Drafting fixes for Apple/XNU Darwin Connectivity issues

Co-Authored-By: Aleksandr Kalashnikov <33665156+sleep3r@users.noreply.github.com>

src/api/runtime_zero.rs

@@ -50,6 +50,7 @@ pub(super) struct RuntimeGatesData {
 
 #[derive(Serialize)]
 pub(super) struct EffectiveTimeoutLimits {
+    pub(super) client_first_byte_idle_secs: u64,
     pub(super) client_handshake_secs: u64,
     pub(super) tg_connect_secs: u64,
     pub(super) client_keepalive_secs: u64,
@@ -227,6 +228,7 @@ pub(super) fn build_limits_effective_data(cfg: &ProxyConfig) -> EffectiveLimitsD
         me_reinit_every_secs: cfg.general.effective_me_reinit_every_secs(),
         me_pool_force_close_secs: cfg.general.effective_me_pool_force_close_secs(),
         timeouts: EffectiveTimeoutLimits {
+            client_first_byte_idle_secs: cfg.timeouts.client_first_byte_idle_secs,
             client_handshake_secs: cfg.timeouts.client_handshake,
             tg_connect_secs: cfg.general.tg_connect,
             client_keepalive_secs: cfg.timeouts.client_keepalive,

src/cli.rs

@@ -610,7 +610,8 @@ ip = "0.0.0.0"
 ip = "::"
 
 [timeouts]
-client_handshake = 15
+client_first_byte_idle_secs = 300
+client_handshake = 60
 client_keepalive = 60
 client_ack = 300
 

src/config/defaults.rs

@@ -110,7 +110,11 @@ pub(crate) fn default_replay_window_secs() -> u64 {
 }
 
 pub(crate) fn default_handshake_timeout() -> u64 {
-    30
+    60
+}
+
+pub(crate) fn default_client_first_byte_idle_secs() -> u64 {
+    300
 }
 
 pub(crate) fn default_relay_idle_policy_v2_enabled() -> bool {

src/config/tests/load_idle_policy_tests.rs

@@ -17,6 +17,28 @@ fn remove_temp_config(path: &PathBuf) {
     let _ = fs::remove_file(path);
 }
 
+#[test]
+fn default_timeouts_enable_apple_compatible_handshake_profile() {
+    let cfg = ProxyConfig::default();
+    assert_eq!(cfg.timeouts.client_first_byte_idle_secs, 300);
+    assert_eq!(cfg.timeouts.client_handshake, 60);
+}
+
+#[test]
+fn load_accepts_zero_first_byte_idle_timeout_as_legacy_opt_out() {
+    let path = write_temp_config(
+        r#"
+[timeouts]
+client_first_byte_idle_secs = 0
+"#,
+    );
+
+    let cfg = ProxyConfig::load(&path).expect("config with zero first-byte idle timeout must load");
+    assert_eq!(cfg.timeouts.client_first_byte_idle_secs, 0);
+
+    remove_temp_config(&path);
+}
+
 #[test]
 fn load_rejects_relay_hard_idle_smaller_than_soft_idle_with_clear_error() {
     let path = write_temp_config(

src/config/types.rs

@@ -1319,6 +1319,12 @@ impl Default for ServerConfig {
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct TimeoutsConfig {
+    /// Maximum idle wait in seconds for the first client byte before handshake parsing starts.
+    /// `0` disables the separate idle phase and keeps legacy timeout behavior.
+    #[serde(default = "default_client_first_byte_idle_secs")]
+    pub client_first_byte_idle_secs: u64,
+
+    /// Maximum active handshake duration in seconds after the first client byte is received.
     #[serde(default = "default_handshake_timeout")]
     pub client_handshake: u64,
 
@@ -1358,6 +1364,7 @@ pub struct TimeoutsConfig {
 impl Default for TimeoutsConfig {
     fn default() -> Self {
         Self {
+            client_first_byte_idle_secs: default_client_first_byte_idle_secs(),
             client_handshake: default_handshake_timeout(),
             relay_idle_policy_v2_enabled: default_relay_idle_policy_v2_enabled(),
             relay_client_idle_soft_secs: default_relay_client_idle_soft_secs(),

src/proxy/client.rs

@@ -416,16 +416,68 @@ where
 
     debug!(peer = %real_peer, "New connection (generic stream)");
 
