatal
             Self::BufferOverflow { .. } => false,
-            // Others might allow continuation
             _ => true,
         }
     }
@@ -383,18 +376,18 @@ mod tests {
     
     #[test]
     fn test_handshake_result() {
-        let success: HandshakeResult<i32> = HandshakeResult::Success(42);
+        let success: HandshakeResult<i32, (), ()> = HandshakeResult::Success(42);
         assert!(success.is_success());
         assert!(!success.is_bad_client());
         
-        let bad: HandshakeResult<i32> = HandshakeResult::BadClient;
+        let bad: HandshakeResult<i32, (), ()> = HandshakeResult::BadClient { reader: (), writer: () };
         assert!(!bad.is_success());
         assert!(bad.is_bad_client());
     }
     
     #[test]
     fn test_handshake_result_map() {
-        let success: HandshakeResult<i32> = HandshakeResult::Success(42);
+        let success: HandshakeResult<i32, (), ()> = HandshakeResult::Success(42);
         let mapped = success.map(|x| x * 2);
         
         match mapped {

src/main.rs

@@ -1,13 +1,15 @@
-//! Telemt - MTProxy on Rust
+//! telemt — Telegram MTProto Proxy
 
 use std::net::SocketAddr;
 use std::sync::Arc;
 use std::time::Duration;
 use tokio::net::TcpListener;
 use tokio::signal;
-use tracing::{info, error, warn};
+use tokio::sync::Semaphore;
-use tracing_subscriber::{fmt, EnvFilter};
+use tracing::{debug, error, info, warn};
+use tracing_subscriber::{EnvFilter, fmt, prelude::*, reload};
 
+mod cli;
 mod config;
 mod crypto;
 mod error;
@@ -18,78 +20,356 @@ mod stream;
 mod transport;
 mod util;
 
-use crate::config::ProxyConfig;
+use crate::config::{LogLevel, ProxyConfig};
+use crate::crypto::SecureRandom;
 use crate::proxy::ClientHandler;
-use crate::stats::{Stats, ReplayChecker};
+use crate::stats::{ReplayChecker, Stats};
-use crate::transport::{create_listener, ListenOptions, UpstreamManager};
-use crate::util::ip::detect_ip;
 use crate::stream::BufferPool;
+use crate::transport::middle_proxy::MePool;
+use crate::transport::{ListenOptions, UpstreamManager, create_listener};
+use crate::util::ip::detect_ip;
+
+fn parse_cli() -> (String, bool, Option<String>) {
+    let mut config_path = "config.toml".to_string();
+    let mut silent = false;
+    let mut log_level: Option<String> = None;
+
+    let args: Vec<String> = std::env::args().skip(1).collect();
+
+    // Check for --init first (handled before tokio)
+    if let Some(init_opts) = cli::parse_init_args(&args) {
+        if let Err(e) = cli::run_init(init_opts) {
+            eprintln!("[telemt] Init failed: {}", e);
+            std::process::exit(1);
+        }
+        std::process::exit(0);
+    }
+
+    let mut i = 0;
+    while i < args.len() {
+        match args[i].as_str() {
+            "--silent" | "-s" => {
+                silent = true;
+            }
+            "--log-level" => {
+                i += 1;
+                if i < args.len() {
+                    log_level = Some(args[i].clone());
+                }
+            }
+            s if s.starts_with("--log-level=") => {
+                log_level = Some(s.trim_start_matches("--log-level=").to_string());
+            }
+            "--help" | "-h" => {
+                eprintln!("Usage: telemt [config.toml] [OPTIONS]");
+                eprintln!();
+                eprintln!("Options:");
+                eprintln!("  --silent, -s            Suppress info logs");
+                eprintln!("  --log-level <LEVEL>     debug|verbose|normal|silent");
+                eprintln!("  --help, -h              Show this help");
+                eprintln!();
+                eprintln!("Setup (fire-and-forget):");
+                eprintln!(
+                    "  --init                  Generate config, install systemd service, start"
+                );
+                eprintln!("    --port <PORT>          Listen port (default: 443)");
+                eprintln!(
+                    "    --domain <DOMAIN>      TLS domain for masking (default: www.google.com)"
+                );
+                eprintln!(
+                    "    --secret <HEX>         32-char hex secret (auto-generated if omitted)"
+                );
+                eprintln!("    --user <NAME>          Username (default: user)");
+                eprintln!("    --config-dir <DIR>     Config directory (default: /etc/telemt)");
+                eprintln!("    --no-start             Don't start the service after install");
+                std::process::exit(0);
+            }
+            s if !s.starts_with('-') => {
+                config_path = s.to_string();
+            }
+            other => {
+                eprintln!("Unknown option: {}", other);
+            }
+        }
+        i += 1;
+    }
+
+    (config_path, silent, log_level)
+}
 
 #[tokio::main]
-async fn main() -> Result<(), Box<dyn std::error::Error>> {
+async fn main() -> std::result::Result<(), Box<dyn std::error::Error>> {
-    // Initialize logging
+    let (config_path, cli_silent, cli_log_level) = parse_cli();
-    fmt()
-        .with_env_filter(EnvFilter::from_default_env().add_directive("info".parse().unwrap()))
-        .init();
 
-    // Load config
-    let config_path = std::env::args().nth(1).unwrap_or_else(|| "config.toml".to_string());
     let config = match ProxyConfig::load(&config_path) {
         Ok(c) => c,
         Err(e) => {
-            // If config doesn't exist, try to create default
             if std::path::Path::new(&config_path).exists() {
-                error!("Failed to load config: {}", e);
+                eprintln!("[telemt] Error: {}", e);
                 std::process::exit(1);
             } else {
                 let default = ProxyConfig::default();
-                let toml = toml::to_string_pretty(&default).unwrap();
+                std::fs::write(&config_path, toml::to_string_pretty(&default).unwrap()).unwrap();
-                std::fs::write(&config_path, toml).unwrap();
+                eprintln!("[telemt] Created default config at {}", config_path);
-                info!("Created default config at {}", config_path);
                 default
             }
         }
     };
 
-    config.validate()?;
+    if let Err(e) = config.validate() {
+        eprintln!("[telemt] Invalid config: {}", e);
+        std::process::exit(1);
+    }
 
-    // Log loaded configuration for debugging
+    let has_rust_log = std::env::var("RUST_LOG").is_ok();
-    info!("=== Configuration Loaded ===");
+    let effective_log_level = if cli_silent {
-    info!("TLS Domain: {}", config.censorship.tls_domain);
+        LogLevel::Silent
-    info!("Mask enabled: {}", config.censorship.mask);
+    } else if let Some(ref s) = cli_log_level {
-    info!("Mask host: {}", config.censorship.mask_host.as_deref().unwrap_or(&config.censorship.tls_domain));
+        LogLevel::from_str_loose(s)
-    info!("Mask port: {}", config.censorship.mask_port);
+    } else {
-    info!("Modes: classic={}, secure={}, tls={}", 
+        config.general.log_level.clone()
-        config.general.modes.classic, 
+    };
-        config.general.modes.secure, 
+
-        config.general.modes.tls
+    let (filter_layer, filter_handle) = reload::Layer::new(EnvFilter::new("info"));
+    tracing_subscriber::registry()
+        .with(filter_layer)
+        .with(fmt::Layer::default())
+        .init();
+
+    info!("Telemt MTProxy v{}", env!("CARGO_PKG_VERSION"));
+    info!("Log level: {}", effective_log_level);
+    info!(
+        "Modes: classic={} secure={} tls={}",
+        config.general.modes.classic, config.general.modes.secure, config.general.modes.tls
     );
-    info!("============================");
+    info!("TLS domain: {}", config.censorship.tls_domain);
+    if let Some(ref sock) = config.censorship.mask_unix_sock {
+        info!("Mask: {} -> unix:{}", config.censorship.mask, sock);
+        if !std::path::Path::new(sock).exists() {
+            warn!(
+                "Unix socket '{}' does not exist yet. Masking will fail until it appears.",
+                sock
+            );
+        }
+    } else {
+        info!(
+            "Mask: {} -> {}:{}",
+            config.censorship.mask,
+            config
+                .censorship
+                .mask_host
+                .as_deref()
+                .unwrap_or(&config.censorship.tls_domain),
+            config.censorship.mask_port
+        );
+    }
 
+    if config.censorship.tls_domain == "www.google.com" {
+        warn!("Using default tls_domain. Consider setting a custom domain.");
+    }
+
+    let prefer_ipv6 = config.general.prefer_ipv6;
+    let use_middle_proxy = config.general.use_middle_proxy;
     let config = Arc::new(config);
     let stats = Arc::new(Stats::new());
+    let rng = Arc::new(SecureRandom::new());
 
-    // Initialize global ReplayChecker
+    let replay_checker = Arc::new(ReplayChecker::new(
-    // Using sharded implementation for better concurrency
+        config.access.replay_check_len,
-    let replay_checker = Arc::new(ReplayChecker::new(config.access.replay_check_len));
+        Duration::from_secs(config.access.replay_window_secs),
+    ));
 
-    // Initialize Upstream Manager
     let upstream_manager = Arc::new(UpstreamManager::new(config.upstreams.clone()));
-    
-    // Initialize Buffer Pool
-    // 16KB buffers, max 4096 buffers (~64MB total cached)
     let buffer_pool = Arc::new(BufferPool::with_config(16 * 1024, 4096));
 
-    // Start Health Checks
+    // Connection concurrency limit
-    let um_clone = upstream_manager.clone();
+    let _max_connections = Arc::new(Semaphore::new(10_000));
-    tokio::spawn(async move {
+
-        um_clone.run_health_checks().await;
+    // =====================================================================
+    // Middle Proxy initialization (if enabled)
+    // =====================================================================
+    let me_pool: Option<Arc<MePool>> = if use_middle_proxy {
+        info!("=== Middle Proxy Mode ===");
+
+        // ad_tag (proxy_tag) for advertising
+        let proxy_tag = config.general.ad_tag.as_ref().map(|tag| {
+            hex::decode(tag).unwrap_or_else(|_| {
+                warn!("Invalid ad_tag hex, middle proxy ad_tag will be empty");
+                Vec::new()
+            })
         });
 
-    // Detect public IP if needed (once at startup)
+        // =============================================================
-    let detected_ip = detect_ip().await;
+        // CRITICAL: Download Telegram proxy-secret (NOT user secret!)
+        //
+        // C MTProxy uses TWO separate secrets:
+        //   -S flag    = 16-byte user secret for client obfuscation
+        //   --aes-pwd  = 32-512 byte binary file for ME RPC auth
+        //
+        // proxy-secret is from: https://core.telegram.org/getProxySecret
+        // =============================================================
+        let proxy_secret_path = config.general.proxy_secret_path.as_deref();
+        match crate::transport::middle_proxy::fetch_proxy_secret(proxy_secret_path).await {
+            Ok(proxy_secret) => {
+                info!(
+                    secret_len = proxy_secret.len(),
+                    key_sig = format_args!(
+                        "0x{:08x}",
+                        if proxy_secret.len() >= 4 {
+                            u32::from_le_bytes([
+                                proxy_secret[0],
+                                proxy_secret[1],
+                                proxy_secret[2],
+                                proxy_secret[3],
+                            ])
+                        } else {
+                            0
+                        }
+                    ),
+                    "Proxy-secret loaded"
+                );
+
+                let pool = MePool::new(
+                    proxy_tag,
+                    proxy_secret,
+                    config.general.middle_proxy_nat_ip,
+                    config.general.middle_proxy_nat_probe,
+                    config.general.middle_proxy_nat_stun.clone(),
+                );
+
+                match pool.init(2, &rng).await {
+                    Ok(()) => {
+                        info!("Middle-End pool initialized successfully");
+
+                        // Phase 4: Start health monitor
+                        let pool_clone = pool.clone();
+                        let rng_clone = rng.clone();
+                        tokio::spawn(async move {
+                            crate::transport::middle_proxy::me_health_monitor(
+                                pool_clone, rng_clone, 2,
+                            )
+                            .await;
+                        });
+
+                        Some(pool)
+                    }
+                    Err(e) => {
+                        error!(error = %e, "Failed to initialize ME pool. Falling back to direct mode.");
+                        None
+                    }
+                }
+            }
+            Err(e) => {
+                error!(error = %e, "Failed to fetch proxy-secret. Falling back to direct mode.");
+                None
+            }
+        }
+    } else {
+        None
+    };
+
+    if me_pool.is_some() {
+        info!("Transport: Middle Proxy (supports all DCs including CDN)");
+    } else {
+        info!("Transport: Direct TCP (standard DCs only)");
+    }
+
+    // Startup DC ping (only meaningful in direct mode)
+    if me_pool.is_none() {
+        info!("================= Telegram DC Connectivity =================");
+
+        let ping_results = upstream_manager.ping_all_dcs(prefer_ipv6).await;
+
+        for upstream_result in &ping_results {
+            // Show which IP version is in use and which is fallback
+            if upstream_result.both_available {
+                if prefer_ipv6 {
+                    info!("  IPv6 in use and IPv4 is fallback");
+                } else {
+                    info!("  IPv4 in use and IPv6 is fallback");
+                }
+            } else {
+                let v6_works = upstream_result
+                    .v6_results
+                    .iter()
+                    .any(|r| r.rtt_ms.is_some());
+                let v4_works = upstream_result
+                    .v4_results
+                    .iter()
+                    .any(|r| r.rtt_ms.is_some());
+                if v6_works && !v4_works {
+                    info!("  IPv6 only (IPv4 unavailable)");
+                } else if v4_works && !v6_works {
+                    info!("  IPv4 only (IPv6 unavailable)");
+                } else if !v6_works && !v4_works {
+                    info!("  No connectivity!");
+                }
+            }
+
+            info!("  via {}", upstream_result.upstream_name);
+            info!("============================================================");
+
+            // Print IPv6 results first
+            for dc in &upstream_result.v6_results {
+                let addr_str = format!("{}:{}", dc.dc_addr.ip(), dc.dc_addr.port());
+                match &dc.rtt_ms {
+                    Some(rtt) => {
+                        // Align: IPv6 addresses are longer, use fewer tabs
+                        // [2001:b28:f23d:f001::a]:443 = ~28 chars
+                        info!("    DC{} [IPv6] {}:\t\t{:.0} ms", dc.dc_idx, addr_str, rtt);
+                    }
+                    None => {
+                        let err = dc.error.as_deref().unwrap_or("fail");
+                        info!("    DC{} [IPv6] {}:\t\tFAIL ({})", dc.dc_idx, addr_str, err);
+                    }
+                }
+            }
+
+            info!("============================================================");
+
+            // Print IPv4 results
+            for dc in &upstream_result.v4_results {
+                let addr_str = format!("{}:{}", dc.dc_addr.ip(), dc.dc_addr.port());
+                match &dc.rtt_ms {
+                    Some(rtt) => {
+                        // Align: IPv4 addresses are shorter, use more tabs
+                        // 149.154.175.50:443 = ~18 chars
+                        info!(
+                            "    DC{} [IPv4] {}:\t\t\t\t{:.0} ms",
+                            dc.dc_idx, addr_str, rtt
+                        );
+                    }
+                    None => {
+                        let err = dc.error.as_deref().unwrap_or("fail");
+                        info!(
+                            "    DC{} [IPv4] {}:\t\t\t\tFAIL ({})",
+                            dc.dc_idx, addr_str, err
+                        );
+                    }
+                }
+            }
+
+            info!("============================================================");
+        }
+    }
+
+    // Background tasks
+    let um_clone = upstream_manager.clone();
+    tokio::spawn(async move {
+        um_clone.run_health_checks(prefer_ipv6).await;
+    });
+
+    let rc_clone = replay_checker.clone();
+    tokio::spawn(async move {
+        rc_clone.run_periodic_cleanup().await;
+    });
+
+    let detected_ip = detect_ip().await;
+    debug!(
+        "Detected IPs: v4={:?} v6={:?}",
+        detected_ip.ipv4, detected_ip.ipv6
+    );
 
-    // Start Listeners
     let mut listeners = Vec::new();
 
     for listener_conf in &config.server.listeners {
@@ -104,7 +384,6 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
                 let listener = TcpListener::from_std(socket.into())?;
                 info!("Listening on {}", addr);
 
-                // Determine public IP for tg:// links
                 let public_ip = if let Some(ip) = listener_conf.announce_ip {
                     ip
                 } else if listener_conf.ip.is_unspecified() {
@@ -117,37 +396,39 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
                     listener_conf.ip
                 };
 
-                // Show links for configured users
                 if !config.show_link.is_empty() {
-                    info!("--- Proxy Links for {} ---", public_ip);
+                    info!("--- Proxy Links ({}) ---", public_ip);
                     for user_name in &config.show_link {
                         if let Some(secret) = config.access.users.get(user_name) {
                             info!("User: {}", user_name);
-
                             if config.general.modes.classic {
-                                info!("  Classic: tg://proxy?server={}&port={}&secret={}", 
+                                info!(
-                                    public_ip, config.server.port, secret);
+                                    "  Classic: tg://proxy?server={}&port={}&secret={}",
+                                    public_ip, config.server.port, secret
+                                );
                             }
-
                             if config.general.modes.secure {
-                                info!("  DD:      tg://proxy?server={}&port={}&secret=dd{}", 
+                                info!(
-                                    public_ip, config.server.port, secret);
+                                    "  DD:      tg://proxy?server={}&port={}&secret=dd{}",
+                                    public_ip, config.server.port, secret
+                                );
                             }
-
                             if config.general.modes.tls {
                                 let domain_hex = hex::encode(&config.censorship.tls_domain);
-                                info!("  EE-TLS:  tg://proxy?server={}&port={}&secret=ee{}{}", 
+                                info!(
-                                    public_ip, config.server.port, secret, domain_hex);
+                                    "  EE-TLS:  tg://proxy?server={}&port={}&secret=ee{}{}",
+                                    public_ip, config.server.port, secret, domain_hex
+                                );
                             }
                         } else {
-                            warn!("User '{}' specified in show_link not found in users list", user_name);
+                            warn!("User '{}' in show_link not found", user_name);
                         }
                     }
-                    info!("-----------------------------------");
+                    info!("------------------------");
                 }
 
                 listeners.push(listener);
-            },
+            }
             Err(e) => {
                 error!("Failed to bind to {}: {}", addr, e);
             }
@@ -155,17 +436,28 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     }
 
     if listeners.is_empty() {
-        error!("No listeners could be started. Exiting.");
+        error!("No listeners. Exiting.");
         std::process::exit(1);
     }
 
-    // Accept loop
+    // Switch to user-configured log level after startup
+    let runtime_filter = if has_rust_log {
+        EnvFilter::from_default_env()
+    } else {
+        EnvFilter::new(effective_log_level.to_filter_str())
+    };
+    filter_handle
+        .reload(runtime_filter)
+        .expect("Failed to switch log filter");
+
     for listener in listeners {
         let config = config.clone();
         let stats = stats.clone();
         let upstream_manager = upstream_manager.clone();
         let replay_checker = replay_checker.clone();
         let buffer_pool = buffer_pool.clone();
+        let rng = rng.clone();
+        let me_pool = me_pool.clone();
 
         tokio::spawn(async move {
             loop {
@@ -176,6 +468,8 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
                         let upstream_manager = upstream_manager.clone();
                         let replay_checker = replay_checker.clone();
                         let buffer_pool = buffer_pool.clone();
+                        let rng = rng.clone();
+                        let me_pool = me_pool.clone();
 
                         tokio::spawn(async move {
                             if let Err(e) = ClientHandler::new(
@@ -185,9 +479,14 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
                                 stats,
                                 upstream_manager,
                                 replay_checker,
-                                buffer_pool
+                                buffer_pool,
-                            ).run().await {
+                                rng,
-                                // Log only relevant errors
+                                me_pool,
+                            )
+                            .run()
+                            .await
+                            {
+                                debug!(peer = %peer_addr, error = %e, "Connection error");
                             }
                         });
                     }
@@ -200,7 +499,6 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
         });
     }
 
-    // Wait for signal
     match signal::ctrl_c().await {
         Ok(()) => info!("Shutting down..."),
         Err(e) => error!("Signal error: {}", e),

src/protocol/constants.rs

@@ -1,13 +1,13 @@
 //! Protocol constants and datacenter addresses
 
 use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
-use once_cell::sync::Lazy;
+use std::sync::LazyLock;
 
 // ============= Telegram Datacenters =============
 
 pub const TG_DATACENTER_PORT: u16 = 443;
 
-pub static TG_DATACENTERS_V4: Lazy<Vec<IpAddr>> = Lazy::new(|| {
+pub static TG_DATACENTERS_V4: LazyLock<Vec<IpAddr>> = LazyLock::new(|| {
     vec![
         IpAddr::V4(Ipv4Addr::new(149, 154, 175, 50)),
         IpAddr::V4(Ipv4Addr::new(149, 154, 167, 51)),
@@ -17,7 +17,7 @@ pub static TG_DATACENTERS_V4: Lazy<Vec<IpAddr>> = Lazy::new(|| {
     ]
 });
 
-pub static TG_DATACENTERS_V6: Lazy<Vec<IpAddr>> = Lazy::new(|| {
+pub static TG_DATACENTERS_V6: LazyLock<Vec<IpAddr>> = LazyLock::new(|| {
     vec![
         IpAddr::V6("2001:b28:f23d:f001::a".parse().unwrap()),
         IpAddr::V6("2001:67c:04e8:f002::a".parse().unwrap()),
@@ -29,8 +29,8 @@ pub static TG_DATACENTERS_V6: Lazy<Vec<IpAddr>> = Lazy::new(|| {
 
 // ============= Middle Proxies (for advertising) =============
 
-pub static TG_MIDDLE_PROXIES_V4: Lazy<std::collections::HashMap<i32, Vec<(IpAddr, u16)>>> = 
+pub static TG_MIDDLE_PROXIES_V4: LazyLock<std::collections::HashMap<i32, Vec<(IpAddr, u16)>>> = 
-    Lazy::new(|| {
+    LazyLock::new(|| {
         let mut m = std::collections::HashMap::new();
         m.insert(1, vec![(IpAddr::V4(Ipv4Addr::new(149, 154, 175, 50)), 8888)]);
         m.insert(-1, vec![(IpAddr::V4(Ipv4Addr::new(149, 154, 175, 50)), 8888)]);
@@ -45,8 +45,8 @@ pub static TG_MIDDLE_PROXIES_V4: Lazy<std::collections::HashMap<i32, Vec<(IpAddr
         m
     });
 
-pub static TG_MIDDLE_PROXIES_V6: Lazy<std::collections::HashMap<i32, Vec<(IpAddr, u16)>>> = 
+pub static TG_MIDDLE_PROXIES_V6: LazyLock<std::collections::HashMap<i32, Vec<(IpAddr, u16)>>> = 
-    Lazy::new(|| {
+    LazyLock::new(|| {
         let mut m = std::collections::HashMap::new();
         m.insert(1, vec![(IpAddr::V6("2001:b28:f23d:f001::d".parse().unwrap()), 8888)]);
         m.insert(-1, vec![(IpAddr::V6("2001:b28:f23d:f001::d".parse().unwrap()), 8888)]);
@@ -167,8 +167,6 @@ pub const DEFAULT_ACK_TIMEOUT_SECS: u64 = 300;
 // ============= Buffer Sizes =============
 
 /// Default buffer size
-/// CHANGED: Reduced from 64KB to 16KB to match TLS record size and align with
-/// the new buffering strategy for better iOS upload performance.
 pub const DEFAULT_BUFFER_SIZE: usize = 16384;
 
 /// Small buffer size for bad client handling
@@ -204,6 +202,17 @@ pub static RESERVED_NONCE_CONTINUES: &[[u8; 4]] = &[
 // ============= RPC Constants (for Middle Proxy) =============
 
 /// RPC Proxy Request
+
+/// RPC Flags (from Erlang mtp_rpc.erl)
+pub const RPC_FLAG_NOT_ENCRYPTED: u32 = 0x2;
+pub const RPC_FLAG_HAS_AD_TAG: u32    = 0x8;
+pub const RPC_FLAG_MAGIC: u32          = 0x1000;
+pub const RPC_FLAG_EXTMODE2: u32       = 0x20000;
+pub const RPC_FLAG_PAD: u32            = 0x8000000;
+pub const RPC_FLAG_INTERMEDIATE: u32   = 0x20000000;
+pub const RPC_FLAG_ABRIDGED: u32       = 0x40000000;
+pub const RPC_FLAG_QUICKACK: u32       = 0x80000000;
+
 pub const RPC_PROXY_REQ: [u8; 4] = [0xee, 0xf1, 0xce, 0x36];
 /// RPC Proxy Answer
 pub const RPC_PROXY_ANS: [u8; 4] = [0x0d, 0xda, 0x03, 0x44];
@@ -230,7 +239,56 @@ pub mod rpc_flags {
     pub const FLAG_QUICKACK: u32 = 0x80000000;
 }
 
-#[cfg(test)]
+
+    // ============= Middle-End Proxy Servers =============
+    pub const ME_PROXY_PORT: u16 = 8888;
+    
+    pub static TG_MIDDLE_PROXIES_FLAT_V4: LazyLock<Vec<(IpAddr, u16)>> = LazyLock::new(|| {
+        vec![
+            (IpAddr::V4(Ipv4Addr::new(149, 154, 175, 50)), 8888),
+            (IpAddr::V4(Ipv4Addr::new(149, 154, 161, 144)), 8888),
+            (IpAddr::V4(Ipv4Addr::new(149, 154, 175, 100)), 8888),
+            (IpAddr::V4(Ipv4Addr::new(91, 108, 4, 136)), 8888),
+            (IpAddr::V4(Ipv4Addr::new(91, 108, 56, 183)), 8888),
+        ]
+    });
+    
+    // ============= RPC Constants (u32 native endian) =============
+    // From mtproto-common.h + net-tcp-rpc-common.h + mtproto-proxy.c
+    
+    pub const RPC_NONCE_U32: u32           = 0x7acb87aa;
+    pub const RPC_HANDSHAKE_U32: u32       = 0x7682eef5;
+    pub const RPC_HANDSHAKE_ERROR_U32: u32 = 0x6a27beda;
+    pub const TL_PROXY_TAG_U32: u32        = 0xdb1e26ae;  // mtproto-proxy.c:121
+    
+    // mtproto-common.h
+    pub const RPC_PROXY_REQ_U32: u32       = 0x36cef1ee;
+    pub const RPC_PROXY_ANS_U32: u32       = 0x4403da0d;
+    pub const RPC_CLOSE_CONN_U32: u32      = 0x1fcf425d;
+    pub const RPC_CLOSE_EXT_U32: u32       = 0x5eb634a2;
+    pub const RPC_SIMPLE_ACK_U32: u32      = 0x3bac409b;
+    pub const RPC_PING_U32: u32            = 0x5730a2df;
+    pub const RPC_PONG_U32: u32            = 0x8430eaa7;
+    
+    pub const RPC_CRYPTO_NONE_U32: u32 = 0;
+    pub const RPC_CRYPTO_AES_U32: u32  = 1;
+    
+    pub mod proxy_flags {
+        pub const FLAG_HAS_AD_TAG: u32    = 1;
+        pub const FLAG_NOT_ENCRYPTED: u32 = 0x2;
+        pub const FLAG_HAS_AD_TAG2: u32   = 0x8;
+        pub const FLAG_MAGIC: u32         = 0x1000;
+        pub const FLAG_EXTMODE2: u32      = 0x20000;
+        pub const FLAG_PAD: u32           = 0x8000000;
+        pub const FLAG_INTERMEDIATE: u32  = 0x20000000;
+        pub const FLAG_ABRIDGED: u32      = 0x40000000;
+        pub const FLAG_QUICKACK: u32      = 0x80000000;
+    }
+    
+    pub const ME_CONNECT_TIMEOUT_SECS: u64 = 5;
+    pub const ME_HANDSHAKE_TIMEOUT_SECS: u64 = 10;
+    
+    #[cfg(test)]
 mod tests {
     use super::*;
     

src/protocol/obfuscation.rs

@@ -1,10 +1,13 @@
 //! MTProto Obfuscation
 
+use zeroize::Zeroize;
 use crate::crypto::{sha256, AesCtr};
 use crate::error::Result;
 use super::constants::*;
 
 /// Obfuscation parameters from handshake
+///
+/// Key material is zeroized on drop.
 #[derive(Debug, Clone)]
 pub struct ObfuscationParams {
     /// Key for decrypting client -> proxy traffic
@@ -21,25 +24,31 @@ pub struct ObfuscationParams {
     pub dc_idx: i16,
 }
 
+impl Drop for ObfuscationParams {
+    fn drop(&mut self) {
+        self.decrypt_key.zeroize();
+        self.decrypt_iv.zeroize();
+        self.encrypt_key.zeroize();
+        self.encrypt_iv.zeroize();
+    }
+}
+
 impl ObfuscationParams {
     /// Parse obfuscation parameters from handshake bytes
     /// Returns None if handshake doesn't match any user secret
     pub fn from_handshake(
         handshake: &[u8; HANDSHAKE_LEN],
-        secrets: &[(String, Vec<u8>)], // (username, secret_bytes)
+        secrets: &[(String, Vec<u8>)],
     ) -> Option<(Self, String)> {
-        // Extract prekey and IV for decryption
         let dec_prekey_iv = &handshake[SKIP_LEN..SKIP_LEN + PREKEY_LEN + IV_LEN];
         let dec_prekey = &dec_prekey_iv[..PREKEY_LEN];
         let dec_iv_bytes = &dec_prekey_iv[PREKEY_LEN..];
         
-        // Reversed for encryption direction
         let enc_prekey_iv: Vec<u8> = dec_prekey_iv.iter().rev().copied().collect();
         let enc_prekey = &enc_prekey_iv[..PREKEY_LEN];
         let enc_iv_bytes = &enc_prekey_iv[PREKEY_LEN..];
         
         for (username, secret) in secrets {
-            // Derive decryption key
             let mut dec_key_input = Vec::with_capacity(PREKEY_LEN + secret.len());
             dec_key_input.extend_from_slice(dec_prekey);
             dec_key_input.extend_from_slice(secret);
@@ -47,26 +56,22 @@ impl ObfuscationParams {
             
             let decrypt_iv = u128::from_be_bytes(dec_iv_bytes.try_into().unwrap());
             
-            // Create decryptor and decrypt handshake
             let mut decryptor = AesCtr::new(&decrypt_key, decrypt_iv);
             let decrypted = decryptor.decrypt(handshake);
             
-            // Check protocol tag
             let tag_bytes: [u8; 4] = decrypted[PROTO_TAG_POS..PROTO_TAG_POS + 4]
                 .try_into()
                 .unwrap();
             
             let proto_tag = match ProtoTag::from_bytes(tag_bytes) {
                 Some(tag) => tag,
-                None => continue, // Try next secret
+                None => continue,
             };
             
-            // Extract DC index
             let dc_idx = i16::from_le_bytes(
                 decrypted[DC_IDX_POS..DC_IDX_POS + 2].try_into().unwrap()
             );
             
-            // Derive encryption key
             let mut enc_key_input = Vec::with_capacity(PREKEY_LEN + secret.len());
             enc_key_input.extend_from_slice(enc_prekey);
             enc_key_input.extend_from_slice(secret);
@@ -123,18 +128,15 @@ pub fn generate_nonce<R: FnMut(usize) -> Vec<u8>>(mut random_bytes: R) -> [u8; H
 
 /// Check if nonce is valid (not matching reserved patterns)
 pub fn is_valid_nonce(nonce: &[u8; HANDSHAKE_LEN]) -> bool {
-    // Check first byte
     if RESERVED_NONCE_FIRST_BYTES.contains(&nonce[0]) {
         return false;
     }
     
-    // Check first 4 bytes
     let first_four: [u8; 4] = nonce[..4].try_into().unwrap();
     if RESERVED_NONCE_BEGINNINGS.contains(&first_four) {
         return false;
     }
     
-    // Check bytes 4-7
     let continue_four: [u8; 4] = nonce[4..8].try_into().unwrap();
     if RESERVED_NONCE_CONTINUES.contains(&continue_four) {
         return false;
@@ -147,12 +149,10 @@ pub fn is_valid_nonce(nonce: &[u8; HANDSHAKE_LEN]) -> bool {
 pub fn prepare_tg_nonce(
     nonce: &mut [u8; HANDSHAKE_LEN],
     proto_tag: ProtoTag,
-    enc_key_iv: Option<&[u8]>, // For fast mode
+    enc_key_iv: Option<&[u8]>,
 ) {
-    // Set protocol tag
     nonce[PROTO_TAG_POS..PROTO_TAG_POS + 4].copy_from_slice(&proto_tag.to_bytes());
     
-    // For fast mode, copy the reversed enc_key_iv
     if let Some(key_iv) = enc_key_iv {
         let reversed: Vec<u8> = key_iv.iter().rev().copied().collect();
         nonce[SKIP_LEN..SKIP_LEN + KEY_LEN + IV_LEN].copy_from_slice(&reversed);
@@ -161,14 +161,12 @@ pub fn prepare_tg_nonce(
 
 /// Encrypt the outgoing nonce for Telegram
 pub fn encrypt_nonce(nonce: &[u8; HANDSHAKE_LEN]) -> Vec<u8> {
-    // Derive encryption key from the nonce itself
     let key_iv = &nonce[SKIP_LEN..SKIP_LEN + KEY_LEN + IV_LEN];
     let enc_key = sha256(key_iv);
     let enc_iv = u128::from_be_bytes(key_iv[..IV_LEN].try_into().unwrap());
     
     let mut encryptor = AesCtr::new(&enc_key, enc_iv);
     
-    // Only encrypt from PROTO_TAG_POS onwards
     let mut result = nonce.to_vec();
     let encrypted_part = encryptor.encrypt(&nonce[PROTO_TAG_POS..]);
     result[PROTO_TAG_POS..].copy_from_slice(&encrypted_part);
@@ -182,22 +180,18 @@ mod tests {
     
     #[test]
     fn test_is_valid_nonce() {
-        // Valid nonce
         let mut valid = [0x42u8; HANDSHAKE_LEN];
         valid[4..8].copy_from_slice(&[1, 2, 3, 4]);
         assert!(is_valid_nonce(&valid));
         
-        // Invalid: starts with 0xef
         let mut invalid = [0x00u8; HANDSHAKE_LEN];
         invalid[0] = 0xef;
         assert!(!is_valid_nonce(&invalid));
         
-        // Invalid: starts with HEAD
         let mut invalid = [0x00u8; HANDSHAKE_LEN];
         invalid[..4].copy_from_slice(b"HEAD");
         assert!(!is_valid_nonce(&invalid));
         
-        // Invalid: bytes 4-7 are zeros
         let mut invalid = [0x42u8; HANDSHAKE_LEN];
         invalid[4..8].copy_from_slice(&[0, 0, 0, 0]);
         assert!(!is_valid_nonce(&invalid));

src/protocol/tls.rs

@@ -4,7 +4,7 @@
 //! for domain fronting. The handshake looks like valid TLS 1.3 but
 //! actually carries MTProto authentication data.
 
