v1.10.0

changelog.md

@@ -1,5 +1,15 @@
 # Changelog
 
+## 2026-03-29 - 1.10.0 - feat(rust-server, rust-client, ts-interfaces)
+add configurable packet forwarding with TUN and userspace NAT modes
+
+- introduce forwardingMode options for client and server configuration interfaces
+- add server-side forwarding engines for kernel TUN, userspace socket NAT, and testing mode
+- add a smoltcp-based userspace NAT implementation for packet forwarding without root-only TUN routing
+- enable client-side TUN forwarding support with route setup, packet I/O, and cleanup
+- centralize raw packet destination IP extraction in tunnel utilities for shared routing logic
+- update test command timeout and logging flags
+
 ## 2026-03-29 - 1.9.0 - feat(server)
 add PROXY protocol v2 support for real client IP handling and connection ACLs
 

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@push.rocks/smartvpn",
-  "version": "1.9.0",
+  "version": "1.10.0",
   "private": false,
   "description": "A VPN solution with TypeScript control plane and Rust data plane daemon",
   "type": "module",
@@ -12,7 +12,7 @@
   "scripts": {
     "build": "(tsbuild tsfolders) && (tsrust)",
     "test:before": "(tsrust)",
-    "test": "tstest test/ --verbose",
+    "test": "tstest test/ --verbose--verbose  --logfile --timeout 60",
     "buildDocs": "tsdoc"
   },
   "repository": {

rust/Cargo.lock

@@ -237,6 +237,12 @@ version = "3.20.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5d20789868f4b01b2f2caec9f5c4e0213b41e3e5702a50157d699ae31ced2fcb"
 
+[[package]]
+name = "byteorder"
+version = "1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1fd0f2584146f6f2ef48085050886acf353beff7305ebd1ae69500e27c67f64b"
+
 [[package]]
 name = "bytes"
 version = "1.11.1"
@@ -488,6 +494,47 @@ version = "2.10.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d7a1e2f27636f116493b8b860f5546edb47c8d8f8ea73e1d2a20be88e28d1fea"
 
+[[package]]
+name = "defmt"
+version = "0.3.100"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f0963443817029b2024136fc4dd07a5107eb8f977eaf18fcd1fdeb11306b64ad"
+dependencies = [
+ "defmt 1.0.1",
+]
+
+[[package]]
+name = "defmt"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "548d977b6da32fa1d1fda2876453da1e7df63ad0304c8b3dae4dbe7b96f39b78"
+dependencies = [
+ "bitflags 1.3.2",
+ "defmt-macros",
+]
+
+[[package]]
+name = "defmt-macros"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3d4fc12a85bcf441cfe44344c4b72d58493178ce635338a3f3b78943aceb258e"
+dependencies = [
+ "defmt-parser",
+ "proc-macro-error2",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "defmt-parser"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "10d60334b3b2e7c9d91ef8150abfb6fa4c1c39ebbcf4a81c2e346aad939fee3e"
+dependencies = [
+ "thiserror 2.0.18",
+]
+
 [[package]]
 name = "deranged"
 version = "0.5.8"
@@ -714,6 +761,25 @@ dependencies = [
  "polyval",
 ]
 
+[[package]]
+name = "hash32"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "47d60b12902ba28e2730cd37e95b8c9223af2808df9e902d4df49588d1470606"
+dependencies = [
+ "byteorder",
+]
+
+[[package]]
+name = "heapless"
+version = "0.9.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2af2455f757db2b292a9b1768c4b70186d443bcb3b316252d6b540aec1cd89ed"
+dependencies = [
+ "hash32",
+ "stable_deref_trait",
+]
+
 [[package]]
 name = "heck"
 version = "0.5.0"
@@ -915,6 +981,12 @@ version = "0.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "112b39cec0b298b6c1999fee3e31427f74f676e4cb9879ed1a121b43661a4154"
 
+[[package]]
+name = "managed"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0ca88d725a0a943b096803bd34e73a4437208b6077654cc4ecb2947a5f91618d"
+
 [[package]]
 name = "matchers"
 version = "0.2.0"
@@ -1116,6 +1188,28 @@ dependencies = [
  "zerocopy",
 ]
 
