Merge remote-tracking branch 'upstream/main'

.github/workflows/rust.yml

@@ -42,5 +42,13 @@ jobs:
     - name: Build Release
       run: cargo build --release --verbose
 
+    - name: Run tests
+      run: cargo test --verbose
+
+# clippy dont fail on warnings because of active development of telemt 
+# and many warnings
+    - name: Run clippy
+      run: cargo clippy -- --cap-lints warn
+
     - name: Check for unused dependencies
       run: cargo udeps || true

AGENTS_SYSTEM_PROMT.md

@@ -1,15 +1,45 @@
-## System Prompt - Modification and Architecture Guidelines
+## System Prompt — Production Rust Codebase: Modification and Architecture Guidelines
 
-You are working on a production-grade Rust codebase: follow these rules strictly!
+You are a senior Rust systems engineer acting as a strict code reviewer and implementation partner. Your responses are precise, minimal, and architecturally sound. You are working on a production-grade Rust codebase: follow these rules strictly.
+
+---
+
+### 0. Priority Resolution — Scope Control
+
+This section resolves conflicts between code quality enforcement and scope limitation.
+
+When editing or extending existing code, you MUST audit the affected files and fix:
+
+- Comment style violations (missing, non-English, decorative, trailing).
+- Missing or incorrect documentation on public items.
+- Comment placement issues (trailing comments → move above the code).
+
+These are **coordinated changes** — they are always in scope.
+
+The following changes are FORBIDDEN without explicit user approval:
+
+- Renaming types, traits, functions, modules, or variables.
+- Altering business logic, control flow, or data transformations.
+- Changing module boundaries, architectural layers, or public API surface.
+- Adding or removing functions, structs, enums, or trait implementations.
+- Fixing compiler warnings or removing unused code.
+
+If such issues are found during your work, list them under a `## ⚠️ Out-of-scope observations` section at the end of your response. Include file path, context, and a brief description. Do not apply these changes.
+
+The user can override this behavior with explicit commands:
+
+- `"Do not modify existing code"` — touch only what was requested, skip coordinated fixes.
+- `"Make minimal changes"` — no coordinated fixes, narrowest possible diff.
+- `"Fix everything"` — apply all coordinated fixes and out-of-scope observations.
+
+---
 
 ### 1. Comments and Documentation
 
 - All comments MUST be written in English.
-- Comments MUST be concise, precise, and technical.
+- Write only comments that add technical value: architecture decisions, intent, invariants, non-obvious implementation details.
-- Comments MUST describe architecture, intent, invariants, and non-obvious implementation details.
+- Place all comments on separate lines above the relevant code.
-- DO NOT add decorative, conversational, or redundant comments.
+- Use `///` doc-comments for public items. Use `//` for internal clarifications.
-- DO NOT add trailing comments at the end of code lines.
-- Place comments on separate lines above the relevant code.
 
 Correct example:
 
@@ -18,21 +48,25 @@ Correct example:
 fn handle_authenticated_client(...) { ... }
 ```
 
-Incorrect example:
+Incorrect examples:
 
 ```rust
-let x = 5; // set x to 5 lol
+let x = 5; // set x to 5
+```
+
+```rust
+// This function does stuff
+fn do_stuff() { ... }
 ```
 
 ---
 
 ### 2. File Size and Module Structure
 
-- DO NOT create files larger than 350–550 lines.
+- Files MUST NOT exceed 350–550 lines.
-- If a file exceeds this limit, split it into submodules.
+- If a file exceeds this limit, split it into submodules organized by responsibility (e.g., protocol, transport, state, handlers).
-- Organize submodules logically by responsibility (e.g., protocol, transport, state, handlers).
+- Parent modules MUST declare and describe their submodules.
-- Parent modules MUST declare and describe submodules.
+- Maintain clear architectural boundaries between modules.
-- Use local git for versioning and diffs, write CORRECT and FULL comments to commits with descriptions
 
 Correct example:
 
@@ -48,46 +82,43 @@ pub mod relay;
 pub mod state;
 ```
 
-* Maintain clear architectural boundaries between modules.
+Git discipline:
+
+- Use local git for versioning and diffs.
+- Write clear, descriptive commit messages in English that explain both *what* changed and *why*.
 
 ---
 
 ### 3. Formatting
 
-- DO NOT run `cargo fmt`.
+- Preserve the existing formatting style of the project exactly as-is.
-- DO NOT reformat existing code unless explicitly instructed.
+- Reformat code only when explicitly instructed to do so.
-- Preserve the existing formatting style of the project.
+- Do not run `cargo fmt` unless explicitly instructed.
 
 ---
 
 ### 4. Change Safety and Validation
 
-- DO NOT guess intent, behavior, or missing requirements.
+- If anything is unclear, STOP and ask specific, targeted questions before proceeding.
-- If anything is unclear, STOP and ask questions.
+- List exactly what is ambiguous and offer possible interpretations for the user to choose from.
+- Prefer clarification over assumptions. Do not guess intent, behavior, or missing requirements.
 - Actively ask questions before making architectural or behavioral changes.
-- Prefer clarification over assumptions.
 
 ---
 
 ### 5. Warnings and Unused Code
 
-- DO NOT fix warnings unless explicitly instructed.
+- Leave all warnings, unused variables, functions, imports, and dead code untouched unless explicitly instructed to modify them.
-- DO NOT remove:
+- These may be intentional or part of work-in-progress code.
-
+- `todo!()` and `unimplemented!()` are permitted and should not be removed or replaced unless explicitly instructed.
-  - unused variables
-  - unused functions
-  - unused imports
-  - dead code
-
-These may be intentional.
 
 ---
 
 ### 6. Architectural Integrity
 
 - Preserve existing architecture unless explicitly instructed to refactor.
-- DO NOT introduce hidden behavioral changes.
+- Do not introduce hidden behavioral changes.
-- DO NOT introduce implicit refactors.
+- Do not introduce implicit refactors.
 - Keep changes minimal, isolated, and intentional.
 
 ---
@@ -96,17 +127,81 @@ These may be intentional.
 
 You MUST:
 
-- Maintain architectural consistency.
+- Maintain architectural consistency with the existing codebase.
-- Document non-obvious logic.
+- Document non-obvious logic with comments that describe *why*, not *what*.
-- Avoid unrelated changes.
+- Limit changes strictly to the requested scope (plus coordinated fixes per Section 0).
-- Avoid speculative improvements.
+- Keep all existing symbol names unless renaming is explicitly requested.
+- Preserve global formatting as-is.
 
 You MUST NOT:
 
-- Refactor unrelated code.
+- Use placeholders: no `// ... rest of code`, no `// implement here`, no `/* TODO */` stubs that replace existing working code. Write full, working implementation. If the implementation is unclear, ask first.
-- Rename symbols without explicit reason.
+- Refactor code outside the requested scope.
-- Change formatting globally.
+- Make speculative improvements.
+
+Note: `todo!()` and `unimplemented!()` are allowed as idiomatic Rust markers for genuinely unfinished code paths.
 
 ---
 
-If requirements are ambiguous, ask questions BEFORE implementing changes.
+### 8. Decision Process for Complex Changes
+
+When facing a non-trivial modification, follow this sequence:
+
+1. **Clarify**: Restate the task in one sentence to confirm understanding.
+2. **Assess impact**: Identify which modules, types, and invariants are affected.
+3. **Propose**: Describe the intended change before implementing it.
+4. **Implement**: Make the minimal, isolated change.
+5. **Verify**: Explain why the change preserves existing behavior and architectural integrity.
+
+---
+
+### 9. Context Awareness
+
+- When provided with partial code, assume the rest of the codebase exists and functions correctly unless stated otherwise.
+- Reference existing types, functions, and module structures by their actual names as shown in the provided code.
+- When the provided context is insufficient to make a safe change, request the missing context explicitly.
+
+---
+
+### 10. Response Format
+
+#### Language Policy
+
+- Code, comments, commit messages, documentation: **English**.
+- Reasoning and explanations in response text: **Russian**.
+
+#### Response Structure
+
+Your response MUST consist of two sections:
+
+**Section 1: `## Reasoning` (in Russian)**
+
+- What needs to be done and why.
+- Which files and modules are affected.
+- Architectural decisions and their rationale.
+- Potential risks or side effects.
+
+**Section 2: `## Changes`**
+
+- For each modified or created file: the filename on a separate line in backticks, followed by the code block.
+- For files **under 200 lines**: return the full file with all changes applied.
+- For files **over 200 lines**: return only the changed functions/blocks with at least 3 lines of surrounding context above and below. If the user requests the full file, provide it.
+- New files: full file content.
+- End with a suggested git commit message in English.
+
+#### Reporting Out-of-Scope Issues
+
+If during modification you discover issues outside the requested scope (potential bugs, unsafe code, architectural concerns, missing error handling, unused imports, dead code):
+
+- Do not fix them silently.
+- List them under `## ⚠️ Out-of-scope observations` at the end of your response.
+- Include: file path, line/function context, brief description of the issue, and severity estimate.
+
+#### Splitting Protocol
+
+If the response exceeds the output limit:
+
+1. End the current part with: **SPLIT: PART N — CONTINUE? (remaining: file_list)**
+2. List the files that will be provided in subsequent parts.
+3. Wait for user confirmation before continuing.
+4. No single file may be split across parts.

