v1.16.3

changelog.md

@@ -1,5 +1,12 @@
 # Changelog
 
+## 2026-03-31 - 1.16.3 - fix(rust-nat)
+defer TCP bridge startup until handshake completion and buffer partial NAT socket writes
+
+- Start TCP bridge tasks only after the smoltcp socket becomes active to prevent server data from arriving before the client handshake completes.
+- Buffer pending TCP payloads and flush partial writes so bridge-to-socket data is not silently lost under backpressure.
+- Keep closing TCP sessions alive until FIN processing completes and add logging for dropped packets when bridge or route channels are full.
+
 ## 2026-03-31 - 1.16.2 - fix(wireguard)
 sync runtime peer management with client registration and derive the correct server public key from the WireGuard private key
 

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@push.rocks/smartvpn",
-  "version": "1.16.2",
+  "version": "1.16.3",
   "private": false,
   "description": "A VPN solution with TypeScript control plane and Rust data plane daemon",
   "type": "module",

rust/src/userspace_nat.rs

@@ -101,7 +101,7 @@ impl Device for VirtualIpDevice {
         let mut caps = DeviceCapabilities::default();
         caps.medium = Medium::Ip;
         caps.max_transmission_unit = self.mtu;
-        caps.max_burst_size = Some(1);
+        caps.max_burst_size = None;
         caps
     }
 }
@@ -124,6 +124,14 @@ struct TcpSession {
     bridge_data_tx: mpsc::Sender<Vec<u8>>,
     #[allow(dead_code)]
     client_ip: Ipv4Addr,
+    /// Bridge task has been spawned (deferred until handshake completes)
+    bridge_started: bool,
+    /// Address to connect the bridge task to (may differ from dst if policy rewrote it)
+    connect_addr: SocketAddr,
+    /// Buffered data from bridge waiting to be written to smoltcp socket
+    pending_send: Vec<u8>,
+    /// Session is closing (FIN in progress), don't accept new SYNs
+    closing: bool,
 }
 
 struct UdpSession {
@@ -308,7 +316,9 @@ impl NatEngine {
 
                 // SYN without ACK = new connection
                 let is_syn = (flags & 0x02) != 0 && (flags & 0x10) == 0;
-                if is_syn && !self.tcp_sessions.contains_key(&key) {
+                // Skip if session exists (including closing sessions — let FIN complete)
+                let session_exists = self.tcp_sessions.contains_key(&key);
+                if is_syn && !session_exists {
                     match self.evaluate_destination(dst_ip, dst_port) {
                         DestinationAction::Drop => {
                             debug!("NAT: destination policy blocked TCP {}:{} -> {}:{}", src_ip, src_port, dst_ip, dst_port);
@@ -376,22 +386,23 @@ impl NatEngine {
         let handle = self.sockets.add(socket);
 
         // Channel for sending data from NAT engine to bridge task
-        let (data_tx, data_rx) = mpsc::channel::<Vec<u8>>(256);
+        let (data_tx, _data_rx) = mpsc::channel::<Vec<u8>>(256);
 
         let session = TcpSession {
             smoltcp_handle: handle,
             bridge_data_tx: data_tx,
             client_ip: key.src_ip,
+            bridge_started: false,
+            connect_addr,
+            pending_send: Vec::new(),
+            closing: false,
         };
         self.tcp_sessions.insert(key.clone(), session);
 
-        // Spawn bridge task that connects to the resolved destination
-        let bridge_tx = self.bridge_tx.clone();
-        let key_clone = key.clone();
-        let proxy_protocol = self.proxy_protocol;
-        tokio::spawn(async move {
-            tcp_bridge_task(key_clone, data_rx, bridge_tx, proxy_protocol, connect_addr).await;
-        });
+        // NOTE: Bridge task is NOT spawned here — it will be spawned in process()
+        // once the smoltcp handshake completes (socket.is_active() == true).
+        // This prevents data from the real server arriving before the VPN client
+        // handshake is done, which would cause silent data loss.
 
         debug!(
             "NAT: new TCP session {}:{} -> {}:{}",
@@ -451,13 +462,54 @@ impl NatEngine {
         self.iface
             .poll(now, &mut self.device, &mut self.sockets);
 