+[[package]]
+name = "proc-macro-error-attr2"
+version = "2.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "96de42df36bb9bba5542fe9f1a054b8cc87e172759a1868aa05c1f3acc89dfc5"
+dependencies = [
+ "proc-macro2",
+ "quote",
+]
+
+[[package]]
+name = "proc-macro-error2"
+version = "2.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "11ec05c52be0a07b08061f7dd003e7d7092e0472bc731b4af7bb1ef876109802"
+dependencies = [
+ "proc-macro-error-attr2",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "proc-macro2"
 version = "1.0.106"
@@ -1598,6 +1692,7 @@ dependencies = [
  "rustls-pki-types",
  "serde",
  "serde_json",
+ "smoltcp",
  "snow",
  "thiserror 2.0.18",
  "tokio",
@@ -1609,6 +1704,20 @@ dependencies = [
  "webpki-roots 1.0.6",
 ]
 
+[[package]]
+name = "smoltcp"
+version = "0.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ac729b0a77bd092a3f06ddaddc59fe0d67f48ba0de45a9abe707c2842c7f8767"
+dependencies = [
+ "bitflags 1.3.2",
+ "byteorder",
+ "cfg-if",
+ "defmt 0.3.100",
+ "heapless",
+ "managed",
+]
+
 [[package]]
 name = "snow"
 version = "0.9.6"
@@ -1635,6 +1744,12 @@ dependencies = [
  "windows-sys 0.60.2",
 ]
 
+[[package]]
+name = "stable_deref_trait"
+version = "1.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6ce2be8dc25455e1f91df71bfa12ad37d7af1092ae736f3a6cd0e37bc7810596"
+
 [[package]]
 name = "strsim"
 version = "0.11.1"

rust/Cargo.toml

@@ -35,6 +35,7 @@ rustls-pemfile = "2"
 webpki-roots = "1"
 mimalloc = "0.1"
 boringtun = "0.7"
+smoltcp = { version = "0.13", default-features = false, features = ["medium-ip", "proto-ipv4", "socket-tcp", "socket-udp", "alloc"] }
 chrono = { version = "0.4", features = ["serde"] }
 ipnet = "2"
 

rust/src/client.rs

@@ -1,6 +1,7 @@
 use anyhow::Result;
 use bytes::BytesMut;
 use serde::Deserialize;
+use std::net::Ipv4Addr;
 use std::sync::Arc;
 use tokio::sync::{mpsc, watch, RwLock};
 use tracing::{info, error, warn, debug};
@@ -12,6 +13,7 @@ use crate::telemetry::ConnectionQuality;
 use crate::transport;
 use crate::transport_trait::{self, TransportSink, TransportStream};
 use crate::quic_transport;
+use crate::tunnel::{self, TunConfig};
 
 /// Client configuration (matches TS IVpnClientConfig).
 #[derive(Debug, Clone, Deserialize)]
@@ -30,6 +32,9 @@ pub struct ClientConfig {
     pub transport: Option<String>,
     /// For QUIC: SHA-256 hash of server certificate (base64) for cert pinning.
     pub server_cert_hash: Option<String>,
+    /// Forwarding mode: "tun" (TUN device, requires root) or "testing" (no TUN).
+    /// Default: "testing".
+    pub forwarding_mode: Option<String>,
 }
 
 /// Client statistics.
@@ -234,6 +239,31 @@ impl VpnClient {
 
         info!("Connected to VPN, assigned IP: {}", assigned_ip);
 