-use crate::crypto::{sha256_hmac, random::SECURE_RANDOM};
+use crate::crypto::{sha256_hmac, SecureRandom};
 use crate::error::{ProxyError, Result};
 use super::constants::*;
 use std::time::{SystemTime, UNIX_EPOCH};
@@ -315,8 +315,8 @@ pub fn validate_tls_handshake(
 ///
 /// This generates random bytes that look like a valid X25519 public key.
 /// Since we're not doing real TLS, the actual cryptographic properties don't matter.
-pub fn gen_fake_x25519_key() -> [u8; 32] {
+pub fn gen_fake_x25519_key(rng: &SecureRandom) -> [u8; 32] {
-    let bytes = SECURE_RANDOM.bytes(32);
+    let bytes = rng.bytes(32);
     bytes.try_into().unwrap()
 }
 
@@ -333,8 +333,9 @@ pub fn build_server_hello(
     client_digest: &[u8; TLS_DIGEST_LEN],
     session_id: &[u8],
     fake_cert_len: usize,
+    rng: &SecureRandom,
 ) -> Vec<u8> {
-    let x25519_key = gen_fake_x25519_key();
+    let x25519_key = gen_fake_x25519_key(rng);
     
     // Build ServerHello
     let server_hello = ServerHelloBuilder::new(session_id.to_vec())
@@ -351,7 +352,7 @@ pub fn build_server_hello(
     ];
     
     // Build fake certificate (Application Data record)
-    let fake_cert = SECURE_RANDOM.bytes(fake_cert_len);
+    let fake_cert = rng.bytes(fake_cert_len);
     let mut app_data_record = Vec::with_capacity(5 + fake_cert_len);
     app_data_record.push(TLS_RECORD_APPLICATION);
     app_data_record.extend_from_slice(&TLS_VERSION);
@@ -489,8 +490,9 @@ mod tests {
     
     #[test]
     fn test_gen_fake_x25519_key() {
-        let key1 = gen_fake_x25519_key();
+        let rng = SecureRandom::new();
-        let key2 = gen_fake_x25519_key();
+        let key1 = gen_fake_x25519_key(&rng);
+        let key2 = gen_fake_x25519_key(&rng);
         
         assert_eq!(key1.len(), 32);
         assert_eq!(key2.len(), 32);
@@ -545,7 +547,8 @@ mod tests {
         let client_digest = [0x42u8; 32];
         let session_id = vec![0xAA; 32];
         
-        let response = build_server_hello(secret, &client_digest, &session_id, 2048);
+        let rng = SecureRandom::new();
+        let response = build_server_hello(secret, &client_digest, &session_id, 2048, &rng);
         
         // Should have at least 3 records
         assert!(response.len() > 100);
@@ -577,8 +580,9 @@ mod tests {
         let client_digest = [0x42u8; 32];
         let session_id = vec![0xAA; 32];
         
-        let response1 = build_server_hello(secret, &client_digest, &session_id, 1024);
+        let rng = SecureRandom::new();
-        let response2 = build_server_hello(secret, &client_digest, &session_id, 1024);
+        let response1 = build_server_hello(secret, &client_digest, &session_id, 1024, &rng);
+        let response2 = build_server_hello(secret, &client_digest, &session_id, 1024, &rng);
         
         // Digest position should have non-zero data
         let digest1 = &response1[TLS_DIGEST_POS..TLS_DIGEST_POS + TLS_DIGEST_LEN];

src/proxy/client.rs

@@ -3,32 +3,28 @@
 use std::net::SocketAddr;
 use std::sync::Arc;
 use std::time::Duration;
+use tokio::io::{AsyncRead, AsyncReadExt, AsyncWrite};
 use tokio::net::TcpStream;
-use tokio::io::{AsyncRead, AsyncWrite, AsyncReadExt, AsyncWriteExt};
 use tokio::time::timeout;
-use tracing::{debug, info, warn, error, trace};
+use tracing::{debug, warn};
 
 use crate::config::ProxyConfig;
-use crate::error::{ProxyError, Result, HandshakeResult};
+use crate::crypto::SecureRandom;
+use crate::error::{HandshakeResult, ProxyError, Result};
 use crate::protocol::constants::*;
 use crate::protocol::tls;
-use crate::stats::{Stats, ReplayChecker};
+use crate::stats::{ReplayChecker, Stats};
-use crate::transport::{configure_client_socket, UpstreamManager};
+use crate::stream::{BufferPool, CryptoReader, CryptoWriter};
-use crate::stream::{CryptoReader, CryptoWriter, FakeTlsReader, FakeTlsWriter, BufferPool};
+use crate::transport::middle_proxy::MePool;
-use crate::crypto::AesCtr;
+use crate::transport::{UpstreamManager, configure_client_socket};
 
-// Use absolute paths to avoid confusion
+use crate::proxy::direct_relay::handle_via_direct;
-use crate::proxy::handshake::{
+use crate::proxy::handshake::{HandshakeSuccess, handle_mtproto_handshake, handle_tls_handshake};
-    handle_tls_handshake, handle_mtproto_handshake, 
-    HandshakeSuccess, generate_tg_nonce, encrypt_tg_nonce,
-};
-use crate::proxy::relay::relay_bidirectional;
 use crate::proxy::masking::handle_bad_client;
+use crate::proxy::middle_relay::handle_via_middle_proxy;
 
-/// Client connection handler (builder struct)
 pub struct ClientHandler;
 
-/// Running client handler with stream and context
 pub struct RunningClientHandler {
     stream: TcpStream,
     peer: SocketAddr,
@@ -37,10 +33,11 @@ pub struct RunningClientHandler {
     replay_checker: Arc<ReplayChecker>,
     upstream_manager: Arc<UpstreamManager>,
     buffer_pool: Arc<BufferPool>,
+    rng: Arc<SecureRandom>,
+    me_pool: Option<Arc<MePool>>,
 }
 
 impl ClientHandler {
-    /// Create new client handler instance
     pub fn new(
         stream: TcpStream,
         peer: SocketAddr,
@@ -49,6 +46,8 @@ impl ClientHandler {
         upstream_manager: Arc<UpstreamManager>,
         replay_checker: Arc<ReplayChecker>,
         buffer_pool: Arc<BufferPool>,
+        rng: Arc<SecureRandom>,
+        me_pool: Option<Arc<MePool>>,
     ) -> RunningClientHandler {
         RunningClientHandler {
             stream,
@@ -58,19 +57,19 @@ impl ClientHandler {
             replay_checker,
             upstream_manager,
             buffer_pool,
+            rng,
+            me_pool,
         }
     }
 }
 
 impl RunningClientHandler {
-    /// Run the client handler
     pub async fn run(mut self) -> Result<()> {
         self.stats.increment_connects_all();
 
         let peer = self.peer;
         debug!(peer = %peer, "New connection");
 
-        // Configure socket
         if let Err(e) = configure_client_socket(
             &self.stream,
             self.config.timeouts.client_keepalive,
@@ -79,16 +78,10 @@ impl RunningClientHandler {
             debug!(peer = %peer, error = %e, "Failed to configure client socket");
         }
 
-        // Perform handshake with timeout
         let handshake_timeout = Duration::from_secs(self.config.timeouts.client_handshake);
-        
-        // Clone stats for error handling block
         let stats = self.stats.clone();
 
-        let result = timeout(
+        let result = timeout(handshake_timeout, self.do_handshake()).await;
-            handshake_timeout,
-            self.do_handshake()
-        ).await;
 
         match result {
             Ok(Ok(())) => {
@@ -107,16 +100,14 @@ impl RunningClientHandler {
         }
     }
 
-    /// Perform handshake and relay
     async fn do_handshake(mut self) -> Result<()> {
-        // Read first bytes to determine handshake type
         let mut first_bytes = [0u8; 5];
         self.stream.read_exact(&mut first_bytes).await?;
 
         let is_tls = tls::is_tls_handshake(&first_bytes[..3]);
         let peer = self.peer;
 
-        debug!(peer = %peer, is_tls = is_tls, first_bytes = %hex::encode(&first_bytes), "Handshake type detected");
+        debug!(peer = %peer, is_tls = is_tls, "Handshake type detected");
 
         if is_tls {
             self.handle_tls_client(first_bytes).await
@@ -125,14 +116,9 @@ impl RunningClientHandler {
         }
     }
 
-    /// Handle TLS-wrapped client
+    async fn handle_tls_client(mut self, first_bytes: [u8; 5]) -> Result<()> {
-    async fn handle_tls_client(
-        mut self,
-        first_bytes: [u8; 5],
-    ) -> Result<()> {
         let peer = self.peer;
 
-        // Read TLS handshake length
         let tls_len = u16::from_be_bytes([first_bytes[3], first_bytes[4]]) as usize;
 
         debug!(peer = %peer, tls_len = tls_len, "Reading TLS handshake");
@@ -140,27 +126,23 @@ impl RunningClientHandler {
         if tls_len < 512 {
             debug!(peer = %peer, tls_len = tls_len, "TLS handshake too short");
             self.stats.increment_connects_bad();
-            // FIX: Split stream into reader/writer for handle_bad_client
             let (reader, writer) = self.stream.into_split();
             handle_bad_client(reader, writer, &first_bytes, &self.config).await;
             return Ok(());
         }
 
-        // Read full TLS handshake
         let mut handshake = vec![0u8; 5 + tls_len];
         handshake[..5].copy_from_slice(&first_bytes);
         self.stream.read_exact(&mut handshake[5..]).await?;
 
-        // Extract fields before consuming self.stream
         let config = self.config.clone();
         let replay_checker = self.replay_checker.clone();
         let stats = self.stats.clone();
         let buffer_pool = self.buffer_pool.clone();
 
-        // Split stream for reading/writing
+        let local_addr = self.stream.local_addr().map_err(ProxyError::Io)?;
         let (read_half, write_half) = self.stream.into_split();
 
-        // Handle TLS handshake
         let (mut tls_reader, tls_writer, _tls_user) = match handle_tls_handshake(
             &handshake,
             read_half,
@@ -168,7 +150,10 @@ impl RunningClientHandler {
             peer,
             &config,
             &replay_checker,
-        ).await {
+            &self.rng,
+        )
+        .await
+        {
             HandshakeResult::Success(result) => result,
             HandshakeResult::BadClient { reader, writer } => {
                 stats.increment_connects_bad();
@@ -178,13 +163,12 @@ impl RunningClientHandler {
             HandshakeResult::Error(e) => return Err(e),
         };
 
-        // Read MTProto handshake through TLS
         debug!(peer = %peer, "Reading MTProto handshake through TLS");
         let mtproto_data = tls_reader.read_exact(HANDSHAKE_LEN).await?;
-        let mtproto_handshake: [u8; HANDSHAKE_LEN] = mtproto_data[..].try_into()
+        let mtproto_handshake: [u8; HANDSHAKE_LEN] = mtproto_data[..]
+            .try_into()
             .map_err(|_| ProxyError::InvalidHandshake("Short MTProto handshake".into()))?;
 
-        // Handle MTProto handshake
         let (crypto_reader, crypto_writer, success) = match handle_mtproto_handshake(
             &mtproto_handshake,
             tls_reader,
@@ -193,12 +177,16 @@ impl RunningClientHandler {
             &config,
             &replay_checker,
             true,
-        ).await {
+        )
+        .await
+        {
             HandshakeResult::Success(result) => result,
-            HandshakeResult::BadClient { reader, writer } => {
+            HandshakeResult::BadClient {
+                reader: _,
+                writer: _,
+            } => {
                 stats.increment_connects_bad();
-                // Valid TLS but invalid MTProto - drop
+                debug!(peer = %peer, "Valid TLS but invalid MTProto handshake");
-                debug!(peer = %peer, "Valid TLS but invalid MTProto handshake - dropping");
                 return Ok(());
             }
             HandshakeResult::Error(e) => return Err(e),
@@ -211,42 +199,37 @@ impl RunningClientHandler {
             self.upstream_manager,
             self.stats,
             self.config,
-            buffer_pool
+            buffer_pool,
-        ).await
+            self.rng,
+            self.me_pool,
+            local_addr,
+        )
+        .await
     }
 
-    /// Handle direct (non-TLS) client
+    async fn handle_direct_client(mut self, first_bytes: [u8; 5]) -> Result<()> {
-    async fn handle_direct_client(
-        mut self,
-        first_bytes: [u8; 5],
-    ) -> Result<()> {
         let peer = self.peer;
 
-        // Check if non-TLS modes are enabled
         if !self.config.general.modes.classic && !self.config.general.modes.secure {
             debug!(peer = %peer, "Non-TLS modes disabled");
             self.stats.increment_connects_bad();
-            // FIX: Split stream into reader/writer for handle_bad_client
             let (reader, writer) = self.stream.into_split();
             handle_bad_client(reader, writer, &first_bytes, &self.config).await;
             return Ok(());
         }
 
-        // Read rest of handshake
         let mut handshake = [0u8; HANDSHAKE_LEN];
         handshake[..5].copy_from_slice(&first_bytes);
         self.stream.read_exact(&mut handshake[5..]).await?;
 
-        // Extract fields
         let config = self.config.clone();
         let replay_checker = self.replay_checker.clone();
         let stats = self.stats.clone();
         let buffer_pool = self.buffer_pool.clone();
 
-        // Split stream
+        let local_addr = self.stream.local_addr().map_err(ProxyError::Io)?;
         let (read_half, write_half) = self.stream.into_split();
 
-        // Handle MTProto handshake
         let (crypto_reader, crypto_writer, success) = match handle_mtproto_handshake(
             &handshake,
             read_half,
@@ -255,7 +238,9 @@ impl RunningClientHandler {
             &config,
             &replay_checker,
             false,
-        ).await {
+        )
+        .await
+        {
             HandshakeResult::Success(result) => result,
             HandshakeResult::BadClient { reader, writer } => {
                 stats.increment_connects_bad();
@@ -272,11 +257,18 @@ impl RunningClientHandler {
             self.upstream_manager,
             self.stats,
             self.config,
-            buffer_pool
+            buffer_pool,
-        ).await
+            self.rng,
+            self.me_pool,
+            local_addr,
+        )
+        .await
     }
 
-    /// Static version of handle_authenticated_inner
+    /// Main dispatch after successful handshake.
+    /// Two modes:
+    ///   - Direct: TCP relay to TG DC (existing behavior)  
+    ///   - Middle Proxy: RPC multiplex through ME pool (new — supports CDN DCs)
     async fn handle_authenticated_static<R, W>(
         client_reader: CryptoReader<R>,
         client_writer: CryptoWriter<W>,
@@ -285,6 +277,9 @@ impl RunningClientHandler {
         stats: Arc<Stats>,
         config: Arc<ProxyConfig>,
         buffer_pool: Arc<BufferPool>,
+        rng: Arc<SecureRandom>,
+        me_pool: Option<Arc<MePool>>,
+        local_addr: SocketAddr,
     ) -> Result<()>
     where
         R: AsyncRead + Unpin + Send + 'static,
@@ -292,149 +287,68 @@ impl RunningClientHandler {
     {
         let user = &success.user;
 
-        // Check user limits
         if let Err(e) = Self::check_user_limits_static(user, &config, &stats) {
             warn!(user = %user, error = %e, "User limit exceeded");
             return Err(e);
         }
 
-        // Get datacenter address
+        // Decide: middle proxy or direct
-        let dc_addr = Self::get_dc_addr_static(success.dc_idx, &config)?;
+        if config.general.use_middle_proxy {
-        
+            if let Some(ref pool) = me_pool {
-        info!(
+                return handle_via_middle_proxy(
-            user = %user,
-            peer = %success.peer,
-            dc = success.dc_idx,
-            dc_addr = %dc_addr,
-            proto = ?success.proto_tag,
-            fast_mode = config.general.fast_mode,
-            "Connecting to Telegram"
-        );
-        
-        // Connect to Telegram via UpstreamManager
-        let tg_stream = upstream_manager.connect(dc_addr).await?;
-        
-        debug!(peer = %success.peer, dc_addr = %dc_addr, "Connected to Telegram, performing handshake");
-        
-        // Perform Telegram handshake and get crypto streams
-        let (tg_reader, tg_writer) = Self::do_tg_handshake_static(
-            tg_stream, 
-            &success,
-            &config,
-        ).await?;
-        
-        debug!(peer = %success.peer, "Telegram handshake complete, starting relay");
-        
-        // Update stats
-        stats.increment_user_connects(user);
-        stats.increment_user_curr_connects(user);
-        
-        // Relay traffic using buffer pool
-        let relay_result = relay_bidirectional(
                     client_reader,
                     client_writer,
-            tg_reader,
+                    success,
-            tg_writer,
+                    pool.clone(),
-            user,
+                    stats,
-            Arc::clone(&stats),
+                    config,
                     buffer_pool,
-        ).await;
+                    local_addr,
-        
+                )
-        // Update stats
+                .await;
-        stats.decrement_user_curr_connects(user);
+            }
-        
+            warn!("use_middle_proxy=true but MePool not initialized, falling back to direct");
-        match &relay_result {
-            Ok(()) => debug!(user = %user, peer = %success.peer, "Relay completed normally"),
-            Err(e) => debug!(user = %user, peer = %success.peer, error = %e, "Relay ended with error"),
         }
 
-        relay_result
+        // Direct mode (original behavior)
+        handle_via_direct(
+            client_reader,
+            client_writer,
+            success,
+            upstream_manager,
+            stats,
+            config,
+            buffer_pool,
+            rng,
+        )
+        .await
     }
 
-    /// Check user limits (static version)
     fn check_user_limits_static(user: &str, config: &ProxyConfig, stats: &Stats) -> Result<()> {
-        // Check expiration
         if let Some(expiration) = config.access.user_expirations.get(user) {
             if chrono::Utc::now() > *expiration {
-                return Err(ProxyError::UserExpired { user: user.to_string() });
+                return Err(ProxyError::UserExpired {
+                    user: user.to_string(),
+                });
             }
         }
 
-        // Check connection limit
         if let Some(limit) = config.access.user_max_tcp_conns.get(user) {
-            let current = stats.get_user_curr_connects(user);
+            if stats.get_user_curr_connects(user) >= *limit as u64 {
-            if current >= *limit as u64 {
+                return Err(ProxyError::ConnectionLimitExceeded {
-                return Err(ProxyError::ConnectionLimitExceeded { user: user.to_string() });
+                    user: user.to_string(),
+                });
             }
         }
 
-        // Check data quota
         if let Some(quota) = config.access.user_data_quota.get(user) {
-            let used = stats.get_user_total_octets(user);
+            if stats.get_user_total_octets(user) >= *quota {
-            if used >= *quota {
+                return Err(ProxyError::DataQuotaExceeded {
-                return Err(ProxyError::DataQuotaExceeded { user: user.to_string() });
+                    user: user.to_string(),
+                });
             }
         }
 
         Ok(())
     }
-    
-    /// Get datacenter address by index (static version)
-    fn get_dc_addr_static(dc_idx: i16, config: &ProxyConfig) -> Result<SocketAddr> {
-        let idx = (dc_idx.abs() - 1) as usize;
-        
-        let datacenters = if config.general.prefer_ipv6 {
-            &*TG_DATACENTERS_V6
-        } else {
-            &*TG_DATACENTERS_V4
-        };
-        
-        datacenters.get(idx)
-            .map(|ip| SocketAddr::new(*ip, TG_DATACENTER_PORT))
-            .ok_or_else(|| ProxyError::InvalidHandshake(
-                format!("Invalid DC index: {}", dc_idx)
-            ))
-    }
-    
-    /// Perform handshake with Telegram server (static version)
-    async fn do_tg_handshake_static(
-        mut stream: TcpStream,
-        success: &HandshakeSuccess,
-        config: &ProxyConfig,
-    ) -> Result<(CryptoReader<tokio::net::tcp::OwnedReadHalf>, CryptoWriter<tokio::net::tcp::OwnedWriteHalf>)> {
-        // Generate nonce with keys for TG
-        let (nonce, tg_enc_key, tg_enc_iv, tg_dec_key, tg_dec_iv) = generate_tg_nonce(
-            success.proto_tag,
-            &success.dec_key,  // Client's dec key
-            success.dec_iv,
-            config.general.fast_mode,
-        );
-        
-        // Encrypt nonce
-        let encrypted_nonce = encrypt_tg_nonce(&nonce);
-        
-        debug!(
-            peer = %success.peer,
-            nonce_head = %hex::encode(&nonce[..16]),
-            encrypted_head = %hex::encode(&encrypted_nonce[..16]),
-            "Sending nonce to Telegram"
-        );
-        
-        // Send to Telegram
-        stream.write_all(&encrypted_nonce).await?;
-        stream.flush().await?;
-        
-        debug!(peer = %success.peer, "Nonce sent to Telegram");
-        
-        // Split stream and wrap with crypto
-        let (read_half, write_half) = stream.into_split();
-        
-        let decryptor = AesCtr::new(&tg_dec_key, tg_dec_iv);
-        let encryptor = AesCtr::new(&tg_enc_key, tg_enc_iv);
-        
-        let tg_reader = CryptoReader::new(read_half, decryptor);
-        let tg_writer = CryptoWriter::new(write_half, encryptor);
-        
-        Ok((tg_reader, tg_writer))
-    }
 }

src/proxy/direct_relay.rs

@@ -0,0 +1,163 @@
+use std::net::SocketAddr;
+use std::sync::Arc;
+
+use tokio::io::{AsyncRead, AsyncWrite, AsyncWriteExt};
+use tokio::net::TcpStream;
+use tracing::{debug, info, warn};
+
+use crate::config::ProxyConfig;
+use crate::crypto::SecureRandom;
+use crate::error::Result;
+use crate::protocol::constants::*;
+use crate::proxy::handshake::{HandshakeSuccess, encrypt_tg_nonce_with_ciphers, generate_tg_nonce};
+use crate::proxy::relay::relay_bidirectional;
+use crate::stats::Stats;
+use crate::stream::{BufferPool, CryptoReader, CryptoWriter};
+use crate::transport::UpstreamManager;
+
+pub(crate) async fn handle_via_direct<R, W>(
+    client_reader: CryptoReader<R>,
+    client_writer: CryptoWriter<W>,
+    success: HandshakeSuccess,
+    upstream_manager: Arc<UpstreamManager>,
+    stats: Arc<Stats>,
+    config: Arc<ProxyConfig>,
+    buffer_pool: Arc<BufferPool>,
+    rng: Arc<SecureRandom>,
+) -> Result<()>
+where
+    R: AsyncRead + Unpin + Send + 'static,
+    W: AsyncWrite + Unpin + Send + 'static,
+{
+    let user = &success.user;
+    let dc_addr = get_dc_addr_static(success.dc_idx, &config)?;
+
+    info!(
+        user = %user,
+        peer = %success.peer,
+        dc = success.dc_idx,
+        dc_addr = %dc_addr,
+        proto = ?success.proto_tag,
+        mode = "direct",
+        "Connecting to Telegram DC"
+    );
+
+    let tg_stream = upstream_manager
+        .connect(dc_addr, Some(success.dc_idx))
+        .await?;
+
+    debug!(peer = %success.peer, dc_addr = %dc_addr, "Connected, performing TG handshake");
+
+    let (tg_reader, tg_writer) =
+        do_tg_handshake_static(tg_stream, &success, &config, rng.as_ref()).await?;
+
+    debug!(peer = %success.peer, "TG handshake complete, starting relay");
+
+    stats.increment_user_connects(user);
+    stats.increment_user_curr_connects(user);
+
+    let relay_result = relay_bidirectional(
+        client_reader,
+        client_writer,
+        tg_reader,
+        tg_writer,
+        user,
+        Arc::clone(&stats),
+        buffer_pool,
+    )
+    .await;
+
+    stats.decrement_user_curr_connects(user);
+
+    match &relay_result {
+        Ok(()) => debug!(user = %user, "Direct relay completed"),
+        Err(e) => debug!(user = %user, error = %e, "Direct relay ended with error"),
+    }
+
+    relay_result
+}
+
+fn get_dc_addr_static(dc_idx: i16, config: &ProxyConfig) -> Result<SocketAddr> {
+    let datacenters = if config.general.prefer_ipv6 {
+        &*TG_DATACENTERS_V6
+    } else {
+        &*TG_DATACENTERS_V4
+    };
+
+    let num_dcs = datacenters.len();
+
+    let dc_key = dc_idx.to_string();
+    if let Some(addr_str) = config.dc_overrides.get(&dc_key) {
+        match addr_str.parse::<SocketAddr>() {
+            Ok(addr) => {
+                debug!(dc_idx = dc_idx, addr = %addr, "Using DC override from config");
+                return Ok(addr);
+            }
+            Err(_) => {
+                warn!(dc_idx = dc_idx, addr_str = %addr_str,
+                        "Invalid DC override address in config, ignoring");
+            }
+        }
+    }
+
+    let abs_dc = dc_idx.unsigned_abs() as usize;
+    if abs_dc >= 1 && abs_dc <= num_dcs {
+        return Ok(SocketAddr::new(datacenters[abs_dc - 1], TG_DATACENTER_PORT));
+    }
+
+    let default_dc = config.default_dc.unwrap_or(2) as usize;
+    let fallback_idx = if default_dc >= 1 && default_dc <= num_dcs {
+        default_dc - 1
+    } else {
+        1
+    };
+
+    info!(
+        original_dc = dc_idx,
+        fallback_dc = (fallback_idx + 1) as u16,
+        fallback_addr = %datacenters[fallback_idx],
+        "Special DC ---> default_cluster"
+    );
+
+    Ok(SocketAddr::new(
+        datacenters[fallback_idx],
+        TG_DATACENTER_PORT,
+    ))
+}
+
+async fn do_tg_handshake_static(
+    mut stream: TcpStream,
+    success: &HandshakeSuccess,
+    config: &ProxyConfig,
+    rng: &SecureRandom,
+) -> Result<(
+    CryptoReader<tokio::net::tcp::OwnedReadHalf>,
+    CryptoWriter<tokio::net::tcp::OwnedWriteHalf>,
+)> {
+    let (nonce, _tg_enc_key, _tg_enc_iv, _tg_dec_key, _tg_dec_iv) = generate_tg_nonce(
+        success.proto_tag,
+        success.dc_idx,
+        &success.dec_key,
+        success.dec_iv,
+        rng,
+        config.general.fast_mode,
+    );
+
+    let (encrypted_nonce, tg_encryptor, tg_decryptor) = encrypt_tg_nonce_with_ciphers(&nonce);
+
+    debug!(
+        peer = %success.peer,
+        nonce_head = %hex::encode(&nonce[..16]),
+        "Sending nonce to Telegram"
+    );
+
+    stream.write_all(&encrypted_nonce).await?;
+    stream.flush().await?;
+
+    let (read_half, write_half) = stream.into_split();
+
+    Ok((
+        CryptoReader::new(read_half, tg_decryptor),
+        CryptoWriter::new(write_half, tg_encryptor),
+    ))
+}

src/proxy/handshake.rs

@@ -1,11 +1,11 @@
-//! MTProto Handshake Magics
+//! MTProto Handshake
 
 use std::net::SocketAddr;
 use tokio::io::{AsyncRead, AsyncWrite, AsyncWriteExt};
 use tracing::{debug, warn, trace, info};
+use zeroize::Zeroize;
 
-use crate::crypto::{sha256, AesCtr};
+use crate::crypto::{sha256, AesCtr, SecureRandom};
-use crate::crypto::random::SECURE_RANDOM;
 use crate::protocol::constants::*;
 use crate::protocol::tls;
 use crate::stream::{FakeTlsReader, FakeTlsWriter, CryptoReader, CryptoWriter};
@@ -14,6 +14,9 @@ use crate::stats::ReplayChecker;
 use crate::config::ProxyConfig;
 
 /// Result of successful handshake
+///
+/// Key material (`dec_key`, `dec_iv`, `enc_key`, `enc_iv`) is
+/// zeroized on drop.
 #[derive(Debug, Clone)]
 pub struct HandshakeSuccess {
     /// Authenticated user name
@@ -34,6 +37,15 @@ pub struct HandshakeSuccess {
     pub is_tls: bool,
 }
 
+impl Drop for HandshakeSuccess {
+    fn drop(&mut self) {
+        self.dec_key.zeroize();
+        self.dec_iv.zeroize();
+        self.enc_key.zeroize();
+        self.enc_iv.zeroize();
+    }
+}
+
 /// Handle fake TLS handshake
 pub async fn handle_tls_handshake<R, W>(
     handshake: &[u8],
@@ -42,6 +54,7 @@ pub async fn handle_tls_handshake<R, W>(
     peer: SocketAddr,
     config: &ProxyConfig,
     replay_checker: &ReplayChecker,
+    rng: &SecureRandom,
 ) -> HandshakeResult<(FakeTlsReader<R>, FakeTlsWriter<W>, String), R, W>
 where
     R: AsyncRead + Unpin,
@@ -49,30 +62,25 @@ where
 {
     debug!(peer = %peer, handshake_len = handshake.len(), "Processing TLS handshake");
 
-    // Check minimum length
     if handshake.len() < tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN + 1 {
         debug!(peer = %peer, "TLS handshake too short");
         return HandshakeResult::BadClient { reader, writer };
     }
 
-    // Extract digest for replay check
     let digest = &handshake[tls::TLS_DIGEST_POS..tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN];
     let digest_half = &digest[..tls::TLS_DIGEST_HALF_LEN];
 
-    // Check for replay
     if replay_checker.check_tls_digest(digest_half) {
         warn!(peer = %peer, "TLS replay attack detected (duplicate digest)");
         return HandshakeResult::BadClient { reader, writer };
     }
 
-    // Build secrets list
     let secrets: Vec<(String, Vec<u8>)> = config.access.users.iter()
         .filter_map(|(name, hex)| {
             hex::decode(hex).ok().map(|bytes| (name.clone(), bytes))
         })
         .collect();
 
-    // Validate handshake
     let validation = match tls::validate_tls_handshake(
         handshake,
         &secrets,
@@ -89,18 +97,17 @@ where
         }
     };
 
-    // Get secret for response
     let secret = match secrets.iter().find(|(name, _)| *name == validation.user) {
         Some((_, s)) => s,
         None => return HandshakeResult::BadClient { reader, writer },
     };
 