+        // Start bridge tasks for sessions whose handshake just completed
+        let bridge_tx_clone = self.bridge_tx.clone();
+        let proxy_protocol = self.proxy_protocol;
+        for (key, session) in self.tcp_sessions.iter_mut() {
+            if !session.bridge_started && !session.closing {
+                let socket = self.sockets.get_mut::<tcp::Socket>(session.smoltcp_handle);
+                if socket.is_active() {
+                    session.bridge_started = true;
+                    // Recreate the data channel — the old receiver was dropped
+                    let (data_tx, data_rx) = mpsc::channel::<Vec<u8>>(256);
+                    session.bridge_data_tx = data_tx;
+                    let btx = bridge_tx_clone.clone();
+                    let k = key.clone();
+                    let addr = session.connect_addr;
+                    let pp = proxy_protocol;
+                    tokio::spawn(async move {
+                        tcp_bridge_task(k, data_rx, btx, pp, addr).await;
+                    });
+                    debug!("NAT: TCP handshake complete, starting bridge for {}:{} -> {}:{}",
+                        key.src_ip, key.src_port, key.dst_ip, key.dst_port);
+                }
+            }
+        }
+
+        // Flush pending send buffers to smoltcp sockets
+        for (_key, session) in self.tcp_sessions.iter_mut() {
+            if !session.pending_send.is_empty() {
+                let socket = self.sockets.get_mut::<tcp::Socket>(session.smoltcp_handle);
+                if socket.can_send() {
+                    match socket.send_slice(&session.pending_send) {
+                        Ok(written) if written > 0 => {
+                            session.pending_send.drain(..written);
+                        }
+                        _ => {}
+                    }
+                }
+            }
+        }
+
         // Bridge: read data from smoltcp TCP sockets → send to bridge tasks
         let mut closed_tcp: Vec<SessionKey> = Vec::new();
+        let mut tcp_outbound: Vec<(mpsc::Sender<Vec<u8>>, Vec<u8>)> = Vec::new();
         for (key, session) in &self.tcp_sessions {
             let socket = self.sockets.get_mut::<tcp::Socket>(session.smoltcp_handle);
-            if socket.can_recv() {
+            if session.bridge_started && socket.can_recv() {
+                let sender = session.bridge_data_tx.clone();
                 let _ = socket.recv(|data| {
-                    let _ = session.bridge_data_tx.try_send(data.to_vec());
+                    tcp_outbound.push((sender.clone(), data.to_vec()));
                     (data.len(), ())
                 });
             }
@@ -467,6 +519,13 @@ impl NatEngine {
             }
         }
 
+        // Send TCP data to bridge tasks (outside borrow of self.tcp_sessions)
+        for (sender, data) in tcp_outbound {
+            if sender.try_send(data).is_err() {
+                debug!("NAT: bridge channel full, TCP data dropped");
+            }
+        }
+
         // Clean up closed TCP sessions
         for key in closed_tcp {
             if let Some(session) = self.tcp_sessions.remove(&key) {
@@ -479,7 +538,9 @@ impl NatEngine {
         for (_key, session) in &self.udp_sessions {
             let socket = self.sockets.get_mut::<udp::Socket>(session.smoltcp_handle);
             while let Ok((data, _meta)) = socket.recv() {
-                let _ = session.bridge_data_tx.try_send(data.to_vec());
+                if session.bridge_data_tx.try_send(data.to_vec()).is_err() {
+                    debug!("NAT: bridge channel full, UDP data dropped");
+                }
             }
         }
 
@@ -488,7 +549,9 @@ impl NatEngine {
         for packet in self.device.drain_tx() {
             if let Some(std::net::IpAddr::V4(dst_ip)) = tunnel::extract_dst_ip(&packet) {
                 if let Some(sender) = routes.get(&dst_ip) {
-                    let _ = sender.try_send(packet);
+                    if sender.try_send(packet).is_err() {
+                        debug!("NAT: tun_routes channel full for {}, packet dropped", dst_ip);
+                    }
                 }
             }
         }
@@ -497,22 +560,51 @@ impl NatEngine {
     fn handle_bridge_message(&mut self, msg: BridgeMessage) {
         match msg {
             BridgeMessage::TcpData { key, data } => {
-                if let Some(session) = self.tcp_sessions.get(&key) {
+                if let Some(session) = self.tcp_sessions.get_mut(&key) {
                     let socket =
                         self.sockets.get_mut::<tcp::Socket>(session.smoltcp_handle);
                     if socket.can_send() {
-                        let _ = socket.send_slice(&data);
+                        // Try to write directly first
+                        let all_data = if session.pending_send.is_empty() {
+                            &data
+                        } else {
+                            session.pending_send.extend_from_slice(&data);
+                            &session.pending_send.clone()
+                        };
+                        match socket.send_slice(all_data) {
+                            Ok(written) if written < all_data.len() => {
+                                // Partial write — buffer the rest
+                                if session.pending_send.is_empty() {
+                                    session.pending_send = data[written..].to_vec();
+                                } else {
+                                    session.pending_send.drain(..written);
+                                }
+                            }
+                            Ok(_) => {
+                                // Full write — clear any pending data
+                                session.pending_send.clear();
+                            }
+                            Err(_) => {
+                                // Write failed — buffer everything
+                                if session.pending_send.is_empty() {
+                                    session.pending_send = data;
+                                }
+                            }
+                        }
+                    } else {
+                        // Can't send yet — buffer for later
+                        session.pending_send.extend_from_slice(&data);
                     }
                 }
             }
             BridgeMessage::TcpClosed { key } => {
-                if let Some(session) = self.tcp_sessions.remove(&key) {
+                if let Some(session) = self.tcp_sessions.get_mut(&key) {
                     let socket =
                         self.sockets.get_mut::<tcp::Socket>(session.smoltcp_handle);
                     socket.close();
+                    session.closing = true;
                     // Don't remove from SocketSet yet — let smoltcp send FIN
                     // It will be cleaned up in process() when is_open() returns false
-                    self.tcp_sessions.insert(key, session);
                 }
             }
             BridgeMessage::UdpData { key, data } => {

ts/00_commitinfo_data.ts

@@ -3,6 +3,6 @@
  */
 export const commitinfo = {
   name: '@push.rocks/smartvpn',
-  version: '1.16.2',
+  version: '1.16.3',
   description: 'A VPN solution with TypeScript control plane and Rust data plane daemon'
 }