Cargo.lock

@@ -591,6 +591,25 @@ dependencies = [
  "wasip3",
 ]
 
+[[package]]
+name = "h2"
+version = "0.4.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2f44da3a8150a6703ed5d34e164b875fd14c2cdab9af1252a9a1020bde2bdc54"
+dependencies = [
+ "atomic-waker",
+ "bytes",
+ "fnv",
+ "futures-core",
+ "futures-sink",
+ "http",
+ "indexmap",
+ "slab",
+ "tokio",
+ "tokio-util",
+ "tracing",
+]
+
 [[package]]
 name = "half"
 version = "2.7.1"
@@ -694,6 +713,12 @@ version = "1.10.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6dbf3de79e51f3d586ab4cb9d5c3e2c14aa28ed23d180cf89b4df0454a69cc87"
 
+[[package]]
+name = "httpdate"
+version = "1.0.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "df3b46402a9d5adb4c86a0cf463f42e19994e3ee891101b1841f30a545cb49a9"
+
 [[package]]
 name = "hyper"
 version = "1.8.1"
@@ -704,9 +729,11 @@ dependencies = [
  "bytes",
  "futures-channel",
  "futures-core",
+ "h2",
  "http",
  "http-body",
  "httparse",
+ "httpdate",
  "itoa",
  "pin-project-lite",
  "pin-utils",
@@ -1757,6 +1784,10 @@ dependencies = [
  "futures",
  "hex",
  "hmac",
+ "http-body-util",
+ "httpdate",
+ "hyper",
+ "hyper-util",
  "libc",
  "lru",
  "md-5",
@@ -1929,8 +1960,12 @@ checksum = "9ae9cec805b01e8fc3fd2fe289f89149a9b66dd16786abd8b19cfa7b48cb0098"
 dependencies = [
  "bytes",
  "futures-core",
+ "futures-io",
  "futures-sink",
+ "futures-util",
+ "hashbrown 0.15.5",
  "pin-project-lite",
+ "slab",
  "tokio",
 ]
 

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "telemt"
-version = "3.0.0"
+version = "3.0.3"
 edition = "2024"
 
 [dependencies]