+    let first_byte = if config.timeouts.client_first_byte_idle_secs == 0 {
+        None
+    } else {
+        let idle_timeout = Duration::from_secs(config.timeouts.client_first_byte_idle_secs);
+        let mut first_byte = [0u8; 1];
+        match timeout(idle_timeout, stream.read(&mut first_byte)).await {
+            Ok(Ok(0)) => {
+                debug!(peer = %real_peer, "Connection closed before first client byte");
+                return Ok(());
+            }
+            Ok(Ok(_)) => Some(first_byte[0]),
+            Ok(Err(e))
+                if matches!(
+                    e.kind(),
+                    std::io::ErrorKind::UnexpectedEof
+                        | std::io::ErrorKind::ConnectionReset
+                        | std::io::ErrorKind::ConnectionAborted
+                        | std::io::ErrorKind::BrokenPipe
+                        | std::io::ErrorKind::NotConnected
+                ) =>
+            {
+                debug!(
+                    peer = %real_peer,
+                    error = %e,
+                    "Connection closed before first client byte"
+                );
+                return Ok(());
+            }
+            Ok(Err(e)) => {
+                debug!(
+                    peer = %real_peer,
+                    error = %e,
+                    "Failed while waiting for first client byte"
+                );
+                return Err(ProxyError::Io(e));
+            }
+            Err(_) => {
+                debug!(
+                    peer = %real_peer,
+                    idle_secs = config.timeouts.client_first_byte_idle_secs,
+                    "Closing idle pooled connection before first client byte"
+                );
+                return Ok(());
+            }
+        }
+    };
+
     let handshake_timeout = handshake_timeout_with_mask_grace(&config);
     let stats_for_timeout = stats.clone();
     let config_for_timeout = config.clone();
     let beobachten_for_timeout = beobachten.clone();
     let peer_for_timeout = real_peer.ip();
 
-    // Phase 1: handshake (with timeout)
+    // Phase 2: active handshake (with timeout after the first client byte)
     let outcome = match timeout(handshake_timeout, async {
         let mut first_bytes = [0u8; 5];
-        stream.read_exact(&mut first_bytes).await?;
+        if let Some(first_byte) = first_byte {
+            first_bytes[0] = first_byte;
+            stream.read_exact(&mut first_bytes[1..]).await?;
+        } else {
+            stream.read_exact(&mut first_bytes).await?;
+        }
 
         let is_tls = tls::is_tls_handshake(&first_bytes[..3]);
         debug!(peer = %real_peer, is_tls = is_tls, "Handshake type detected");
@@ -736,36 +788,9 @@ impl RunningClientHandler {
             debug!(peer = %peer, error = %e, "Failed to configure client socket");
         }
 
-        let handshake_timeout = handshake_timeout_with_mask_grace(&self.config);
+        let outcome = match self.do_handshake().await? {
-        let stats = self.stats.clone();
+            Some(outcome) => outcome,
-        let config_for_timeout = self.config.clone();
+            None => return Ok(()),
-        let beobachten_for_timeout = self.beobachten.clone();
-        let peer_for_timeout = peer.ip();
-
-        // Phase 1: handshake (with timeout)
-        let outcome = match timeout(handshake_timeout, self.do_handshake()).await {
-            Ok(Ok(outcome)) => outcome,
-            Ok(Err(e)) => {
-                debug!(peer = %peer, error = %e, "Handshake failed");
-                record_handshake_failure_class(
-                    &beobachten_for_timeout,
-                    &config_for_timeout,
-                    peer_for_timeout,
-                    &e,
-                );
-                return Err(e);
-            }
-            Err(_) => {
-                stats.increment_handshake_timeouts();
-                debug!(peer = %peer, "Handshake timeout");
-                record_beobachten_class(
-                    &beobachten_for_timeout,
-                    &config_for_timeout,
-                    peer_for_timeout,
-                    "other",
-                );
-                return Err(ProxyError::TgHandshakeTimeout);
-            }
         };
 