-    // Build and send response
     let response = tls::build_server_hello(
         secret,
         &validation.digest,
         &validation.session_id,
         config.censorship.fake_cert_len,
+        rng,
     );
 
     debug!(peer = %peer, response_len = response.len(), "Sending TLS ServerHello");
@@ -115,7 +122,6 @@ where
         return HandshakeResult::Error(ProxyError::Io(e));
     }
 
-    // Record for replay protection only after successful handshake
     replay_checker.add_tls_digest(digest_half);
 
     info!(
@@ -147,26 +153,21 @@ where
 {
     trace!(peer = %peer, handshake = ?hex::encode(handshake), "MTProto handshake bytes");
 
-    // Extract prekey and IV
     let dec_prekey_iv = &handshake[SKIP_LEN..SKIP_LEN + PREKEY_LEN + IV_LEN];
 
-    // Check for replay
     if replay_checker.check_handshake(dec_prekey_iv) {
         warn!(peer = %peer, "MTProto replay attack detected");
         return HandshakeResult::BadClient { reader, writer };
     }
 
-    // Reversed for encryption direction
     let enc_prekey_iv: Vec<u8> = dec_prekey_iv.iter().rev().copied().collect();
 
-    // Try each user's secret
     for (user, secret_hex) in &config.access.users {
         let secret = match hex::decode(secret_hex) {
             Ok(s) => s,
             Err(_) => continue,
         };
 
-        // Derive decryption key
         let dec_prekey = &dec_prekey_iv[..PREKEY_LEN];
         let dec_iv_bytes = &dec_prekey_iv[PREKEY_LEN..];
 
@@ -177,11 +178,9 @@ where
 
         let dec_iv = u128::from_be_bytes(dec_iv_bytes.try_into().unwrap());
 
-        // Decrypt handshake to check protocol tag
         let mut decryptor = AesCtr::new(&dec_key, dec_iv);
         let decrypted = decryptor.decrypt(handshake);
 
-        // Check protocol tag
         let tag_bytes: [u8; 4] = decrypted[PROTO_TAG_POS..PROTO_TAG_POS + 4]
             .try_into()
             .unwrap();
@@ -191,7 +190,6 @@ where
             None => continue,
         };
 
-        // Check if mode is enabled
         let mode_ok = match proto_tag {
             ProtoTag::Secure => {
                 if is_tls { config.general.modes.tls } else { config.general.modes.secure }
@@ -204,12 +202,10 @@ where
             continue;
         }
 
-        // Extract DC index
         let dc_idx = i16::from_le_bytes(
             decrypted[DC_IDX_POS..DC_IDX_POS + 2].try_into().unwrap()
         );
 
-        // Derive encryption key
         let enc_prekey = &enc_prekey_iv[..PREKEY_LEN];
         let enc_iv_bytes = &enc_prekey_iv[PREKEY_LEN..];
 
@@ -220,11 +216,8 @@ where
 
         let enc_iv = u128::from_be_bytes(enc_iv_bytes.try_into().unwrap());
 
-        // Record for replay protection
         replay_checker.add_handshake(dec_prekey_iv);
 
-        // Create new cipher instances
-        let decryptor = AesCtr::new(&dec_key, dec_iv);
         let encryptor = AesCtr::new(&enc_key, enc_iv);
 
         let success = HandshakeSuccess {
@@ -262,12 +255,14 @@ where
 /// Generate nonce for Telegram connection
 pub fn generate_tg_nonce(
     proto_tag: ProtoTag, 
+    dc_idx: i16,
     client_dec_key: &[u8; 32],
     client_dec_iv: u128,
+    rng: &SecureRandom,
     fast_mode: bool,
 ) -> ([u8; HANDSHAKE_LEN], [u8; 32], u128, [u8; 32], u128) {
     loop {
-        let bytes = SECURE_RANDOM.bytes(HANDSHAKE_LEN);
+        let bytes = rng.bytes(HANDSHAKE_LEN);
         let mut nonce: [u8; HANDSHAKE_LEN] = bytes.try_into().unwrap();
 
         if RESERVED_NONCE_FIRST_BYTES.contains(&nonce[0]) { continue; }
@@ -279,6 +274,8 @@ pub fn generate_tg_nonce(
         if RESERVED_NONCE_CONTINUES.contains(&continue_four) { continue; }
 
         nonce[PROTO_TAG_POS..PROTO_TAG_POS + 4].copy_from_slice(&proto_tag.to_bytes());
+        // CRITICAL: write dc_idx so upstream DC knows where to route
+        nonce[DC_IDX_POS..DC_IDX_POS + 2].copy_from_slice(&dc_idx.to_le_bytes());
 
         if fast_mode {
             nonce[SKIP_LEN..SKIP_LEN + KEY_LEN].copy_from_slice(client_dec_key);
@@ -299,19 +296,32 @@ pub fn generate_tg_nonce(
     }
 }
 
-/// Encrypt nonce for sending to Telegram
+/// Encrypt nonce for sending to Telegram and return cipher objects with correct counter state
-pub fn encrypt_tg_nonce(nonce: &[u8; HANDSHAKE_LEN]) -> Vec<u8> {
+pub fn encrypt_tg_nonce_with_ciphers(nonce: &[u8; HANDSHAKE_LEN]) -> (Vec<u8>, AesCtr, AesCtr) {
     let enc_key_iv = &nonce[SKIP_LEN..SKIP_LEN + KEY_LEN + IV_LEN];
-    let key: [u8; 32] = enc_key_iv[..KEY_LEN].try_into().unwrap();
+    let dec_key_iv: Vec<u8> = enc_key_iv.iter().rev().copied().collect();
-    let iv = u128::from_be_bytes(enc_key_iv[KEY_LEN..].try_into().unwrap());
 
-    let mut encryptor = AesCtr::new(&key, iv);
+    let enc_key: [u8; 32] = enc_key_iv[..KEY_LEN].try_into().unwrap();
-    let encrypted_full = encryptor.encrypt(nonce);
+    let enc_iv = u128::from_be_bytes(enc_key_iv[KEY_LEN..].try_into().unwrap());
+
+    let dec_key: [u8; 32] = dec_key_iv[..KEY_LEN].try_into().unwrap();
+    let dec_iv = u128::from_be_bytes(dec_key_iv[KEY_LEN..].try_into().unwrap());
+
+    let mut encryptor = AesCtr::new(&enc_key, enc_iv);
+    let encrypted_full = encryptor.encrypt(nonce);  // counter: 0 → 4
 
     let mut result = nonce[..PROTO_TAG_POS].to_vec();
     result.extend_from_slice(&encrypted_full[PROTO_TAG_POS..]);
 
-    result
+    let decryptor = AesCtr::new(&dec_key, dec_iv);
+
+    (result, encryptor, decryptor)
+}
+
+/// Encrypt nonce for sending to Telegram (legacy function for compatibility)
+pub fn encrypt_tg_nonce(nonce: &[u8; HANDSHAKE_LEN]) -> Vec<u8> {
+    let (encrypted, _, _) = encrypt_tg_nonce_with_ciphers(nonce);
+    encrypted
 }
 
 #[cfg(test)]
@@ -323,13 +333,12 @@ mod tests {
         let client_dec_key = [0x42u8; 32];
         let client_dec_iv = 12345u128;
 
-        let (nonce, tg_enc_key, tg_enc_iv, tg_dec_key, tg_dec_iv) = 
+        let rng = SecureRandom::new();
-            generate_tg_nonce(ProtoTag::Secure, &client_dec_key, client_dec_iv, false);
+        let (nonce, _tg_enc_key, _tg_enc_iv, _tg_dec_key, _tg_dec_iv) = 
+            generate_tg_nonce(ProtoTag::Secure, 2, &client_dec_key, client_dec_iv, &rng, false);
 
-        // Check length
         assert_eq!(nonce.len(), HANDSHAKE_LEN);
 
-        // Check proto tag is set
         let tag_bytes: [u8; 4] = nonce[PROTO_TAG_POS..PROTO_TAG_POS + 4].try_into().unwrap();
         assert_eq!(ProtoTag::from_bytes(tag_bytes), Some(ProtoTag::Secure));
     }
@@ -339,17 +348,35 @@ mod tests {
         let client_dec_key = [0x42u8; 32];
         let client_dec_iv = 12345u128;
 
+        let rng = SecureRandom::new();
         let (nonce, _, _, _, _) = 
-            generate_tg_nonce(ProtoTag::Secure, &client_dec_key, client_dec_iv, false);
+            generate_tg_nonce(ProtoTag::Secure, 2, &client_dec_key, client_dec_iv, &rng, false);
 
         let encrypted = encrypt_tg_nonce(&nonce);
 
         assert_eq!(encrypted.len(), HANDSHAKE_LEN);
-        
-        // First PROTO_TAG_POS bytes should be unchanged
         assert_eq!(&encrypted[..PROTO_TAG_POS], &nonce[..PROTO_TAG_POS]);
-        
-        // Rest should be different (encrypted)
         assert_ne!(&encrypted[PROTO_TAG_POS..], &nonce[PROTO_TAG_POS..]);
     }
+
+    #[test]
+    fn test_handshake_success_zeroize_on_drop() {
+        let success = HandshakeSuccess {
+            user: "test".to_string(),
+            dc_idx: 2,
+            proto_tag: ProtoTag::Secure,
+            dec_key: [0xAA; 32],
+            dec_iv: 0xBBBBBBBB,
+            enc_key: [0xCC; 32],
+            enc_iv: 0xDDDDDDDD,
+            peer: "127.0.0.1:1234".parse().unwrap(),
+            is_tls: true,
+        };
+
+        assert_eq!(success.dec_key, [0xAA; 32]);
+        assert_eq!(success.enc_key, [0xCC; 32]);
+
+        drop(success);
+        // Drop impl zeroizes key material without panic
+    }
 }

src/proxy/masking.rs

@@ -3,12 +3,17 @@
 use std::time::Duration;
 use std::str;
 use tokio::net::TcpStream;
+#[cfg(unix)]
+use tokio::net::UnixStream;
 use tokio::io::{AsyncRead, AsyncWrite, AsyncReadExt, AsyncWriteExt};
 use tokio::time::timeout;
 use tracing::debug;
 use crate::config::ProxyConfig;
 
 const MASK_TIMEOUT: Duration = Duration::from_secs(5);
+    /// Maximum duration for the entire masking relay.
+    /// Limits resource consumption from slow-loris attacks and port scanners.
+    const MASK_RELAY_TIMEOUT: Duration = Duration::from_secs(60);
 const MASK_BUFFER_SIZE: usize = 8192;
 
 /// Detect client type based on initial data
@@ -42,8 +47,8 @@ fn detect_client_type(data: &[u8]) -> &'static str {
 
 /// Handle a bad client by forwarding to mask host
 pub async fn handle_bad_client<R, W>(
-    mut reader: R,
+    reader: R,
-    mut writer: W,
+    writer: W,
     initial_data: &[u8],
     config: &ProxyConfig,
 )
@@ -59,6 +64,34 @@ where
 
     let client_type = detect_client_type(initial_data);
 
+    // Connect via Unix socket or TCP
+    #[cfg(unix)]
+    if let Some(ref sock_path) = config.censorship.mask_unix_sock {
+        debug!(
+            client_type = client_type,
+            sock = %sock_path,
+            data_len = initial_data.len(),
+            "Forwarding bad client to mask unix socket"
+        );
+
+        let connect_result = timeout(MASK_TIMEOUT, UnixStream::connect(sock_path)).await;
+        match connect_result {
+            Ok(Ok(stream)) => {
+                let (mask_read, mask_write) = stream.into_split();
+                relay_to_mask(reader, writer, mask_read, mask_write, initial_data).await;
+            }
+            Ok(Err(e)) => {
+                debug!(error = %e, "Failed to connect to mask unix socket");
+                consume_client_data(reader).await;
+            }
+            Err(_) => {
+                debug!("Timeout connecting to mask unix socket");
+                consume_client_data(reader).await;
+            }
+        }
+        return;
+    }
+
     let mask_host = config.censorship.mask_host.as_deref()
         .unwrap_or(&config.censorship.tls_domain);
     let mask_port = config.censorship.mask_port;
@@ -73,27 +106,37 @@ where
 
     // Connect to mask host
     let mask_addr = format!("{}:{}", mask_host, mask_port);
-    let connect_result = timeout(
+    let connect_result = timeout(MASK_TIMEOUT, TcpStream::connect(&mask_addr)).await;
-        MASK_TIMEOUT,
+    match connect_result {
-        TcpStream::connect(&mask_addr)
+        Ok(Ok(stream)) => {
-    ).await;
+            let (mask_read, mask_write) = stream.into_split();
-    
+            relay_to_mask(reader, writer, mask_read, mask_write, initial_data).await;
-    let mask_stream = match connect_result {
+        }
-        Ok(Ok(s)) => s,
         Ok(Err(e)) => {
             debug!(error = %e, "Failed to connect to mask host");
             consume_client_data(reader).await;
-            return;
         }
         Err(_) => {
             debug!("Timeout connecting to mask host");
             consume_client_data(reader).await;
-            return;
         }
-    };
+    }
-    
+}
-    let (mut mask_read, mut mask_write) = mask_stream.into_split();
 
+/// Relay traffic between client and mask backend
+async fn relay_to_mask<R, W, MR, MW>(
+    mut reader: R,
+    mut writer: W,
+    mut mask_read: MR,
+    mut mask_write: MW,
+    initial_data: &[u8],
+)
+where
+    R: AsyncRead + Unpin + Send + 'static,
+    W: AsyncWrite + Unpin + Send + 'static,
+    MR: AsyncRead + Unpin + Send + 'static,
+    MW: AsyncWrite + Unpin + Send + 'static,
+{
     // Send initial data to mask host
     if mask_write.write_all(initial_data).await.is_err() {
         return;

src/proxy/middle_relay.rs

@@ -0,0 +1,254 @@
+use std::net::SocketAddr;
+use std::sync::Arc;
+
+use tokio::io::{AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt};
+use tracing::{debug, info, trace};
+
+use crate::config::ProxyConfig;
+use crate::error::{ProxyError, Result};
+use crate::protocol::constants::*;
+use crate::proxy::handshake::HandshakeSuccess;
+use crate::stats::Stats;
+use crate::stream::{BufferPool, CryptoReader, CryptoWriter};
+use crate::transport::middle_proxy::{MePool, MeResponse, proto_flags_for_tag};
+
+pub(crate) async fn handle_via_middle_proxy<R, W>(
+    mut crypto_reader: CryptoReader<R>,
+    mut crypto_writer: CryptoWriter<W>,
+    success: HandshakeSuccess,
+    me_pool: Arc<MePool>,
+    stats: Arc<Stats>,
+    _config: Arc<ProxyConfig>,
+    _buffer_pool: Arc<BufferPool>,
+    local_addr: SocketAddr,
+) -> Result<()>
+where
+    R: AsyncRead + Unpin + Send + 'static,
+    W: AsyncWrite + Unpin + Send + 'static,
+{
+    let user = success.user.clone();
+    let peer = success.peer;
+    let proto_tag = success.proto_tag;
+
+    info!(
+        user = %user,
+        peer = %peer,
+        dc = success.dc_idx,
+        proto = ?proto_tag,
+        mode = "middle_proxy",
+        "Routing via Middle-End"
+    );
+
+    let (conn_id, mut me_rx) = me_pool.registry().register().await;
+
+    stats.increment_user_connects(&user);
+    stats.increment_user_curr_connects(&user);
+
+    let proto_flags = proto_flags_for_tag(proto_tag, me_pool.has_proxy_tag());
+    debug!(
+        user = %user,
+        conn_id,
+        proto_flags = format_args!("0x{:08x}", proto_flags),
+        "ME relay started"
+    );
+
+    let translated_local_addr = me_pool.translate_our_addr(local_addr);
+
+    let result: Result<()> = loop {
+        tokio::select! {
+            client_frame = read_client_payload(&mut crypto_reader, proto_tag) => {
+                match client_frame {
+                    Ok(Some(payload)) => {
+                        trace!(conn_id, bytes = payload.len(), "C->ME frame");
+                        stats.add_user_octets_from(&user, payload.len() as u64);
+                        me_pool.send_proxy_req(
+                            conn_id,
+                            success.dc_idx,
+                            peer,
+                            translated_local_addr,
+                            &payload,
+                            proto_flags,
+                        ).await?;
+                    }
+                    Ok(None) => {
+                        debug!(conn_id, "Client EOF");
+                        let _ = me_pool.send_close(conn_id).await;
+                        break Ok(());
+                    }
+                    Err(e) => break Err(e),
+                }
+            }
+            me_msg = me_rx.recv() => {
+                match me_msg {
+                    Some(MeResponse::Data { flags, data }) => {
+                        trace!(conn_id, bytes = data.len(), flags, "ME->C data");
+                        stats.add_user_octets_to(&user, data.len() as u64);
+                        write_client_payload(&mut crypto_writer, proto_tag, flags, &data).await?;
+                    }
+                    Some(MeResponse::Ack(confirm)) => {
+                        trace!(conn_id, confirm, "ME->C quickack");
+                        write_client_ack(&mut crypto_writer, proto_tag, confirm).await?;
+                    }
+                    Some(MeResponse::Close) => {
+                        debug!(conn_id, "ME sent close");
+                        break Ok(());
+                    }
+                    None => {
+                        debug!(conn_id, "ME channel closed");
+                        break Err(ProxyError::Proxy("ME connection lost".into()));
+                    }
+                }
+            }
+        }
+    };
+
+    debug!(user = %user, conn_id, "ME relay cleanup");
+    me_pool.registry().unregister(conn_id).await;
+    stats.decrement_user_curr_connects(&user);
+    result
+}
+
+async fn read_client_payload<R>(
+    client_reader: &mut CryptoReader<R>,
+    proto_tag: ProtoTag,
+) -> Result<Option<Vec<u8>>>
+where
+    R: AsyncRead + Unpin + Send + 'static,
+{
+    let len = match proto_tag {
+        ProtoTag::Abridged => {
+            let mut first = [0u8; 1];
+            match client_reader.read_exact(&mut first).await {
+                Ok(_) => {}
+                Err(e) if e.kind() == std::io::ErrorKind::UnexpectedEof => return Ok(None),
+                Err(e) => return Err(ProxyError::Io(e)),
+            }
+
+            let len_words = if (first[0] & 0x7f) == 0x7f {
+                let mut ext = [0u8; 3];
+                client_reader
+                    .read_exact(&mut ext)
+                    .await
+                    .map_err(ProxyError::Io)?;
+                u32::from_le_bytes([ext[0], ext[1], ext[2], 0]) as usize
+            } else {
+                (first[0] & 0x7f) as usize
+            };
+
+            len_words
+                .checked_mul(4)
+                .ok_or_else(|| ProxyError::Proxy("Abridged frame length overflow".into()))?
+        }
+        ProtoTag::Intermediate | ProtoTag::Secure => {
+            let mut len_buf = [0u8; 4];
+            match client_reader.read_exact(&mut len_buf).await {
+                Ok(_) => {}
+                Err(e) if e.kind() == std::io::ErrorKind::UnexpectedEof => return Ok(None),
+                Err(e) => return Err(ProxyError::Io(e)),
+            }
+            (u32::from_le_bytes(len_buf) & 0x7fff_ffff) as usize
+        }
+    };
+
+    if len > 16 * 1024 * 1024 {
+        return Err(ProxyError::Proxy(format!("Frame too large: {len}")));
+    }
+
+    let mut payload = vec![0u8; len];
+    client_reader
+        .read_exact(&mut payload)
+        .await
+        .map_err(ProxyError::Io)?;
+    Ok(Some(payload))
+}
+
+async fn write_client_payload<W>(
+    client_writer: &mut CryptoWriter<W>,
+    proto_tag: ProtoTag,
+    flags: u32,
+    data: &[u8],
+) -> Result<()>
+where
+    W: AsyncWrite + Unpin + Send + 'static,
+{
+    let quickack = (flags & RPC_FLAG_QUICKACK) != 0;
+
+    match proto_tag {
+        ProtoTag::Abridged => {
+            if data.len() % 4 != 0 {
+                return Err(ProxyError::Proxy(format!(
+                    "Abridged payload must be 4-byte aligned, got {}",
+                    data.len()
+                )));
+            }
+
+            let len_words = data.len() / 4;
+            if len_words < 0x7f {
+                let mut first = len_words as u8;
+                if quickack {
+                    first |= 0x80;
+                }
+                client_writer
+                    .write_all(&[first])
+                    .await
+                    .map_err(ProxyError::Io)?;
+            } else if len_words < (1 << 24) {
+                let mut first = 0x7fu8;
+                if quickack {
+                    first |= 0x80;
+                }
+                let lw = (len_words as u32).to_le_bytes();
+                client_writer
+                    .write_all(&[first, lw[0], lw[1], lw[2]])
+                    .await
+                    .map_err(ProxyError::Io)?;
+            } else {
+                return Err(ProxyError::Proxy(format!(
+                    "Abridged frame too large: {}",
+                    data.len()
+                )));
+            }
+
+            client_writer
+                .write_all(data)
+                .await
+                .map_err(ProxyError::Io)?;
+        }
+        ProtoTag::Intermediate | ProtoTag::Secure => {
+            let mut len = data.len() as u32;
+            if quickack {
+                len |= 0x8000_0000;
+            }
+            client_writer
+                .write_all(&len.to_le_bytes())
+                .await
+                .map_err(ProxyError::Io)?;
+            client_writer
+                .write_all(data)
+                .await
+                .map_err(ProxyError::Io)?;
+        }
+    }
+
+    client_writer.flush().await.map_err(ProxyError::Io)
+}
+
+async fn write_client_ack<W>(
+    client_writer: &mut CryptoWriter<W>,
+    proto_tag: ProtoTag,
+    confirm: u32,
+) -> Result<()>
+where
+    W: AsyncWrite + Unpin + Send + 'static,
+{
+    let bytes = if proto_tag == ProtoTag::Abridged {
+        confirm.to_be_bytes()
+    } else {
+        confirm.to_le_bytes()
+    };
+    client_writer
+        .write_all(&bytes)
+        .await
+        .map_err(ProxyError::Io)?;
+    client_writer.flush().await.map_err(ProxyError::Io)
+}

src/proxy/mod.rs

@@ -1,11 +1,13 @@
 //! Proxy Defs
 
-pub mod handshake;
 pub mod client;
-pub mod relay;
+pub mod direct_relay;
+pub mod handshake;
 pub mod masking;
+pub mod middle_relay;
+pub mod relay;
 
-pub use handshake::*;
 pub use client::ClientHandler;
-pub use relay::*;
+pub use handshake::*;
 pub use masking::*;
+pub use relay::*;

src/proxy/relay.rs

@@ -1,27 +1,320 @@
-//! Bidirectional Relay
+//! Bidirectional Relay — poll-based, no head-of-line blocking
+//!
+//! ## What changed and why
+//!
+//! Previous implementation used a single-task `select! { biased; ... }` loop
+//! where each branch called `write_all()`. This caused head-of-line blocking:
+//! while `write_all()` waited for a slow writer (e.g. client on 3G downloading
+//! media), the entire loop was blocked — the other direction couldn't make progress.
+//!
+//! Symptoms observed in production:
+//! - Media loading at ~8 KB/s despite fast server connection
+//! - Stop-and-go pattern with 50–500ms gaps between chunks
+//! - `biased` select starving S→C direction
+//! - Some users unable to load media at all
+//!
+//! ## New architecture
+//!
+//! Uses `tokio::io::copy_bidirectional` which polls both directions concurrently
+//! in a single task via non-blocking `poll_read` / `poll_write` calls:
+//!
+//! Old (select! + write_all — BLOCKING):
+//!
+//!   loop {
+//!       select! {
+//!           biased;
+//!           data = client.read()  => { server.write_all(data).await; }  ← BLOCKS here
+//!           data = server.read()  => { client.write_all(data).await; }  ← can't run
+//!       }
+//!   }
+//!
+//! New (copy_bidirectional — CONCURRENT):
+//!
+//!   poll(cx) {
+//!       // Both directions polled in the same poll cycle
+//!       C→S: poll_read(client) → poll_write(server)   // non-blocking
+//!       S→C: poll_read(server) → poll_write(client)   // non-blocking
+//!       // If one writer is Pending, the other direction still progresses
+//!   }
+//!
+//! Benefits:
+//! - No head-of-line blocking: slow client download doesn't block uploads
+//! - No biased starvation: fair polling of both directions
+//! - Proper flush: `copy_bidirectional` calls `poll_flush` when reader stalls,
+//!   so CryptoWriter's pending ciphertext is always drained (fixes "stuck at 95%")
+//! - No deadlock risk: old write_all could deadlock when both TCP buffers filled;
+//!   poll-based approach lets TCP flow control work correctly
+//!
+//! Stats tracking:
+//! - `StatsIo` wraps client side, intercepts `poll_read` / `poll_write`
+//! - `poll_read` on client = C→S (client sending) → `octets_from`, `msgs_from`
+//! - `poll_write` on client = S→C (to client)     → `octets_to`, `msgs_to`
+//! - `SharedCounters` (atomics) let the watchdog read stats without locking
 
+use std::io;
+use std::pin::Pin;
 use std::sync::Arc;
+use std::sync::atomic::{AtomicU64, Ordering};
+use std::task::{Context, Poll};
 use std::time::Duration;
-use tokio::io::{AsyncRead, AsyncWrite, AsyncReadExt, AsyncWriteExt};
+use tokio::io::{AsyncRead, AsyncWrite, AsyncWriteExt, ReadBuf, copy_bidirectional};
 use tokio::time::Instant;
-use tracing::{debug, trace, warn, info};
+use tracing::{debug, trace, warn};
 use crate::error::Result;
 use crate::stats::Stats;
 use crate::stream::BufferPool;
-use std::sync::atomic::{AtomicU64, Ordering};
 
-// Activity timeout for iOS compatibility (30 minutes)
+// ============= Constants =============
-const ACTIVITY_TIMEOUT_SECS: u64 = 1800;
 
-/// Relay data bidirectionally between client and server
+/// Activity timeout for iOS compatibility.
+///
+/// iOS keeps Telegram connections alive in background for up to 30 minutes.
+/// Closing earlier causes unnecessary reconnects and handshake overhead.
+const ACTIVITY_TIMEOUT: Duration = Duration::from_secs(1800);
+
+/// Watchdog check interval — also used for periodic rate logging.
+///
+/// 10 seconds gives responsive timeout detection (±10s accuracy)
+/// without measurable overhead from atomic reads.
+const WATCHDOG_INTERVAL: Duration = Duration::from_secs(10);
+
+// ============= CombinedStream =============
+
+/// Combines separate read and write halves into a single bidirectional stream.
+///
+/// `copy_bidirectional` requires `AsyncRead + AsyncWrite` on each side,
+/// but the handshake layer produces split reader/writer pairs
+/// (e.g. `CryptoReader<FakeTlsReader<OwnedReadHalf>>` + `CryptoWriter<...>`).
+///
+/// This wrapper reunifies them with zero overhead — each trait method
+/// delegates directly to the corresponding half. No buffering, no copies.
+///
+/// Safety: `poll_read` only touches `reader`, `poll_write` only touches `writer`,
+/// so there's no aliasing even though both are called on the same `&mut self`.
+struct CombinedStream<R, W> {
+    reader: R,
+    writer: W,
+}
+
+impl<R, W> CombinedStream<R, W> {
+    fn new(reader: R, writer: W) -> Self {
+        Self { reader, writer }
+    }
+}
+
+impl<R: AsyncRead + Unpin, W: Unpin> AsyncRead for CombinedStream<R, W> {
+    #[inline]
+    fn poll_read(
+        self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        buf: &mut ReadBuf<'_>,
+    ) -> Poll<io::Result<()>> {
+        Pin::new(&mut self.get_mut().reader).poll_read(cx, buf)
+    }
+}
+
+impl<R: Unpin, W: AsyncWrite + Unpin> AsyncWrite for CombinedStream<R, W> {
+    #[inline]
+    fn poll_write(
+        self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        buf: &[u8],
+    ) -> Poll<io::Result<usize>> {
+        Pin::new(&mut self.get_mut().writer).poll_write(cx, buf)
+    }
+
+    #[inline]
+    fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+        Pin::new(&mut self.get_mut().writer).poll_flush(cx)
+    }
+
+    #[inline]
+    fn poll_shutdown(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+        Pin::new(&mut self.get_mut().writer).poll_shutdown(cx)
+    }
+}
+
+// ============= SharedCounters =============
+
+/// Atomic counters shared between the relay (via StatsIo) and the watchdog task.
+///
+/// Using `Relaxed` ordering is sufficient because:
+/// - Counters are monotonically increasing (no ABA problem)
+/// - Slight staleness in watchdog reads is harmless (±10s check interval anyway)
+/// - No ordering dependencies between different counters
+struct SharedCounters {
+    /// Bytes read from client (C→S direction)
+    c2s_bytes: AtomicU64,
+    /// Bytes written to client (S→C direction)
+    s2c_bytes: AtomicU64,
+    /// Number of poll_read completions (≈ C→S chunks)
+    c2s_ops: AtomicU64,
+    /// Number of poll_write completions (≈ S→C chunks)
+    s2c_ops: AtomicU64,
+    /// Milliseconds since relay epoch of last I/O activity
+    last_activity_ms: AtomicU64,
+}
+
+impl SharedCounters {
+    fn new() -> Self {
+        Self {
+            c2s_bytes: AtomicU64::new(0),
+            s2c_bytes: AtomicU64::new(0),
+            c2s_ops: AtomicU64::new(0),
+            s2c_ops: AtomicU64::new(0),
+            last_activity_ms: AtomicU64::new(0),
+        }
+    }
+
+    /// Record activity at this instant.
+    #[inline]
+    fn touch(&self, now: Instant, epoch: Instant) {
+        let ms = now.duration_since(epoch).as_millis() as u64;
+        self.last_activity_ms.store(ms, Ordering::Relaxed);
+    }
+
+    /// How long since last recorded activity.
+    fn idle_duration(&self, now: Instant, epoch: Instant) -> Duration {
+        let last_ms = self.last_activity_ms.load(Ordering::Relaxed);
+        let now_ms = now.duration_since(epoch).as_millis() as u64;
+        Duration::from_millis(now_ms.saturating_sub(last_ms))
+    }
+}
+
+// ============= StatsIo =============
+
+/// Transparent I/O wrapper that tracks per-user statistics and activity.
+///
+/// Wraps the **client** side of the relay. Direction mapping:
+///
+/// | poll method  | direction | stats updated                        |
+/// |-------------|-----------|--------------------------------------|
+/// | `poll_read`  | C→S       | `octets_from`, `msgs_from`, counters |
+/// | `poll_write` | S→C       | `octets_to`, `msgs_to`, counters     |
+///
+/// Both update the shared activity timestamp for the watchdog.
+///
+/// Note on message counts: the original code counted one `read()`/`write_all()`
+/// as one "message". Here we count `poll_read`/`poll_write` completions instead.
+/// Byte counts are identical; op counts may differ slightly due to different
+/// internal buffering in `copy_bidirectional`. This is fine for monitoring.
+struct StatsIo<S> {
+    inner: S,
+    counters: Arc<SharedCounters>,
+    stats: Arc<Stats>,
+    user: String,
+    epoch: Instant,
+}
+
+impl<S> StatsIo<S> {
+    fn new(
+        inner: S,
+        counters: Arc<SharedCounters>,
+        stats: Arc<Stats>,
+        user: String,
+        epoch: Instant,
+    ) -> Self {
+        // Mark initial activity so the watchdog doesn't fire before data flows
+        counters.touch(Instant::now(), epoch);
+        Self { inner, counters, stats, user, epoch }
+    }
+}
+
+impl<S: AsyncRead + Unpin> AsyncRead for StatsIo<S> {
+    fn poll_read(
+        self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        buf: &mut ReadBuf<'_>,
+    ) -> Poll<io::Result<()>> {
+        let this = self.get_mut();
+        let before = buf.filled().len();
+
+        match Pin::new(&mut this.inner).poll_read(cx, buf) {
+            Poll::Ready(Ok(())) => {
+                let n = buf.filled().len() - before;
+                if n > 0 {
+                    // C→S: client sent data
+                    this.counters.c2s_bytes.fetch_add(n as u64, Ordering::Relaxed);
+                    this.counters.c2s_ops.fetch_add(1, Ordering::Relaxed);
+                    this.counters.touch(Instant::now(), this.epoch);
+
+                    this.stats.add_user_octets_from(&this.user, n as u64);
+                    this.stats.increment_user_msgs_from(&this.user);
+
+                    trace!(user = %this.user, bytes = n, "C->S");
+                }
+                Poll::Ready(Ok(()))
+            }
+            other => other,
+        }
+    }
+}
+
+impl<S: AsyncWrite + Unpin> AsyncWrite for StatsIo<S> {
+    fn poll_write(
+        self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        buf: &[u8],
+    ) -> Poll<io::Result<usize>> {
+        let this = self.get_mut();
+
+        match Pin::new(&mut this.inner).poll_write(cx, buf) {
+            Poll::Ready(Ok(n)) => {
+                if n > 0 {
+                    // S→C: data written to client
+                    this.counters.s2c_bytes.fetch_add(n as u64, Ordering::Relaxed);
+                    this.counters.s2c_ops.fetch_add(1, Ordering::Relaxed);
+                    this.counters.touch(Instant::now(), this.epoch);
+
+                    this.stats.add_user_octets_to(&this.user, n as u64);
+                    this.stats.increment_user_msgs_to(&this.user);
+
+                    trace!(user = %this.user, bytes = n, "S->C");
+                }
+                Poll::Ready(Ok(n))
+            }
+            other => other,
+        }
+    }
+
+    #[inline]
+    fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+        Pin::new(&mut self.get_mut().inner).poll_flush(cx)
+    }
+
+    #[inline]
+    fn poll_shutdown(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+        Pin::new(&mut self.get_mut().inner).poll_shutdown(cx)
+    }
+}
+
+// ============= Relay =============
+
+/// Relay data bidirectionally between client and server.
+///
+/// Uses `tokio::io::copy_bidirectional` for concurrent, non-blocking data transfer.
+///
+/// ## API compatibility
+///
+/// Signature is identical to the previous implementation. The `_buffer_pool`
+/// parameter is retained for call-site compatibility — `copy_bidirectional`
+/// manages its own internal buffers (8 KB per direction).
+///
+/// ## Guarantees preserved
+///
+/// - Activity timeout: 30 minutes of inactivity → clean shutdown
+/// - Per-user stats: bytes and ops counted per direction
+/// - Periodic rate logging: every 10 seconds when active
+/// - Clean shutdown: both write sides are shut down on exit
+/// - Error propagation: I/O errors are returned as `ProxyError::Io`
 pub async fn relay_bidirectional<CR, CW, SR, SW>(
-    mut client_reader: CR,
+    client_reader: CR,
-    mut client_writer: CW,
+    client_writer: CW,
-    mut server_reader: SR,
+    server_reader: SR,
-    mut server_writer: SW,
+    server_writer: SW,
     user: &str,
     stats: Arc<Stats>,
-    buffer_pool: Arc<BufferPool>,
+    _buffer_pool: Arc<BufferPool>,
 ) -> Result<()>
 where
     CR: AsyncRead + Unpin + Send + 'static,
@@ -29,234 +322,145 @@ where
     SR: AsyncRead + Unpin + Send + 'static,
     SW: AsyncWrite + Unpin + Send + 'static,
 {
-    let user_c2s = user.to_string();
+    let epoch = Instant::now();
-    let user_s2c = user.to_string();
+    let counters = Arc::new(SharedCounters::new());
+    let user_owned = user.to_string();
 