README.md

@@ -210,11 +210,18 @@ then Ctrl+X -> Y -> Enter to save
 ```toml
 # === General Settings ===
 [general]
+# prefer_ipv6 is deprecated; use [network].prefer
 prefer_ipv6 = false
 fast_mode = true
 use_middle_proxy = false
 # ad_tag = "..."
 
+[network]
+ipv4 = true
+ipv6 = true   # set false to disable, omit for auto
+prefer = 4    # 4 or 6
+multipath = false
+
 [general.modes]
 classic = false
 secure = false

config.toml

@@ -1,10 +1,19 @@
 # === General Settings ===
 [general]
-prefer_ipv6 = true
+# prefer_ipv6 is deprecated; use [network].prefer instead
+prefer_ipv6 = false
 fast_mode = true
 use_middle_proxy = true
 #ad_tag = "00000000000000000000000000000000"
 
+[network]
+# Enable/disable families; ipv6 = true/false/auto(None)
+ipv4 = true
+ipv6 = true
+# prefer = 4 or 6
+prefer = 4
+multipath = false
+
 # 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

src/cli.rs

@@ -189,11 +189,18 @@ r#"# Telemt MTProxy — auto-generated config
 show_link = ["{username}"]
 
 [general]
+# prefer_ipv6 is deprecated; use [network].prefer
 prefer_ipv6 = false
 fast_mode = true
 use_middle_proxy = false
 log_level = "normal"
 
+[network]
+ipv4 = true
+ipv6 = true
+prefer = 4
+multipath = false
+
 [general.modes]
 classic = false
 secure = false

src/config/mod.rs

@@ -54,6 +54,10 @@ fn default_metrics_whitelist() -> Vec<IpAddr> {
     vec!["127.0.0.1".parse().unwrap(), "::1".parse().unwrap()]
 }
 
+fn default_prefer_4() -> u8 {
+    4
+}
+
 fn default_unknown_dc_log_path() -> Option<String> {
     Some("unknown-dc.txt".to_string())
 }
@@ -185,6 +189,32 @@ impl std::fmt::Display for LogLevel {
     }
 }
 
+fn validate_network_cfg(net: &mut NetworkConfig) -> Result<()> {
+    if !net.ipv4 && matches!(net.ipv6, Some(false)) {
+        return Err(ProxyError::Config(
+            "Both ipv4 and ipv6 are disabled in [network]".to_string(),
+        ));
+    }
+
+    if net.prefer != 4 && net.prefer != 6 {
+        return Err(ProxyError::Config(
+            "network.prefer must be 4 or 6".to_string(),
+        ));
+    }
+
+    if !net.ipv4 && net.prefer == 4 {
+        warn!("prefer=4 but ipv4=false; forcing prefer=6");
+        net.prefer = 6;
+    }
+
+    if matches!(net.ipv6, Some(false)) && net.prefer == 6 {
+        warn!("prefer=6 but ipv6=false; forcing prefer=4");
+        net.prefer = 4;
+    }
+
+    Ok(())
+}
+
 // ============= Sub-Configs =============
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
@@ -207,6 +237,34 @@ impl Default for ProxyModes {
     }
 }
 
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct NetworkConfig {
+    #[serde(default = "default_true")]
+    pub ipv4: bool,
+
+    /// None = auto-detect IPv6 availability
+    #[serde(default)]
+    pub ipv6: Option<bool>,
+
+    /// 4 or 6
+    #[serde(default = "default_prefer_4")]
+    pub prefer: u8,
+
+    #[serde(default)]
+    pub multipath: bool,
+}
+
+impl Default for NetworkConfig {
+    fn default() -> Self {
+        Self {
+            ipv4: true,
+            ipv6: None,
+            prefer: 4,
+            multipath: false,
+        }
+    }
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct GeneralConfig {
     #[serde(default)]
@@ -609,6 +667,9 @@ pub struct ProxyConfig {
     #[serde(default)]
     pub general: GeneralConfig,
 
+    #[serde(default)]
+    pub network: NetworkConfig,
+
     #[serde(default)]
     pub server: ServerConfig,
 
@@ -697,6 +758,16 @@ impl ProxyConfig {
             config.censorship.mask_host = Some(config.censorship.tls_domain.clone());
         }
 
+        // Migration: prefer_ipv6 -> network.prefer
+        if config.general.prefer_ipv6 {
+            if config.network.prefer == 4 {
+                config.network.prefer = 6;
+            }
+            warn!("prefer_ipv6 is deprecated, use [network].prefer = 6");
+        }
+
+        validate_network_cfg(&mut config.network)?;
+
         // Random fake_cert_len
         use rand::Rng;
         config.censorship.fake_cert_len = rand::rng().gen_range(1024..4096);

src/main.rs

@@ -16,6 +16,7 @@ mod config;
 mod crypto;
 mod error;
 mod ip_tracker;
+mod network;
 mod metrics;
 mod protocol;
 mod proxy;
@@ -27,16 +28,14 @@ mod util;
 use crate::config::{LogLevel, ProxyConfig};
 use crate::crypto::SecureRandom;
 use crate::ip_tracker::UserIpTracker;
+use crate::network::probe::{decide_network_capabilities, log_probe_result, run_probe};
 use crate::proxy::ClientHandler;
 use crate::stats::{ReplayChecker, Stats};
 use crate::stream::BufferPool;
 use crate::transport::middle_proxy::{
     MePool, fetch_proxy_config, run_me_ping, MePingFamily, MePingSample, format_sample_line,
-    stun_probe,
 };
 use crate::transport::{ListenOptions, UpstreamManager, create_listener};
-use crate::util::ip::detect_ip;
-use crate::protocol::constants::{TG_MIDDLE_PROXIES_V4, TG_MIDDLE_PROXIES_V6};
 
 fn parse_cli() -> (String, bool, Option<String>) {
     let mut config_path = "config.toml".to_string();
@@ -219,8 +218,17 @@ async fn main() -> std::result::Result<(), Box<dyn std::error::Error>> {
         warn!("Using default tls_domain. Consider setting a custom domain.");
     }
 
-    let prefer_ipv6 = config.general.prefer_ipv6;
+    let probe = run_probe(
-    let mut use_middle_proxy = config.general.use_middle_proxy;
+        &config.network,
+        config.general.middle_proxy_nat_stun.clone(),
+        config.general.middle_proxy_nat_probe,
+    )
+    .await?;
+    let decision = decide_network_capabilities(&config.network, &probe);
+    log_probe_result(&probe, &decision);
+
+    let prefer_ipv6 = decision.prefer_ipv6();
+    let mut use_middle_proxy = config.general.use_middle_proxy && (decision.ipv4_me || decision.ipv6_me);
     let config = Arc::new(config);
     let stats = Arc::new(Stats::new());
     let rng = Arc::new(SecureRandom::new());
@@ -244,40 +252,10 @@ async fn main() -> std::result::Result<(), Box<dyn std::error::Error>> {
     // Connection concurrency limit
     let _max_connections = Arc::new(Semaphore::new(10_000));
 
-    // STUN check before choosing transport
+    if use_middle_proxy && !decision.ipv4_me && !decision.ipv6_me {
-    if use_middle_proxy {
+        warn!("No usable IP family for Middle Proxy detected; falling back to direct DC");
-        match stun_probe(config.general.middle_proxy_nat_stun.clone()).await {
-            Ok(Some(probe)) => {
-                info!(
-                    local_ip = %probe.local_addr.ip(),
-                    reflected_ip = %probe.reflected_addr.ip(),
-                    "STUN Autodetect:"
-                );
-                if probe.local_addr.ip() != probe.reflected_addr.ip()
-                    && !config.general.stun_iface_mismatch_ignore
-                {
-                    match crate::transport::middle_proxy::detect_public_ip().await {
-                        Some(ip) => {
-                            info!(
-                                local_ip = %probe.local_addr.ip(),
-                                reflected_ip = %probe.reflected_addr.ip(),
-                                public_ip = %ip,
-                                "STUN mismatch but public IP auto-detected, continuing with middle proxy"
-                            );
-                        }
-                        None => {
-                            warn!(
-                                "STUN/IP-on-Interface mismatch and public IP auto-detect failed -> fallback to direct-DC"
-                            );
         use_middle_proxy = false;
     }
-                    }
-                }
-            }
-            Ok(None) => warn!("STUN probe returned no address; continuing"),
-            Err(e) => warn!(error = %e, "STUN probe failed; continuing"),
-        }
-    }
 
     // =====================================================================
     // Middle Proxy initialization (if enabled)
@@ -351,6 +329,8 @@ match crate::transport::middle_proxy::fetch_proxy_secret(proxy_secret_path).awai
                     cfg_v4.map.clone(),
                     cfg_v6.map.clone(),
                     cfg_v4.default_dc.or(cfg_v6.default_dc),
+                    decision.clone(),
+                    rng.clone(),
                 );
 
                 match pool.init(2, &rng).await {
@@ -482,7 +462,12 @@ match crate::transport::middle_proxy::fetch_proxy_secret(proxy_secret_path).awai
     info!("================= Telegram DC Connectivity =================");
 
     let ping_results = upstream_manager
-        .ping_all_dcs(prefer_ipv6, &config.dc_overrides)
+        .ping_all_dcs(
+            prefer_ipv6,
+            &config.dc_overrides,
+            decision.ipv4_dc,
+            decision.ipv6_dc,
+        )
         .await;
 
 	for upstream_result in &ping_results {
@@ -559,8 +544,15 @@ match crate::transport::middle_proxy::fetch_proxy_secret(proxy_secret_path).awai
 
     // Background tasks
     let um_clone = upstream_manager.clone();
+    let decision_clone = decision.clone();
     tokio::spawn(async move {
-        um_clone.run_health_checks(prefer_ipv6).await;
+        um_clone
+            .run_health_checks(
+                prefer_ipv6,
+                decision_clone.ipv4_dc,
+                decision_clone.ipv6_dc,
+            )
+            .await;
     });
 
     let rc_clone = replay_checker.clone();