         // Phase 2: relay (WITHOUT handshake timeout — relay has its own activity timeouts)
@@ -774,7 +799,7 @@ impl RunningClientHandler {
         }
     }
 
-    async fn do_handshake(mut self) -> Result<HandshakeOutcome> {
+    async fn do_handshake(mut self) -> Result<Option<HandshakeOutcome>> {
         let mut local_addr = self.stream.local_addr().map_err(ProxyError::Io)?;
 
         if self.proxy_protocol_enabled {
@@ -849,19 +874,107 @@ impl RunningClientHandler {
             }
         }
 
-        let mut first_bytes = [0u8; 5];
+        let first_byte = if self.config.timeouts.client_first_byte_idle_secs == 0 {
-        self.stream.read_exact(&mut first_bytes).await?;
+            None
-
-        let is_tls = tls::is_tls_handshake(&first_bytes[..3]);
-        let peer = self.peer;
-
-        debug!(peer = %peer, is_tls = is_tls, "Handshake type detected");
-
-        if is_tls {
-            self.handle_tls_client(first_bytes, local_addr).await
         } else {
-            self.handle_direct_client(first_bytes, local_addr).await
+            let idle_timeout = Duration::from_secs(self.config.timeouts.client_first_byte_idle_secs);
-        }
+            let mut first_byte = [0u8; 1];
+            match timeout(idle_timeout, self.stream.read(&mut first_byte)).await {
+                Ok(Ok(0)) => {
+                    debug!(peer = %self.peer, "Connection closed before first client byte");
+                    return Ok(None);
+                }
+                Ok(Ok(_)) => Some(first_byte[0]),
+                Ok(Err(e))
+                    if matches!(
+                        e.kind(),
+                        std::io::ErrorKind::UnexpectedEof
+                            | std::io::ErrorKind::ConnectionReset
+                            | std::io::ErrorKind::ConnectionAborted
+                            | std::io::ErrorKind::BrokenPipe
+                            | std::io::ErrorKind::NotConnected
+                    ) =>
+                {
+                    debug!(
+                        peer = %self.peer,
+                        error = %e,
+                        "Connection closed before first client byte"
+                    );
+                    return Ok(None);
+                }
+                Ok(Err(e)) => {
+                    debug!(
+                        peer = %self.peer,
+                        error = %e,
+                        "Failed while waiting for first client byte"
+                    );
+                    return Err(ProxyError::Io(e));
+                }
+                Err(_) => {
+                    debug!(
+                        peer = %self.peer,
+                        idle_secs = self.config.timeouts.client_first_byte_idle_secs,
+                        "Closing idle pooled connection before first client byte"
+                    );
+                    return Ok(None);
+                }
+            }
+        };
+
+        let handshake_timeout = handshake_timeout_with_mask_grace(&self.config);
+        let stats = self.stats.clone();
+        let config_for_timeout = self.config.clone();
+        let beobachten_for_timeout = self.beobachten.clone();
+        let peer_for_timeout = self.peer.ip();
+        let peer_for_log = self.peer;
+
+        let outcome = match timeout(handshake_timeout, async {
+            let mut first_bytes = [0u8; 5];
+            if let Some(first_byte) = first_byte {
+                first_bytes[0] = first_byte;
+                self.stream.read_exact(&mut first_bytes[1..]).await?;
+            } else {
+                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, "Handshake type detected");
+
+            if is_tls {
+                self.handle_tls_client(first_bytes, local_addr).await
+            } else {
+                self.handle_direct_client(first_bytes, local_addr).await
+            }
+        })
+        .await
+        {
+            Ok(Ok(outcome)) => outcome,
+            Ok(Err(e)) => {
+                debug!(peer = %peer_for_log, error = %e, "Handshake failed");
+                record_handshake_failure_class(
+                    &beobachten_for_timeout,
+                    &config_for_timeout,
+                    peer_for_timeout,
+                    &e,
+                );
+                return Err(e);
+            }
+            Err(_) => {
+                stats.increment_handshake_timeouts();
+                debug!(peer = %peer_for_log, "Handshake timeout");
+                record_beobachten_class(
+                    &beobachten_for_timeout,
+                    &config_for_timeout,
+                    peer_for_timeout,
+                    "other",
+                );
+                return Err(ProxyError::TgHandshakeTimeout);
+            }
+        };
+
+        Ok(Some(outcome))
     }
 