-    let stats_c2s = Arc::clone(&stats);
+    // ── Combine split halves into bidirectional streams ──────────────
-    let stats_s2c = Arc::clone(&stats);
+    let client_combined = CombinedStream::new(client_reader, client_writer);
+    let mut server = CombinedStream::new(server_reader, server_writer);
 
-    let c2s_bytes = Arc::new(AtomicU64::new(0));
+    // Wrap client with stats/activity tracking
-    let s2c_bytes = Arc::new(AtomicU64::new(0));
+    let mut client = StatsIo::new(
-    let c2s_bytes_clone = Arc::clone(&c2s_bytes);
+        client_combined,
-    let s2c_bytes_clone = Arc::clone(&s2c_bytes);
+        Arc::clone(&counters),
+        Arc::clone(&stats),
+        user_owned.clone(),
+        epoch,
+    );
 
-    let activity_timeout = Duration::from_secs(ACTIVITY_TIMEOUT_SECS);
+    // ── Watchdog: activity timeout + periodic rate logging ──────────
+    let wd_counters = Arc::clone(&counters);
+    let wd_user = user_owned.clone();
 
-    let pool_c2s = buffer_pool.clone();
+    let watchdog = async {
-    let pool_s2c = buffer_pool.clone();
+        let mut prev_c2s: u64 = 0;
-    
+        let mut prev_s2c: u64 = 0;
-    // Client -> Server task
-    let c2s = tokio::spawn(async move {
-        // Get buffer from pool
-        let mut pooled_buf = pool_c2s.get();
-        // CRITICAL FIX: BytesMut from pool has len 0. We must resize it to be usable as &mut [u8].
-        // We use the full capacity.
-        let cap = pooled_buf.capacity();
-        pooled_buf.resize(cap, 0);
-        
-        let mut total_bytes = 0u64;
-        let mut prev_total_bytes = 0u64;
-        let mut msg_count = 0u64;
-        let mut last_activity = Instant::now();
-        let mut last_log = Instant::now();
 
         loop {
-            // Read with timeout
+            tokio::time::sleep(WATCHDOG_INTERVAL).await;
-            let read_result = tokio::time::timeout(
-                activity_timeout,
-                client_reader.read(&mut pooled_buf)
-            ).await;
 
-            match read_result {
+            let now = Instant::now();
-                Err(_) => {
+            let idle = wd_counters.idle_duration(now, epoch);
+
+            // ── Activity timeout ────────────────────────────────────
+            if idle >= ACTIVITY_TIMEOUT {
+                let c2s = wd_counters.c2s_bytes.load(Ordering::Relaxed);
+                let s2c = wd_counters.s2c_bytes.load(Ordering::Relaxed);
                 warn!(
-                        user = %user_c2s,
+                    user = %wd_user,
-                        total_bytes = total_bytes,
+                    c2s_bytes = c2s,
-                        msgs = msg_count,
+                    s2c_bytes = s2c,
-                        idle_secs = last_activity.elapsed().as_secs(),
+                    idle_secs = idle.as_secs(),
-                        "Activity timeout (C->S) - no data received"
+                    "Activity timeout"
                 );
-                    let _ = server_writer.shutdown().await;
+                return; // Causes select! to cancel copy_bidirectional
-                    break;
             }
 
-                Ok(Ok(0)) => {
+            // ── Periodic rate logging ───────────────────────────────
+            let c2s = wd_counters.c2s_bytes.load(Ordering::Relaxed);
+            let s2c = wd_counters.s2c_bytes.load(Ordering::Relaxed);
+            let c2s_delta = c2s - prev_c2s;
+            let s2c_delta = s2c - prev_s2c;
+
+            if c2s_delta > 0 || s2c_delta > 0 {
+                let secs = WATCHDOG_INTERVAL.as_secs_f64();
                 debug!(
-                        user = %user_c2s, 
+                    user = %wd_user,
-                        total_bytes = total_bytes,
+                    c2s_kbps = (c2s_delta as f64 / secs / 1024.0) as u64,
-                        msgs = msg_count,
+                    s2c_kbps = (s2c_delta as f64 / secs / 1024.0) as u64,
-                        "Client closed connection (C->S)"
+                    c2s_total = c2s,
+                    s2c_total = s2c,
+                    "Relay active"
                 );
-                    let _ = server_writer.shutdown().await;
-                    break;
             }
 
-                Ok(Ok(n)) => {
+            prev_c2s = c2s;
-                    total_bytes += n as u64;
+            prev_s2c = s2c;
-                    msg_count += 1;
+        }
-                    last_activity = Instant::now();
+    };
-                    c2s_bytes_clone.store(total_bytes, Ordering::Relaxed);
 
-                    stats_c2s.add_user_octets_from(&user_c2s, n as u64);
+    // ── Run bidirectional copy + watchdog concurrently ───────────────
-                    stats_c2s.increment_user_msgs_from(&user_c2s);
+    //
+    // copy_bidirectional polls both directions in the same poll() call:
+    //   C→S: poll_read(client/StatsIo) → poll_write(server)
+    //   S→C: poll_read(server)         → poll_write(client/StatsIo)
+    //
+    // When one direction's writer returns Pending, the other direction
+    // continues — no head-of-line blocking.
+    //
+    // When the watchdog fires, select! drops the copy future,
+    // releasing the &mut borrows on client and server.
+    let copy_result = tokio::select! {
+        result = copy_bidirectional(&mut client, &mut server) => Some(result),
+        _ = watchdog => None, // Activity timeout — cancel relay
+    };
 
-                    trace!(
+    // ── Clean shutdown ──────────────────────────────────────────────
-                        user = %user_c2s,
+    // After select!, the losing future is dropped, borrows released.
-                        bytes = n,
+    // Shut down both write sides for clean TCP FIN.
-                        total = total_bytes,
+    let _ = client.shutdown().await;
-                        "C->S data"
+    let _ = server.shutdown().await;
-                    );
 
-                    // Log activity every 10 seconds with correct rate
+    // ── Final logging ───────────────────────────────────────────────
-                    let elapsed = last_log.elapsed();
+    let c2s_ops = counters.c2s_ops.load(Ordering::Relaxed);
-                    if elapsed > Duration::from_secs(10) {
+    let s2c_ops = counters.s2c_ops.load(Ordering::Relaxed);
-                        let delta = total_bytes - prev_total_bytes;
+    let duration = epoch.elapsed();
-                        let rate = delta as f64 / elapsed.as_secs_f64();
 
+    match copy_result {
+        Some(Ok((c2s, s2c))) => {
+            // Normal completion — one side closed the connection
             debug!(
-                            user = %user_c2s,
+                user = %user_owned,
-                            total_bytes = total_bytes,
+                c2s_bytes = c2s,
-                            msgs = msg_count,
+                s2c_bytes = s2c,
-                            rate_kbps = (rate / 1024.0) as u64,
+                c2s_msgs = c2s_ops,
-                            "C->S transfer in progress"
+                s2c_msgs = s2c_ops,
-                        );
+                duration_secs = duration.as_secs(),
-                        
-                        last_log = Instant::now();
-                        prev_total_bytes = total_bytes;
-                    }
-                    
-                    if let Err(e) = server_writer.write_all(&pooled_buf[..n]).await {
-                        debug!(user = %user_c2s, error = %e, "Failed to write to server");
-                        break;
-                    }
-                    if let Err(e) = server_writer.flush().await {
-                        debug!(user = %user_c2s, error = %e, "Failed to flush to server");
-                        break;
-                    }
-                }
-                
-                Ok(Err(e)) => {
-                    debug!(user = %user_c2s, error = %e, total_bytes = total_bytes, "Client read error");
-                    break;
-                }
-            }
-        }
-    });
-    
-    // Server -> Client task
-    let s2c = tokio::spawn(async move {
-        // Get buffer from pool
-        let mut pooled_buf = pool_s2c.get();
-        // CRITICAL FIX: Resize buffer
-        let cap = pooled_buf.capacity();
-        pooled_buf.resize(cap, 0);
-
-        let mut total_bytes = 0u64;
-        let mut prev_total_bytes = 0u64;
-        let mut msg_count = 0u64;
-        let mut last_activity = Instant::now();
-        let mut last_log = Instant::now();
-        
-        loop {
-            let read_result = tokio::time::timeout(
-                activity_timeout,
-                server_reader.read(&mut pooled_buf)
-            ).await;
-            
-            match read_result {
-                Err(_) => {
-                    warn!(
-                        user = %user_s2c,
-                        total_bytes = total_bytes,
-                        msgs = msg_count,
-                        idle_secs = last_activity.elapsed().as_secs(),
-                        "Activity timeout (S->C) - no data received"
-                    );
-                    let _ = client_writer.shutdown().await;
-                    break;
-                }
-                
-                Ok(Ok(0)) => {
-                    debug!(
-                        user = %user_s2c,
-                        total_bytes = total_bytes,
-                        msgs = msg_count,
-                        "Server closed connection (S->C)"
-                    );
-                    let _ = client_writer.shutdown().await;
-                    break;
-                }
-                
-                Ok(Ok(n)) => {
-                    total_bytes += n as u64;
-                    msg_count += 1;
-                    last_activity = Instant::now();
-                    s2c_bytes_clone.store(total_bytes, Ordering::Relaxed);
-                    
-                    stats_s2c.add_user_octets_to(&user_s2c, n as u64);
-                    stats_s2c.increment_user_msgs_to(&user_s2c);
-                    
-                    trace!(
-                        user = %user_s2c,
-                        bytes = n,
-                        total = total_bytes,
-                        "S->C data"
-                    );
-                    
-                    let elapsed = last_log.elapsed();
-                    if elapsed > Duration::from_secs(10) {
-                        let delta = total_bytes - prev_total_bytes;
-                        let rate = delta as f64 / elapsed.as_secs_f64();
-                        
-                        debug!(
-                            user = %user_s2c,
-                            total_bytes = total_bytes,
-                            msgs = msg_count,
-                            rate_kbps = (rate / 1024.0) as u64,
-                            "S->C transfer in progress"
-                        );
-                        
-                        last_log = Instant::now();
-                        prev_total_bytes = total_bytes;
-                    }
-                    
-                    if let Err(e) = client_writer.write_all(&pooled_buf[..n]).await {
-                        debug!(user = %user_s2c, error = %e, "Failed to write to client");
-                        break;
-                    }
-                    if let Err(e) = client_writer.flush().await {
-                        debug!(user = %user_s2c, error = %e, "Failed to flush to client");
-                        break;
-                    }
-                }
-                
-                Ok(Err(e)) => {
-                    debug!(user = %user_s2c, error = %e, total_bytes = total_bytes, "Server read error");
-                    break;
-                }
-            }
-        }
-    });
-    
-    // Wait for either direction to complete
-    tokio::select! {
-        result = c2s => {
-            if let Err(e) = result {
-                warn!(error = %e, "C->S task panicked");
-            }
-        }
-        result = s2c => {
-            if let Err(e) = result {
-                warn!(error = %e, "S->C task panicked");
-            }
-        }
-    }
-    
-    debug!(
-        c2s_bytes = c2s_bytes.load(Ordering::Relaxed),
-        s2c_bytes = s2c_bytes.load(Ordering::Relaxed),
                 "Relay finished"
             );
-    
             Ok(())
+        }
+        Some(Err(e)) => {
+            // I/O error in one of the directions
+            let c2s = counters.c2s_bytes.load(Ordering::Relaxed);
+            let s2c = counters.s2c_bytes.load(Ordering::Relaxed);
+            debug!(
+                user = %user_owned,
+                c2s_bytes = c2s,
+                s2c_bytes = s2c,
+                c2s_msgs = c2s_ops,
+                s2c_msgs = s2c_ops,
+                duration_secs = duration.as_secs(),
+                error = %e,
+                "Relay error"
+            );
+            Err(e.into())
+        }
+        None => {
+            // Activity timeout (watchdog fired)
+            let c2s = counters.c2s_bytes.load(Ordering::Relaxed);
+            let s2c = counters.s2c_bytes.load(Ordering::Relaxed);
+            debug!(
+                user = %user_owned,
+                c2s_bytes = c2s,
+                s2c_bytes = s2c,
+                c2s_msgs = c2s_ops,
+                s2c_msgs = s2c_ops,
+                duration_secs = duration.as_secs(),
+                "Relay finished (activity timeout)"
+            );
+            Ok(())
+        }
+    }
 }

src/stats/mod.rs

@@ -1,31 +1,28 @@
-//! Statistics
+//! Statistics and replay protection
 
 use std::sync::atomic::{AtomicU64, Ordering};
 use std::sync::Arc;
-use std::time::Instant;
+use std::time::{Instant, Duration};
 use dashmap::DashMap;
-use parking_lot::{RwLock, Mutex};
+use parking_lot::Mutex;
 use lru::LruCache;
 use std::num::NonZeroUsize;
 use std::hash::{Hash, Hasher};
 use std::collections::hash_map::DefaultHasher;
+use std::collections::VecDeque;
+use tracing::debug;
+
+// ============= Stats =============
 
-/// Thread-safe statistics
 #[derive(Default)]
 pub struct Stats {
-    // Global counters
     connects_all: AtomicU64,
     connects_bad: AtomicU64,
     handshake_timeouts: AtomicU64,
-    
-    // Per-user stats
     user_stats: DashMap<String, UserStats>,
-    
+    start_time: parking_lot::RwLock<Option<Instant>>,
-    // Start time
-    start_time: RwLock<Option<Instant>>,
 }
 
-/// Per-user statistics
 #[derive(Default)]
 pub struct UserStats {
     pub connects: AtomicU64,
@@ -43,42 +40,20 @@ impl Stats {
         stats
     }
     
-    // Global stats
+    pub fn increment_connects_all(&self) { self.connects_all.fetch_add(1, Ordering::Relaxed); }
-    pub fn increment_connects_all(&self) {
+    pub fn increment_connects_bad(&self) { self.connects_bad.fetch_add(1, Ordering::Relaxed); }
-        self.connects_all.fetch_add(1, Ordering::Relaxed);
+    pub fn increment_handshake_timeouts(&self) { self.handshake_timeouts.fetch_add(1, Ordering::Relaxed); }
-    }
+    pub fn get_connects_all(&self) -> u64 { self.connects_all.load(Ordering::Relaxed) }
+    pub fn get_connects_bad(&self) -> u64 { self.connects_bad.load(Ordering::Relaxed) }
     
-    pub fn increment_connects_bad(&self) {
-        self.connects_bad.fetch_add(1, Ordering::Relaxed);
-    }
-    
-    pub fn increment_handshake_timeouts(&self) {
-        self.handshake_timeouts.fetch_add(1, Ordering::Relaxed);
-    }
-    
-    pub fn get_connects_all(&self) -> u64 {
-        self.connects_all.load(Ordering::Relaxed)
-    }
-    
-    pub fn get_connects_bad(&self) -> u64 {
-        self.connects_bad.load(Ordering::Relaxed)
-    }
-    
-    // User stats
     pub fn increment_user_connects(&self, user: &str) {
-        self.user_stats
+        self.user_stats.entry(user.to_string()).or_default()
-            .entry(user.to_string())
+            .connects.fetch_add(1, Ordering::Relaxed);
-            .or_default()
-            .connects
-            .fetch_add(1, Ordering::Relaxed);
     }
     
     pub fn increment_user_curr_connects(&self, user: &str) {
-        self.user_stats
+        self.user_stats.entry(user.to_string()).or_default()
-            .entry(user.to_string())
+            .curr_connects.fetch_add(1, Ordering::Relaxed);
-            .or_default()
-            .curr_connects
-            .fetch_add(1, Ordering::Relaxed);
     }
     
     pub fn decrement_user_curr_connects(&self, user: &str) {
@@ -88,47 +63,33 @@ impl Stats {
     }
     
     pub fn get_user_curr_connects(&self, user: &str) -> u64 {
-        self.user_stats
+        self.user_stats.get(user)
-            .get(user)
             .map(|s| s.curr_connects.load(Ordering::Relaxed))
             .unwrap_or(0)
     }
     
     pub fn add_user_octets_from(&self, user: &str, bytes: u64) {
-        self.user_stats
+        self.user_stats.entry(user.to_string()).or_default()
-            .entry(user.to_string())
+            .octets_from_client.fetch_add(bytes, Ordering::Relaxed);
-            .or_default()
-            .octets_from_client
-            .fetch_add(bytes, Ordering::Relaxed);
     }
     
     pub fn add_user_octets_to(&self, user: &str, bytes: u64) {
-        self.user_stats
+        self.user_stats.entry(user.to_string()).or_default()
-            .entry(user.to_string())
+            .octets_to_client.fetch_add(bytes, Ordering::Relaxed);
-            .or_default()
-            .octets_to_client
-            .fetch_add(bytes, Ordering::Relaxed);
     }
     
     pub fn increment_user_msgs_from(&self, user: &str) {
-        self.user_stats
+        self.user_stats.entry(user.to_string()).or_default()
-            .entry(user.to_string())
+            .msgs_from_client.fetch_add(1, Ordering::Relaxed);
-            .or_default()
-            .msgs_from_client
-            .fetch_add(1, Ordering::Relaxed);
     }
     
     pub fn increment_user_msgs_to(&self, user: &str) {
-        self.user_stats
+        self.user_stats.entry(user.to_string()).or_default()
-            .entry(user.to_string())
+            .msgs_to_client.fetch_add(1, Ordering::Relaxed);
-            .or_default()
-            .msgs_to_client
-            .fetch_add(1, Ordering::Relaxed);
     }
     
     pub fn get_user_total_octets(&self, user: &str) -> u64 {
-        self.user_stats
+        self.user_stats.get(user)
-            .get(user)
             .map(|s| {
                 s.octets_from_client.load(Ordering::Relaxed) +
                 s.octets_to_client.load(Ordering::Relaxed)
@@ -143,57 +104,209 @@ impl Stats {
     }
 }
 
-/// Sharded Replay attack checker using LRU cache
+// ============= Replay Checker =============
-/// Uses multiple independent LRU caches to reduce lock contention
+
 pub struct ReplayChecker {
-    shards: Vec<Mutex<LruCache<Vec<u8>, ()>>>,
+    shards: Vec<Mutex<ReplayShard>>,
     shard_mask: usize,
+    window: Duration,
+    checks: AtomicU64,
+    hits: AtomicU64,
+    additions: AtomicU64,
+    cleanups: AtomicU64,
+}
+
+struct ReplayEntry {
+    seen_at: Instant,
+    seq: u64,
+}
+
+struct ReplayShard {
+    cache: LruCache<Box<[u8]>, ReplayEntry>,
+    queue: VecDeque<(Instant, Box<[u8]>, u64)>,
+    seq_counter: u64,
+}
+
+impl ReplayShard {
+    fn new(cap: NonZeroUsize) -> Self {
+        Self {
+            cache: LruCache::new(cap),
+            queue: VecDeque::with_capacity(cap.get()),
+            seq_counter: 0,
+        }
+    }
+    
+    fn next_seq(&mut self) -> u64 {
+        self.seq_counter += 1;
+        self.seq_counter
+    }
+
+    fn cleanup(&mut self, now: Instant, window: Duration) {
+        if window.is_zero() {
+            return;
+        }
+        let cutoff = now.checked_sub(window).unwrap_or(now);
+        
+        while let Some((ts, _, _)) = self.queue.front() {
+            if *ts >= cutoff {
+                break;
+            }
+            let (_, key, queue_seq) = self.queue.pop_front().unwrap();
+            
+            // Use key.as_ref() to get &[u8] — avoids Borrow<Q> ambiguity
+            // between Borrow<[u8]> and Borrow<Box<[u8]>>
+            if let Some(entry) = self.cache.peek(key.as_ref()) {
+                if entry.seq == queue_seq {
+                    self.cache.pop(key.as_ref());
+                }
+            }
+        }
+    }
+    
+    fn check(&mut self, key: &[u8], now: Instant, window: Duration) -> bool {
+        self.cleanup(now, window);
+        // key is &[u8], resolves Q=[u8] via Box<[u8]>: Borrow<[u8]>
+        self.cache.get(key).is_some()
+    }
+    
+    fn add(&mut self, key: &[u8], now: Instant, window: Duration) {
+        self.cleanup(now, window);
+        
+        let seq = self.next_seq();
+        let boxed_key: Box<[u8]> = key.into();
+        
+        self.cache.put(boxed_key.clone(), ReplayEntry { seen_at: now, seq });
+        self.queue.push_back((now, boxed_key, seq));
+    }
+    
+    fn len(&self) -> usize {
+        self.cache.len()
+    }
 }
 
 impl ReplayChecker {
-    /// Create new replay checker with specified capacity per shard
+    pub fn new(total_capacity: usize, window: Duration) -> Self {
-    /// Total capacity = capacity * num_shards
-    pub fn new(total_capacity: usize) -> Self {
-        // Use 64 shards for good concurrency
         let num_shards = 64;
         let shard_capacity = (total_capacity / num_shards).max(1);
         let cap = NonZeroUsize::new(shard_capacity).unwrap();
 
         let mut shards = Vec::with_capacity(num_shards);
         for _ in 0..num_shards {
-            shards.push(Mutex::new(LruCache::new(cap)));
+            shards.push(Mutex::new(ReplayShard::new(cap)));
         }
 
         Self {
             shards,
             shard_mask: num_shards - 1,
+            window,
+            checks: AtomicU64::new(0),
+            hits: AtomicU64::new(0),
+            additions: AtomicU64::new(0),
+            cleanups: AtomicU64::new(0),
         }
     }
 
-    fn get_shard(&self, key: &[u8]) -> usize {
+    fn get_shard_idx(&self, key: &[u8]) -> usize {
         let mut hasher = DefaultHasher::new();
         key.hash(&mut hasher);
         (hasher.finish() as usize) & self.shard_mask
     }
 
-    pub fn check_handshake(&self, data: &[u8]) -> bool {
+    fn check(&self, data: &[u8]) -> bool {
-        let shard_idx = self.get_shard(data);
+        self.checks.fetch_add(1, Ordering::Relaxed);
-        self.shards[shard_idx].lock().contains(&data.to_vec())
+        let idx = self.get_shard_idx(data);
+        let mut shard = self.shards[idx].lock();
+        let found = shard.check(data, Instant::now(), self.window);
+        if found {
+            self.hits.fetch_add(1, Ordering::Relaxed);
+        }
+        found
     }
 
-    pub fn add_handshake(&self, data: &[u8]) {
+    fn add(&self, data: &[u8]) {
-        let shard_idx = self.get_shard(data);
+        self.additions.fetch_add(1, Ordering::Relaxed);
-        self.shards[shard_idx].lock().put(data.to_vec(), ());
+        let idx = self.get_shard_idx(data);
+        let mut shard = self.shards[idx].lock();
+        shard.add(data, Instant::now(), self.window);
     }
 
-    pub fn check_tls_digest(&self, data: &[u8]) -> bool {
+    pub fn check_handshake(&self, data: &[u8]) -> bool { self.check(data) }
-        let shard_idx = self.get_shard(data);
+    pub fn add_handshake(&self, data: &[u8]) { self.add(data) }
-        self.shards[shard_idx].lock().contains(&data.to_vec())
+    pub fn check_tls_digest(&self, data: &[u8]) -> bool { self.check(data) }
+    pub fn add_tls_digest(&self, data: &[u8]) { self.add(data) }
+    
+    pub fn stats(&self) -> ReplayStats {
+        let mut total_entries = 0;
+        let mut total_queue_len = 0;
+        for shard in &self.shards {
+            let s = shard.lock();
+            total_entries += s.cache.len();
+            total_queue_len += s.queue.len();
         }
         
-    pub fn add_tls_digest(&self, data: &[u8]) {
+        ReplayStats {
-        let shard_idx = self.get_shard(data);
+            total_entries,
-        self.shards[shard_idx].lock().put(data.to_vec(), ());
+            total_queue_len,
+            total_checks: self.checks.load(Ordering::Relaxed),
+            total_hits: self.hits.load(Ordering::Relaxed),
+            total_additions: self.additions.load(Ordering::Relaxed),
+            total_cleanups: self.cleanups.load(Ordering::Relaxed),
+            num_shards: self.shards.len(),
+            window_secs: self.window.as_secs(),
+        }
+    }
+    
+    pub async fn run_periodic_cleanup(&self) {
+        let interval = if self.window.as_secs() > 60 {
+            Duration::from_secs(30)
+        } else {
+            Duration::from_secs(self.window.as_secs().max(1) / 2)
+        };
+        
+        loop {
+            tokio::time::sleep(interval).await;
+            
+            let now = Instant::now();
+            let mut cleaned = 0usize;
+            
+            for shard_mutex in &self.shards {
+                let mut shard = shard_mutex.lock();
+                let before = shard.len();
+                shard.cleanup(now, self.window);
+                let after = shard.len();
+                cleaned += before.saturating_sub(after);
+            }
+            
+            self.cleanups.fetch_add(1, Ordering::Relaxed);
+            
+            if cleaned > 0 {
+                debug!(cleaned = cleaned, "Replay checker: periodic cleanup");
+            }
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct ReplayStats {
+    pub total_entries: usize,
+    pub total_queue_len: usize,
+    pub total_checks: u64,
+    pub total_hits: u64,
+    pub total_additions: u64,
+    pub total_cleanups: u64,
+    pub num_shards: usize,
+    pub window_secs: u64,
+}
+
+impl ReplayStats {
+    pub fn hit_rate(&self) -> f64 {
+        if self.total_checks == 0 { 0.0 }
+        else { (self.total_hits as f64 / self.total_checks as f64) * 100.0 }
+    }
+    
+    pub fn ghost_ratio(&self) -> f64 {
+        if self.total_entries == 0 { 0.0 }
+        else { self.total_queue_len as f64 / self.total_entries as f64 }
     }
 }
 
@@ -204,28 +317,60 @@ mod tests {
     #[test]
     fn test_stats_shared_counters() {
         let stats = Arc::new(Stats::new());
-        
+        stats.increment_connects_all();
-        let stats1 = Arc::clone(&stats);
+        stats.increment_connects_all();
-        let stats2 = Arc::clone(&stats);
+        stats.increment_connects_all();
-        
-        stats1.increment_connects_all();
-        stats2.increment_connects_all();
-        stats1.increment_connects_all();
-        
         assert_eq!(stats.get_connects_all(), 3);
     }
     
     #[test]
-    fn test_replay_checker_sharding() {
+    fn test_replay_checker_basic() {
-        let checker = ReplayChecker::new(100);
+        let checker = ReplayChecker::new(100, Duration::from_secs(60));
-        let data1 = b"test1";
+        assert!(!checker.check_handshake(b"test1"));
-        let data2 = b"test2";
+        checker.add_handshake(b"test1");
+        assert!(checker.check_handshake(b"test1"));
+        assert!(!checker.check_handshake(b"test2"));
+    }
     
-        checker.add_handshake(data1);
+    #[test]
-        assert!(checker.check_handshake(data1));
+    fn test_replay_checker_duplicate_add() {
-        assert!(!checker.check_handshake(data2));
+        let checker = ReplayChecker::new(100, Duration::from_secs(60));
+        checker.add_handshake(b"dup");
+        checker.add_handshake(b"dup");
+        assert!(checker.check_handshake(b"dup"));
+    }
     
-        checker.add_handshake(data2);
+    #[test]
-        assert!(checker.check_handshake(data2));
+    fn test_replay_checker_expiration() {
+        let checker = ReplayChecker::new(100, Duration::from_millis(50));
+        checker.add_handshake(b"expire");
+        assert!(checker.check_handshake(b"expire"));
+        std::thread::sleep(Duration::from_millis(100));
+        assert!(!checker.check_handshake(b"expire"));
+    }
+    
+    #[test]
+    fn test_replay_checker_stats() {
+        let checker = ReplayChecker::new(100, Duration::from_secs(60));
+        checker.add_handshake(b"k1");
+        checker.add_handshake(b"k2");
+        checker.check_handshake(b"k1");
+        checker.check_handshake(b"k3");
+        let stats = checker.stats();
+        assert_eq!(stats.total_additions, 2);
+        assert_eq!(stats.total_checks, 2);
+        assert_eq!(stats.total_hits, 1);
+    }
+    
+    #[test]
+    fn test_replay_checker_many_keys() {
+        let checker = ReplayChecker::new(1000, Duration::from_secs(60));
+        for i in 0..500u32 {
+            checker.add(&i.to_le_bytes());
+        }
+        for i in 0..500u32 {
+            assert!(checker.check(&i.to_le_bytes()));
+        }
+        assert_eq!(checker.stats().total_entries, 500);
     }
 }

src/stream/frame.rs

@@ -5,8 +5,10 @@
 
 use bytes::{Bytes, BytesMut};
 use std::io::Result;
+use std::sync::Arc;
 
 use crate::protocol::constants::ProtoTag;
+use crate::crypto::SecureRandom;
 
 // ============= Frame Types =============
 
@@ -147,11 +149,11 @@ pub trait FrameCodec: Send + Sync {
 // ============= Codec Factory =============
 
 /// Create a frame codec for the given protocol tag
-pub fn create_codec(proto_tag: ProtoTag) -> Box<dyn FrameCodec> {
+pub fn create_codec(proto_tag: ProtoTag, rng: Arc<SecureRandom>) -> Box<dyn FrameCodec> {
     match proto_tag {
         ProtoTag::Abridged => Box::new(crate::stream::frame_codec::AbridgedCodec::new()),
         ProtoTag::Intermediate => Box::new(crate::stream::frame_codec::IntermediateCodec::new()),
-        ProtoTag::Secure => Box::new(crate::stream::frame_codec::SecureCodec::new()),
+        ProtoTag::Secure => Box::new(crate::stream::frame_codec::SecureCodec::new(rng)),
     }
 }
 

src/stream/frame_codec.rs

@@ -5,9 +5,11 @@
 
 use bytes::{Bytes, BytesMut, BufMut};
 use std::io::{self, Error, ErrorKind};
+use std::sync::Arc;
 use tokio_util::codec::{Decoder, Encoder};
 
 use crate::protocol::constants::ProtoTag;
+use crate::crypto::SecureRandom;
 use super::frame::{Frame, FrameMeta, FrameCodec as FrameCodecTrait};
 