@@ -568,16 +560,31 @@ match crate::transport::middle_proxy::fetch_proxy_secret(proxy_secret_path).awai
         rc_clone.run_periodic_cleanup().await;
     });
 
-    let detected_ip = detect_ip().await;
+    let detected_ip_v4: Option<std::net::IpAddr> = probe
+        .reflected_ipv4
+        .map(|s| s.ip())
+        .or_else(|| probe.detected_ipv4.map(std::net::IpAddr::V4));
+    let detected_ip_v6: Option<std::net::IpAddr> = probe
+        .reflected_ipv6
+        .map(|s| s.ip())
+        .or_else(|| probe.detected_ipv6.map(std::net::IpAddr::V6));
     debug!(
         "Detected IPs: v4={:?} v6={:?}",
-        detected_ip.ipv4, detected_ip.ipv6
+        detected_ip_v4, detected_ip_v6
     );
 
     let mut listeners = Vec::new();
 
     for listener_conf in &config.server.listeners {
         let addr = SocketAddr::new(listener_conf.ip, config.server.port);
+        if addr.is_ipv4() && !decision.ipv4_dc {
+            warn!(%addr, "Skipping IPv4 listener: IPv4 disabled by [network]");
+            continue;
+        }
+        if addr.is_ipv6() && !decision.ipv6_dc {
+            warn!(%addr, "Skipping IPv6 listener: IPv6 disabled by [network]");
+            continue;
+        }
         let options = ListenOptions {
             ipv6_only: listener_conf.ip.is_ipv6(),
             ..Default::default()
@@ -594,11 +601,11 @@ match crate::transport::middle_proxy::fetch_proxy_secret(proxy_secret_path).awai
                 } else if listener_conf.ip.is_unspecified() {
                     // Auto-detect for unspecified addresses
                     if listener_conf.ip.is_ipv4() {
-                        detected_ip.ipv4
+                        detected_ip_v4
                             .map(|ip| ip.to_string())
                             .unwrap_or_else(|| listener_conf.ip.to_string())
                     } else {
-                        detected_ip.ipv6
+                        detected_ip_v6
                             .map(|ip| ip.to_string())
                             .unwrap_or_else(|| listener_conf.ip.to_string())
                     }
@@ -626,9 +633,8 @@ match crate::transport::middle_proxy::fetch_proxy_secret(proxy_secret_path).awai
         let (host, port) = if let Some(ref h) = config.general.links.public_host {
             (h.clone(), config.general.links.public_port.unwrap_or(config.server.port))
         } else {
-            let ip = detected_ip
+            let ip = detected_ip_v4
-                .ipv4
+                .or(detected_ip_v6)
-                .or(detected_ip.ipv6)
                 .map(|ip| ip.to_string());
             if ip.is_none() {
                 warn!("show_link is configured but public IP could not be detected. Set public_host in config.");

src/network/mod.rs

@@ -0,0 +1,4 @@
+pub mod probe;
+pub mod stun;
+
+pub use stun::IpFamily;

src/network/probe.rs

@@ -0,0 +1,225 @@
+use std::net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr, UdpSocket};
+
+use tracing::{info, warn};
+
+use crate::config::NetworkConfig;
+use crate::error::Result;
+use crate::network::stun::{stun_probe_dual, DualStunResult, IpFamily};
+
+#[derive(Debug, Clone, Default)]
+pub struct NetworkProbe {
+    pub detected_ipv4: Option<Ipv4Addr>,
+    pub detected_ipv6: Option<Ipv6Addr>,
+    pub reflected_ipv4: Option<SocketAddr>,
+    pub reflected_ipv6: Option<SocketAddr>,
+    pub ipv4_is_bogon: bool,
+    pub ipv6_is_bogon: bool,
+    pub ipv4_nat_detected: bool,
+    pub ipv6_nat_detected: bool,
+    pub ipv4_usable: bool,
+    pub ipv6_usable: bool,
+}
+
+#[derive(Debug, Clone, Default)]
+pub struct NetworkDecision {
+    pub ipv4_dc: bool,
+    pub ipv6_dc: bool,
+    pub ipv4_me: bool,
+    pub ipv6_me: bool,
+    pub effective_prefer: u8,
+    pub effective_multipath: bool,
+}
+
+impl NetworkDecision {
+    pub fn prefer_ipv6(&self) -> bool {
+        self.effective_prefer == 6
+    }
+
+    pub fn me_families(&self) -> Vec<IpFamily> {
+        let mut res = Vec::new();
+        if self.ipv4_me {
+            res.push(IpFamily::V4);
+        }
+        if self.ipv6_me {
+            res.push(IpFamily::V6);
+        }
+        res
+    }
+}
+
+pub async fn run_probe(config: &NetworkConfig, stun_addr: Option<String>, nat_probe: bool) -> Result<NetworkProbe> {
+    let mut probe = NetworkProbe::default();
+
+    probe.detected_ipv4 = detect_local_ip_v4();
+    probe.detected_ipv6 = detect_local_ip_v6();
+
+    probe.ipv4_is_bogon = probe.detected_ipv4.map(is_bogon_v4).unwrap_or(false);
+    probe.ipv6_is_bogon = probe.detected_ipv6.map(is_bogon_v6).unwrap_or(false);
+
+    let stun_server = stun_addr.unwrap_or_else(|| "stun.l.google.com:19302".to_string());
+    let stun_res = if nat_probe {
+        stun_probe_dual(&stun_server).await?
+    } else {
+        DualStunResult::default()
+    };
+    probe.reflected_ipv4 = stun_res.v4.map(|r| r.reflected_addr);
+    probe.reflected_ipv6 = stun_res.v6.map(|r| r.reflected_addr);
+
+    probe.ipv4_nat_detected = match (probe.detected_ipv4, probe.reflected_ipv4) {
+        (Some(det), Some(reflected)) => det != reflected.ip(),
+        _ => false,
+    };
+    probe.ipv6_nat_detected = match (probe.detected_ipv6, probe.reflected_ipv6) {
+        (Some(det), Some(reflected)) => det != reflected.ip(),
+        _ => false,
+    };
+
+    probe.ipv4_usable = config.ipv4
+        && probe.detected_ipv4.is_some()
+        && (!probe.ipv4_is_bogon || probe.reflected_ipv4.map(|r| !is_bogon(r.ip())).unwrap_or(false));
+
+    let ipv6_enabled = config.ipv6.unwrap_or(probe.detected_ipv6.is_some());
+    probe.ipv6_usable = ipv6_enabled
+        && probe.detected_ipv6.is_some()
+        && (!probe.ipv6_is_bogon || probe.reflected_ipv6.map(|r| !is_bogon(r.ip())).unwrap_or(false));
+
+    Ok(probe)
+}
+
+pub fn decide_network_capabilities(config: &NetworkConfig, probe: &NetworkProbe) -> NetworkDecision {
+    let mut decision = NetworkDecision::default();
+
+    decision.ipv4_dc = config.ipv4 && probe.detected_ipv4.is_some();
+    decision.ipv6_dc = config.ipv6.unwrap_or(probe.detected_ipv6.is_some()) && probe.detected_ipv6.is_some();
+
+    decision.ipv4_me = config.ipv4
+        && probe.detected_ipv4.is_some()
+        && (!probe.ipv4_is_bogon || probe.reflected_ipv4.is_some());
+
+    let ipv6_enabled = config.ipv6.unwrap_or(probe.detected_ipv6.is_some());
+    decision.ipv6_me = ipv6_enabled
+        && probe.detected_ipv6.is_some()
+        && (!probe.ipv6_is_bogon || probe.reflected_ipv6.is_some());
+
+    decision.effective_prefer = match config.prefer {
+        6 if decision.ipv6_me || decision.ipv6_dc => 6,
+        4 if decision.ipv4_me || decision.ipv4_dc => 4,
+        6 => {
+            warn!("prefer=6 requested but IPv6 unavailable; falling back to IPv4");
+            4
+        }
+        _ => 4,
+    };
+
+    let me_families = decision.ipv4_me as u8 + decision.ipv6_me as u8;
+    decision.effective_multipath = config.multipath && me_families >= 2;
+
+    decision
+}
+
+fn detect_local_ip_v4() -> Option<Ipv4Addr> {
+    let socket = UdpSocket::bind("0.0.0.0:0").ok()?;
+    socket.connect("8.8.8.8:80").ok()?;
+    match socket.local_addr().ok()?.ip() {
+        IpAddr::V4(v4) => Some(v4),
+        _ => None,
+    }
+}
+
+fn detect_local_ip_v6() -> Option<Ipv6Addr> {
+    let socket = UdpSocket::bind("[::]:0").ok()?;
+    socket.connect("[2001:4860:4860::8888]:80").ok()?;
+    match socket.local_addr().ok()?.ip() {
+        IpAddr::V6(v6) => Some(v6),
+        _ => None,
+    }
+}
+
+pub fn is_bogon(ip: IpAddr) -> bool {
+    match ip {
+        IpAddr::V4(v4) => is_bogon_v4(v4),
+        IpAddr::V6(v6) => is_bogon_v6(v6),
+    }
+}
+
+pub fn is_bogon_v4(ip: Ipv4Addr) -> bool {
+    let octets = ip.octets();
+    if ip.is_private() || ip.is_loopback() || ip.is_link_local() {
+        return true;
+    }
+    if octets[0] == 0 {
+        return true;
+    }
+    if octets[0] == 100 && (octets[1] & 0xC0) == 64 {
+        return true;
+    }
+    if octets[0] == 192 && octets[1] == 0 && octets[2] == 0 {
+        return true;
+    }
+    if octets[0] == 192 && octets[1] == 0 && octets[2] == 2 {
+        return true;
+    }
+    if octets[0] == 198 && (octets[1] & 0xFE) == 18 {
+        return true;
+    }
+    if octets[0] == 198 && octets[1] == 51 && octets[2] == 100 {
+        return true;
+    }
+    if octets[0] == 203 && octets[1] == 0 && octets[2] == 113 {
+        return true;
+    }
+    if ip.is_multicast() {
+        return true;
+    }
+    if octets[0] >= 240 {
+        return true;
+    }
+    if ip.is_broadcast() {
+        return true;
+    }
+    false
+}
+
+pub fn is_bogon_v6(ip: Ipv6Addr) -> bool {
+    if ip.is_unspecified() || ip.is_loopback() || ip.is_unique_local() {
+        return true;
+    }
+    let segs = ip.segments();
+    if (segs[0] & 0xFFC0) == 0xFE80 {
+        return true;
+    }
+    if segs[0..5] == [0, 0, 0, 0, 0] && segs[5] == 0xFFFF {
+        return true;
+    }
+    if segs[0] == 0x0100 && segs[1..4] == [0, 0, 0] {
+        return true;
+    }
+    if segs[0] == 0x2001 && segs[1] == 0x0db8 {
+        return true;
+    }
+    if segs[0] == 0x2002 {
+        return true;
+    }
+    if ip.is_multicast() {
+        return true;
+    }
+    false
+}
+
+pub fn log_probe_result(probe: &NetworkProbe, decision: &NetworkDecision) {