     async fn handle_tls_client(

src/proxy/tests/client_security_tests.rs

@@ -1,8 +1,10 @@
 use super::*;
 use crate::config::{UpstreamConfig, UpstreamType};
-use crate::crypto::AesCtr;
+use crate::crypto::{AesCtr, sha256, sha256_hmac};
-use crate::crypto::sha256_hmac;
+use crate::protocol::constants::{
-use crate::protocol::constants::ProtoTag;
+    DC_IDX_POS, HANDSHAKE_LEN, IV_LEN, PREKEY_LEN, PROTO_TAG_POS, ProtoTag, SKIP_LEN,
+    TLS_RECORD_CHANGE_CIPHER,
+};
 use crate::protocol::tls;
 use crate::proxy::handshake::HandshakeSuccess;
 use crate::stream::{CryptoReader, CryptoWriter};
@@ -1319,6 +1321,163 @@ async fn running_client_handler_increments_connects_all_exactly_once() {
     );
 }
 
+#[tokio::test(start_paused = true)]
+async fn idle_pooled_connection_closes_cleanly_in_generic_stream_path() {
+    let mut cfg = ProxyConfig::default();
+    cfg.general.beobachten = false;
+    cfg.timeouts.client_first_byte_idle_secs = 1;
+
+    let config = Arc::new(cfg);
+    let stats = Arc::new(Stats::new());
+    let upstream_manager = Arc::new(UpstreamManager::new(
+        vec![UpstreamConfig {
+            upstream_type: UpstreamType::Direct {
+                interface: None,
+                bind_addresses: None,
+            },
+            weight: 1,
+            enabled: true,
+            scopes: String::new(),
+            selected_scope: String::new(),
+        }],
+        1,
+        1,
+        1,
+        10,
+        1,
+        false,
+        stats.clone(),
+    ));
+    let replay_checker = Arc::new(ReplayChecker::new(128, Duration::from_secs(60)));
+    let buffer_pool = Arc::new(BufferPool::new());
+    let rng = Arc::new(SecureRandom::new());
+    let route_runtime = Arc::new(RouteRuntimeController::new(RelayRouteMode::Direct));
+    let ip_tracker = Arc::new(UserIpTracker::new());
+    let beobachten = Arc::new(BeobachtenStore::new());
+
+    let (server_side, _client_side) = duplex(4096);
+    let peer: SocketAddr = "198.51.100.169:55200".parse().unwrap();
+
+    let handler = tokio::spawn(handle_client_stream(
+        server_side,
+        peer,
+        config,
+        stats.clone(),
+        upstream_manager,
+        replay_checker,
+        buffer_pool,
+        rng,
+        None,
+        route_runtime,
+        None,
+        ip_tracker,
+        beobachten,
+        false,
+    ));
+
+    // Let the spawned handler arm the idle-phase timeout before advancing paused time.
+    tokio::task::yield_now().await;
+    tokio::time::advance(Duration::from_secs(2)).await;
+    tokio::task::yield_now().await;
+
+    let result = tokio::time::timeout(Duration::from_secs(1), handler)
+        .await
+        .unwrap()
+        .unwrap();
+    assert!(result.is_ok());
+    assert_eq!(stats.get_handshake_timeouts(), 0);
+    assert_eq!(stats.get_connects_bad(), 0);
+}
+
+#[tokio::test(start_paused = true)]
+async fn idle_pooled_connection_closes_cleanly_in_client_handler_path() {