+        // Optionally create TUN device for IP packet forwarding (requires root)
+        let tun_enabled = config.forwarding_mode.as_deref() == Some("tun");
+        let (tun_reader, tun_writer, tun_subnet) = if tun_enabled {
+            let client_tun_ip: Ipv4Addr = assigned_ip.parse()?;
+            let mtu = ip_info["mtu"].as_u64().unwrap_or(1420) as u16;
+            let tun_config = TunConfig {
+                name: "svpn-client0".to_string(),
+                address: client_tun_ip,
+                netmask: Ipv4Addr::new(255, 255, 255, 0),
+                mtu,
+            };
+            let tun_device = tunnel::create_tun(&tun_config)?;
+
+            // Add route for VPN subnet through the TUN device
+            let gateway_str = ip_info["gateway"].as_str().unwrap_or("10.8.0.1");
+            let gateway: Ipv4Addr = gateway_str.parse().unwrap_or(Ipv4Addr::new(10, 8, 0, 1));
+            let subnet = format!("{}/24", Ipv4Addr::from(u32::from(gateway) & 0xFFFFFF00));
+            tunnel::add_route(&subnet, &tun_config.name).await?;
+
+            let (reader, writer) = tokio::io::split(tun_device);
+            (Some(reader), Some(writer), Some(subnet))
+        } else {
+            (None, None, None)
+        };
+
         // Create adaptive keepalive monitor (use custom interval if configured)
         let ka_config = config.keepalive_interval_secs.map(|secs| {
             let mut cfg = keepalive::AdaptiveKeepaliveConfig::default();
@@ -260,6 +290,9 @@ impl VpnClient {
             handle.signal_rx,
             handle.ack_tx,
             link_health,
+            tun_reader,
+            tun_writer,
+            tun_subnet,
         ));
 
         Ok(assigned_ip_clone)
@@ -356,8 +389,14 @@ async fn client_loop(
     mut signal_rx: mpsc::Receiver<KeepaliveSignal>,
     ack_tx: mpsc::Sender<()>,
     link_health: Arc<RwLock<LinkHealth>>,
+    mut tun_reader: Option<tokio::io::ReadHalf<tun::AsyncDevice>>,
+    mut tun_writer: Option<tokio::io::WriteHalf<tun::AsyncDevice>>,
+    tun_subnet: Option<String>,
 ) {
+    use tokio::io::{AsyncReadExt, AsyncWriteExt};
+
     let mut buf = vec![0u8; 65535];
+    let mut tun_buf = vec![0u8; 65536];
 
     loop {
         tokio::select! {
@@ -373,6 +412,14 @@ async fn client_loop(
                                             let mut s = stats.write().await;
                                             s.bytes_received += len as u64;
                                             s.packets_received += 1;
+                                            drop(s);
+
+                                            // Write decrypted packet to TUN device (if enabled)
+                                            if let Some(ref mut writer) = tun_writer {
+                                                if let Err(e) = writer.write_all(&buf[..len]).await {
+                                                    warn!("TUN write error: {}", e);
+                                                }
+                                            }
                                         }
                                         Err(e) => {
                                             warn!("Decrypt error: {}", e);
@@ -407,6 +454,50 @@ async fn client_loop(
                     }
                 }
             }
+            // Read outbound packets from TUN and send to server (only when TUN enabled)
+            result = async {
+                match tun_reader {
+                    Some(ref mut reader) => reader.read(&mut tun_buf).await,
+                    None => std::future::pending::<std::io::Result<usize>>().await,
+                }
+            } => {
+                match result {
+                    Ok(0) => {
+                        info!("TUN device closed");
+                        break;
+                    }
+                    Ok(n) => {
+                        match noise_transport.write_message(&tun_buf[..n], &mut buf) {
+                            Ok(len) => {
+                                let frame = Frame {
+                                    packet_type: PacketType::IpPacket,
+                                    payload: buf[..len].to_vec(),
+                                };
+                                let mut frame_bytes = BytesMut::new();
+                                if <FrameCodec as tokio_util::codec::Encoder<Frame>>::encode(
+                                    &mut FrameCodec, frame, &mut frame_bytes
+                                ).is_ok() {
+                                    if sink.send_reliable(frame_bytes.to_vec()).await.is_err() {
+                                        warn!("Failed to send TUN packet to server");
+                                        break;
+                                    }
+                                    let mut s = stats.write().await;
+                                    s.bytes_sent += n as u64;
+                                    s.packets_sent += 1;
+                                }
+                            }
+                            Err(e) => {
+                                warn!("Noise encrypt error: {}", e);
+                                break;
+                            }
+                        }
+                    }
+                    Err(e) => {
+                        warn!("TUN read error: {}", e);
+                        break;
+                    }
+                }
+            }
             signal = signal_rx.recv() => {
                 match signal {
                     Some(KeepaliveSignal::SendPing(timestamp_ms)) => {
@@ -456,6 +547,13 @@ async fn client_loop(
             }
         }
     }
+
+    // Cleanup: remove TUN route if enabled
+    if let Some(ref subnet) = tun_subnet {
+        if let Err(e) = tunnel::remove_route(subnet, "svpn-client0").await {
+            warn!("Failed to remove client TUN route: {}", e);
+        }
+    }
 }
 