+    info!(
+        ipv4 = probe.detected_ipv4.as_ref().map(|v| v.to_string()).unwrap_or_else(|| "-".into()),
+        ipv6 = probe.detected_ipv6.as_ref().map(|v| v.to_string()).unwrap_or_else(|| "-".into()),
+        reflected_v4 = probe.reflected_ipv4.as_ref().map(|v| v.ip().to_string()).unwrap_or_else(|| "-".into()),
+        reflected_v6 = probe.reflected_ipv6.as_ref().map(|v| v.ip().to_string()).unwrap_or_else(|| "-".into()),
+        ipv4_bogon = probe.ipv4_is_bogon,
+        ipv6_bogon = probe.ipv6_is_bogon,
+        ipv4_me = decision.ipv4_me,
+        ipv6_me = decision.ipv6_me,
+        ipv4_dc = decision.ipv4_dc,
+        ipv6_dc = decision.ipv6_dc,
+        prefer = decision.effective_prefer,
+        multipath = decision.effective_multipath,
+        "Network capabilities resolved"
+    );
+}

src/network/stun.rs

@@ -0,0 +1,186 @@
+use std::net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr};
+
+use tokio::net::{lookup_host, UdpSocket};
+
+use crate::error::{ProxyError, Result};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum IpFamily {
+    V4,
+    V6,
+}
+
+#[derive(Debug, Clone, Copy)]
+pub struct StunProbeResult {
+    pub local_addr: SocketAddr,
+    pub reflected_addr: SocketAddr,
+    pub family: IpFamily,
+}
+
+#[derive(Debug, Default, Clone)]
+pub struct DualStunResult {
+    pub v4: Option<StunProbeResult>,
+    pub v6: Option<StunProbeResult>,
+}
+
+pub async fn stun_probe_dual(stun_addr: &str) -> Result<DualStunResult> {
+    let (v4, v6) = tokio::join!(
+        stun_probe_family(stun_addr, IpFamily::V4),
+        stun_probe_family(stun_addr, IpFamily::V6),
+    );
+
+    Ok(DualStunResult {
+        v4: v4?,
+        v6: v6?,
+    })
+}
+
+pub async fn stun_probe_family(stun_addr: &str, family: IpFamily) -> Result<Option<StunProbeResult>> {
+    use rand::RngCore;
+
+    let bind_addr = match family {
+        IpFamily::V4 => "0.0.0.0:0",
+        IpFamily::V6 => "[::]:0",
+    };
+
+    let socket = UdpSocket::bind(bind_addr)
+        .await
+        .map_err(|e| ProxyError::Proxy(format!("STUN bind failed: {e}")))?;
+
+    let target_addr = resolve_stun_addr(stun_addr, family).await?;
+    if let Some(addr) = target_addr {
+        socket
+            .connect(addr)
+            .await
+            .map_err(|e| ProxyError::Proxy(format!("STUN connect failed: {e}")))?;
+    } else {
+        return Ok(None);
+    }
+
+    let mut req = [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::rng().fill_bytes(&mut req[8..20]); // transaction ID
+
+    socket
+        .send(&req)
+        .await
+        .map_err(|e| ProxyError::Proxy(format!("STUN send failed: {e}")))?;
+
+    let mut buf = [0u8; 256];
+    let n = socket
+        .recv(&mut buf)
+        .await
+        .map_err(|e| ProxyError::Proxy(format!("STUN recv failed: {e}")))?;
+    if n < 20 {
+        return Ok(None);
+    }
+
+    let magic = 0x2112A442u32.to_be_bytes();
+    let txid = &req[8..20];
+    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_byte = buf[idx + 1];
+                let port_bytes = [buf[idx + 2], buf[idx + 3]];
+                let len_check = match family_byte {
+                    0x01 => 4,
+                    0x02 => 16,
+                    _ => 0,
+                };
+                if len_check == 0 || alen < 4 + len_check {
+                    break;
+                }
+
+                let raw_ip = &buf[idx + 4..idx + 4 + len_check];
+                let mut port = u16::from_be_bytes(port_bytes);
+
+                let reflected_ip = if atype == 0x0020 {
+                    port ^= ((magic[0] as u16) << 8) | magic[1] as u16;
+                    match family_byte {
+                        0x01 => {
+                            let ip = [
+                                raw_ip[0] ^ magic[0],
+                                raw_ip[1] ^ magic[1],
+                                raw_ip[2] ^ magic[2],
+                                raw_ip[3] ^ magic[3],
+                            ];
+                            IpAddr::V4(Ipv4Addr::new(ip[0], ip[1], ip[2], ip[3]))
+                        }
+                        0x02 => {
+                            let mut ip = [0u8; 16];
+                            let xor_key = [magic.as_slice(), txid].concat();
+                            for (i, b) in raw_ip.iter().enumerate().take(16) {
+                                ip[i] = *b ^ xor_key[i];
+                            }
+                            IpAddr::V6(Ipv6Addr::from(ip))
+                        }
+                        _ => {
+                            idx += (alen + 3) & !3;
+                            continue;
+                        }
+                    }
+                } else {
+                    match family_byte {
+                        0x01 => IpAddr::V4(Ipv4Addr::new(raw_ip[0], raw_ip[1], raw_ip[2], raw_ip[3])),
+                        0x02 => IpAddr::V6(Ipv6Addr::from(<[u8; 16]>::try_from(raw_ip).unwrap())),
+                        _ => {
+                            idx += (alen + 3) & !3;
+                            continue;
+                        }
+                    }
+                };
+
+                let reflected_addr = SocketAddr::new(reflected_ip, port);
+                let local_addr = socket
+                    .local_addr()
+                    .map_err(|e| ProxyError::Proxy(format!("STUN local_addr failed: {e}")))?;
+
+                return Ok(Some(StunProbeResult {
+                    local_addr,
+                    reflected_addr,
+                    family,
+                }));
+            }
+            _ => {}
+        }
+
+        idx += (alen + 3) & !3;
+    }
+
+    Ok(None)
+}
+
+async fn resolve_stun_addr(stun_addr: &str, family: IpFamily) -> Result<Option<SocketAddr>> {
+    if let Ok(addr) = stun_addr.parse::<SocketAddr>() {
+        return Ok(match (addr.is_ipv4(), family) {
+            (true, IpFamily::V4) | (false, IpFamily::V6) => Some(addr),
+            _ => None,
+        });
+    }
+
+    let addrs = lookup_host(stun_addr)
+        .await
+        .map_err(|e| ProxyError::Proxy(format!("STUN resolve failed: {e}")))?;
+
+    let target = addrs
+        .filter(|a| match (a.is_ipv4(), family) {
+            (true, IpFamily::V4) => true,
+            (false, IpFamily::V6) => true,
+            _ => false,
+        })
+        .next();
+    Ok(target)
+}

src/proxy/direct_relay.rs

@@ -80,7 +80,8 @@ where
 }
 
 fn get_dc_addr_static(dc_idx: i16, config: &ProxyConfig) -> Result<SocketAddr> {
-    let datacenters = if config.general.prefer_ipv6 {
+    let prefer_v6 = config.network.prefer == 6 && config.network.ipv6.unwrap_or(true);
+    let datacenters = if prefer_v6 {
         &*TG_DATACENTERS_V6
     } else {
         &*TG_DATACENTERS_V4
@@ -90,7 +91,6 @@ fn get_dc_addr_static(dc_idx: i16, config: &ProxyConfig) -> Result<SocketAddr> {
 
     let dc_key = dc_idx.to_string();
     if let Some(addrs) = config.dc_overrides.get(&dc_key) {
-        let prefer_v6 = config.general.prefer_ipv6;
         let mut parsed = Vec::new();
         for addr_str in addrs {
             match addr_str.parse::<SocketAddr>() {

src/transport/middle_proxy/handshake.rs

@@ -16,6 +16,7 @@ use tracing::{debug, info, warn};
 
 use crate::crypto::{SecureRandom, build_middleproxy_prekey, derive_middleproxy_keys, sha256};
 use crate::error::{ProxyError, Result};
+use crate::network::IpFamily;
 use crate::protocol::constants::{
     ME_CONNECT_TIMEOUT_SECS, ME_HANDSHAKE_TIMEOUT_SECS, RPC_CRYPTO_AES_U32, RPC_HANDSHAKE_ERROR_U32,
     RPC_HANDSHAKE_U32, RPC_PING_U32, RPC_PONG_U32, RPC_NONCE_U32,
@@ -101,8 +102,13 @@ impl MePool {
         let peer_addr = stream.peer_addr().map_err(ProxyError::Io)?;
 
         let _ = self.maybe_detect_nat_ip(local_addr.ip()).await;
+        let family = if local_addr.ip().is_ipv4() {
+            IpFamily::V4
+        } else {
+            IpFamily::V6
+        };
         let reflected = if self.nat_probe {
-            self.maybe_reflect_public_addr().await
+            self.maybe_reflect_public_addr(family).await
         } else {
             None
         };

src/transport/middle_proxy/health.rs

@@ -1,4 +1,4 @@
-use std::collections::HashMap;
+use std::collections::{HashMap, HashSet};
 use std::net::SocketAddr;
 use std::sync::Arc;
 use std::time::{Duration, Instant};
@@ -7,17 +7,40 @@ use tracing::{debug, info, warn};
 use rand::seq::SliceRandom;
 
 use crate::crypto::SecureRandom;
+use crate::network::IpFamily;
 
 use super::MePool;
 
 pub async fn me_health_monitor(pool: Arc<MePool>, rng: Arc<SecureRandom>, _min_connections: usize) {
-    let mut backoff: HashMap<i32, u64> = HashMap::new();
+    let mut backoff: HashMap<(i32, IpFamily), u64> = HashMap::new();
-    let mut last_attempt: HashMap<i32, Instant> = HashMap::new();
+    let mut last_attempt: HashMap<(i32, IpFamily), Instant> = HashMap::new();
     loop {
         tokio::time::sleep(Duration::from_secs(30)).await;
-        // Per-DC coverage check
+        check_family(IpFamily::V4, &pool, &rng, &mut backoff, &mut last_attempt).await;
-        let map = pool.proxy_map_v4.read().await.clone();
+        check_family(IpFamily::V6, &pool, &rng, &mut backoff, &mut last_attempt).await;