 // ============= Unified Codec =============
@@ -21,14 +23,17 @@ pub struct FrameCodec {
     proto_tag: ProtoTag,
     /// Maximum allowed frame size
     max_frame_size: usize,
+    /// RNG for secure padding
+    rng: Arc<SecureRandom>,
 }
 
 impl FrameCodec {
     /// Create a new codec for the given protocol
-    pub fn new(proto_tag: ProtoTag) -> Self {
+    pub fn new(proto_tag: ProtoTag, rng: Arc<SecureRandom>) -> Self {
         Self {
             proto_tag,
             max_frame_size: 16 * 1024 * 1024, // 16MB default
+            rng,
         }
     }
     
@@ -64,7 +69,7 @@ impl Encoder<Frame> for FrameCodec {
         match self.proto_tag {
             ProtoTag::Abridged => encode_abridged(&frame, dst),
             ProtoTag::Intermediate => encode_intermediate(&frame, dst),
-            ProtoTag::Secure => encode_secure(&frame, dst),
+            ProtoTag::Secure => encode_secure(&frame, dst, &self.rng),
         }
     }
 }
@@ -288,9 +293,7 @@ fn decode_secure(src: &mut BytesMut, max_size: usize) -> io::Result<Option<Frame
     Ok(Some(Frame::with_meta(data, meta)))
 }
 
-fn encode_secure(frame: &Frame, dst: &mut BytesMut) -> io::Result<()> {
+fn encode_secure(frame: &Frame, dst: &mut BytesMut, rng: &SecureRandom) -> io::Result<()> {
-    use crate::crypto::random::SECURE_RANDOM;
-    
     let data = &frame.data;
     
     // Simple ACK: just send data
@@ -303,10 +306,10 @@ fn encode_secure(frame: &Frame, dst: &mut BytesMut) -> io::Result<()> {
     // Generate padding to make length not divisible by 4
     let padding_len = if data.len() % 4 == 0 {
         // Add 1-3 bytes to make it non-aligned
-        (SECURE_RANDOM.range(3) + 1) as usize
+        (rng.range(3) + 1) as usize
     } else {
         // Already non-aligned, can add 0-3
-        SECURE_RANDOM.range(4) as usize
+        rng.range(4) as usize
     };
     
     let total_len = data.len() + padding_len;
@@ -321,7 +324,7 @@ fn encode_secure(frame: &Frame, dst: &mut BytesMut) -> io::Result<()> {
     dst.extend_from_slice(data);
     
     if padding_len > 0 {
-        let padding = SECURE_RANDOM.bytes(padding_len);
+        let padding = rng.bytes(padding_len);
         dst.extend_from_slice(&padding);
     }
     
@@ -445,19 +448,21 @@ impl FrameCodecTrait for IntermediateCodec {
 /// Secure Intermediate protocol codec
 pub struct SecureCodec {
     max_frame_size: usize,
+    rng: Arc<SecureRandom>,
 }
 
 impl SecureCodec {
-    pub fn new() -> Self {
+    pub fn new(rng: Arc<SecureRandom>) -> Self {
         Self {
             max_frame_size: 16 * 1024 * 1024,
+            rng,
         }
     }
 }
 
 impl Default for SecureCodec {
     fn default() -> Self {
-        Self::new()
+        Self::new(Arc::new(SecureRandom::new()))
     }
 }
 
@@ -474,7 +479,7 @@ impl Encoder<Frame> for SecureCodec {
     type Error = io::Error;
     
     fn encode(&mut self, frame: Frame, dst: &mut BytesMut) -> Result<(), Self::Error> {
-        encode_secure(&frame, dst)
+        encode_secure(&frame, dst, &self.rng)
     }
 }
 
@@ -485,7 +490,7 @@ impl FrameCodecTrait for SecureCodec {
     
     fn encode(&self, frame: &Frame, dst: &mut BytesMut) -> io::Result<usize> {
         let before = dst.len();
-        encode_secure(frame, dst)?;
+        encode_secure(frame, dst, &self.rng)?;
         Ok(dst.len() - before)
     }
     
@@ -506,6 +511,8 @@ mod tests {
     use tokio_util::codec::{FramedRead, FramedWrite};
     use tokio::io::duplex;
     use futures::{SinkExt, StreamExt};
+    use crate::crypto::SecureRandom;
+    use std::sync::Arc;
     
     #[tokio::test]
     async fn test_framed_abridged() {
@@ -541,8 +548,8 @@ mod tests {
     async fn test_framed_secure() {
         let (client, server) = duplex(4096);
         
-        let mut writer = FramedWrite::new(client, SecureCodec::new());
+        let mut writer = FramedWrite::new(client, SecureCodec::new(Arc::new(SecureRandom::new())));
-        let mut reader = FramedRead::new(server, SecureCodec::new());
+        let mut reader = FramedRead::new(server, SecureCodec::new(Arc::new(SecureRandom::new())));
         
         let original = Bytes::from_static(&[1, 2, 3, 4, 5, 6, 7, 8]);
         let frame = Frame::new(original.clone());
@@ -557,8 +564,8 @@ mod tests {
         for proto_tag in [ProtoTag::Abridged, ProtoTag::Intermediate, ProtoTag::Secure] {
             let (client, server) = duplex(4096);
             
-            let mut writer = FramedWrite::new(client, FrameCodec::new(proto_tag));
+            let mut writer = FramedWrite::new(client, FrameCodec::new(proto_tag, Arc::new(SecureRandom::new())));
-            let mut reader = FramedRead::new(server, FrameCodec::new(proto_tag));
+            let mut reader = FramedRead::new(server, FrameCodec::new(proto_tag, Arc::new(SecureRandom::new())));
             
             // Use 4-byte aligned data for abridged compatibility
             let original = Bytes::from_static(&[1, 2, 3, 4, 5, 6, 7, 8]);
@@ -607,7 +614,7 @@ mod tests {
     
     #[test]
     fn test_frame_too_large() {
-        let mut codec = FrameCodec::new(ProtoTag::Intermediate)
+        let mut codec = FrameCodec::new(ProtoTag::Intermediate, Arc::new(SecureRandom::new()))
             .with_max_frame_size(100);
         
         // Create a "frame" that claims to be very large

src/stream/frame_stream.rs

@@ -4,8 +4,8 @@ use bytes::{Bytes, BytesMut};
 use std::io::{Error, ErrorKind, Result};
 use tokio::io::{AsyncRead, AsyncWrite, AsyncReadExt, AsyncWriteExt};
 use crate::protocol::constants::*;
-use crate::crypto::crc32;
+use crate::crypto::{crc32, SecureRandom};
-use crate::crypto::random::SECURE_RANDOM;
+use std::sync::Arc;
 use super::traits::{FrameMeta, LayeredStream};
 
 // ============= Abridged (Compact) Frame =============
@@ -251,11 +251,12 @@ impl<R> LayeredStream<R> for SecureIntermediateFrameReader<R> {
 /// Writer for secure intermediate MTProto framing
 pub struct SecureIntermediateFrameWriter<W> {
     upstream: W,
+    rng: Arc<SecureRandom>,
 }
 
 impl<W> SecureIntermediateFrameWriter<W> {
-    pub fn new(upstream: W) -> Self {
+    pub fn new(upstream: W, rng: Arc<SecureRandom>) -> Self {
-        Self { upstream }
+        Self { upstream, rng }
     }
 }
 
@@ -267,8 +268,8 @@ impl<W: AsyncWrite + Unpin> SecureIntermediateFrameWriter<W> {
         }
         
         // Add random padding (0-3 bytes)
-        let padding_len = SECURE_RANDOM.range(4);
+        let padding_len = self.rng.range(4);
-        let padding = SECURE_RANDOM.bytes(padding_len);
+        let padding = self.rng.bytes(padding_len);
         
         let total_len = data.len() + padding_len;
         let len_bytes = (total_len as u32).to_le_bytes();
@@ -454,11 +455,11 @@ pub enum FrameWriterKind<W> {
 }
 
 impl<W: AsyncWrite + Unpin> FrameWriterKind<W> {
-    pub fn new(upstream: W, proto_tag: ProtoTag) -> Self {
+    pub fn new(upstream: W, proto_tag: ProtoTag, rng: Arc<SecureRandom>) -> Self {
         match proto_tag {
             ProtoTag::Abridged => FrameWriterKind::Abridged(AbridgedFrameWriter::new(upstream)),
             ProtoTag::Intermediate => FrameWriterKind::Intermediate(IntermediateFrameWriter::new(upstream)),
-            ProtoTag::Secure => FrameWriterKind::SecureIntermediate(SecureIntermediateFrameWriter::new(upstream)),
+            ProtoTag::Secure => FrameWriterKind::SecureIntermediate(SecureIntermediateFrameWriter::new(upstream, rng)),
         }
     }
     
@@ -483,6 +484,8 @@ impl<W: AsyncWrite + Unpin> FrameWriterKind<W> {
 mod tests {
     use super::*;
     use tokio::io::duplex;
+    use std::sync::Arc;
+    use crate::crypto::SecureRandom;
     
     #[tokio::test]
     async fn test_abridged_roundtrip() {
@@ -539,7 +542,7 @@ mod tests {
     async fn test_secure_intermediate_padding() {
         let (client, server) = duplex(1024);
         
-        let mut writer = SecureIntermediateFrameWriter::new(client);
+        let mut writer = SecureIntermediateFrameWriter::new(client, Arc::new(SecureRandom::new()));
         let mut reader = SecureIntermediateFrameReader::new(server);
         
         let data = vec![1u8, 2, 3, 4, 5, 6, 7, 8];
@@ -572,7 +575,7 @@ mod tests {
     async fn test_frame_reader_kind() {
         let (client, server) = duplex(1024);
         
-        let mut writer = FrameWriterKind::new(client, ProtoTag::Intermediate);
+        let mut writer = FrameWriterKind::new(client, ProtoTag::Intermediate, Arc::new(SecureRandom::new()));
         let mut reader = FrameReaderKind::new(server, ProtoTag::Intermediate);
         
         let data = vec![1u8, 2, 3, 4];

src/transport/middle_proxy.rs

@@ -0,0 +1,925 @@
+//! Middle Proxy RPC Transport
+//!
+//! Implements Telegram Middle-End RPC protocol for routing to ALL DCs (including CDN).
+//!
+//! ## Phase 3 fixes:
+//! - ROOT CAUSE: Use Telegram proxy-secret (binary file) not user secret
+//! - Streaming handshake response (no fixed-size read deadlock)
+//! - Health monitoring + reconnection
+//! - Hex diagnostics for debugging
+
+use std::collections::HashMap;
+use std::net::{IpAddr, Ipv4Addr, SocketAddr};
+use std::sync::Arc;
+use std::sync::atomic::{AtomicU64, Ordering};
+use std::time::Duration;
+use bytes::{Bytes, BytesMut};
+use tokio::io::{AsyncReadExt, AsyncWriteExt};
+use tokio::net::TcpStream;
+use tokio::sync::{mpsc, Mutex, RwLock};
+use tokio::time::{timeout, Instant};
+use tracing::{debug, info, trace, warn, error};
+
+use crate::crypto::{crc32, derive_middleproxy_keys, AesCbc, SecureRandom};
+use crate::error::{ProxyError, Result};
+use crate::protocol::constants::*;
+
+// ========== Proxy Secret Fetching ==========
+
+/// Fetch the Telegram proxy-secret binary file.
+///
+/// This is NOT the user secret (-S flag, 16 bytes hex for clients).
+/// This is the infrastructure secret (--aes-pwd in C MTProxy),
+/// a binary file of 32-512 bytes used for ME RPC key derivation.
+///
+/// Strategy: try local cache, then download from Telegram.
+pub async fn fetch_proxy_secret(cache_path: Option<&str>) -> Result<Vec<u8>> {
+    let cache = cache_path.unwrap_or("proxy-secret");
+
+    // 1. Try local cache (< 24h old)
+    if let Ok(metadata) = tokio::fs::metadata(cache).await {
+        if let Ok(modified) = metadata.modified() {
+            let age = std::time::SystemTime::now()
+                .duration_since(modified)
+                .unwrap_or(Duration::from_secs(u64::MAX));
+            if age < Duration::from_secs(86400) {
+                if let Ok(data) = tokio::fs::read(cache).await {
+                    if data.len() >= 32 {
+                        info!(
+                            path = cache,
+                            len = data.len(),
+                            age_hours = age.as_secs() / 3600,
+                            "Loaded proxy-secret from cache"
+                        );
+                        return Ok(data);
+                    }
+                    warn!(path = cache, len = data.len(), "Cached proxy-secret too short");
+                }
+            }
+        }
+    }
+
+    // 2. Download from Telegram
+    info!("Downloading proxy-secret from core.telegram.org...");
+    let data = download_proxy_secret().await?;
+
+    // 3. Cache locally (best-effort)
+    if let Err(e) = tokio::fs::write(cache, &data).await {
+        warn!(error = %e, "Failed to cache proxy-secret (non-fatal)");
+    } else {
+        debug!(path = cache, len = data.len(), "Cached proxy-secret");
+    }
+
+    Ok(data)
+}
+
+async fn download_proxy_secret() -> Result<Vec<u8>> {
+    let url = "https://core.telegram.org/getProxySecret";
+    let resp = reqwest::get(url)
+        .await
+        .map_err(|e| ProxyError::Proxy(format!("Failed to download proxy-secret: {}", e)))?;
+
+    if !resp.status().is_success() {
+        return Err(ProxyError::Proxy(format!(
+            "proxy-secret download HTTP {}", resp.status()
+        )));
+    }
+
+    let data = resp.bytes().await
+        .map_err(|e| ProxyError::Proxy(format!("Read proxy-secret body: {}", e)))?
+        .to_vec();
+
+    if data.len() < 32 {
+        return Err(ProxyError::Proxy(format!(
+            "proxy-secret too short: {} bytes (need >= 32)", data.len()
+        )));
+    }
+
+    info!(len = data.len(), "Downloaded proxy-secret OK");
+    Ok(data)
+}
+
+// ========== RPC Frame helpers ==========
+
+/// Build an RPC frame: [len(4) | seq_no(4) | payload | crc32(4)]
+fn build_rpc_frame(seq_no: i32, payload: &[u8]) -> Vec<u8> {
+    let total_len = (4 + 4 + payload.len() + 4) as u32;
+    let mut f = Vec::with_capacity(total_len as usize);
+    f.extend_from_slice(&total_len.to_le_bytes());
+    f.extend_from_slice(&seq_no.to_le_bytes());
+    f.extend_from_slice(payload);
+    let c = crc32(&f);
+    f.extend_from_slice(&c.to_le_bytes());
+    f
+}
+
+/// Read one plaintext RPC frame. Returns (seq_no, payload).
+async fn read_rpc_frame_plaintext(
+    rd: &mut (impl AsyncReadExt + Unpin),
+) -> Result<(i32, Vec<u8>)> {
+    let mut len_buf = [0u8; 4];
+    rd.read_exact(&mut len_buf).await.map_err(ProxyError::Io)?;
+    let total_len = u32::from_le_bytes(len_buf) as usize;
+
+    if total_len < 12 || total_len > (1 << 24) {
+        return Err(ProxyError::InvalidHandshake(
+            format!("Bad RPC frame length: {}", total_len),
+        ));
+    }
+
+    let mut rest = vec![0u8; total_len - 4];
+    rd.read_exact(&mut rest).await.map_err(ProxyError::Io)?;
+
+    let mut full = Vec::with_capacity(total_len);
+    full.extend_from_slice(&len_buf);
+    full.extend_from_slice(&rest);
+
+    let crc_offset = total_len - 4;
+    let expected_crc = u32::from_le_bytes([
+        full[crc_offset], full[crc_offset + 1],
+        full[crc_offset + 2], full[crc_offset + 3],
+    ]);
+    let actual_crc = crc32(&full[..crc_offset]);
+    if expected_crc != actual_crc {
+        return Err(ProxyError::InvalidHandshake(
+            format!("CRC mismatch: 0x{:08x} vs 0x{:08x}", expected_crc, actual_crc),
+        ));
+    }
+
+    let seq_no = i32::from_le_bytes([full[4], full[5], full[6], full[7]]);
+    let payload = full[8..crc_offset].to_vec();
+    Ok((seq_no, payload))
+}
+
+// ========== RPC Nonce (32 bytes payload) ==========
+
+fn build_nonce_payload(key_selector: u32, crypto_ts: u32, nonce: &[u8; 16]) -> [u8; 32] {
+    let mut p = [0u8; 32];
+    p[0..4].copy_from_slice(&RPC_NONCE_U32.to_le_bytes());
+    p[4..8].copy_from_slice(&key_selector.to_le_bytes());
+    p[8..12].copy_from_slice(&RPC_CRYPTO_AES_U32.to_le_bytes());
+    p[12..16].copy_from_slice(&crypto_ts.to_le_bytes());
+    p[16..32].copy_from_slice(nonce);
+    p
+}
+
+fn parse_nonce_payload(d: &[u8]) -> Result<(u32, u32, [u8; 16])> {
+    if d.len() < 32 {
+        return Err(ProxyError::InvalidHandshake(
+            format!("Nonce payload too short: {} bytes", d.len()),
+        ));
+    }
+    let t = u32::from_le_bytes([d[0], d[1], d[2], d[3]]);
+    if t != RPC_NONCE_U32 {
+        return Err(ProxyError::InvalidHandshake(
+            format!("Expected RPC_NONCE 0x{:08x}, got 0x{:08x}", RPC_NONCE_U32, t),
+        ));
+    }
+    let schema = u32::from_le_bytes([d[8], d[9], d[10], d[11]]);
+    let ts = u32::from_le_bytes([d[12], d[13], d[14], d[15]]);
+    let mut nonce = [0u8; 16];
+    nonce.copy_from_slice(&d[16..32]);
+    Ok((schema, ts, nonce))
+}
+
+// ========== RPC Handshake (32 bytes payload) ==========
+
+fn build_handshake_payload(our_ip: u32, our_port: u16, peer_ip: u32, peer_port: u16) -> [u8; 32] {
+    let mut p = [0u8; 32];
+    p[0..4].copy_from_slice(&RPC_HANDSHAKE_U32.to_le_bytes());
+    // flags = 0 at offset 4..8
+
+    // sender_pid: {ip(4), port(2), pid(2), utime(4)} at offset 8..20
+    p[8..12].copy_from_slice(&our_ip.to_le_bytes());
+    p[12..14].copy_from_slice(&our_port.to_le_bytes());
+    let pid = (std::process::id() & 0xFFFF) as u16;
+    p[14..16].copy_from_slice(&pid.to_le_bytes());
+    let utime = std::time::SystemTime::now()
+        .duration_since(std::time::UNIX_EPOCH)
+        .unwrap_or_default()
+        .as_secs() as u32;
+    p[16..20].copy_from_slice(&utime.to_le_bytes());
+
+    // peer_pid: {ip(4), port(2), pid(2), utime(4)} at offset 20..32
+    p[20..24].copy_from_slice(&peer_ip.to_le_bytes());
+    p[24..26].copy_from_slice(&peer_port.to_le_bytes());
+    p
+}
+
+// ========== CBC helpers ==========
+
+fn cbc_encrypt_padded(key: &[u8; 32], iv: &[u8; 16], plaintext: &[u8]) -> Result<(Vec<u8>, [u8; 16])> {
+    let pad = (16 - (plaintext.len() % 16)) % 16;
+    let mut buf = plaintext.to_vec();
+    let pad_pattern: [u8; 4] = [0x04, 0x00, 0x00, 0x00];
+    for i in 0..pad {
+        buf.push(pad_pattern[i % 4]);
+    }
+    let cipher = AesCbc::new(*key, *iv);
+    cipher.encrypt_in_place(&mut buf)
+        .map_err(|e| ProxyError::Crypto(format!("CBC encrypt: {}", e)))?;
+    let mut new_iv = [0u8; 16];
+    if buf.len() >= 16 {
+        new_iv.copy_from_slice(&buf[buf.len() - 16..]);
+    }
+    Ok((buf, new_iv))
+}
+
+fn cbc_decrypt_inplace(key: &[u8; 32], iv: &[u8; 16], data: &mut [u8]) -> Result<[u8; 16]> {
+    let mut new_iv = [0u8; 16];
+    if data.len() >= 16 {
+        new_iv.copy_from_slice(&data[data.len() - 16..]);
+    }
+    AesCbc::new(*key, *iv)
+        .decrypt_in_place(data)
+        .map_err(|e| ProxyError::Crypto(format!("CBC decrypt: {}", e)))?;
+    Ok(new_iv)
+}
+
+// ========== IPv4 helpers ==========
+
+fn ipv4_to_mapped_v6(ip: Ipv4Addr) -> [u8; 16] {
+    let mut buf = [0u8; 16];
+    buf[10] = 0xFF;
+    buf[11] = 0xFF;
+    let o = ip.octets();
+    buf[12] = o[0]; buf[13] = o[1]; buf[14] = o[2]; buf[15] = o[3];
+    buf
+}
+
+fn addr_to_ip_u32(addr: &SocketAddr) -> u32 {
+    match addr.ip() {
+        IpAddr::V4(v4) => u32::from_be_bytes(v4.octets()),
+        IpAddr::V6(v6) => {
+            if let Some(v4) = v6.to_ipv4_mapped() {
+                u32::from_be_bytes(v4.octets())
+            } else { 0 }
+        }
+    }
+}
+
+// ========== ME Response ==========
+
+#[derive(Debug)]
+pub enum MeResponse {
+    Data(Bytes),
+    Ack(u32),
+    Close,
+}
+
+// ========== Connection Registry ==========
+
+pub struct ConnRegistry {
+    map: RwLock<HashMap<u64, mpsc::Sender<MeResponse>>>,
+    next_id: AtomicU64,
+}
+
+impl ConnRegistry {
+    pub fn new() -> Self {
+        Self {
+            map: RwLock::new(HashMap::new()),
+            next_id: AtomicU64::new(1),
+        }
+    }
+    pub async fn register(&self) -> (u64, mpsc::Receiver<MeResponse>) {
+        let id = self.next_id.fetch_add(1, Ordering::Relaxed);
+        let (tx, rx) = mpsc::channel(256);
+        self.map.write().await.insert(id, tx);
+        (id, rx)
+    }
+    pub async fn unregister(&self, id: u64) {
+        self.map.write().await.remove(&id);
+    }
+    pub async fn route(&self, id: u64, resp: MeResponse) -> bool {
+        let m = self.map.read().await;
+        if let Some(tx) = m.get(&id) {
+            tx.send(resp).await.is_ok()
+        } else { false }
+    }
+}
+
+// ========== RPC Writer (streaming CBC) ==========
+
+struct RpcWriter {
+    writer: tokio::io::WriteHalf<TcpStream>,
+    key: [u8; 32],
+    iv: [u8; 16],
+    seq_no: i32,
+}
+
+impl RpcWriter {
+    async fn send(&mut self, payload: &[u8]) -> Result<()> {
+        let frame = build_rpc_frame(self.seq_no, payload);
+        self.seq_no += 1;
+
+        let pad = (16 - (frame.len() % 16)) % 16;
+        let mut buf = frame;
+        let pad_pattern: [u8; 4] = [0x04, 0x00, 0x00, 0x00];
+        for i in 0..pad {
+            buf.push(pad_pattern[i % 4]);
+        }
+
+        let cipher = AesCbc::new(self.key, self.iv);
+        cipher.encrypt_in_place(&mut buf)
+            .map_err(|e| ProxyError::Crypto(format!("{}", e)))?;
+
+        if buf.len() >= 16 {
+            self.iv.copy_from_slice(&buf[buf.len() - 16..]);
+        }
+        self.writer.write_all(&buf).await.map_err(ProxyError::Io)
+    }
+}
+
+// ========== RPC_PROXY_REQ ==========
+
+
+fn build_proxy_req_payload(
+    conn_id: u64,
+    client_addr: SocketAddr,
+    our_addr: SocketAddr,
+    data: &[u8],
+    proxy_tag: Option<&[u8]>,
+    proto_flags: u32,
+) -> Vec<u8> {
+    // flags are pre-calculated by proto_flags_for_tag
+    // We just need to ensure FLAG_HAS_AD_TAG is set if we have a tag (it is set by default in our new function, but let's be safe)
+    let mut flags = proto_flags;
+
+    // The C code logic:
+    // flags = (transport_flags) | 0x1000 | 0x20000 | 0x8 (if tag)
+    // Our proto_flags_for_tag returns: 0x8 | 0x1000 | 0x20000 | transport_flags
+    // So we are good.
+
+    let b_cap = 128 + data.len();
+    let mut b = Vec::with_capacity(b_cap);
+
+    b.extend_from_slice(&RPC_PROXY_REQ_U32.to_le_bytes());
+    b.extend_from_slice(&flags.to_le_bytes());
+    b.extend_from_slice(&conn_id.to_le_bytes());
+
+    // Client IP (16 bytes IPv4-mapped-v6) + port (4 bytes)
+    match client_addr.ip() {
+        IpAddr::V4(v4) => b.extend_from_slice(&ipv4_to_mapped_v6(v4)),
+        IpAddr::V6(v6) => b.extend_from_slice(&v6.octets()),
+    }
+    b.extend_from_slice(&(client_addr.port() as u32).to_le_bytes());
+
+    // Our IP (16 bytes) + port (4 bytes)
+    match our_addr.ip() {
+        IpAddr::V4(v4) => b.extend_from_slice(&ipv4_to_mapped_v6(v4)),
+        IpAddr::V6(v6) => b.extend_from_slice(&v6.octets()),
+    }
+    b.extend_from_slice(&(our_addr.port() as u32).to_le_bytes());
+
+    // Extra section (proxy_tag)
+    if flags & 12 != 0 {
+        let extra_start = b.len();
+        b.extend_from_slice(&0u32.to_le_bytes()); // placeholder
+
+        if let Some(tag) = proxy_tag {
+            b.extend_from_slice(&TL_PROXY_TAG_U32.to_le_bytes());
+            // TL string encoding
+            if tag.len() < 254 {
+                b.push(tag.len() as u8);
+                b.extend_from_slice(tag);
+                let pad = (4 - ((1 + tag.len()) % 4)) % 4;
+                b.extend(std::iter::repeat(0u8).take(pad));
+            } else {
+                b.push(0xfe);
+                let len_bytes = (tag.len() as u32).to_le_bytes();
+                b.extend_from_slice(&len_bytes[..3]);
+                b.extend_from_slice(tag);
+                let pad = (4 - (tag.len() % 4)) % 4;
+                b.extend(std::iter::repeat(0u8).take(pad));
+            }
+        }
+
+        let extra_bytes = (b.len() - extra_start - 4) as u32;
+        let eb = extra_bytes.to_le_bytes();
+        b[extra_start..extra_start + 4].copy_from_slice(&eb);
+    }
+
+    b.extend_from_slice(data);
+    b
+}
+
+// ========== ME Pool ==========
+
+pub struct MePool {
+    registry: Arc<ConnRegistry>,
+    writers: Arc<RwLock<Vec<Arc<Mutex<RpcWriter>>>>>,
+    rr: AtomicU64,
+    proxy_tag: Option<Vec<u8>>,
+    /// Telegram proxy-secret (binary, 32-512 bytes)
+    proxy_secret: Vec<u8>,
+    pool_size: usize,
+}
+
+impl MePool {
+    pub fn new(proxy_tag: Option<Vec<u8>>, proxy_secret: Vec<u8>) -> Arc<Self> {
+        Arc::new(Self {
+            registry: Arc::new(ConnRegistry::new()),
+            writers: Arc::new(RwLock::new(Vec::new())),
+            rr: AtomicU64::new(0),
+            proxy_tag,
+            proxy_secret,
+            pool_size: 2,
+        })
+    }
+
+    pub fn registry(&self) -> &Arc<ConnRegistry> {
+        &self.registry
+    }
+
+    fn writers_arc(&self) -> Arc<RwLock<Vec<Arc<Mutex<RpcWriter>>>>> {
+        self.writers.clone()
+    }
+
+    /// key_selector = first 4 bytes of proxy-secret as LE u32
+    /// C: main_secret.key_signature via union { char secret[]; int key_signature; }
+    fn key_selector(&self) -> u32 {
+        if self.proxy_secret.len() >= 4 {
+            u32::from_le_bytes([
+                self.proxy_secret[0], self.proxy_secret[1],
+                self.proxy_secret[2], self.proxy_secret[3],
+            ])
+        } else { 0 }
+    }
+
+    pub async fn init(
+        self: &Arc<Self>,
+        pool_size: usize,
+        rng: &SecureRandom,
+    ) -> Result<()> {
+        let addrs = &*TG_MIDDLE_PROXIES_FLAT_V4;
+        let ks = self.key_selector();
+        info!(
+            me_servers = addrs.len(),
+            pool_size,
+            key_selector = format_args!("0x{:08x}", ks),
+            secret_len = self.proxy_secret.len(),
+            "Initializing ME pool"
+        );
+
+        for &(ip, port) in addrs.iter() {
+            for i in 0..pool_size {
+                let addr = SocketAddr::new(ip, port);
+                match self.connect_one(addr, rng).await {
+                    Ok(()) => info!(%addr, idx = i, "ME connected"),
+                    Err(e) => warn!(%addr, idx = i, error = %e, "ME connect failed"),
+                }
+            }
+            if self.writers.read().await.len() >= pool_size {
+                break;
+            }
+        }
+
+        if self.writers.read().await.is_empty() {
+            return Err(ProxyError::Proxy("No ME connections".into()));
+        }
+        Ok(())
+    }
+
+    async fn connect_one(
+        self: &Arc<Self>,
+        addr: SocketAddr,
+        rng: &SecureRandom,
+    ) -> Result<()> {
+        let secret = &self.proxy_secret;
+        if secret.len() < 32 {
+            return Err(ProxyError::Proxy("proxy-secret too short for ME auth".into()));
+        }
+
+        // ===== TCP connect =====
+        let stream = timeout(
+            Duration::from_secs(ME_CONNECT_TIMEOUT_SECS),
+            TcpStream::connect(addr),
+        )
+        .await
+        .map_err(|_| ProxyError::ConnectionTimeout { addr: addr.to_string() })?
+        .map_err(ProxyError::Io)?;
+        stream.set_nodelay(true).ok();
+
+        let local_addr = stream.local_addr().map_err(ProxyError::Io)?;
+        let peer_addr = stream.peer_addr().map_err(ProxyError::Io)?;
+        let (mut rd, mut wr) = tokio::io::split(stream);
+
+        // ===== 1. Send RPC nonce (plaintext, seq=-2) =====
+        let my_nonce: [u8; 16] = rng.bytes(16).try_into().unwrap();
+        let crypto_ts = std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .unwrap_or_default()
+            .as_secs() as u32;
+        let ks = self.key_selector();
+
+        let nonce_payload = build_nonce_payload(ks, crypto_ts, &my_nonce);
+        let nonce_frame = build_rpc_frame(-2, &nonce_payload);
+
+        debug!(
+            %addr,
+            frame_len = nonce_frame.len(),
+            key_sel = format_args!("0x{:08x}", ks),
+            crypto_ts,
+            "Sending nonce"
+        );
+
+        wr.write_all(&nonce_frame).await.map_err(ProxyError::Io)?;
+        wr.flush().await.map_err(ProxyError::Io)?;
+
+        // ===== 2. Read server nonce (plaintext, seq=-2) =====
+        let (srv_seq, srv_nonce_payload) = timeout(
+            Duration::from_secs(ME_HANDSHAKE_TIMEOUT_SECS),
+            read_rpc_frame_plaintext(&mut rd),
+        )
+        .await
+        .map_err(|_| ProxyError::TgHandshakeTimeout)??;
+
+        if srv_seq != -2 {
+            return Err(ProxyError::InvalidHandshake(
+                format!("Expected seq=-2, got {}", srv_seq),
+            ));
+        }
+
+        let (schema, _srv_ts, srv_nonce) = parse_nonce_payload(&srv_nonce_payload)?;
+        if schema != RPC_CRYPTO_AES_U32 {
+            return Err(ProxyError::InvalidHandshake(
+                format!("Unsupported crypto schema: 0x{:x}", schema),
+            ));
+        }
+
+        debug!(%addr, "Nonce exchange OK, deriving keys");
+
+        // ===== 3. Derive AES-256-CBC keys =====
+        // C buffer layout:
+        //   [0..16]  nonce_server (srv_nonce)
+        //   [16..32] nonce_client (my_nonce)
+        //   [32..36] client_timestamp
+        //   [36..40] server_ip
+        //   [40..42] client_port
+        //   [42..48] "CLIENT" or "SERVER"
+        //   [48..52] client_ip
+        //   [52..54] server_port
+        //   [54..54+N] secret (proxy-secret binary)
+        //   [54+N..70+N] nonce_server
+        //   nonce_client(16)
+
+        let ts_bytes = crypto_ts.to_le_bytes();
+        let server_ip = addr_to_ip_u32(&peer_addr);
+        let client_ip = addr_to_ip_u32(&local_addr);
+        let server_ip_bytes = server_ip.to_le_bytes();
+        let client_ip_bytes = client_ip.to_le_bytes();
+        let server_port_bytes = peer_addr.port().to_le_bytes();
+        let client_port_bytes = local_addr.port().to_le_bytes();
+
+        let (wk, wi) = derive_middleproxy_keys(
+            &srv_nonce, &my_nonce, &ts_bytes,
+            Some(&server_ip_bytes), &client_port_bytes,
+            b"CLIENT",
+            Some(&client_ip_bytes), &server_port_bytes,
+            secret, None, None,
+        );
+        let (rk, ri) = derive_middleproxy_keys(
+            &srv_nonce, &my_nonce, &ts_bytes,
+            Some(&server_ip_bytes), &client_port_bytes,
+            b"SERVER",
+            Some(&client_ip_bytes), &server_port_bytes,
+            secret, None, None,
+        );
+
+        debug!(
+            %addr,
+            write_key = %hex::encode(&wk[..8]),
+            read_key = %hex::encode(&rk[..8]),
+            "Keys derived"
+        );
+
+        // ===== 4. Send encrypted handshake (seq=-1) =====
+        let hs_payload = build_handshake_payload(
+            client_ip, local_addr.port(),
+            server_ip, peer_addr.port(),
+        );
+        let hs_frame = build_rpc_frame(-1, &hs_payload);
+        let (encrypted_hs, write_iv) = cbc_encrypt_padded(&wk, &wi, &hs_frame)?;
+        wr.write_all(&encrypted_hs).await.map_err(ProxyError::Io)?;
+        wr.flush().await.map_err(ProxyError::Io)?;
+
+        debug!(%addr, enc_len = encrypted_hs.len(), "Sent encrypted handshake");
+
+        // ===== 5. Read encrypted handshake response (STREAMING) =====
+        // Server sends encrypted handshake. C crypto layer may send partial
+        // blocks (only complete 16-byte blocks get encrypted at a time).
+        // We read incrementally and decrypt block-by-block.
+        let deadline = Instant::now() + Duration::from_secs(ME_HANDSHAKE_TIMEOUT_SECS);
+        let mut enc_buf = BytesMut::with_capacity(256);
+        let mut dec_buf = BytesMut::with_capacity(256);
+        let mut read_iv = ri;
+        let mut handshake_ok = false;
+
+        while Instant::now() < deadline && !handshake_ok {
+            let remaining = deadline - Instant::now();
+            let mut tmp = [0u8; 256];
+            let n = match timeout(remaining, rd.read(&mut tmp)).await {
+                Ok(Ok(0)) => return Err(ProxyError::Io(std::io::Error::new(
+                    std::io::ErrorKind::UnexpectedEof, "ME closed during handshake",
+                ))),
+                Ok(Ok(n)) => n,
+                Ok(Err(e)) => return Err(ProxyError::Io(e)),
+                Err(_) => return Err(ProxyError::TgHandshakeTimeout),
+            };
+            enc_buf.extend_from_slice(&tmp[..n]);
+
+            // Decrypt complete 16-byte blocks
+            let blocks = enc_buf.len() / 16 * 16;
+            if blocks > 0 {
+                let mut chunk = vec![0u8; blocks];
+                chunk.copy_from_slice(&enc_buf[..blocks]);
+                let new_iv = cbc_decrypt_inplace(&rk, &read_iv, &mut chunk)?;
+                read_iv = new_iv;
+                dec_buf.extend_from_slice(&chunk);
+                let _ = enc_buf.split_to(blocks);
+            }
+
+            // Try to parse RPC frame from decrypted data
+            while dec_buf.len() >= 4 {
+                let fl = u32::from_le_bytes([
+                    dec_buf[0], dec_buf[1], dec_buf[2], dec_buf[3],
+                ]) as usize;
+
+                // Skip noop padding
+                if fl == 4 {
+                    let _ = dec_buf.split_to(4);
+                    continue;
+                }
+                if fl < 12 || fl > (1 << 24) {
+                    return Err(ProxyError::InvalidHandshake(
+                        format!("Bad HS response frame len: {}", fl),
+                    ));
+                }
+                if dec_buf.len() < fl {
+                    break; // need more data
+                }
+
+                let frame = dec_buf.split_to(fl);
+
+                // CRC32 check
+                let pe = fl - 4;
+                let ec = u32::from_le_bytes([
+                    frame[pe], frame[pe + 1], frame[pe + 2], frame[pe + 3],
+                ]);
+                let ac = crc32(&frame[..pe]);
+                if ec != ac {
+                    return Err(ProxyError::InvalidHandshake(
+                        format!("HS CRC mismatch: 0x{:08x} vs 0x{:08x}", ec, ac),
+                    ));
+                }
+
+                // Check type
+                let hs_type = u32::from_le_bytes([
+                    frame[8], frame[9], frame[10], frame[11],
+                ]);
+                if hs_type == RPC_HANDSHAKE_ERROR_U32 {
+                    let err_code = if frame.len() >= 16 {
+                        i32::from_le_bytes([frame[12], frame[13], frame[14], frame[15]])
+                    } else { -1 };
+                    return Err(ProxyError::InvalidHandshake(
+                        format!("ME rejected handshake (error={})", err_code),
+                    ));
+                }
+                if hs_type != RPC_HANDSHAKE_U32 {
+                    return Err(ProxyError::InvalidHandshake(
+                        format!("Expected HANDSHAKE 0x{:08x}, got 0x{:08x}", RPC_HANDSHAKE_U32, hs_type),
+                    ));
+                }
+
+                handshake_ok = true;
+                break;
+            }
+        }
+
+        if !handshake_ok {
+            return Err(ProxyError::TgHandshakeTimeout);
+        }
+
+        info!(%addr, "RPC handshake OK");
+
+        // ===== 6. Setup writer + reader =====
+        let rpc_w = Arc::new(Mutex::new(RpcWriter {
+            writer: wr,
+            key: wk,
+            iv: write_iv,
+            seq_no: 0,
+        }));
+        self.writers.write().await.push(rpc_w.clone());
+
+        let reg = self.registry.clone();
+        let w_pong = rpc_w.clone();
+        let w_pool = self.writers_arc();
+        tokio::spawn(async move {
+            if let Err(e) = reader_loop(rd, rk, read_iv, reg, enc_buf, dec_buf, w_pong.clone()).await {
+                warn!(error = %e, "ME reader ended");
+            }
+            // Remove dead writer from pool
+            let mut ws = w_pool.write().await;
+            ws.retain(|w| !Arc::ptr_eq(w, &w_pong));
+            info!(remaining = ws.len(), "Dead ME writer removed from pool");
+        });
+
+        Ok(())
+    }
+
+    pub async fn send_proxy_req(
+        &self,
+        conn_id: u64,
+        client_addr: SocketAddr,
+        our_addr: SocketAddr,
+        data: &[u8],
+        proto_flags: u32,
+    ) -> Result<()> {
+        let payload = build_proxy_req_payload(
+            conn_id, client_addr, our_addr, data,
+            self.proxy_tag.as_deref(), proto_flags,
+        );
+        loop {
+            let ws = self.writers.read().await;
+            if ws.is_empty() {
+                return Err(ProxyError::Proxy("All ME connections dead".into()));
+            }
+            let idx = self.rr.fetch_add(1, Ordering::Relaxed) as usize % ws.len();
+            let w = ws[idx].clone();
+            drop(ws);
+            match w.lock().await.send(&payload).await {
+                Ok(()) => return Ok(()),
+                Err(e) => {
+                    warn!(error = %e, "ME write failed, removing dead conn");
+                    let mut ws = self.writers.write().await;
+                    ws.retain(|o| !Arc::ptr_eq(o, &w));
+                    if ws.is_empty() {
+                        return Err(ProxyError::Proxy("All ME connections dead".into()));
+                    }
+                }
+            }
+        }
+    }
+
+    pub async fn send_close(&self, conn_id: u64) -> Result<()> {
+        let ws = self.writers.read().await;
+        if !ws.is_empty() {
+            let w = ws[0].clone();
+            drop(ws);
+            let mut p = Vec::with_capacity(12);
+            p.extend_from_slice(&RPC_CLOSE_EXT_U32.to_le_bytes());
+            p.extend_from_slice(&conn_id.to_le_bytes());
+            if let Err(e) = w.lock().await.send(&p).await {
+                debug!(error = %e, "ME close write failed");
+                let mut ws = self.writers.write().await;
+                ws.retain(|o| !Arc::ptr_eq(o, &w));
+            }
+        }
+        self.registry.unregister(conn_id).await;
+        Ok(())
+    }
+
+    pub fn connection_count(&self) -> usize {
+        self.writers.try_read().map(|w| w.len()).unwrap_or(0)
+    }
+}
+
+// ========== Reader Loop ==========
+
+async fn reader_loop(
+    mut rd: tokio::io::ReadHalf<TcpStream>,
+    dk: [u8; 32],
+    mut div: [u8; 16],
+    reg: Arc<ConnRegistry>,
+    mut enc_leftover: BytesMut,
+    mut dec: BytesMut,
+    writer: Arc<Mutex<RpcWriter>>,
+) -> Result<()> {
+    let mut raw = enc_leftover;
+    loop {
+        let mut tmp = [0u8; 16384];
+        let n = rd.read(&mut tmp).await.map_err(ProxyError::Io)?;
+        if n == 0 { return Ok(()); }
+        raw.extend_from_slice(&tmp[..n]);
+
+        // Decrypt complete 16-byte blocks
+        let blocks = raw.len() / 16 * 16;
+        if blocks > 0 {
+            let mut new_iv = [0u8; 16];
+            new_iv.copy_from_slice(&raw[blocks - 16..blocks]);
+            let mut chunk = vec![0u8; blocks];
+            chunk.copy_from_slice(&raw[..blocks]);
+            AesCbc::new(dk, div)
+                .decrypt_in_place(&mut chunk)
+                .map_err(|e| ProxyError::Crypto(format!("{}", e)))?;
+            div = new_iv;
+            dec.extend_from_slice(&chunk);
+            let _ = raw.split_to(blocks);
+        }
+
+        // Parse RPC frames
+        while dec.len() >= 12 {
+            let fl = u32::from_le_bytes([dec[0], dec[1], dec[2], dec[3]]) as usize;
+            if fl == 4 { let _ = dec.split_to(4); continue; }
+            if fl < 12 || fl > (1 << 24) {
+                warn!(frame_len = fl, "Invalid RPC frame len");
+                dec.clear();
+                break;
+            }
+            if dec.len() < fl { break; }
+
+            let frame = dec.split_to(fl);
+            let pe = fl - 4;
+            let ec = u32::from_le_bytes([frame[pe], frame[pe+1], frame[pe+2], frame[pe+3]]);
+            if crc32(&frame[..pe]) != ec {
+                warn!("CRC mismatch in data frame");
+                continue;
+            }
+
+            let payload = &frame[8..pe];
+            if payload.len() < 4 { continue; }
+            let pt = u32::from_le_bytes([payload[0], payload[1], payload[2], payload[3]]);
+            let body = &payload[4..];
+
+            if pt == RPC_PROXY_ANS_U32 && body.len() >= 12 {
+                let flags = u32::from_le_bytes(body[0..4].try_into().unwrap());
+                let cid = u64::from_le_bytes(body[4..12].try_into().unwrap());
+                let data = Bytes::copy_from_slice(&body[12..]);
+                trace!(cid, len = data.len(), flags, "ANS");
+                reg.route(cid, MeResponse::Data(data)).await;
+            } else if pt == RPC_SIMPLE_ACK_U32 && body.len() >= 12 {
+                let cid = u64::from_le_bytes(body[0..8].try_into().unwrap());
+                let cfm = u32::from_le_bytes(body[8..12].try_into().unwrap());
+                trace!(cid, cfm, "ACK");
+                reg.route(cid, MeResponse::Ack(cfm)).await;
+            } else if pt == RPC_CLOSE_EXT_U32 && body.len() >= 8 {
+                let cid = u64::from_le_bytes(body[0..8].try_into().unwrap());
+                debug!(cid, "CLOSE_EXT from ME");
+                reg.route(cid, MeResponse::Close).await;
+                reg.unregister(cid).await;
+            } else if pt == RPC_CLOSE_CONN_U32 && body.len() >= 8 {
+                let cid = u64::from_le_bytes(body[0..8].try_into().unwrap());
+                debug!(cid, "CLOSE_CONN from ME");
+                reg.route(cid, MeResponse::Close).await;
+                reg.unregister(cid).await;
+            } else if pt == RPC_PING_U32 && body.len() >= 8 {
+                let ping_id = i64::from_le_bytes(body[0..8].try_into().unwrap());
+                trace!(ping_id, "RPC_PING -> PONG");
+                let mut pong = Vec::with_capacity(12);
+                pong.extend_from_slice(&RPC_PONG_U32.to_le_bytes());
+                pong.extend_from_slice(&ping_id.to_le_bytes());
+                if let Err(e) = writer.lock().await.send(&pong).await {
+                    warn!(error = %e, "PONG send failed");
+                    break;
+                }
+            } else {
+                debug!(rpc_type = format_args!("0x{:08x}", pt), len = body.len(), "Unknown RPC");
+            }
+        }
+    }
+}
+
+// ========== Proto flags ==========
+
+/// Map ProtoTag to C-compatible RPC_PROXY_REQ transport flags.
+/// C: RPC_F_COMPACT(0x40000000)=abridged, RPC_F_MEDIUM(0x20000000)=intermediate/secure
+/// The 0x1000(magic) and 0x8(proxy_tag) are added inside build_proxy_req_payload.
+
+pub fn proto_flags_for_tag(tag: crate::protocol::constants::ProtoTag) -> u32 {
+    use crate::protocol::constants::*;
+    let mut flags = RPC_FLAG_HAS_AD_TAG | RPC_FLAG_MAGIC | RPC_FLAG_EXTMODE2;
+    match tag {
+        ProtoTag::Abridged     => flags | RPC_FLAG_ABRIDGED,
+        ProtoTag::Intermediate => flags | RPC_FLAG_INTERMEDIATE,
+        ProtoTag::Secure       => flags | RPC_FLAG_PAD | RPC_FLAG_INTERMEDIATE,
+    }
+}
+
+
+// ========== Health Monitor (Phase 4) ==========
+
+pub async fn me_health_monitor(
+    pool: Arc<MePool>,
+    rng: Arc<SecureRandom>,
+    min_connections: usize,
+) {
+    loop {
+        tokio::time::sleep(Duration::from_secs(30)).await;
+        let current = pool.writers.read().await.len();
+        if current < min_connections {
+            warn!(current, min = min_connections, "ME pool below minimum, reconnecting...");
+            let addrs = TG_MIDDLE_PROXIES_FLAT_V4.clone();
+            for &(ip, port) in addrs.iter() {
+                let needed = min_connections.saturating_sub(pool.writers.read().await.len());
+                if needed == 0 { break; }
+                for _ in 0..needed {
+                    let addr = SocketAddr::new(ip, port);
+                    match pool.connect_one(addr, &rng).await {
+                        Ok(()) => info!(%addr, "ME reconnected"),
+                        Err(e) => debug!(%addr, error = %e, "ME reconnect failed"),
+                    }
+                }
+            }
+        }
+    }
+}