+    let front_listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+    let front_addr = front_listener.local_addr().unwrap();
+
+    let mut cfg = ProxyConfig::default();
+    cfg.general.beobachten = false;
+    cfg.timeouts.client_first_byte_idle_secs = 1;
+
+    let config = Arc::new(cfg);
+    let stats = Arc::new(Stats::new());
+    let upstream_manager = Arc::new(UpstreamManager::new(
+        vec![UpstreamConfig {
+            upstream_type: UpstreamType::Direct {
+                interface: None,
+                bind_addresses: None,
+            },
+            weight: 1,
+            enabled: true,
+            scopes: String::new(),
+            selected_scope: String::new(),
+        }],
+        1,
+        1,
+        1,
+        10,
+        1,
+        false,
+        stats.clone(),
+    ));
+    let replay_checker = Arc::new(ReplayChecker::new(128, Duration::from_secs(60)));
+    let buffer_pool = Arc::new(BufferPool::new());
+    let rng = Arc::new(SecureRandom::new());
+    let route_runtime = Arc::new(RouteRuntimeController::new(RelayRouteMode::Direct));
+    let ip_tracker = Arc::new(UserIpTracker::new());
+    let beobachten = Arc::new(BeobachtenStore::new());
+
+    let server_task = {
+        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 route_runtime = route_runtime.clone();
+        let ip_tracker = ip_tracker.clone();
+        let beobachten = beobachten.clone();
+
+        tokio::spawn(async move {
+            let (stream, peer) = front_listener.accept().await.unwrap();
+            let real_peer_report = Arc::new(std::sync::Mutex::new(None));
+            ClientHandler::new(
+                stream,
+                peer,
+                config,
+                stats,
+                upstream_manager,
+                replay_checker,
+                buffer_pool,
+                rng,
+                None,
+                route_runtime,
+                None,
+                ip_tracker,
+                beobachten,
+                false,
+                real_peer_report,
+            )
+            .run()
+            .await
+        })
+    };
+
+    let _client = TcpStream::connect(front_addr).await.unwrap();
+
+    // Let the accepted connection reach the idle wait before advancing paused time.
+    tokio::task::yield_now().await;
+    tokio::time::advance(Duration::from_secs(2)).await;
+    tokio::task::yield_now().await;
+
+    let result = tokio::time::timeout(Duration::from_secs(1), server_task)
+        .await
+        .unwrap()
+        .unwrap();
+    assert!(result.is_ok());
+    assert_eq!(stats.get_handshake_timeouts(), 0);
+    assert_eq!(stats.get_connects_bad(), 0);
+}
+
 #[tokio::test]
 async fn partial_tls_header_stall_triggers_handshake_timeout() {
     let mut cfg = ProxyConfig::default();
@@ -1487,6 +1646,147 @@ fn wrap_tls_application_data(payload: &[u8]) -> Vec<u8> {
     record
 }
 