-        let writer_addrs: std::collections::HashSet<SocketAddr> = pool
+    }
+}
+
+async fn check_family(
+    family: IpFamily,
+    pool: &Arc<MePool>,
+    rng: &Arc<SecureRandom>,
+    backoff: &mut HashMap<(i32, IpFamily), u64>,
+    last_attempt: &mut HashMap<(i32, IpFamily), Instant>,
+) {
+    let enabled = match family {
+        IpFamily::V4 => pool.decision.ipv4_me,
+        IpFamily::V6 => pool.decision.ipv6_me,
+    };
+    if !enabled {
+        return;
+    }
+
+    let map = match family {
+        IpFamily::V4 => pool.proxy_map_v4.read().await.clone(),
+        IpFamily::V6 => pool.proxy_map_v6.read().await.clone(),
+    };
+    let writer_addrs: HashSet<SocketAddr> = pool
         .writers
         .read()
         .await
@@ -31,83 +54,37 @@ pub async fn me_health_monitor(pool: Arc<MePool>, rng: Arc<SecureRandom>, _min_c
             .map(|(ip, port)| SocketAddr::new(*ip, *port))
             .collect();
         let has_coverage = dc_addrs.iter().any(|a| writer_addrs.contains(a));
-            if !has_coverage {
+        if has_coverage {
-                let delay = *backoff.get(dc).unwrap_or(&30);
+            continue;
+        }
+        let key = (*dc, family);
+        let delay = *backoff.get(&key).unwrap_or(&30);
         let now = Instant::now();
-                if let Some(last) = last_attempt.get(dc) {
+        if let Some(last) = last_attempt.get(&key) {
             if now.duration_since(*last).as_secs() < delay {
                 continue;
             }
         }
-                warn!(dc = %dc, delay, "DC has no ME coverage, reconnecting...");
+        warn!(dc = %dc, delay, ?family, "DC has no ME coverage, reconnecting...");
         let mut shuffled = dc_addrs.clone();
         shuffled.shuffle(&mut rand::rng());
         let mut reconnected = false;
         for addr in shuffled {
-                    match pool.connect_one(addr, &rng).await {
+            match pool.connect_one(addr, rng.as_ref()).await {
                 Ok(()) => {
-                            info!(%addr, dc = %dc, "ME reconnected for DC coverage");
+                    info!(%addr, dc = %dc, ?family, "ME reconnected for DC coverage");
-                            backoff.insert(*dc, 30);
+                    backoff.insert(key, 30);
-                            last_attempt.insert(*dc, now);
+                    last_attempt.insert(key, now);
                     reconnected = true;
                     break;
                 }
-                        Err(e) => debug!(%addr, dc = %dc, error = %e, "ME reconnect failed"),
+                Err(e) => debug!(%addr, dc = %dc, error = %e, ?family, "ME reconnect failed"),
             }
         }
         if !reconnected {
-                    let next = (*backoff.get(dc).unwrap_or(&30)).saturating_mul(2).min(300);
+            let next = (*backoff.get(&key).unwrap_or(&30)).saturating_mul(2).min(300);
-                    backoff.insert(*dc, next);
+            backoff.insert(key, next);
-                    last_attempt.insert(*dc, now);
+            last_attempt.insert(key, now);
-                }
-            }
-        }
-
-        // IPv6 coverage check (if available)
-        let map_v6 = pool.proxy_map_v6.read().await.clone();
-        let writer_addrs_v6: std::collections::HashSet<SocketAddr> = pool
-            .writers
-            .read()
-            .await
-            .iter()
-            .map(|w| w.addr)
-            .collect();
-        for (dc, addrs) in map_v6.iter() {
-            let dc_addrs: Vec<SocketAddr> = addrs
-                .iter()
-                .map(|(ip, port)| SocketAddr::new(*ip, *port))
-                .collect();
-            let has_coverage = dc_addrs.iter().any(|a| writer_addrs_v6.contains(a));
-            if !has_coverage {
-                let delay = *backoff.get(dc).unwrap_or(&30);
-                let now = Instant::now();
-                if let Some(last) = last_attempt.get(dc) {
-                    if now.duration_since(*last).as_secs() < delay {
-                        continue;
-                    }
-                }
-                warn!(dc = %dc, delay, "IPv6 DC has no ME coverage, reconnecting...");
-                let mut shuffled = dc_addrs.clone();
-                shuffled.shuffle(&mut rand::rng());
-                let mut reconnected = false;
-                for addr in shuffled {
-                    match pool.connect_one(addr, &rng).await {
-                        Ok(()) => {
-                            info!(%addr, dc = %dc, "ME reconnected for IPv6 DC coverage");
-                            backoff.insert(*dc, 30);
-                            last_attempt.insert(*dc, now);
-                            reconnected = true;
-                            break;
-                        }
-                        Err(e) => debug!(%addr, dc = %dc, error = %e, "ME reconnect failed (IPv6)"),
-                    }
-                }
-                if !reconnected {
-                    let next = (*backoff.get(dc).unwrap_or(&30)).saturating_mul(2).min(300);
-                    backoff.insert(*dc, next);
-                    last_attempt.insert(*dc, now);
-                }
-            }
         }
     }
 }

src/transport/middle_proxy/mod.rs

@@ -19,7 +19,7 @@ use bytes::Bytes;
 pub use health::me_health_monitor;
 pub use ping::{run_me_ping, format_sample_line, MePingReport, MePingSample, MePingFamily};
 pub use pool::MePool;
-pub use pool_nat::{stun_probe, detect_public_ip, StunProbeResult};
+pub use pool_nat::{stun_probe, detect_public_ip};
 pub use registry::ConnRegistry;
 pub use secret::fetch_proxy_secret;
 pub use config_updater::{fetch_proxy_config, me_config_updater};

src/transport/middle_proxy/ping.rs

@@ -1,3 +1,4 @@
+use std::collections::HashMap;
 use std::net::{IpAddr, SocketAddr};
 use std::sync::Arc;
 
@@ -92,8 +93,16 @@ mod tests {
 pub async fn run_me_ping(pool: &Arc<MePool>, rng: &SecureRandom) -> Vec<MePingReport> {
     let mut reports = Vec::new();
 
-    let v4_map = pool.proxy_map_v4.read().await.clone();
+    let v4_map = if pool.decision.ipv4_me {
-    let v6_map = pool.proxy_map_v6.read().await.clone();
+        pool.proxy_map_v4.read().await.clone()
+    } else {
+        HashMap::new()
+    };
+    let v6_map = if pool.decision.ipv6_me {
+        pool.proxy_map_v6.read().await.clone()
+    } else {
+        HashMap::new()
+    };
 
     let mut grouped: Vec<(MePingFamily, i32, Vec<(IpAddr, u16)>)> = Vec::new();
     for (dc, addrs) in v4_map {

src/transport/middle_proxy/pool.rs

@@ -12,6 +12,8 @@ use std::time::Duration;
 
 use crate::crypto::SecureRandom;
 use crate::error::{ProxyError, Result};
+use crate::network::probe::NetworkDecision;
+use crate::network::IpFamily;
 use crate::protocol::constants::*;
 
 use super::ConnRegistry;
@@ -36,6 +38,8 @@ pub struct MePool {
     pub(super) registry: Arc<ConnRegistry>,
     pub(super) writers: Arc<RwLock<Vec<MeWriter>>>,
     pub(super) rr: AtomicU64,
+    pub(super) decision: NetworkDecision,
+    pub(super) rng: Arc<SecureRandom>,
     pub(super) proxy_tag: Option<Vec<u8>>,
     pub(super) proxy_secret: Arc<RwLock<Vec<u8>>>,
     pub(super) nat_ip_cfg: Option<IpAddr>,
@@ -48,10 +52,16 @@ pub struct MePool {
     pub(super) next_writer_id: AtomicU64,
     pub(super) ping_tracker: Arc<Mutex<HashMap<i64, (std::time::Instant, u64)>>>,
     pub(super) rtt_stats: Arc<Mutex<HashMap<u64, (f64, f64)>>>,
-    pub(super) nat_reflection_cache: Arc<Mutex<Option<(std::time::Instant, std::net::SocketAddr)>>>,
+    pub(super) nat_reflection_cache: Arc<Mutex<NatReflectionCache>>,
     pool_size: usize,
 }
 
+#[derive(Debug, Default)]
+pub struct NatReflectionCache {
+    pub v4: Option<(std::time::Instant, std::net::SocketAddr)>,
+    pub v6: Option<(std::time::Instant, std::net::SocketAddr)>,
+}
+
 impl MePool {
     pub fn new(
         proxy_tag: Option<Vec<u8>>,
@@ -62,11 +72,15 @@ impl MePool {
         proxy_map_v4: HashMap<i32, Vec<(IpAddr, u16)>>,
         proxy_map_v6: HashMap<i32, Vec<(IpAddr, u16)>>,
         default_dc: Option<i32>,
+        decision: NetworkDecision,
+        rng: Arc<SecureRandom>,
     ) -> Arc<Self> {
         Arc::new(Self {
             registry: Arc::new(ConnRegistry::new()),
             writers: Arc::new(RwLock::new(Vec::new())),
             rr: AtomicU64::new(0),
+            decision,
+            rng,
             proxy_tag,
             proxy_secret: Arc::new(RwLock::new(proxy_secret)),
             nat_ip_cfg: nat_ip,
@@ -80,7 +94,7 @@ impl MePool {
             next_writer_id: AtomicU64::new(1),
             ping_tracker: Arc::new(Mutex::new(HashMap::new())),
             rtt_stats: Arc::new(Mutex::new(HashMap::new())),
-            nat_reflection_cache: Arc::new(Mutex::new(None)),
+            nat_reflection_cache: Arc::new(Mutex::new(NatReflectionCache::default())),
         })
     }
 
@@ -103,15 +117,12 @@ impl MePool {
 
     pub async fn reconcile_connections(self: &Arc<Self>, rng: &SecureRandom) {
         use std::collections::HashSet;
-        let map = self.proxy_map_v4.read().await.clone();
-        let dc_addrs: Vec<(i32, Vec<(IpAddr, u16)>)> = map
-            .iter()
-            .map(|(dc, addrs)| (*dc, addrs.clone()))
-            .collect();
         let writers = self.writers.read().await;