src/transport/middle_proxy/codec.rs

@@ -0,0 +1,179 @@
+use tokio::io::{AsyncReadExt, AsyncWriteExt};
+
+use crate::crypto::{AesCbc, crc32};
+use crate::error::{ProxyError, Result};
+use crate::protocol::constants::*;
+
+pub(crate) fn build_rpc_frame(seq_no: i32, payload: &[u8]) -> Vec<u8> {
+    let total_len = (4 + 4 + payload.len() + 4) as u32;
+    let mut frame = Vec::with_capacity(total_len as usize);
+    frame.extend_from_slice(&total_len.to_le_bytes());
+    frame.extend_from_slice(&seq_no.to_le_bytes());
+    frame.extend_from_slice(payload);
+    let c = crc32(&frame);
+    frame.extend_from_slice(&c.to_le_bytes());
+    frame
+}
+
+pub(crate) async fn read_rpc_frame_plaintext(
+    rd: &mut (impl AsyncReadExt + Unpin),
+) -> Result<(i32, Vec<u8>)> {
+    let mut len_buf = [0u8; 4];
+    rd.read_exact(&mut len_buf).await.map_err(ProxyError::Io)?;
+    let total_len = u32::from_le_bytes(len_buf) as usize;
+
+    if !(12..=(1 << 24)).contains(&total_len) {
+        return Err(ProxyError::InvalidHandshake(format!(
+            "Bad RPC frame length: {total_len}"
+        )));
+    }
+
+    let mut rest = vec![0u8; total_len - 4];
+    rd.read_exact(&mut rest).await.map_err(ProxyError::Io)?;
+
+    let mut full = Vec::with_capacity(total_len);
+    full.extend_from_slice(&len_buf);
+    full.extend_from_slice(&rest);
+
+    let crc_offset = total_len - 4;
+    let expected_crc = u32::from_le_bytes(full[crc_offset..crc_offset + 4].try_into().unwrap());
+    let actual_crc = crc32(&full[..crc_offset]);
+    if expected_crc != actual_crc {
+        return Err(ProxyError::InvalidHandshake(format!(
+            "CRC mismatch: 0x{expected_crc:08x} vs 0x{actual_crc:08x}"
+        )));
+    }
+
+    let seq_no = i32::from_le_bytes(full[4..8].try_into().unwrap());
+    let payload = full[8..crc_offset].to_vec();
+    Ok((seq_no, payload))
+}
+
+pub(crate) fn build_nonce_payload(key_selector: u32, crypto_ts: u32, nonce: &[u8; 16]) -> [u8; 32] {
+    let mut p = [0u8; 32];
+    p[0..4].copy_from_slice(&RPC_NONCE_U32.to_le_bytes());
+    p[4..8].copy_from_slice(&key_selector.to_le_bytes());
+    p[8..12].copy_from_slice(&RPC_CRYPTO_AES_U32.to_le_bytes());
+    p[12..16].copy_from_slice(&crypto_ts.to_le_bytes());
+    p[16..32].copy_from_slice(nonce);
+    p
+}
+
+pub(crate) fn parse_nonce_payload(d: &[u8]) -> Result<(u32, u32, u32, [u8; 16])> {
+    if d.len() < 32 {
+        return Err(ProxyError::InvalidHandshake(format!(
+            "Nonce payload too short: {} bytes",
+            d.len()
+        )));
+    }
+
+    let t = u32::from_le_bytes(d[0..4].try_into().unwrap());
+    if t != RPC_NONCE_U32 {
+        return Err(ProxyError::InvalidHandshake(format!(
+            "Expected RPC_NONCE 0x{RPC_NONCE_U32:08x}, got 0x{t:08x}"
+        )));
+    }
+
+    let key_select = u32::from_le_bytes(d[4..8].try_into().unwrap());
+    let schema = u32::from_le_bytes(d[8..12].try_into().unwrap());
+    let ts = u32::from_le_bytes(d[12..16].try_into().unwrap());
+    let mut nonce = [0u8; 16];
+    nonce.copy_from_slice(&d[16..32]);
+    Ok((key_select, schema, ts, nonce))
+}
+
+pub(crate) fn build_handshake_payload(
+    our_ip: [u8; 4],
+    our_port: u16,
+    peer_ip: [u8; 4],
+    peer_port: u16,
+) -> [u8; 32] {
+    let mut p = [0u8; 32];
+    p[0..4].copy_from_slice(&RPC_HANDSHAKE_U32.to_le_bytes());
+
+    // Keep C memory layout compatibility for PID IPv4 bytes.
+    p[8..12].copy_from_slice(&our_ip);
+    p[12..14].copy_from_slice(&our_port.to_le_bytes());
+    let pid = (std::process::id() & 0xffff) as u16;
+    p[14..16].copy_from_slice(&pid.to_le_bytes());
+    let utime = std::time::SystemTime::now()
+        .duration_since(std::time::UNIX_EPOCH)
+        .unwrap_or_default()
+        .as_secs() as u32;
+    p[16..20].copy_from_slice(&utime.to_le_bytes());
+
+    p[20..24].copy_from_slice(&peer_ip);
+    p[24..26].copy_from_slice(&peer_port.to_le_bytes());
+    p
+}
+
+pub(crate) fn cbc_encrypt_padded(
+    key: &[u8; 32],
+    iv: &[u8; 16],
+    plaintext: &[u8],
+) -> Result<(Vec<u8>, [u8; 16])> {
+    let pad = (16 - (plaintext.len() % 16)) % 16;
+    let mut buf = plaintext.to_vec();
+    let pad_pattern: [u8; 4] = [0x04, 0x00, 0x00, 0x00];
+    for i in 0..pad {
+        buf.push(pad_pattern[i % 4]);
+    }
+
+    let cipher = AesCbc::new(*key, *iv);
+    cipher
+        .encrypt_in_place(&mut buf)
+        .map_err(|e| ProxyError::Crypto(format!("CBC encrypt: {e}")))?;
+
+    let mut new_iv = [0u8; 16];
+    if buf.len() >= 16 {
+        new_iv.copy_from_slice(&buf[buf.len() - 16..]);
+    }
+    Ok((buf, new_iv))
+}
+
+pub(crate) fn cbc_decrypt_inplace(
+    key: &[u8; 32],
+    iv: &[u8; 16],
+    data: &mut [u8],
+) -> Result<[u8; 16]> {
+    let mut new_iv = [0u8; 16];
+    if data.len() >= 16 {
+        new_iv.copy_from_slice(&data[data.len() - 16..]);
+    }
+
+    AesCbc::new(*key, *iv)
+        .decrypt_in_place(data)
+        .map_err(|e| ProxyError::Crypto(format!("CBC decrypt: {e}")))?;
+    Ok(new_iv)
+}
+
+pub(crate) struct RpcWriter {
+    pub(crate) writer: tokio::io::WriteHalf<tokio::net::TcpStream>,
+    pub(crate) key: [u8; 32],
+    pub(crate) iv: [u8; 16],
+    pub(crate) seq_no: i32,
+}
+
+impl RpcWriter {
+    pub(crate) async fn send(&mut self, payload: &[u8]) -> Result<()> {
+        let frame = build_rpc_frame(self.seq_no, payload);
+        self.seq_no += 1;
+
+        let pad = (16 - (frame.len() % 16)) % 16;
+        let mut buf = frame;
+        let pad_pattern: [u8; 4] = [0x04, 0x00, 0x00, 0x00];
+        for i in 0..pad {
+            buf.push(pad_pattern[i % 4]);
+        }
+
+        let cipher = AesCbc::new(self.key, self.iv);
+        cipher
+            .encrypt_in_place(&mut buf)
+            .map_err(|e| ProxyError::Crypto(format!("{e}")))?;
+
+        if buf.len() >= 16 {
+            self.iv.copy_from_slice(&buf[buf.len() - 16..]);
+        }
+        self.writer.write_all(&buf).await.map_err(ProxyError::Io)
+    }
+}

src/transport/middle_proxy/health.rs

@@ -0,0 +1,38 @@
+use std::net::SocketAddr;
+use std::sync::Arc;
+use std::time::Duration;
+
+use tracing::{debug, info, warn};
+
+use crate::crypto::SecureRandom;
+use crate::protocol::constants::TG_MIDDLE_PROXIES_FLAT_V4;
+
+use super::MePool;
+
+pub async fn me_health_monitor(pool: Arc<MePool>, rng: Arc<SecureRandom>, min_connections: usize) {
+    loop {
+        tokio::time::sleep(Duration::from_secs(30)).await;
+        let current = pool.connection_count();
+        if current < min_connections {
+            warn!(
+                current,
+                min = min_connections,
+                "ME pool below minimum, reconnecting..."
+            );
+            let addrs = TG_MIDDLE_PROXIES_FLAT_V4.clone();
+            for &(ip, port) in addrs.iter() {
+                let needed = min_connections.saturating_sub(pool.connection_count());
+                if needed == 0 {
+                    break;
+                }
+                for _ in 0..needed {
+                    let addr = SocketAddr::new(ip, port);
+                    match pool.connect_one(addr, &rng).await {
+                        Ok(()) => info!(%addr, "ME reconnected"),
+                        Err(e) => debug!(%addr, error = %e, "ME reconnect failed"),
+                    }
+                }
+            }
+        }
+    }
+}

src/transport/middle_proxy/mod.rs

@@ -0,0 +1,26 @@
+//! Middle Proxy RPC transport.
+
+mod codec;
+mod health;
+mod pool;
+mod pool_nat;
+mod reader;
+mod registry;
+mod send;
+mod secret;
+mod wire;
+
+use bytes::Bytes;
+
+pub use health::me_health_monitor;
+pub use pool::MePool;
+pub use registry::ConnRegistry;
+pub use secret::fetch_proxy_secret;
+pub use wire::proto_flags_for_tag;
+
+#[derive(Debug)]
+pub enum MeResponse {
+    Data { flags: u32, data: Bytes },
+    Ack(u32),
+    Close,
+}