 /// Try to connect via QUIC. Returns transport halves on success.

rust/src/lib.rs

@@ -21,3 +21,4 @@ pub mod wireguard;
 pub mod client_registry;
 pub mod acl;
 pub mod proxy_protocol;
+pub mod userspace_nat;

rust/src/server.rs

@@ -19,6 +19,7 @@ use crate::ratelimit::TokenBucket;
 use crate::transport;
 use crate::transport_trait::{self, TransportSink, TransportStream};
 use crate::quic_transport;
+use crate::tunnel::{self, TunConfig};
 
 /// Dead-peer timeout: 3x max keepalive interval (Healthy=60s).
 const DEAD_PEER_TIMEOUT: Duration = Duration::from_secs(180);
@@ -37,6 +38,9 @@ pub struct ServerConfig {
     pub mtu: Option<u16>,
     pub keepalive_interval_secs: Option<u64>,
     pub enable_nat: Option<bool>,
+    /// Forwarding mode: "tun" (kernel TUN, requires root), "socket" (userspace NAT),
+    /// or "testing" (monitoring only, no forwarding). Default: "testing".
+    pub forwarding_mode: Option<String>,
     /// Default rate limit for new clients (bytes/sec). None = unlimited.
     pub default_rate_limit_bytes_per_sec: Option<u64>,
     /// Default burst size for new clients (bytes). None = unlimited.
@@ -94,6 +98,16 @@ pub struct ServerStatistics {
     pub total_connections: u64,
 }
 
+/// The forwarding engine determines how decrypted IP packets are routed.
+pub enum ForwardingEngine {
+    /// Kernel TUN device — packets written to the TUN, kernel handles routing.
+    Tun(tokio::io::WriteHalf<tun::AsyncDevice>),
+    /// Userspace NAT — packets sent to smoltcp-based NAT engine via channel.
+    Socket(mpsc::Sender<Vec<u8>>),
+    /// Testing/monitoring — packets are counted but not forwarded.
+    Testing,
+}
+
 /// Shared server state.
 pub struct ServerState {
     pub config: ServerConfig,
@@ -104,6 +118,12 @@ pub struct ServerState {
     pub mtu_config: MtuConfig,
     pub started_at: std::time::Instant,
     pub client_registry: RwLock<ClientRegistry>,
+    /// The forwarding engine for decrypted IP packets.
+    pub forwarding_engine: Mutex<ForwardingEngine>,
+    /// Routing table: assigned VPN IP → channel sender for return packets.
+    pub tun_routes: RwLock<HashMap<Ipv4Addr, mpsc::Sender<Vec<u8>>>>,
+    /// Shutdown signal for the forwarding background task (TUN reader or NAT engine).
+    pub tun_shutdown: mpsc::Sender<()>,
 }
 