         let current: HashSet<SocketAddr> = writers.iter().map(|w| w.addr).collect();
         drop(writers);
 
+        for family in self.family_order() {
+            let map = self.proxy_map_for_family(family).await;
             for (_dc, addrs) in map.iter() {
                 let dc_addrs: Vec<SocketAddr> = addrs
                     .iter()
@@ -127,6 +138,10 @@ impl MePool {
                     }
                 }
             }
+            if !self.decision.effective_multipath && !current.is_empty() {
+                break;
+            }
+        }
     }
 
     pub async fn update_proxy_maps(
@@ -181,21 +196,51 @@ impl MePool {
         }
     }
 
+    pub(super) fn family_order(&self) -> Vec<IpFamily> {
+        let mut order = Vec::new();
+        if self.decision.prefer_ipv6() {
+            if self.decision.ipv6_me {
+                order.push(IpFamily::V6);
+            }
+            if self.decision.ipv4_me {
+                order.push(IpFamily::V4);
+            }
+        } else {
+            if self.decision.ipv4_me {
+                order.push(IpFamily::V4);
+            }
+            if self.decision.ipv6_me {
+                order.push(IpFamily::V6);
+            }
+        }
+        order
+    }
+
+    async fn proxy_map_for_family(&self, family: IpFamily) -> HashMap<i32, Vec<(IpAddr, u16)>> {
+        match family {
+            IpFamily::V4 => self.proxy_map_v4.read().await.clone(),
+            IpFamily::V6 => self.proxy_map_v6.read().await.clone(),
+        }
+    }
+
     pub async fn init(self: &Arc<Self>, pool_size: usize, rng: &Arc<SecureRandom>) -> Result<()> {
-        let map = self.proxy_map_v4.read().await.clone();
+        let family_order = self.family_order();
-        let dc_addrs: Vec<(i32, Vec<(IpAddr, u16)>)> = map
-            .iter()
-            .map(|(dc, addrs)| (*dc, addrs.clone()))
-            .collect();
         let ks = self.key_selector().await;
         info!(
-            me_servers = map.len(),
+            me_servers = self.proxy_map_v4.read().await.len(),
             pool_size,
             key_selector = format_args!("0x{ks:08x}"),
             secret_len = self.proxy_secret.read().await.len(),
             "Initializing ME pool"
         );
 
+        for family in family_order {
+            let map = self.proxy_map_for_family(family).await;
+            let dc_addrs: Vec<(i32, Vec<(IpAddr, u16)>)> = map
+                .iter()
+                .map(|(dc, addrs)| (*dc, addrs.clone()))
+                .collect();
+
             // Ensure at least one connection per DC; run DCs in parallel.
             let mut join = tokio::task::JoinSet::new();
             for (dc, addrs) in dc_addrs.iter().cloned() {
@@ -226,6 +271,11 @@ impl MePool {
                 }
             }
 
+            if !self.decision.effective_multipath && self.connection_count() > 0 {
+                break;
+            }
+        }
+
         if self.writers.read().await.is_empty() {
             return Err(ProxyError::Proxy("No ME connections".into()));
         }
@@ -309,14 +359,15 @@ impl MePool {
                     }
                     _ = tokio::time::sleep(Duration::from_secs(wait)) => {}
                 }
+                let sent_id = ping_id;
                 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());
+                p.extend_from_slice(&sent_id.to_le_bytes());
-                ping_id = ping_id.wrapping_add(1);
                 {
                     let mut tracker = ping_tracker_ping.lock().await;
-                    tracker.insert(ping_id, (std::time::Instant::now(), writer_id));
+                    tracker.insert(sent_id, (std::time::Instant::now(), writer_id));
                 }
+                ping_id = ping_id.wrapping_add(1);
                 if let Err(e) = rpc_w_ping.lock().await.send(&p).await {
                     debug!(error = %e, "Active ME ping failed, removing dead writer");
                     cancel_ping.cancel();

src/transport/middle_proxy/pool_nat.rs

@@ -4,19 +4,14 @@ use std::time::Duration;
 use tracing::{info, warn};
 
 use crate::error::{ProxyError, Result};
+use crate::network::probe::is_bogon;
+use crate::network::stun::{stun_probe_dual, IpFamily, StunProbeResult};
 
 use super::MePool;
 use std::time::Instant;
-
+pub async fn stun_probe(stun_addr: Option<String>) -> Result<crate::network::stun::DualStunResult> {
-#[derive(Debug, Clone, Copy)]
-pub struct StunProbeResult {
-    pub local_addr: std::net::SocketAddr,
-    pub reflected_addr: std::net::SocketAddr,
-}
-
-pub async fn stun_probe(stun_addr: Option<String>) -> Result<Option<StunProbeResult>> {
     let stun_addr = stun_addr.unwrap_or_else(|| "stun.l.google.com:19302".to_string());
-    fetch_stun_binding(&stun_addr).await
+    stun_probe_dual(&stun_addr).await
 }
 
 pub async fn detect_public_ip() -> Option<IpAddr> {
@@ -35,7 +30,7 @@ impl MePool {
 
         match (ip, nat_ip) {
             (IpAddr::V4(src), IpAddr::V4(dst))
-                if is_privateish(IpAddr::V4(src))
+                if is_bogon(IpAddr::V4(src))
                     || src.is_loopback()
                     || src.is_unspecified() =>
             {
@@ -55,7 +50,7 @@ impl MePool {
     ) -> 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() {
+            if is_bogon(addr.ip()) || addr.ip().is_loopback() || addr.ip().is_unspecified() {
                 r.ip()
             } else {
                 self.translate_ip_for_nat(addr.ip())
@@ -73,7 +68,7 @@ impl MePool {
             return self.nat_ip_cfg;
         }
 
-        if !(is_privateish(local_ip) || local_ip.is_loopback() || local_ip.is_unspecified()) {
+        if !(is_bogon(local_ip) || local_ip.is_loopback() || local_ip.is_unspecified()) {
             return None;
         }
 
@@ -98,12 +93,19 @@ impl MePool {
         }
     }
 
-    pub(super) async fn maybe_reflect_public_addr(&self) -> Option<std::net::SocketAddr> {
+    pub(super) async fn maybe_reflect_public_addr(
+        &self,
+        family: IpFamily,
+    ) -> Option<std::net::SocketAddr> {
         const STUN_CACHE_TTL: Duration = Duration::from_secs(600);
         if let Ok(mut cache) = self.nat_reflection_cache.try_lock() {
-            if let Some((ts, addr)) = *cache {
+            let slot = match family {
+                IpFamily::V4 => &mut cache.v4,
+                IpFamily::V6 => &mut cache.v6,
+            };
+            if let Some((ts, addr)) = slot {
                 if ts.elapsed() < STUN_CACHE_TTL {
-                    return Some(addr);
+                    return Some(*addr);
                 }
             }
         }
@@ -112,12 +114,20 @@ impl MePool {
             .nat_stun
             .clone()
             .unwrap_or_else(|| "stun.l.google.com:19302".to_string());
-        match fetch_stun_binding(&stun_addr).await {
+        match stun_probe_dual(&stun_addr).await {
-            Ok(sa) => {
+            Ok(res) => {
-                if let Some(result) = sa {
+                let picked: Option<StunProbeResult> = match family {
-                    info!(local = %result.local_addr, reflected = %result.reflected_addr, "NAT probe: reflected address");
+                    IpFamily::V4 => res.v4,
+                    IpFamily::V6 => res.v6,
+                };
+                if let Some(result) = picked {
+                    info!(local = %result.local_addr, reflected = %result.reflected_addr, family = ?family, "NAT probe: reflected address");
                     if let Ok(mut cache) = self.nat_reflection_cache.try_lock() {
-                        *cache = Some((Instant::now(), result.reflected_addr));
+                        let slot = match family {
+                            IpFamily::V4 => &mut cache.v4,
+                            IpFamily::V6 => &mut cache.v6,
+                        };
+                        *slot = Some((Instant::now(), result.reflected_addr));
                     }
                     Some(result.reflected_addr)
                 } else {
@@ -158,98 +168,3 @@ async fn fetch_public_ipv4_once(url: &str) -> Result<Option<Ipv4Addr>> {
     let ip = text.trim().parse().ok();
     Ok(ip)
 }
-
-async fn fetch_stun_binding(stun_addr: &str) -> Result<Option<StunProbeResult>> {
-    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::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)
-                };
-                let reflected = std::net::SocketAddr::new(
-                    IpAddr::V4(Ipv4Addr::new(ip[0], ip[1], ip[2], ip[3])),
-                    port,
-                );
-                let local_addr = socket.local_addr().map_err(|e| {
-                    ProxyError::Proxy(format!("STUN local_addr failed: {e}"))
-                })?;
-                return Ok(Some(StunProbeResult {
-                    local_addr,
-                    reflected_addr: reflected,
-                }));
-            }
-            _ => {}
-        }
-        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

@@ -152,6 +152,9 @@ pub(crate) async fn reader_loop(
                     entry.1 = entry.1 * 0.8 + rtt * 0.2;
                     if rtt < entry.0 {
                         entry.0 = rtt;
+                    } else {
+                        // allow slow baseline drift upward to avoid stale minimum