src/transport/middle_proxy/pool.rs

@@ -0,0 +1,499 @@
+use std::net::{IpAddr, SocketAddr};
+use std::sync::Arc;
+use std::sync::OnceLock;
+use std::sync::atomic::AtomicU64;
+use std::time::Duration;
+
+use bytes::BytesMut;
+use rand::Rng;
+use tokio::io::{AsyncReadExt, AsyncWriteExt};
+use tokio::net::TcpStream;
+use tokio::sync::{Mutex, RwLock};
+use tokio::time::{Instant, timeout};
+use tracing::{debug, info, warn};
+
+use crate::crypto::{SecureRandom, build_middleproxy_prekey, derive_middleproxy_keys, sha256};
+use crate::error::{ProxyError, Result};
+use crate::protocol::constants::*;
+
+use super::ConnRegistry;
+use super::codec::{
+    RpcWriter, build_handshake_payload, build_nonce_payload, build_rpc_frame, cbc_decrypt_inplace,
+    cbc_encrypt_padded, parse_nonce_payload, read_rpc_frame_plaintext,
+};
+use super::reader::reader_loop;
+use super::wire::{IpMaterial, extract_ip_material};
+
+const ME_ACTIVE_PING_SECS: u64 = 25;
+const ME_ACTIVE_PING_JITTER_SECS: i64 = 5;
+
+pub struct MePool {
+    pub(super) registry: Arc<ConnRegistry>,
+    pub(super) writers: Arc<RwLock<Vec<(SocketAddr, Arc<Mutex<RpcWriter>>)>>> ,
+    pub(super) rr: AtomicU64,
+    pub(super) proxy_tag: Option<Vec<u8>>,
+    proxy_secret: Vec<u8>,
+    pub(super) nat_ip_cfg: Option<IpAddr>,
+    pub(super) nat_ip_detected: OnceLock<IpAddr>,
+    pub(super) nat_probe: bool,
+    pub(super) nat_stun: Option<String>,
+    pool_size: usize,
+}
+
+impl MePool {
+    pub fn new(
+        proxy_tag: Option<Vec<u8>>,
+        proxy_secret: Vec<u8>,
+        nat_ip: Option<IpAddr>,
+        nat_probe: bool,
+        nat_stun: Option<String>,
+    ) -> Arc<Self> {
+        Arc::new(Self {
+            registry: Arc::new(ConnRegistry::new()),
+            writers: Arc::new(RwLock::new(Vec::new())),
+            rr: AtomicU64::new(0),
+            proxy_tag,
+            proxy_secret,
+            nat_ip_cfg: nat_ip,
+            nat_ip_detected: OnceLock::new(),
+            nat_probe,
+            nat_stun,
+            pool_size: 2,
+        })
+    }
+
+    pub fn has_proxy_tag(&self) -> bool {
+        self.proxy_tag.is_some()
+    }
+
+    pub fn translate_our_addr(&self, addr: SocketAddr) -> SocketAddr {
+        let ip = self.translate_ip_for_nat(addr.ip());
+        SocketAddr::new(ip, addr.port())
+    }
+
+    pub fn registry(&self) -> &Arc<ConnRegistry> {
+        &self.registry
+    }
+
+    fn writers_arc(&self) -> Arc<RwLock<Vec<(SocketAddr, Arc<Mutex<RpcWriter>>)>>>
+    {
+        self.writers.clone()
+    }
+
+    fn key_selector(&self) -> u32 {
+        if self.proxy_secret.len() >= 4 {
+            u32::from_le_bytes([
+                self.proxy_secret[0],
+                self.proxy_secret[1],
+                self.proxy_secret[2],
+                self.proxy_secret[3],
+            ])
+        } else {
+            0
+        }
+    }
+
+    pub async fn init(self: &Arc<Self>, pool_size: usize, rng: &SecureRandom) -> Result<()> {
+        let addrs = &*TG_MIDDLE_PROXIES_FLAT_V4;
+        let ks = self.key_selector();
+        info!(
+            me_servers = addrs.len(),
+            pool_size,
+            key_selector = format_args!("0x{ks:08x}"),
+            secret_len = self.proxy_secret.len(),
+            "Initializing ME pool"
+        );
+
+        for &(ip, port) in addrs.iter() {
+            for i in 0..pool_size {
+                let addr = SocketAddr::new(ip, port);
+                match self.connect_one(addr, rng).await {
+                    Ok(()) => info!(%addr, idx = i, "ME connected"),
+                    Err(e) => warn!(%addr, idx = i, error = %e, "ME connect failed"),
+                }
+            }
+            if self.writers.read().await.len() >= pool_size {
+                break;
+            }
+        }
+
+        if self.writers.read().await.is_empty() {
+            return Err(ProxyError::Proxy("No ME connections".into()));
+        }
+        Ok(())
+    }
+
+    pub(crate) async fn connect_one(
+        self: &Arc<Self>,
+        addr: SocketAddr,
+        rng: &SecureRandom,
+    ) -> Result<()> {
+        let secret = &self.proxy_secret;
+        if secret.len() < 32 {
+            return Err(ProxyError::Proxy(
+                "proxy-secret too short for ME auth".into(),
+            ));
+        }
+
+        let stream = timeout(
+            Duration::from_secs(ME_CONNECT_TIMEOUT_SECS),
+            TcpStream::connect(addr),
+        )
+        .await
+        .map_err(|_| ProxyError::ConnectionTimeout {
+            addr: addr.to_string(),
+        })?
+        .map_err(ProxyError::Io)?;
+        stream.set_nodelay(true).ok();
+
+        let local_addr = stream.local_addr().map_err(ProxyError::Io)?;
+        let peer_addr = stream.peer_addr().map_err(ProxyError::Io)?;
+        let _ = self.maybe_detect_nat_ip(local_addr.ip()).await;
+        let reflected = if self.nat_probe {
+            self.maybe_reflect_public_addr().await
+        } else {
+            None
+        };
+        let local_addr_nat = self.translate_our_addr_with_reflection(local_addr, reflected);
+        let peer_addr_nat =
+            SocketAddr::new(self.translate_ip_for_nat(peer_addr.ip()), peer_addr.port());
+        let (mut rd, mut wr) = tokio::io::split(stream);
+
+        let my_nonce: [u8; 16] = rng.bytes(16).try_into().unwrap();
+        let crypto_ts = std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .unwrap_or_default()
+            .as_secs() as u32;
+
+        let ks = self.key_selector();
+        let nonce_payload = build_nonce_payload(ks, crypto_ts, &my_nonce);
+        let nonce_frame = build_rpc_frame(-2, &nonce_payload);
+        let dump = hex_dump(&nonce_frame[..nonce_frame.len().min(44)]);
+        info!(
+            key_selector = format_args!("0x{ks:08x}"),
+            crypto_ts,
+            frame_len = nonce_frame.len(),
+            nonce_frame_hex = %dump,
+            "Sending ME nonce frame"
+        );
+        wr.write_all(&nonce_frame).await.map_err(ProxyError::Io)?;
+        wr.flush().await.map_err(ProxyError::Io)?;
+
+        let (srv_seq, srv_nonce_payload) = timeout(
+            Duration::from_secs(ME_HANDSHAKE_TIMEOUT_SECS),
+            read_rpc_frame_plaintext(&mut rd),
+        )
+        .await
+        .map_err(|_| ProxyError::TgHandshakeTimeout)??;
+
+        if srv_seq != -2 {
+            return Err(ProxyError::InvalidHandshake(format!(
+                "Expected seq=-2, got {srv_seq}"
+            )));
+        }
+
+        let (srv_key_select, schema, srv_ts, srv_nonce) = parse_nonce_payload(&srv_nonce_payload)?;
+        if schema != RPC_CRYPTO_AES_U32 {
+            warn!(schema = format_args!("0x{schema:08x}"), "Unsupported ME crypto schema");
+            return Err(ProxyError::InvalidHandshake(format!(
+                "Unsupported crypto schema: 0x{schema:x}"
+            )));
+        }
+
+        if srv_key_select != ks {
+            return Err(ProxyError::InvalidHandshake(format!(
+                "Server key_select 0x{srv_key_select:08x} != client 0x{ks:08x}"
+            )));
+        }
+
+        let skew = crypto_ts.abs_diff(srv_ts);
+        if skew > 30 {
+            return Err(ProxyError::InvalidHandshake(format!(
+                "nonce crypto_ts skew too large: client={crypto_ts}, server={srv_ts}, skew={skew}s"
+            )));
+        }
+
+        info!(
+            %local_addr,
+            %local_addr_nat,
+            reflected_ip = reflected.map(|r| r.ip()).as_ref().map(ToString::to_string),
+            %peer_addr,
+            %peer_addr_nat,
+            key_selector = format_args!("0x{ks:08x}"),
+            crypto_schema = format_args!("0x{schema:08x}"),
+            skew_secs = skew,
+            "ME key derivation parameters"
+        );
+
+        let ts_bytes = crypto_ts.to_le_bytes();
+        let server_port_bytes = peer_addr_nat.port().to_le_bytes();
+        let client_port_bytes = local_addr_nat.port().to_le_bytes();
+
+        let server_ip = extract_ip_material(peer_addr_nat);
+        let client_ip = extract_ip_material(local_addr_nat);
+
+        let (srv_ip_opt, clt_ip_opt, clt_v6_opt, srv_v6_opt, hs_our_ip, hs_peer_ip) =
+            match (server_ip, client_ip) {
+                (IpMaterial::V4(srv), IpMaterial::V4(clt)) => {
+                    (Some(srv), Some(clt), None, None, clt, srv)
+                }
+                (IpMaterial::V6(srv), IpMaterial::V6(clt)) => {
+                    let zero = [0u8; 4];
+                    (None, None, Some(clt), Some(srv), zero, zero)
+                }
+                _ => {
+                    return Err(ProxyError::InvalidHandshake(
+                        "mixed IPv4/IPv6 endpoints are not supported for ME key derivation"
+                            .to_string(),
+                    ));
+                }
+            };
+
+        let diag_level: u8 = std::env::var("ME_DIAG")
+            .ok()
+            .and_then(|v| v.parse().ok())
+            .unwrap_or(0);
+
+        let prekey_client = build_middleproxy_prekey(
+            &srv_nonce,
+            &my_nonce,
+            &ts_bytes,
+            srv_ip_opt.as_ref().map(|x| &x[..]),
+            &client_port_bytes,
+            b"CLIENT",
+            clt_ip_opt.as_ref().map(|x| &x[..]),
+            &server_port_bytes,
+            secret,
+            clt_v6_opt.as_ref(),
+            srv_v6_opt.as_ref(),
+        );
+        let prekey_server = build_middleproxy_prekey(
+            &srv_nonce,
+            &my_nonce,
+            &ts_bytes,
+            srv_ip_opt.as_ref().map(|x| &x[..]),
+            &client_port_bytes,
+            b"SERVER",
+            clt_ip_opt.as_ref().map(|x| &x[..]),
+            &server_port_bytes,
+            secret,
+            clt_v6_opt.as_ref(),
+            srv_v6_opt.as_ref(),
+        );
+
+        let (wk, wi) = derive_middleproxy_keys(
+            &srv_nonce,
+            &my_nonce,
+            &ts_bytes,
+            srv_ip_opt.as_ref().map(|x| &x[..]),
+            &client_port_bytes,
+            b"CLIENT",
+            clt_ip_opt.as_ref().map(|x| &x[..]),
+            &server_port_bytes,
+            secret,
+            clt_v6_opt.as_ref(),
+            srv_v6_opt.as_ref(),
+        );
+        let (rk, ri) = derive_middleproxy_keys(
+            &srv_nonce,
+            &my_nonce,
+            &ts_bytes,
+            srv_ip_opt.as_ref().map(|x| &x[..]),
+            &client_port_bytes,
+            b"SERVER",
+            clt_ip_opt.as_ref().map(|x| &x[..]),
+            &server_port_bytes,
+            secret,
+            clt_v6_opt.as_ref(),
+            srv_v6_opt.as_ref(),
+        );
+
+        let hs_payload =
+            build_handshake_payload(hs_our_ip, local_addr.port(), hs_peer_ip, peer_addr.port());
+        let hs_frame = build_rpc_frame(-1, &hs_payload);
+        if diag_level >= 1 {
+            info!(
+                write_key = %hex_dump(&wk),
+                write_iv = %hex_dump(&wi),
+                read_key = %hex_dump(&rk),
+                read_iv = %hex_dump(&ri),
+                srv_ip = %srv_ip_opt.map(|ip| hex_dump(&ip)).unwrap_or_default(),
+                clt_ip = %clt_ip_opt.map(|ip| hex_dump(&ip)).unwrap_or_default(),
+                srv_port = %hex_dump(&server_port_bytes),
+                clt_port = %hex_dump(&client_port_bytes),
+                crypto_ts = %hex_dump(&ts_bytes),
+                nonce_srv = %hex_dump(&srv_nonce),
+                nonce_clt = %hex_dump(&my_nonce),
+                prekey_sha256_client = %hex_dump(&sha256(&prekey_client)),
+                prekey_sha256_server = %hex_dump(&sha256(&prekey_server)),
+                hs_plain = %hex_dump(&hs_frame),
+                proxy_secret_sha256 = %hex_dump(&sha256(secret)),
+                "ME diag: derived keys and handshake plaintext"
+            );
+        }
+        if diag_level >= 2 {
+            info!(
+                prekey_client = %hex_dump(&prekey_client),
+                prekey_server = %hex_dump(&prekey_server),
+                "ME diag: full prekey buffers"
+            );
+        }
+
+        let (encrypted_hs, write_iv) = cbc_encrypt_padded(&wk, &wi, &hs_frame)?;
+        if diag_level >= 1 {
+            info!(
+                hs_cipher = %hex_dump(&encrypted_hs),
+                "ME diag: handshake ciphertext"
+            );
+        }
+        wr.write_all(&encrypted_hs).await.map_err(ProxyError::Io)?;
+        wr.flush().await.map_err(ProxyError::Io)?;
+
+        let deadline = Instant::now() + Duration::from_secs(ME_HANDSHAKE_TIMEOUT_SECS);
+        let mut enc_buf = BytesMut::with_capacity(256);
+        let mut dec_buf = BytesMut::with_capacity(256);
+        let mut read_iv = ri;
+        let mut handshake_ok = false;
+
+        while Instant::now() < deadline && !handshake_ok {
+            let remaining = deadline - Instant::now();
+            let mut tmp = [0u8; 256];
+            let n = match timeout(remaining, rd.read(&mut tmp)).await {
+                Ok(Ok(0)) => {
+                    return Err(ProxyError::Io(std::io::Error::new(
+                        std::io::ErrorKind::UnexpectedEof,
+                        "ME closed during handshake",
+                    )));
+                }
+                Ok(Ok(n)) => n,
+                Ok(Err(e)) => return Err(ProxyError::Io(e)),
+                Err(_) => return Err(ProxyError::TgHandshakeTimeout),
+            };
+
+            enc_buf.extend_from_slice(&tmp[..n]);
+
+            let blocks = enc_buf.len() / 16 * 16;
+            if blocks > 0 {
+                let mut chunk = vec![0u8; blocks];
+                chunk.copy_from_slice(&enc_buf[..blocks]);
+                read_iv = cbc_decrypt_inplace(&rk, &read_iv, &mut chunk)?;
+                dec_buf.extend_from_slice(&chunk);
+                let _ = enc_buf.split_to(blocks);
+            }
+
+            while dec_buf.len() >= 4 {
+                let fl = u32::from_le_bytes(dec_buf[0..4].try_into().unwrap()) as usize;
+
+                if fl == 4 {
+                    let _ = dec_buf.split_to(4);
+                    continue;
+                }
+                if !(12..=(1 << 24)).contains(&fl) {
+                    return Err(ProxyError::InvalidHandshake(format!(
+                        "Bad HS response frame len: {fl}"
+                    )));
+                }
+                if dec_buf.len() < fl {
+                    break;
+                }
+
+                let frame = dec_buf.split_to(fl);
+                let pe = fl - 4;
+                let ec = u32::from_le_bytes(frame[pe..pe + 4].try_into().unwrap());
+                let ac = crate::crypto::crc32(&frame[..pe]);
+                if ec != ac {
+                    return Err(ProxyError::InvalidHandshake(format!(
+                        "HS CRC mismatch: 0x{ec:08x} vs 0x{ac:08x}"
+                    )));
+                }
+
+                let hs_type = u32::from_le_bytes(frame[8..12].try_into().unwrap());
+                if hs_type == RPC_HANDSHAKE_ERROR_U32 {
+                    let err_code = if frame.len() >= 16 {
+                        i32::from_le_bytes(frame[12..16].try_into().unwrap())
+                    } else {
+                        -1
+                    };
+                    return Err(ProxyError::InvalidHandshake(format!(
+                        "ME rejected handshake (error={err_code})"
+                    )));
+                }
+                if hs_type != RPC_HANDSHAKE_U32 {
+                    return Err(ProxyError::InvalidHandshake(format!(
+                        "Expected HANDSHAKE 0x{RPC_HANDSHAKE_U32:08x}, got 0x{hs_type:08x}"
+                    )));
+                }
+
+                handshake_ok = true;
+                break;
+            }
+        }
+
+        if !handshake_ok {
+            return Err(ProxyError::TgHandshakeTimeout);
+        }
+
+        info!(%addr, "RPC handshake OK");
+
+        let rpc_w = Arc::new(Mutex::new(RpcWriter {
+            writer: wr,
+            key: wk,
+            iv: write_iv,
+            seq_no: 0,
+        }));
+        self.writers.write().await.push((addr, rpc_w.clone()));
+
+        let reg = self.registry.clone();
+        let w_pong = rpc_w.clone();
+        let w_pool = self.writers_arc();
+        let w_ping = rpc_w.clone();
+        let w_pool_ping = self.writers_arc();
+        tokio::spawn(async move {
+            if let Err(e) =
+                reader_loop(rd, rk, read_iv, reg, enc_buf, dec_buf, w_pong.clone()).await
+            {
+                warn!(error = %e, "ME reader ended");
+            }
+            let mut ws = w_pool.write().await;
+            ws.retain(|(_, w)| !Arc::ptr_eq(w, &w_pong));
+            info!(remaining = ws.len(), "Dead ME writer removed from pool");
+        });
+        tokio::spawn(async move {
+            let mut ping_id: i64 = rand::random::<i64>();
+            loop {
+                let jitter = rand::rng()
+                    .random_range(-ME_ACTIVE_PING_JITTER_SECS..=ME_ACTIVE_PING_JITTER_SECS);
+                let wait = (ME_ACTIVE_PING_SECS as i64 + jitter).max(5) as u64;
+                tokio::time::sleep(Duration::from_secs(wait)).await;
+                let mut p = Vec::with_capacity(12);
+                p.extend_from_slice(&RPC_PING_U32.to_le_bytes());
+                p.extend_from_slice(&ping_id.to_le_bytes());
+                ping_id = ping_id.wrapping_add(1);
+                if let Err(e) = w_ping.lock().await.send(&p).await {
+                    debug!(error = %e, "Active ME ping failed, removing dead writer");
+                    let mut ws = w_pool_ping.write().await;
+                    ws.retain(|(_, w)| !Arc::ptr_eq(w, &w_ping));
+                    break;
+                }
+            }
+        });
+
+        Ok(())
+    }
+
+}
+
+fn hex_dump(data: &[u8]) -> String {
+    const MAX: usize = 64;
+    let mut out = String::with_capacity(data.len() * 2 + 3);
+    for (i, b) in data.iter().take(MAX).enumerate() {
+        if i > 0 {
+            out.push(' ');
+        }
+        out.push_str(&format!("{b:02x}"));
+    }
+    if data.len() > MAX {
+        out.push_str(" …");
+    }
+    out
+}

src/transport/middle_proxy/pool_nat.rs

@@ -0,0 +1,200 @@
+use std::net::{IpAddr, Ipv4Addr};
+
+use tracing::{info, warn};
+
+use crate::error::{ProxyError, Result};
+
+use super::MePool;
+
+impl MePool {
+    pub(super) fn translate_ip_for_nat(&self, ip: IpAddr) -> IpAddr {
+        let nat_ip = self
+            .nat_ip_cfg
+            .or_else(|| self.nat_ip_detected.get().copied());
+
+        let Some(nat_ip) = nat_ip else {
+            return ip;
+        };
+
+        match (ip, nat_ip) {
+            (IpAddr::V4(src), IpAddr::V4(dst))
+                if is_privateish(IpAddr::V4(src))
+                    || src.is_loopback()
+                    || src.is_unspecified() =>
+            {
+                IpAddr::V4(dst)
+            }
+            (IpAddr::V6(src), IpAddr::V6(dst)) if src.is_loopback() || src.is_unspecified() => {
+                IpAddr::V6(dst)
+            }
+            (orig, _) => orig,
+        }
+    }
+
+    pub(super) fn translate_our_addr_with_reflection(
+        &self,
+        addr: std::net::SocketAddr,
+        reflected: Option<std::net::SocketAddr>,
+    ) -> std::net::SocketAddr {
+        let ip = if let Some(r) = reflected {
+            // Use reflected IP (not port) only when local address is non-public.
+            if is_privateish(addr.ip()) || addr.ip().is_loopback() || addr.ip().is_unspecified() {
+                r.ip()
+            } else {
+                self.translate_ip_for_nat(addr.ip())
+            }
+        } else {
+            self.translate_ip_for_nat(addr.ip())
+        };
+
+        // Keep the kernel-assigned TCP source port; STUN port can differ.
+        std::net::SocketAddr::new(ip, addr.port())
+    }
+
+    pub(super) async fn maybe_detect_nat_ip(&self, local_ip: IpAddr) -> Option<IpAddr> {
+        if self.nat_ip_cfg.is_some() {
+            return self.nat_ip_cfg;
+        }
+
+        if !(is_privateish(local_ip) || local_ip.is_loopback() || local_ip.is_unspecified()) {
+            return None;
+        }
+
+        if let Some(ip) = self.nat_ip_detected.get().copied() {
+            return Some(ip);
+        }
+
+        match fetch_public_ipv4().await {
+            Ok(Some(ip)) => {
+                let _ = self.nat_ip_detected.set(IpAddr::V4(ip));
+                info!(public_ip = %ip, "Auto-detected public IP for NAT translation");
+                Some(IpAddr::V4(ip))
+            }
+            Ok(None) => None,
+            Err(e) => {
+                warn!(error = %e, "Failed to auto-detect public IP");
+                None
+            }
+        }
+    }
+
+    pub(super) async fn maybe_reflect_public_addr(&self) -> Option<std::net::SocketAddr> {
+        let stun_addr = self
+            .nat_stun
+            .clone()
+            .unwrap_or_else(|| "stun.l.google.com:19302".to_string());
+        match fetch_stun_binding(&stun_addr).await {
+            Ok(sa) => {
+                if let Some(sa) = sa {
+                    info!(%sa, "NAT probe: reflected address");
+                }
+                sa
+            }
+            Err(e) => {
+                warn!(error = %e, "NAT probe failed");
+                None
+            }
+        }
+    }
+}
+
+async fn fetch_public_ipv4() -> Result<Option<Ipv4Addr>> {
+    let res = reqwest::get("https://checkip.amazonaws.com").await.map_err(|e| {
+        ProxyError::Proxy(format!("public IP detection request failed: {e}"))
+    })?;
+
+    let text = res.text().await.map_err(|e| {
+        ProxyError::Proxy(format!("public IP detection read failed: {e}"))
+    })?;
+
+    let ip = text.trim().parse().ok();
+    Ok(ip)
+}
+
+async fn fetch_stun_binding(stun_addr: &str) -> Result<Option<std::net::SocketAddr>> {
+    use rand::RngCore;
+    use tokio::net::UdpSocket;
+
+    let socket = UdpSocket::bind("0.0.0.0:0")
+        .await
+        .map_err(|e| ProxyError::Proxy(format!("STUN bind failed: {e}")))?;
+    socket
+        .connect(stun_addr)
+        .await
+        .map_err(|e| ProxyError::Proxy(format!("STUN connect failed: {e}")))?;
+
+    // Build minimal Binding Request.
+    let mut req = vec![0u8; 20];
+    req[0..2].copy_from_slice(&0x0001u16.to_be_bytes()); // Binding Request
+    req[2..4].copy_from_slice(&0u16.to_be_bytes()); // length
+    req[4..8].copy_from_slice(&0x2112A442u32.to_be_bytes()); // magic cookie
+    rand::thread_rng().fill_bytes(&mut req[8..20]);
+
+    socket
+        .send(&req)
+        .await
+        .map_err(|e| ProxyError::Proxy(format!("STUN send failed: {e}")))?;
+
+    let mut buf = [0u8; 128];
+    let n = socket
+        .recv(&mut buf)
+        .await
+        .map_err(|e| ProxyError::Proxy(format!("STUN recv failed: {e}")))?;
+    if n < 20 {
+        return Ok(None);
+    }
+
+    // Parse attributes.
+    let mut idx = 20;
+    while idx + 4 <= n {
+        let atype = u16::from_be_bytes(buf[idx..idx + 2].try_into().unwrap());
+        let alen = u16::from_be_bytes(buf[idx + 2..idx + 4].try_into().unwrap()) as usize;
+        idx += 4;
+        if idx + alen > n {
+            break;
+        }
+        match atype {
+            0x0020 /* XOR-MAPPED-ADDRESS */ | 0x0001 /* MAPPED-ADDRESS */ => {
+                if alen < 8 {
+                    break;
+                }
+                let family = buf[idx + 1];
+                if family != 0x01 {
+                    // only IPv4 supported here
+                    break;
+                }
+                let port_bytes = [buf[idx + 2], buf[idx + 3]];
+                let ip_bytes = [buf[idx + 4], buf[idx + 5], buf[idx + 6], buf[idx + 7]];
+
+                let (port, ip) = if atype == 0x0020 {
+                    let magic = 0x2112A442u32.to_be_bytes();
+                    let port = u16::from_be_bytes(port_bytes) ^ ((magic[0] as u16) << 8 | magic[1] as u16);
+                    let ip = [
+                        ip_bytes[0] ^ magic[0],
+                        ip_bytes[1] ^ magic[1],
+                        ip_bytes[2] ^ magic[2],
+                        ip_bytes[3] ^ magic[3],
+                    ];
+                    (port, ip)
+                } else {
+                    (u16::from_be_bytes(port_bytes), ip_bytes)
+                };
+                return Ok(Some(std::net::SocketAddr::new(
+                    IpAddr::V4(Ipv4Addr::new(ip[0], ip[1], ip[2], ip[3])),
+                    port,
+                )));
+            }
+            _ => {}
+        }
+        idx += (alen + 3) & !3; // 4-byte alignment
+    }
+
+    Ok(None)
+}
+
+fn is_privateish(ip: IpAddr) -> bool {
+    match ip {
+        IpAddr::V4(v4) => v4.is_private() || v4.is_link_local(),
+        IpAddr::V6(v6) => v6.is_unique_local(),
+    }
+}

src/transport/middle_proxy/reader.rs

@@ -0,0 +1,141 @@
+use std::sync::Arc;
+
+use bytes::{Bytes, BytesMut};
+use tokio::io::AsyncReadExt;
+use tokio::net::TcpStream;
+use tokio::sync::Mutex;
+use tracing::{debug, trace, warn};
+
+use crate::crypto::{AesCbc, crc32};
+use crate::error::{ProxyError, Result};
+use crate::protocol::constants::*;
+
+use super::codec::RpcWriter;
+use super::{ConnRegistry, MeResponse};
+
+pub(crate) async fn reader_loop(
+    mut rd: tokio::io::ReadHalf<TcpStream>,
+    dk: [u8; 32],
+    mut div: [u8; 16],
+    reg: Arc<ConnRegistry>,
+    enc_leftover: BytesMut,
+    mut dec: BytesMut,
+    writer: Arc<Mutex<RpcWriter>>,
+) -> Result<()> {
+    let mut raw = enc_leftover;
+
+    loop {
+        let mut tmp = [0u8; 16_384];
+        let n = rd.read(&mut tmp).await.map_err(ProxyError::Io)?;
+        if n == 0 {
+            return Ok(());
+        }
+        raw.extend_from_slice(&tmp[..n]);
+
+        let blocks = raw.len() / 16 * 16;
+        if blocks > 0 {
+            let mut new_iv = [0u8; 16];
+            new_iv.copy_from_slice(&raw[blocks - 16..blocks]);
+
+            let mut chunk = vec![0u8; blocks];
+            chunk.copy_from_slice(&raw[..blocks]);
+            AesCbc::new(dk, div)
+                .decrypt_in_place(&mut chunk)
+                .map_err(|e| ProxyError::Crypto(format!("{e}")))?;
+            div = new_iv;
+            dec.extend_from_slice(&chunk);
+            let _ = raw.split_to(blocks);
+        }
+
+        while dec.len() >= 12 {
+            let fl = u32::from_le_bytes(dec[0..4].try_into().unwrap()) as usize;
+            if fl == 4 {
+                let _ = dec.split_to(4);
+                continue;
+            }
+            if !(12..=(1 << 24)).contains(&fl) {
+                warn!(frame_len = fl, "Invalid RPC frame len");
+                dec.clear();
+                break;
+            }
+            if dec.len() < fl {
+                break;
+            }
+
+            let frame = dec.split_to(fl);
+            let pe = fl - 4;
+            let ec = u32::from_le_bytes(frame[pe..pe + 4].try_into().unwrap());
+            if crc32(&frame[..pe]) != ec {
+                warn!("CRC mismatch in data frame");
+                continue;
+            }
+
+            let payload = &frame[8..pe];
+            if payload.len() < 4 {
+                continue;
+            }
+
+            let pt = u32::from_le_bytes(payload[0..4].try_into().unwrap());
+            let body = &payload[4..];
+
+            if pt == RPC_PROXY_ANS_U32 && body.len() >= 12 {
+                let flags = u32::from_le_bytes(body[0..4].try_into().unwrap());
+                let cid = u64::from_le_bytes(body[4..12].try_into().unwrap());
+                let data = Bytes::copy_from_slice(&body[12..]);
+                trace!(cid, flags, len = data.len(), "RPC_PROXY_ANS");
+
+                let routed = reg.route(cid, MeResponse::Data { flags, data }).await;
+                if !routed {
+                    reg.unregister(cid).await;
+                    send_close_conn(&writer, cid).await;
+                }
+            } else if pt == RPC_SIMPLE_ACK_U32 && body.len() >= 12 {
+                let cid = u64::from_le_bytes(body[0..8].try_into().unwrap());
+                let cfm = u32::from_le_bytes(body[8..12].try_into().unwrap());
+                trace!(cid, cfm, "RPC_SIMPLE_ACK");
+
+                let routed = reg.route(cid, MeResponse::Ack(cfm)).await;
+                if !routed {
+                    reg.unregister(cid).await;
+                    send_close_conn(&writer, cid).await;
+                }
+            } else if pt == RPC_CLOSE_EXT_U32 && body.len() >= 8 {
+                let cid = u64::from_le_bytes(body[0..8].try_into().unwrap());
+                debug!(cid, "RPC_CLOSE_EXT from ME");
+                reg.route(cid, MeResponse::Close).await;
+                reg.unregister(cid).await;
+            } else if pt == RPC_CLOSE_CONN_U32 && body.len() >= 8 {
+                let cid = u64::from_le_bytes(body[0..8].try_into().unwrap());
+                debug!(cid, "RPC_CLOSE_CONN from ME");
+                reg.route(cid, MeResponse::Close).await;
+                reg.unregister(cid).await;
+            } else if pt == RPC_PING_U32 && body.len() >= 8 {
+                let ping_id = i64::from_le_bytes(body[0..8].try_into().unwrap());
+                trace!(ping_id, "RPC_PING -> RPC_PONG");
+                let mut pong = Vec::with_capacity(12);
+                pong.extend_from_slice(&RPC_PONG_U32.to_le_bytes());
+                pong.extend_from_slice(&ping_id.to_le_bytes());
+                if let Err(e) = writer.lock().await.send(&pong).await {
+                    warn!(error = %e, "PONG send failed");
+                    break;
+                }
+            } else {
+                debug!(
+                    rpc_type = format_args!("0x{pt:08x}"),
+                    len = body.len(),
+                    "Unknown RPC"
+                );
+            }
+        }
+    }
+}
+
+async fn send_close_conn(writer: &Arc<Mutex<RpcWriter>>, conn_id: u64) {
+    let mut p = Vec::with_capacity(12);
+    p.extend_from_slice(&RPC_CLOSE_CONN_U32.to_le_bytes());
+    p.extend_from_slice(&conn_id.to_le_bytes());
+
+    if let Err(e) = writer.lock().await.send(&p).await {
+        debug!(conn_id, error = %e, "Failed to send RPC_CLOSE_CONN");
+    }
+}

src/transport/middle_proxy/registry.rs

@@ -0,0 +1,42 @@
+use std::collections::HashMap;
+use std::sync::atomic::{AtomicU64, Ordering};
+
+use tokio::sync::{RwLock, mpsc};
+
+use super::MeResponse;
+
+pub struct ConnRegistry {
+    map: RwLock<HashMap<u64, mpsc::Sender<MeResponse>>>,
+    next_id: AtomicU64,
+}
+
+impl ConnRegistry {
+    pub fn new() -> Self {
+        // Avoid fully predictable conn_id sequence from 1.
+        let start = rand::random::<u64>() | 1;
+        Self {
+            map: RwLock::new(HashMap::new()),
+            next_id: AtomicU64::new(start),
+        }
+    }
+
+    pub async fn register(&self) -> (u64, mpsc::Receiver<MeResponse>) {
+        let id = self.next_id.fetch_add(1, Ordering::Relaxed);
+        let (tx, rx) = mpsc::channel(256);
+        self.map.write().await.insert(id, tx);
+        (id, rx)
+    }
+
+    pub async fn unregister(&self, id: u64) {
+        self.map.write().await.remove(&id);
+    }
+
+    pub async fn route(&self, id: u64, resp: MeResponse) -> bool {
+        let m = self.map.read().await;
+        if let Some(tx) = m.get(&id) {
+            tx.send(resp).await.is_ok()
+        } else {
+            false
+        }
+    }
+}

src/transport/middle_proxy/secret.rs

@@ -0,0 +1,81 @@
+use std::time::Duration;
+
+use tracing::{debug, info, warn};
+
+use crate::error::{ProxyError, Result};
+
+/// Fetch Telegram proxy-secret binary.
+pub async fn fetch_proxy_secret(cache_path: Option<&str>) -> Result<Vec<u8>> {
+    let cache = cache_path.unwrap_or("proxy-secret");
+
+    // 1) Try fresh download first.
+    match download_proxy_secret().await {
+        Ok(data) => {
+            if let Err(e) = tokio::fs::write(cache, &data).await {
+                warn!(error = %e, "Failed to cache proxy-secret (non-fatal)");
+            } else {
+                debug!(path = cache, len = data.len(), "Cached proxy-secret");
+            }
+            return Ok(data);
+        }
+        Err(download_err) => {
+            warn!(error = %download_err, "Proxy-secret download failed, trying cache/file fallback");
+            // Fall through to cache/file.
+        }
+    }
+
+    // 2) Fallback to cache/file regardless of age; require len>=32.
+    match tokio::fs::read(cache).await {
+        Ok(data) if data.len() >= 32 => {
+            let age_hours = tokio::fs::metadata(cache)
+                .await
+                .ok()
+                .and_then(|m| m.modified().ok())
+                .and_then(|m| std::time::SystemTime::now().duration_since(m).ok())
+                .map(|d| d.as_secs() / 3600);
+            info!(
+                path = cache,
+                len = data.len(),
+                age_hours,
+                "Loaded proxy-secret from cache/file after download failure"
+            );
+            Ok(data)
+        }
+        Ok(data) => Err(ProxyError::Proxy(format!(
+            "Cached proxy-secret too short: {} bytes (need >= 32)",
+            data.len()
+        ))),
+        Err(e) => Err(ProxyError::Proxy(format!(
+            "Failed to read proxy-secret cache after download failure: {e}"
+        ))),
+    }
+}
+
+async fn download_proxy_secret() -> Result<Vec<u8>> {
+    let resp = reqwest::get("https://core.telegram.org/getProxySecret")
+        .await
+        .map_err(|e| ProxyError::Proxy(format!("Failed to download proxy-secret: {e}")))?;
+
+    if !resp.status().is_success() {
+        return Err(ProxyError::Proxy(format!(
+            "proxy-secret download HTTP {}",
+            resp.status()
+        )));
+    }
+
+    let data = resp
+        .bytes()
+        .await
+        .map_err(|e| ProxyError::Proxy(format!("Read proxy-secret body: {e}")))?
+        .to_vec();
+
+    if data.len() < 32 {
+        return Err(ProxyError::Proxy(format!(
+            "proxy-secret too short: {} bytes (need >= 32)",
+            data.len()
+        )));
+    }
+
+    info!(len = data.len(), "Downloaded proxy-secret OK");
+    Ok(data)
+}