+fn wrap_tls_ccs_record() -> Vec<u8> {
+    let mut record = Vec::with_capacity(6);
+    record.push(TLS_RECORD_CHANGE_CIPHER);
+    record.extend_from_slice(&[0x03, 0x03]);
+    record.extend_from_slice(&1u16.to_be_bytes());
+    record.push(0x01);
+    record
+}
+
+fn make_valid_mtproto_handshake(
+    secret_hex: &str,
+    proto_tag: ProtoTag,
+    dc_idx: i16,
+) -> [u8; HANDSHAKE_LEN] {
+    let secret = hex::decode(secret_hex).expect("secret hex must decode for mtproto test helper");
+
+    let mut handshake = [0x5Au8; HANDSHAKE_LEN];
+    for (idx, b) in handshake[SKIP_LEN..SKIP_LEN + PREKEY_LEN + IV_LEN]
+        .iter_mut()
+        .enumerate()
+    {
+        *b = (idx as u8).wrapping_add(1);
+    }
+
+    let dec_prekey = &handshake[SKIP_LEN..SKIP_LEN + PREKEY_LEN];
+    let dec_iv_bytes = &handshake[SKIP_LEN + PREKEY_LEN..SKIP_LEN + PREKEY_LEN + IV_LEN];
+
+    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);
+    let dec_key = sha256(&dec_key_input);
+
+    let mut dec_iv_arr = [0u8; IV_LEN];
+    dec_iv_arr.copy_from_slice(dec_iv_bytes);
+    let dec_iv = u128::from_be_bytes(dec_iv_arr);
+
+    let mut stream = AesCtr::new(&dec_key, dec_iv);
+    let keystream = stream.encrypt(&[0u8; HANDSHAKE_LEN]);
+
+    let mut target_plain = [0u8; HANDSHAKE_LEN];
+    target_plain[PROTO_TAG_POS..PROTO_TAG_POS + 4].copy_from_slice(&proto_tag.to_bytes());
+    target_plain[DC_IDX_POS..DC_IDX_POS + 2].copy_from_slice(&dc_idx.to_le_bytes());
+
+    for idx in PROTO_TAG_POS..HANDSHAKE_LEN {
+        handshake[idx] = target_plain[idx] ^ keystream[idx];
+    }
+
+    handshake
+}
+
+#[tokio::test]
+async fn fragmented_tls_mtproto_with_interleaved_ccs_is_accepted() {
+    let secret_hex = "55555555555555555555555555555555";
+    let secret = [0x55u8; 16];
+    let client_hello = make_valid_tls_client_hello(&secret, 0);
+    let mtproto_handshake = make_valid_mtproto_handshake(secret_hex, ProtoTag::Secure, 2);
+
+    let mut cfg = ProxyConfig::default();
+    cfg.general.beobachten = false;
+    cfg.access.ignore_time_skew = true;
+    cfg.access
+        .users
+        .insert("user".to_string(), secret_hex.to_string());
+
+    let config = Arc::new(cfg);
+    let replay_checker = Arc::new(ReplayChecker::new(128, Duration::from_secs(60)));
+    let rng = SecureRandom::new();
+
+    let (server_side, mut client_side) = duplex(131072);
+    let peer: SocketAddr = "198.51.100.85:55007".parse().unwrap();
+    let (read_half, write_half) = tokio::io::split(server_side);
+
+    let (mut tls_reader, tls_writer, tls_user) = match handle_tls_handshake(
+        &client_hello,
+        read_half,
+        write_half,
+        peer,
+        &config,
+        &replay_checker,
+        &rng,
+        None,
+    )
+    .await
+    {
+        HandshakeResult::Success(result) => result,
+        _ => panic!("expected successful TLS handshake"),
+    };
+
+    let mut tls_response_head = [0u8; 5];
+    client_side
+        .read_exact(&mut tls_response_head)
+        .await
+        .unwrap();
+    assert_eq!(tls_response_head[0], 0x16);
+    let tls_response_len = u16::from_be_bytes([tls_response_head[3], tls_response_head[4]]) as usize;
+    let mut tls_response_body = vec![0u8; tls_response_len];
+    client_side
+        .read_exact(&mut tls_response_body)
+        .await
+        .unwrap();
+
+    client_side
+        .write_all(&wrap_tls_application_data(&mtproto_handshake[..13]))
+        .await
+        .unwrap();
+    client_side.write_all(&wrap_tls_ccs_record()).await.unwrap();
+    client_side
+        .write_all(&wrap_tls_application_data(&mtproto_handshake[13..37]))
+        .await
+        .unwrap();
+    client_side.write_all(&wrap_tls_ccs_record()).await.unwrap();
+    client_side
+        .write_all(&wrap_tls_application_data(&mtproto_handshake[37..]))
+        .await
+        .unwrap();
+
+    let mtproto_data = tls_reader.read_exact(HANDSHAKE_LEN).await.unwrap();
+    assert_eq!(&mtproto_data[..], &mtproto_handshake);
+
+    let mtproto_handshake: [u8; HANDSHAKE_LEN] = mtproto_data[..].try_into().unwrap();
+    let (_, _, success) = match handle_mtproto_handshake(
+        &mtproto_handshake,
+        tls_reader,
+        tls_writer,
+        peer,
+        &config,
+        &replay_checker,
+        true,
+        Some(tls_user.as_str()),
+    )
+    .await
+    {
+        HandshakeResult::Success(result) => result,
+        _ => panic!("expected successful MTProto handshake"),
+    };
+
+    assert_eq!(success.user, "user");
+    assert_eq!(success.proto_tag, ProtoTag::Secure);
+    assert_eq!(success.dc_idx, 2);
+}
+
 #[tokio::test]
 async fn valid_tls_path_does_not_fall_back_to_mask_backend() {
     let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();