+                        entry.0 = entry.0 * 0.99 + rtt * 0.01;
                     }
                     let degraded_now = entry.1 > entry.0 * 2.0;
                     degraded.store(degraded_now, Ordering::Relaxed);

src/transport/middle_proxy/rotation.rs

@@ -1,4 +1,5 @@
 use std::sync::Arc;
+use std::sync::atomic::Ordering;
 use std::time::Duration;
 
 use tracing::{info, warn};
@@ -15,7 +16,12 @@ pub async fn me_rotation_task(pool: Arc<MePool>, rng: Arc<SecureRandom>, interva
 
         let candidate = {
             let ws = pool.writers.read().await;
-            ws.get(0).cloned()
+            if ws.is_empty() {
+                None
+            } else {
+                let idx = (pool.rr.load(std::sync::atomic::Ordering::Relaxed) as usize) % ws.len();
+                ws.get(idx).cloned()
+            }
         };
 
         let Some(w) = candidate else {
@@ -34,4 +40,3 @@ pub async fn me_rotation_task(pool: Arc<MePool>, rng: Arc<SecureRandom>, interva
         }
     }
 }
-

src/transport/middle_proxy/send.rs

@@ -3,15 +3,14 @@ use std::sync::Arc;
 use std::sync::atomic::Ordering;
 use std::time::Duration;
 
-use tokio::sync::Mutex;
 use tracing::{debug, warn};
 
 use crate::error::{ProxyError, Result};
+use crate::network::IpFamily;
 use crate::protocol::constants::RPC_CLOSE_EXT_U32;
 
 use super::MePool;
 use super::wire::build_proxy_req_payload;
-use crate::crypto::SecureRandom;
 use rand::seq::SliceRandom;
 use super::registry::ConnMeta;
 
@@ -84,7 +83,7 @@ impl MePool {
                     drop(map);
                     for (ip, port) in shuffled {
                         let addr = SocketAddr::new(ip, port);
-                        if self.connect_one(addr, &SecureRandom::new()).await.is_ok() {
+                        if self.connect_one(addr, self.rng.as_ref()).await.is_ok() {
                             break;
                         }
                     }
@@ -173,34 +172,46 @@ impl MePool {
         writers: &[super::pool::MeWriter],
         target_dc: i16,
     ) -> Vec<usize> {
-        let mut preferred = Vec::<SocketAddr>::new();
         let key = target_dc as i32;
-        let map = self.proxy_map_v4.read().await;
+        let mut preferred = Vec::<SocketAddr>::new();
 
-        if let Some(v) = map.get(&key) {
+        for family in self.family_order() {
+            let map_guard = match family {
+                IpFamily::V4 => self.proxy_map_v4.read().await,
+                IpFamily::V6 => self.proxy_map_v6.read().await,
+            };
+
+            if let Some(v) = map_guard.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) = map.get(&abs) {
+                if let Some(v) = map_guard.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) = map.get(&-abs) {
+                if let Some(v) = map_guard.get(&-abs) {
                     preferred.extend(v.iter().map(|(ip, port)| SocketAddr::new(*ip, *port)));
                 }
             }
             if preferred.is_empty() {
                 let def = self.default_dc.load(Ordering::Relaxed);
                 if def != 0 {
-                if let Some(v) = map.get(&def) {
+                    if let Some(v) = map_guard.get(&def) {
                         preferred.extend(v.iter().map(|(ip, port)| SocketAddr::new(*ip, *port)));
                     }
                 }
             }
 
+            drop(map_guard);
+
+            if !preferred.is_empty() && !self.decision.effective_multipath {
+                break;
+            }
+        }
+
         if preferred.is_empty() {
             return (0..writers.len()).collect();
         }

src/transport/upstream.rs

@@ -355,6 +355,8 @@ impl UpstreamManager {
         &self,
         prefer_ipv6: bool,
         dc_overrides: &HashMap<String, Vec<String>>,
+        ipv4_enabled: bool,
+        ipv6_enabled: bool,
     ) -> Vec<StartupPingResult> {
         let upstreams: Vec<(usize, UpstreamConfig)> = {
             let guard = self.upstreams.read().await;
@@ -374,10 +376,8 @@ impl UpstreamManager {
                 UpstreamType::Socks5 { address, .. } => format!("socks5://{}", address),
             };
 
-            let mut v6_results = Vec::new();
+            let mut v6_results = Vec::with_capacity(NUM_DCS);
-            let mut v4_results = Vec::new();
+            if ipv6_enabled {
-
-            // === 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);
@@ -415,8 +415,20 @@ impl UpstreamManager {
                     };
                     v6_results.push(ping_result);
                 }
+            } else {
+                for dc_zero_idx in 0..NUM_DCS {
+                    let dc_v6 = TG_DATACENTERS_V6[dc_zero_idx];
+                    v6_results.push(DcPingResult {
+                        dc_idx: dc_zero_idx + 1,
+                        dc_addr: SocketAddr::new(dc_v6, TG_DATACENTER_PORT),
+                        rtt_ms: None,
+                        error: Some("ipv6 disabled".to_string()),
+                    });
+                }
+            }
 
-            // === Then ping IPv4 ===
+            let mut v4_results = Vec::with_capacity(NUM_DCS);
+            if ipv4_enabled {
                 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);
@@ -454,6 +466,17 @@ impl UpstreamManager {
                     };
                     v4_results.push(ping_result);
                 }
+            } else {
+                for dc_zero_idx in 0..NUM_DCS {
+                    let dc_v4 = TG_DATACENTERS_V4[dc_zero_idx];
+                    v4_results.push(DcPingResult {
+                        dc_idx: dc_zero_idx + 1,
+                        dc_addr: SocketAddr::new(dc_v4, TG_DATACENTER_PORT),
+                        rtt_ms: None,
+                        error: Some("ipv4 disabled".to_string()),
+                    });
+                }
+            }
 
             // === Ping DC overrides (v4/v6) ===
             for (dc_key, addrs) in dc_overrides {
@@ -470,6 +493,9 @@ impl UpstreamManager {
                     match addr_str.parse::<SocketAddr>() {
                         Ok(addr) => {
                             let is_v6 = addr.is_ipv6();
+                            if (is_v6 && !ipv6_enabled) || (!is_v6 && !ipv4_enabled) {
+                                continue;
+                            }
                             let result = tokio::time::timeout(
                                 Duration::from_secs(DC_PING_TIMEOUT_SECS),
                                 self.ping_single_dc(&upstream_config, addr)
@@ -551,7 +577,7 @@ impl UpstreamManager {
 
     /// 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) {
+    pub async fn run_health_checks(&self, prefer_ipv6: bool, ipv4_enabled: bool, ipv6_enabled: bool) {
         let mut dc_rotation = 0usize;
 
         loop {
@@ -560,16 +586,24 @@ impl UpstreamManager {
             let dc_zero_idx = dc_rotation % NUM_DCS;
             dc_rotation += 1;
 
-            let dc_addr = if prefer_ipv6 {
+            let primary_v6 = SocketAddr::new(TG_DATACENTERS_V6[dc_zero_idx], TG_DATACENTER_PORT);
-                SocketAddr::new(TG_DATACENTERS_V6[dc_zero_idx], TG_DATACENTER_PORT)
+            let primary_v4 = SocketAddr::new(TG_DATACENTERS_V4[dc_zero_idx], TG_DATACENTER_PORT);
+            let dc_addr = if prefer_ipv6 && ipv6_enabled {
+                primary_v6
+            } else if ipv4_enabled {
+                primary_v4
+            } else if ipv6_enabled {
+                primary_v6
             } else {
-                SocketAddr::new(TG_DATACENTERS_V4[dc_zero_idx], TG_DATACENTER_PORT)
+                continue;
             };
 
-            let fallback_addr = if prefer_ipv6 {
+            let fallback_addr = if dc_addr.is_ipv6() && ipv4_enabled {
-                SocketAddr::new(TG_DATACENTERS_V4[dc_zero_idx], TG_DATACENTER_PORT)
+                Some(primary_v4)
+            } else if dc_addr.is_ipv4() && ipv6_enabled {
+                Some(primary_v6)
             } else {
-                SocketAddr::new(TG_DATACENTERS_V6[dc_zero_idx], TG_DATACENTER_PORT)
+                None
             };
 
             let count = self.upstreams.read().await.len();
@@ -608,6 +642,7 @@ impl UpstreamManager {
                         // Try fallback
                         debug!(dc = dc_zero_idx + 1, "Health check failed, trying fallback");
 
+                        if let Some(fallback_addr) = fallback_addr {
                             let start2 = Instant::now();
                             let result2 = tokio::time::timeout(
                                 Duration::from_secs(10),
@@ -652,6 +687,17 @@ impl UpstreamManager {
                                 }
                             }
                             u.last_check = std::time::Instant::now();
+                            continue;
+                        }
+
+                        let mut guard = self.upstreams.write().await;
+                        let u = &mut guard[i];
+                        u.fails += 1;
+                        if u.fails > 3 {
+                            u.healthy = false;
+                            warn!("Upstream unhealthy (no fallback family)");
+                        }
+                        u.last_check = std::time::Instant::now();
                     }
                 }
             }