src/transport/middle_proxy/send.rs

@@ -0,0 +1,146 @@
+use std::net::SocketAddr;
+use std::sync::Arc;
+use std::sync::atomic::Ordering;
+
+use tokio::sync::Mutex;
+use tracing::{debug, warn};
+
+use crate::error::{ProxyError, Result};
+use crate::protocol::constants::{RPC_CLOSE_EXT_U32, TG_MIDDLE_PROXIES_V4};
+
+use super::MePool;
+use super::codec::RpcWriter;
+use super::wire::build_proxy_req_payload;
+
+impl MePool {
+    pub async fn send_proxy_req(
+        &self,
+        conn_id: u64,
+        target_dc: i16,
+        client_addr: SocketAddr,
+        our_addr: SocketAddr,
+        data: &[u8],
+        proto_flags: u32,
+    ) -> Result<()> {
+        let payload = build_proxy_req_payload(
+            conn_id,
+            client_addr,
+            our_addr,
+            data,
+            self.proxy_tag.as_deref(),
+            proto_flags,
+        );
+
+        loop {
+            let ws = self.writers.read().await;
+            if ws.is_empty() {
+                return Err(ProxyError::Proxy("All ME connections dead".into()));
+            }
+            let writers: Vec<(SocketAddr, Arc<Mutex<RpcWriter>>)> = ws.iter().cloned().collect();
+            drop(ws);
+
+            let candidate_indices = candidate_indices_for_dc(&writers, target_dc);
+            if candidate_indices.is_empty() {
+                return Err(ProxyError::Proxy("No ME writers available for target DC".into()));
+            }
+            let start = self.rr.fetch_add(1, Ordering::Relaxed) as usize % candidate_indices.len();
+
+            // Prefer immediately available writer to avoid waiting on stalled connection.
+            for offset in 0..candidate_indices.len() {
+                let cidx = (start + offset) % candidate_indices.len();
+                let idx = candidate_indices[cidx];
+                let w = writers[idx].1.clone();
+                if let Ok(mut guard) = w.try_lock() {
+                    let send_res = guard.send(&payload).await;
+                    drop(guard);
+                    match send_res {
+                        Ok(()) => return Ok(()),
+                        Err(e) => {
+                            warn!(error = %e, "ME write failed, removing dead conn");
+                            let mut ws = self.writers.write().await;
+                            ws.retain(|(_, o)| !Arc::ptr_eq(o, &w));
+                            if ws.is_empty() {
+                                return Err(ProxyError::Proxy("All ME connections dead".into()));
+                            }
+                            continue;
+                        }
+                    }
+                }
+            }
+
+            // All writers are currently busy, wait for the selected one.
+            let w = writers[candidate_indices[start]].1.clone();
+            match w.lock().await.send(&payload).await {
+                Ok(()) => return Ok(()),
+                Err(e) => {
+                    warn!(error = %e, "ME write failed, removing dead conn");
+                    let mut ws = self.writers.write().await;
+                    ws.retain(|(_, o)| !Arc::ptr_eq(o, &w));
+                    if ws.is_empty() {
+                        return Err(ProxyError::Proxy("All ME connections dead".into()));
+                    }
+                }
+            }
+        }
+    }
+
+    pub async fn send_close(&self, conn_id: u64) -> Result<()> {
+        let ws = self.writers.read().await;
+        if !ws.is_empty() {
+            let w = ws[0].1.clone();
+            drop(ws);
+            let mut p = Vec::with_capacity(12);
+            p.extend_from_slice(&RPC_CLOSE_EXT_U32.to_le_bytes());
+            p.extend_from_slice(&conn_id.to_le_bytes());
+            if let Err(e) = w.lock().await.send(&p).await {
+                debug!(error = %e, "ME close write failed");
+                let mut ws = self.writers.write().await;
+                ws.retain(|(_, o)| !Arc::ptr_eq(o, &w));
+            }
+        }
+
+        self.registry.unregister(conn_id).await;
+        Ok(())
+    }
+
+    pub fn connection_count(&self) -> usize {
+        self.writers.try_read().map(|w| w.len()).unwrap_or(0)
+    }
+}
+
+fn candidate_indices_for_dc(
+    writers: &[(SocketAddr, Arc<Mutex<RpcWriter>>)],
+    target_dc: i16,
+) -> Vec<usize> {
+    let mut preferred = Vec::<SocketAddr>::new();
+    let key = target_dc as i32;
+    if let Some(v) = TG_MIDDLE_PROXIES_V4.get(&key) {
+        preferred.extend(v.iter().map(|(ip, port)| SocketAddr::new(*ip, *port)));
+    }
+    if preferred.is_empty() {
+        let abs = key.abs();
+        if let Some(v) = TG_MIDDLE_PROXIES_V4.get(&abs) {
+            preferred.extend(v.iter().map(|(ip, port)| SocketAddr::new(*ip, *port)));
+        }
+    }
+    if preferred.is_empty() {
+        let abs = key.abs();
+        if let Some(v) = TG_MIDDLE_PROXIES_V4.get(&-abs) {
+            preferred.extend(v.iter().map(|(ip, port)| SocketAddr::new(*ip, *port)));
+        }
+    }
+    if preferred.is_empty() {
+        return (0..writers.len()).collect();
+    }
+
+    let mut out = Vec::new();
+    for (idx, (addr, _)) in writers.iter().enumerate() {
+        if preferred.iter().any(|p| p == addr) {
+            out.push(idx);
+        }
+    }
+    if out.is_empty() {
+        return (0..writers.len()).collect();
+    }
+    out
+}

src/transport/middle_proxy/wire.rs

@@ -0,0 +1,106 @@
+use std::net::{IpAddr, Ipv4Addr, SocketAddr};
+
+use crate::protocol::constants::*;
+
+#[derive(Clone, Copy)]
+pub(crate) enum IpMaterial {
+    V4([u8; 4]),
+    V6([u8; 16]),
+}
+
+pub(crate) fn extract_ip_material(addr: SocketAddr) -> IpMaterial {
+    match addr.ip() {
+        IpAddr::V4(v4) => IpMaterial::V4(v4.octets()),
+        IpAddr::V6(v6) => {
+            if let Some(v4) = v6.to_ipv4_mapped() {
+                IpMaterial::V4(v4.octets())
+            } else {
+                IpMaterial::V6(v6.octets())
+            }
+        }
+    }
+}
+
+fn ipv4_to_mapped_v6_c_compat(ip: Ipv4Addr) -> [u8; 16] {
+    let mut buf = [0u8; 16];
+
+    // Matches tl_store_long(0) + tl_store_int(-0x10000).
+    buf[8..12].copy_from_slice(&(-0x10000i32).to_le_bytes());
+
+    // Matches tl_store_int(htonl(remote_ip_host_order)).
+    let host_order = u32::from_ne_bytes(ip.octets());
+    let network_order = host_order.to_be();
+    buf[12..16].copy_from_slice(&network_order.to_le_bytes());
+
+    buf
+}
+
+fn append_mapped_addr_and_port(buf: &mut Vec<u8>, addr: SocketAddr) {
+    match addr.ip() {
+        IpAddr::V4(v4) => buf.extend_from_slice(&ipv4_to_mapped_v6_c_compat(v4)),
+        IpAddr::V6(v6) => buf.extend_from_slice(&v6.octets()),
+    }
+    buf.extend_from_slice(&(addr.port() as u32).to_le_bytes());
+}
+
+pub(crate) fn build_proxy_req_payload(
+    conn_id: u64,
+    client_addr: SocketAddr,
+    our_addr: SocketAddr,
+    data: &[u8],
+    proxy_tag: Option<&[u8]>,
+    proto_flags: u32,
+) -> Vec<u8> {
+    let mut b = Vec::with_capacity(128 + data.len());
+
+    b.extend_from_slice(&RPC_PROXY_REQ_U32.to_le_bytes());
+    b.extend_from_slice(&proto_flags.to_le_bytes());
+    b.extend_from_slice(&conn_id.to_le_bytes());
+
+    append_mapped_addr_and_port(&mut b, client_addr);
+    append_mapped_addr_and_port(&mut b, our_addr);
+
+    if proto_flags & 12 != 0 {
+        let extra_start = b.len();
+        b.extend_from_slice(&0u32.to_le_bytes());
+
+        if let Some(tag) = proxy_tag {
+            b.extend_from_slice(&TL_PROXY_TAG_U32.to_le_bytes());
+
+            if tag.len() < 254 {
+                b.push(tag.len() as u8);
+                b.extend_from_slice(tag);
+                let pad = (4 - ((1 + tag.len()) % 4)) % 4;
+                b.extend(std::iter::repeat_n(0u8, pad));
+            } else {
+                b.push(0xfe);
+                let len_bytes = (tag.len() as u32).to_le_bytes();
+                b.extend_from_slice(&len_bytes[..3]);
+                b.extend_from_slice(tag);
+                let pad = (4 - (tag.len() % 4)) % 4;
+                b.extend(std::iter::repeat_n(0u8, pad));
+            }
+        }
+
+        let extra_bytes = (b.len() - extra_start - 4) as u32;
+        b[extra_start..extra_start + 4].copy_from_slice(&extra_bytes.to_le_bytes());
+    }
+
+    b.extend_from_slice(data);
+    b
+}
+
+pub fn proto_flags_for_tag(tag: crate::protocol::constants::ProtoTag, has_proxy_tag: bool) -> u32 {
+    use crate::protocol::constants::ProtoTag;
+
+    let mut flags = RPC_FLAG_MAGIC | RPC_FLAG_EXTMODE2;
+    if has_proxy_tag {
+        flags |= RPC_FLAG_HAS_AD_TAG;
+    }
+
+    match tag {
+        ProtoTag::Abridged => flags | RPC_FLAG_ABRIDGED,
+        ProtoTag::Intermediate => flags | RPC_FLAG_INTERMEDIATE,
+        ProtoTag::Secure => flags | RPC_FLAG_PAD | RPC_FLAG_INTERMEDIATE,
+    }
+}

src/transport/mod.rs

@@ -10,4 +10,5 @@ pub use pool::ConnectionPool;
 pub use proxy_protocol::{ProxyProtocolInfo, parse_proxy_protocol};
 pub use socket::*;
 pub use socks::*;
-pub use upstream::UpstreamManager;
+pub use upstream::{DcPingResult, StartupPingResult, UpstreamManager};
+pub mod middle_proxy;

src/transport/upstream.rs

@@ -1,26 +1,153 @@
-//! Upstream Management
+//! Upstream Management with per-DC latency-weighted selection
+//! 
+//! IPv6/IPv4 connectivity checks with configurable preference.
 
 use std::net::{SocketAddr, IpAddr};
 use std::sync::Arc;
 use std::time::Duration;
 use tokio::net::TcpStream;
 use tokio::sync::RwLock;
+use tokio::time::Instant;
 use rand::Rng;
-use tracing::{debug, warn, error, info};
+use tracing::{debug, warn, info, trace};
 
 use crate::config::{UpstreamConfig, UpstreamType};
 use crate::error::{Result, ProxyError};
+use crate::protocol::constants::{TG_DATACENTERS_V4, TG_DATACENTERS_V6, TG_DATACENTER_PORT};
 use crate::transport::socket::create_outgoing_socket_bound;
 use crate::transport::socks::{connect_socks4, connect_socks5};
 
+/// Number of Telegram datacenters
+const NUM_DCS: usize = 5;
+
+/// Timeout for individual DC ping attempt
+const DC_PING_TIMEOUT_SECS: u64 = 5;
+
+// ============= RTT Tracking =============
+
+#[derive(Debug, Clone, Copy)]
+struct LatencyEma {
+    value_ms: Option<f64>,
+    alpha: f64,
+}
+
+impl LatencyEma {
+    const fn new(alpha: f64) -> Self {
+        Self { value_ms: None, alpha }
+    }
+
+    fn update(&mut self, sample_ms: f64) {
+        self.value_ms = Some(match self.value_ms {
+            None => sample_ms,
+            Some(prev) => prev * (1.0 - self.alpha) + sample_ms * self.alpha,
+        });
+    }
+
+    fn get(&self) -> Option<f64> {
+        self.value_ms
+    }
+}
+
+// ============= Per-DC IP Preference Tracking =============
+
+/// Tracks which IP version works for each DC
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum IpPreference {
+    /// Not yet tested
+    Unknown,
+    /// IPv6 works
+    PreferV6,
+    /// Only IPv4 works (IPv6 failed)
+    PreferV4,
+    /// Both work
+    BothWork,
+    /// Both failed
+    Unavailable,
+}
+
+impl Default for IpPreference {
+    fn default() -> Self {
+        Self::Unknown
+    }
+}
+
+// ============= Upstream State =============
+
 #[derive(Debug)]
 struct UpstreamState {
     config: UpstreamConfig,
     healthy: bool,
     fails: u32,
     last_check: std::time::Instant,
+    /// Per-DC latency EMA (index 0 = DC1, index 4 = DC5)
+    dc_latency: [LatencyEma; NUM_DCS],
+    /// Per-DC IP version preference (learned from connectivity tests)
+    dc_ip_pref: [IpPreference; NUM_DCS],
 }
 
+impl UpstreamState {
+    fn new(config: UpstreamConfig) -> Self {
+        Self {
+            config,
+            healthy: true,
+            fails: 0,
+            last_check: std::time::Instant::now(),
+            dc_latency: [LatencyEma::new(0.3); NUM_DCS],
+            dc_ip_pref: [IpPreference::Unknown; NUM_DCS],
+        }
+    }
+
+    /// Map DC index to latency array slot (0..NUM_DCS).
+    fn dc_array_idx(dc_idx: i16) -> Option<usize> {
+        let abs_dc = dc_idx.unsigned_abs() as usize;
+        if abs_dc == 0 {
+            return None;
+        }
+        if abs_dc >= 1 && abs_dc <= NUM_DCS {
+            Some(abs_dc - 1)
+        } else {
+            // Unknown DC → default cluster (DC 2, index 1)
+            Some(1)
+        }
+    }
+
+    /// Get latency for a specific DC, falling back to average across all known DCs
+    fn effective_latency(&self, dc_idx: Option<i16>) -> Option<f64> {
+        if let Some(di) = dc_idx.and_then(Self::dc_array_idx) {
+            if let Some(ms) = self.dc_latency[di].get() {
+                return Some(ms);
+            }
+        }
+
+        let (sum, count) = self.dc_latency.iter()
+            .filter_map(|l| l.get())
+            .fold((0.0, 0u32), |(s, c), v| (s + v, c + 1));
+
+        if count > 0 { Some(sum / count as f64) } else { None }
+    }
+}
+
+/// Result of a single DC ping
+#[derive(Debug, Clone)]
+pub struct DcPingResult {
+    pub dc_idx: usize,
+    pub dc_addr: SocketAddr,
+    pub rtt_ms: Option<f64>,
+    pub error: Option<String>,
+}
+
+/// Result of startup ping for one upstream (separate v6/v4 results)
+#[derive(Debug, Clone)]
+pub struct StartupPingResult {
+    pub v6_results: Vec<DcPingResult>,
+    pub v4_results: Vec<DcPingResult>,
+    pub upstream_name: String,
+    /// True if both IPv6 and IPv4 have at least one working DC
+    pub both_available: bool,
+}
+
+// ============= Upstream Manager =============
+
 #[derive(Clone)]
 pub struct UpstreamManager {
     upstreams: Arc<RwLock<Vec<UpstreamState>>>,
@@ -30,12 +157,7 @@ impl UpstreamManager {
     pub fn new(configs: Vec<UpstreamConfig>) -> Self {
         let states = configs.into_iter()
             .filter(|c| c.enabled)
-            .map(|c| UpstreamState {
+            .map(UpstreamState::new)
-                config: c,
-                healthy: true, // Optimistic start
-                fails: 0,
-                last_check: std::time::Instant::now(),
-            })
             .collect();
 
         Self {
@@ -43,48 +165,64 @@ impl UpstreamManager {
         }
     }
 
-    /// Select an upstream using Weighted Round Robin (simplified)
+    /// Select upstream using latency-weighted random selection.
-    async fn select_upstream(&self) -> Option<usize> {
+    async fn select_upstream(&self, dc_idx: Option<i16>) -> Option<usize> {
         let upstreams = self.upstreams.read().await;
         if upstreams.is_empty() {
             return None;
         }
 
-        let healthy_indices: Vec<usize> = upstreams.iter()
+        let healthy: Vec<usize> = upstreams.iter()
             .enumerate()
             .filter(|(_, u)| u.healthy)
             .map(|(i, _)| i)
             .collect();
 
-        if healthy_indices.is_empty() {
+        if healthy.is_empty() {
-            // If all unhealthy, try any random one
+            return Some(rand::rng().gen_range(0..upstreams.len()));
-            return Some(rand::thread_rng().gen_range(0..upstreams.len()));
         }
 
-        // Weighted selection
+        if healthy.len() == 1 {
-        let total_weight: u32 = healthy_indices.iter()
+            return Some(healthy[0]);
-            .map(|&i| upstreams[i].config.weight as u32)
-            .sum();
-            
-        if total_weight == 0 {
-            return Some(healthy_indices[rand::thread_rng().gen_range(0..healthy_indices.len())]);
         }
 
-        let mut choice = rand::thread_rng().gen_range(0..total_weight);
+        let weights: Vec<(usize, f64)> = healthy.iter().map(|&i| {
+            let base = upstreams[i].config.weight as f64;
+            let latency_factor = upstreams[i].effective_latency(dc_idx)
+                .map(|ms| if ms > 1.0 { 1000.0 / ms } else { 1000.0 })
+                .unwrap_or(1.0);
 
-        for &idx in &healthy_indices {
+            (i, base * latency_factor)
-            let weight = upstreams[idx].config.weight as u32;
+        }).collect();
+
+        let total: f64 = weights.iter().map(|(_, w)| w).sum();
+
+        if total <= 0.0 {
+            return Some(healthy[rand::rng().gen_range(0..healthy.len())]);
+        }
+
+        let mut choice: f64 = rand::rng().gen_range(0.0..total);
+
+        for &(idx, weight) in &weights {
             if choice < weight {
+                trace!(
+                    upstream = idx,
+                    dc = ?dc_idx,
+                    weight = format!("{:.2}", weight),
+                    total = format!("{:.2}", total),
+                    "Upstream selected"
+                );
                 return Some(idx);
             }
             choice -= weight;
         }
 
-        Some(healthy_indices[0])
+        Some(healthy[0])
     }
 
-    pub async fn connect(&self, target: SocketAddr) -> Result<TcpStream> {
+    /// Connect to target through a selected upstream.
-        let idx = self.select_upstream().await
+    pub async fn connect(&self, target: SocketAddr, dc_idx: Option<i16>) -> Result<TcpStream> {
+        let idx = self.select_upstream(dc_idx).await
             .ok_or_else(|| ProxyError::Config("No upstreams available".to_string()))?;
 
         let upstream = {
@@ -92,28 +230,33 @@ impl UpstreamManager {
             guard[idx].config.clone()
         };
 
+        let start = Instant::now();
+
         match self.connect_via_upstream(&upstream, target).await {
             Ok(stream) => {
-                // Mark success
+                let rtt_ms = start.elapsed().as_secs_f64() * 1000.0;
                 let mut guard = self.upstreams.write().await;
                 if let Some(u) = guard.get_mut(idx) {
                     if !u.healthy {
-                        debug!("Upstream recovered: {:?}", u.config);
+                        debug!(rtt_ms = format!("{:.1}", rtt_ms), "Upstream recovered");
                     }
                     u.healthy = true;
                     u.fails = 0;
+
+                    if let Some(di) = dc_idx.and_then(UpstreamState::dc_array_idx) {
+                        u.dc_latency[di].update(rtt_ms);
+                    }
                 }
                 Ok(stream)
             },
             Err(e) => {
-                // Mark failure
                 let mut guard = self.upstreams.write().await;
                 if let Some(u) = guard.get_mut(idx) {
                     u.fails += 1;
-                    warn!("Failed to connect via upstream {:?}: {}. Fails: {}", u.config, e, u.fails);
+                    warn!(fails = u.fails, "Upstream failed: {}", e);
                     if u.fails > 3 {
                         u.healthy = false;
-                        warn!("Upstream disabled due to failures: {:?}", u.config);
+                        warn!("Upstream marked unhealthy");
                     }
                 }
                 Err(e)
@@ -129,18 +272,16 @@ impl UpstreamManager {
 
                 let socket = create_outgoing_socket_bound(target, bind_ip)?;
 
-                // Non-blocking connect logic
                 socket.set_nonblocking(true)?;
                 match socket.connect(&target.into()) {
                     Ok(()) => {},
-                    Err(err) if err.raw_os_error() == Some(115) || err.kind() == std::io::ErrorKind::WouldBlock => {},
+                    Err(err) if err.raw_os_error() == Some(libc::EINPROGRESS) || err.kind() == std::io::ErrorKind::WouldBlock => {},
                     Err(err) => return Err(ProxyError::Io(err)),
                 }
 
                 let std_stream: std::net::TcpStream = socket.into();
                 let stream = TcpStream::from_std(std_stream)?;
 
-                // Wait for connection to complete
                 stream.writable().await?;
                 if let Some(e) = stream.take_error()? {
                     return Err(ProxyError::Io(e));
@@ -149,8 +290,6 @@ impl UpstreamManager {
                 Ok(stream)
             },
             UpstreamType::Socks4 { address, interface, user_id } => {
-                info!("Connecting to target {} via SOCKS4 proxy {}", target, address);
-                
                 let proxy_addr: SocketAddr = address.parse()
                     .map_err(|_| ProxyError::Config("Invalid SOCKS4 address".to_string()))?;
 
@@ -159,18 +298,16 @@ impl UpstreamManager {
 
                 let socket = create_outgoing_socket_bound(proxy_addr, bind_ip)?;
 
-                // Non-blocking connect logic
                 socket.set_nonblocking(true)?;
                 match socket.connect(&proxy_addr.into()) {
                     Ok(()) => {},
-                    Err(err) if err.raw_os_error() == Some(115) || err.kind() == std::io::ErrorKind::WouldBlock => {},
+                    Err(err) if err.raw_os_error() == Some(libc::EINPROGRESS) || err.kind() == std::io::ErrorKind::WouldBlock => {},
                     Err(err) => return Err(ProxyError::Io(err)),
                 }
 
                 let std_stream: std::net::TcpStream = socket.into();
                 let mut stream = TcpStream::from_std(std_stream)?;
 
-                // Wait for connection to complete
                 stream.writable().await?;
                 if let Some(e) = stream.take_error()? {
                     return Err(ProxyError::Io(e));
@@ -180,8 +317,6 @@ impl UpstreamManager {
                 Ok(stream)
             },
             UpstreamType::Socks5 { address, interface, username, password } => {
-                info!("Connecting to target {} via SOCKS5 proxy {}", target, address);
-                
                 let proxy_addr: SocketAddr = address.parse()
                     .map_err(|_| ProxyError::Config("Invalid SOCKS5 address".to_string()))?;
 
@@ -190,18 +325,16 @@ impl UpstreamManager {
 
                 let socket = create_outgoing_socket_bound(proxy_addr, bind_ip)?;
 
-                // Non-blocking connect logic
                 socket.set_nonblocking(true)?;
                 match socket.connect(&proxy_addr.into()) {
                     Ok(()) => {},
-                    Err(err) if err.raw_os_error() == Some(115) || err.kind() == std::io::ErrorKind::WouldBlock => {},
+                    Err(err) if err.raw_os_error() == Some(libc::EINPROGRESS) || err.kind() == std::io::ErrorKind::WouldBlock => {},
                     Err(err) => return Err(ProxyError::Io(err)),
                 }
 
                 let std_stream: std::net::TcpStream = socket.into();
                 let mut stream = TcpStream::from_std(std_stream)?;
 
-                // Wait for connection to complete
                 stream.writable().await?;
                 if let Some(e) = stream.take_error()? {
                     return Err(ProxyError::Io(e));
@@ -213,47 +346,282 @@ impl UpstreamManager {
         }
     }
 
-    /// Background task to check health
+    // ============= Startup Ping (test both IPv6 and IPv4) =============
-    pub async fn run_health_checks(&self) {
+
-        // Simple TCP connect check to a known stable DC (e.g. 149.154.167.50:443 - DC2)
+    /// Ping all Telegram DCs through all upstreams.
-        let check_target: SocketAddr = "149.154.167.50:443".parse().unwrap();
+    /// Tests BOTH IPv6 and IPv4, returns separate results for each.
+    pub async fn ping_all_dcs(&self, prefer_ipv6: bool) -> Vec<StartupPingResult> {
+        let upstreams: Vec<(usize, UpstreamConfig)> = {
+            let guard = self.upstreams.read().await;
+            guard.iter().enumerate()
+                .map(|(i, u)| (i, u.config.clone()))
+                .collect()
+        };
+
+        let mut all_results = Vec::new();
+
+        for (upstream_idx, upstream_config) in &upstreams {
+            let upstream_name = match &upstream_config.upstream_type {
+                UpstreamType::Direct { interface } => {
+                    format!("direct{}", interface.as_ref().map(|i| format!(" ({})", i)).unwrap_or_default())
+                }
+                UpstreamType::Socks4 { address, .. } => format!("socks4://{}", address),
+                UpstreamType::Socks5 { address, .. } => format!("socks5://{}", address),
+            };
+
+            let mut v6_results = Vec::new();
+            let mut v4_results = Vec::new();
+
+            // === Ping IPv6 first ===
+            for dc_zero_idx in 0..NUM_DCS {
+                let dc_v6 = TG_DATACENTERS_V6[dc_zero_idx];
+                let addr_v6 = SocketAddr::new(dc_v6, TG_DATACENTER_PORT);
+
+                let result = tokio::time::timeout(
+                    Duration::from_secs(DC_PING_TIMEOUT_SECS),
+                    self.ping_single_dc(&upstream_config, addr_v6)
+                ).await;
+
+                let ping_result = match result {
+                    Ok(Ok(rtt_ms)) => {
+                        let mut guard = self.upstreams.write().await;
+                        if let Some(u) = guard.get_mut(*upstream_idx) {
+                            u.dc_latency[dc_zero_idx].update(rtt_ms);
+                        }
+                        DcPingResult {
+                            dc_idx: dc_zero_idx + 1,
+                            dc_addr: addr_v6,
+                            rtt_ms: Some(rtt_ms),
+                            error: None,
+                        }
+                    }
+                    Ok(Err(e)) => DcPingResult {
+                        dc_idx: dc_zero_idx + 1,
+                        dc_addr: addr_v6,
+                        rtt_ms: None,
+                        error: Some(e.to_string()),
+                    },
+                    Err(_) => DcPingResult {
+                        dc_idx: dc_zero_idx + 1,
+                        dc_addr: addr_v6,
+                        rtt_ms: None,
+                        error: Some("timeout".to_string()),
+                    },
+                };
+                v6_results.push(ping_result);
+            }
+
+            // === Then ping IPv4 ===
+            for dc_zero_idx in 0..NUM_DCS {
+                let dc_v4 = TG_DATACENTERS_V4[dc_zero_idx];
+                let addr_v4 = SocketAddr::new(dc_v4, TG_DATACENTER_PORT);
+
+                let result = tokio::time::timeout(
+                    Duration::from_secs(DC_PING_TIMEOUT_SECS),
+                    self.ping_single_dc(&upstream_config, addr_v4)
+                ).await;
+
+                let ping_result = match result {
+                    Ok(Ok(rtt_ms)) => {
+                        let mut guard = self.upstreams.write().await;
+                        if let Some(u) = guard.get_mut(*upstream_idx) {
+                            u.dc_latency[dc_zero_idx].update(rtt_ms);
+                        }
+                        DcPingResult {
+                            dc_idx: dc_zero_idx + 1,
+                            dc_addr: addr_v4,
+                            rtt_ms: Some(rtt_ms),
+                            error: None,
+                        }
+                    }
+                    Ok(Err(e)) => DcPingResult {
+                        dc_idx: dc_zero_idx + 1,
+                        dc_addr: addr_v4,
+                        rtt_ms: None,
+                        error: Some(e.to_string()),
+                    },
+                    Err(_) => DcPingResult {
+                        dc_idx: dc_zero_idx + 1,
+                        dc_addr: addr_v4,
+                        rtt_ms: None,
+                        error: Some("timeout".to_string()),
+                    },
+                };
+                v4_results.push(ping_result);
+            }
+
+            // Check if both IP versions have at least one working DC
+            let v6_has_working = v6_results.iter().any(|r| r.rtt_ms.is_some());
+            let v4_has_working = v4_results.iter().any(|r| r.rtt_ms.is_some());
+            let both_available = v6_has_working && v4_has_working;
+
+            // Update IP preference for each DC
+            {
+                let mut guard = self.upstreams.write().await;
+                if let Some(u) = guard.get_mut(*upstream_idx) {
+                    for dc_zero_idx in 0..NUM_DCS {
+                        let v6_ok = v6_results[dc_zero_idx].rtt_ms.is_some();
+                        let v4_ok = v4_results[dc_zero_idx].rtt_ms.is_some();
+
+                        u.dc_ip_pref[dc_zero_idx] = match (v6_ok, v4_ok) {
+                            (true, true) => IpPreference::BothWork,
+                            (true, false) => IpPreference::PreferV6,
+                            (false, true) => IpPreference::PreferV4,
+                            (false, false) => IpPreference::Unavailable,
+                        };
+                    }
+                }
+            }
+
+            all_results.push(StartupPingResult {
+                v6_results,
+                v4_results,
+                upstream_name,
+                both_available,
+            });
+        }
+
+        all_results
+    }
+
+    async fn ping_single_dc(&self, config: &UpstreamConfig, target: SocketAddr) -> Result<f64> {
+        let start = Instant::now();
+        let _stream = self.connect_via_upstream(config, target).await?;
+        Ok(start.elapsed().as_secs_f64() * 1000.0)
+    }
+
+    // ============= Health Checks =============
+
+    /// Background health check: rotates through DCs, 30s interval.
+    /// Uses preferred IP version based on config.
+    pub async fn run_health_checks(&self, prefer_ipv6: bool) {
+        let mut dc_rotation = 0usize;
 
         loop {
-            tokio::time::sleep(Duration::from_secs(60)).await;
+            tokio::time::sleep(Duration::from_secs(30)).await;
+
+            let dc_zero_idx = dc_rotation % NUM_DCS;
+            dc_rotation += 1;
+
+            let dc_addr = if prefer_ipv6 {
+                SocketAddr::new(TG_DATACENTERS_V6[dc_zero_idx], TG_DATACENTER_PORT)
+            } else {
+                SocketAddr::new(TG_DATACENTERS_V4[dc_zero_idx], TG_DATACENTER_PORT)
+            };
+
+            let fallback_addr = if prefer_ipv6 {
+                SocketAddr::new(TG_DATACENTERS_V4[dc_zero_idx], TG_DATACENTER_PORT)
+            } else {
+                SocketAddr::new(TG_DATACENTERS_V6[dc_zero_idx], TG_DATACENTER_PORT)
+            };
 
             let count = self.upstreams.read().await.len();
+
             for i in 0..count {
                 let config = {
                     let guard = self.upstreams.read().await;
                     guard[i].config.clone()
                 };
 
+                let start = Instant::now();
                 let result = tokio::time::timeout(
                     Duration::from_secs(10),
-                    self.connect_via_upstream(&config, check_target)
+                    self.connect_via_upstream(&config, dc_addr)
+                ).await;
+
+                match result {
+                    Ok(Ok(_stream)) => {
+                        let rtt_ms = start.elapsed().as_secs_f64() * 1000.0;
+                        let mut guard = self.upstreams.write().await;
+                        let u = &mut guard[i];
+                        u.dc_latency[dc_zero_idx].update(rtt_ms);
+
+                        if !u.healthy {
+                            info!(
+                                rtt = format!("{:.0} ms", rtt_ms),
+                                dc = dc_zero_idx + 1,
+                                "Upstream recovered"
+                            );
+                        }
+                        u.healthy = true;
+                        u.fails = 0;
+                        u.last_check = std::time::Instant::now();
+                    }
+                    Ok(Err(_)) | Err(_) => {
+                        // Try fallback
+                        debug!(dc = dc_zero_idx + 1, "Health check failed, trying fallback");
+
+                        let start2 = Instant::now();
+                        let result2 = tokio::time::timeout(
+                            Duration::from_secs(10),
+                            self.connect_via_upstream(&config, fallback_addr)
                         ).await;
 
                         let mut guard = self.upstreams.write().await;
                         let u = &mut guard[i];
 
-                match result {
+                        match result2 {
                             Ok(Ok(_stream)) => {
+                                let rtt_ms = start2.elapsed().as_secs_f64() * 1000.0;
+                                u.dc_latency[dc_zero_idx].update(rtt_ms);
+
                                 if !u.healthy {
-                            debug!("Upstream recovered: {:?}", u.config);
+                                    info!(
+                                        rtt = format!("{:.0} ms", rtt_ms),
+                                        dc = dc_zero_idx + 1,
+                                        "Upstream recovered (fallback)"
+                                    );
                                 }
                                 u.healthy = true;
                                 u.fails = 0;
                             }
                             Ok(Err(e)) => {
-                        debug!("Health check failed for {:?}: {}", u.config, e);
+                                u.fails += 1;
-                        // Don't mark unhealthy immediately in background check
+                                debug!(dc = dc_zero_idx + 1, fails = u.fails,
+                                    "Health check failed (both): {}", e);
+                                if u.fails > 3 {
+                                    u.healthy = false;
+                                    warn!("Upstream unhealthy (fails)");
+                                }
                             }
                             Err(_) => {
-                        debug!("Health check timeout for {:?}", u.config);
+                                u.fails += 1;
+                                debug!(dc = dc_zero_idx + 1, fails = u.fails,
+                                    "Health check timeout (both)");
+                                if u.fails > 3 {
+                                    u.healthy = false;
+                                    warn!("Upstream unhealthy (timeout)");
+                                }
                             }
                         }
                         u.last_check = std::time::Instant::now();
                     }
                 }
             }
+        }
+    }
+
+    /// Get the preferred IP for a DC (for use by other components)
+    pub async fn get_dc_ip_preference(&self, dc_idx: i16) -> Option<IpPreference> {
+        let guard = self.upstreams.read().await;
+        if guard.is_empty() {
+            return None;
+        }
+
+        UpstreamState::dc_array_idx(dc_idx)
+            .map(|idx| guard[0].dc_ip_pref[idx])
+    }
+
+    /// Get preferred DC address based on config preference
+    pub async fn get_dc_addr(&self, dc_idx: i16, prefer_ipv6: bool) -> Option<SocketAddr> {
+        let arr_idx = UpstreamState::dc_array_idx(dc_idx)?;
+
+        let ip = if prefer_ipv6 {
+            TG_DATACENTERS_V6[arr_idx]
+        } else {
+            TG_DATACENTERS_V4[arr_idx]
+        };
+
+        Some(SocketAddr::new(ip, TG_DATACENTER_PORT))
+    }
 }