 /// The VPN server.
@@ -139,6 +159,51 @@ impl VpnServer {
         }
 
         let link_mtu = config.mtu.unwrap_or(1420);
+        let mode = config.forwarding_mode.as_deref().unwrap_or("testing");
+        let gateway_ip = ip_pool.gateway_addr();
+
+        // Create forwarding engine based on mode
+        enum ForwardingSetup {
+            Tun {
+                writer: tokio::io::WriteHalf<tun::AsyncDevice>,
+                reader: tokio::io::ReadHalf<tun::AsyncDevice>,
+                shutdown_rx: mpsc::Receiver<()>,
+            },
+            Socket {
+                packet_tx: mpsc::Sender<Vec<u8>>,
+                packet_rx: mpsc::Receiver<Vec<u8>>,
+                shutdown_rx: mpsc::Receiver<()>,
+            },
+            Testing,
+        }
+
+        let (setup, fwd_shutdown_tx) = match mode {
+            "tun" => {
+                let tun_config = TunConfig {
+                    name: "svpn0".to_string(),
+                    address: gateway_ip,
+                    netmask: Ipv4Addr::new(255, 255, 255, 0),
+                    mtu: link_mtu,
+                };
+                let tun_device = tunnel::create_tun(&tun_config)?;
+                tunnel::add_route(&config.subnet, &tun_config.name).await?;
+                let (reader, writer) = tokio::io::split(tun_device);
+                let (tx, rx) = mpsc::channel::<()>(1);
+                (ForwardingSetup::Tun { writer, reader, shutdown_rx: rx }, tx)
+            }
+            "socket" => {
+                info!("Starting userspace NAT forwarding (no root required)");
+                let (packet_tx, packet_rx) = mpsc::channel::<Vec<u8>>(4096);
+                let (tx, rx) = mpsc::channel::<()>(1);
+                (ForwardingSetup::Socket { packet_tx, packet_rx, shutdown_rx: rx }, tx)
+            }
+            _ => {
+                info!("Forwarding disabled (testing/monitoring mode)");
+                let (tx, _rx) = mpsc::channel::<()>(1);
+                (ForwardingSetup::Testing, tx)
+            }
+        };
+
         // Compute effective MTU from overhead
         let overhead = TunnelOverhead::default_overhead();
         let mtu_config = MtuConfig::new(overhead.effective_tun_mtu(1500).max(link_mtu));
@@ -158,8 +223,38 @@ impl VpnServer {
             mtu_config,
             started_at: std::time::Instant::now(),
             client_registry: RwLock::new(registry),
+            forwarding_engine: Mutex::new(ForwardingEngine::Testing),
+            tun_routes: RwLock::new(HashMap::new()),
+            tun_shutdown: fwd_shutdown_tx,
         });
 
+        // Spawn the forwarding background task and set the engine
+        match setup {
+            ForwardingSetup::Tun { writer, reader, shutdown_rx } => {
+                *state.forwarding_engine.lock().await = ForwardingEngine::Tun(writer);
+                let tun_state = state.clone();
+                tokio::spawn(async move {
+                    if let Err(e) = run_tun_reader(tun_state, reader, shutdown_rx).await {
+                        error!("TUN reader error: {}", e);
+                    }
+                });
+            }
+            ForwardingSetup::Socket { packet_tx, packet_rx, shutdown_rx } => {
+                *state.forwarding_engine.lock().await = ForwardingEngine::Socket(packet_tx);
+                let nat_engine = crate::userspace_nat::NatEngine::new(
+                    gateway_ip,
+                    link_mtu as usize,
+                    state.clone(),
+                );
+                tokio::spawn(async move {
+                    if let Err(e) = nat_engine.run(packet_rx, shutdown_rx).await {
+                        error!("NAT engine error: {}", e);
+                    }
+                });
+            }
+            ForwardingSetup::Testing => {}
+        }
+
         let (shutdown_tx, mut shutdown_rx) = mpsc::channel::<()>(1);
         self.state = Some(state.clone());
         self.shutdown_tx = Some(shutdown_tx);
@@ -220,6 +315,34 @@ impl VpnServer {
     }
 
     pub async fn stop(&mut self) -> Result<()> {
+        if let Some(ref state) = self.state {
+            let mode = state.config.forwarding_mode.as_deref().unwrap_or("testing");
+
+            match mode {
+                "tun" => {
+                    let _ = state.tun_shutdown.send(()).await;
+                    *state.forwarding_engine.lock().await = ForwardingEngine::Testing;
+                    if let Err(e) = tunnel::remove_route(&state.config.subnet, "svpn0").await {
+                        warn!("Failed to remove TUN route: {}", e);
+                    }
+                }
+                "socket" => {
+                    let _ = state.tun_shutdown.send(()).await;
+                    *state.forwarding_engine.lock().await = ForwardingEngine::Testing;
+                }
+                _ => {}
+            }
+
+            // Clean up NAT rules
+            if state.config.enable_nat.unwrap_or(false) {
+                if let Ok(iface) = crate::network::get_default_interface() {
+                    if let Err(e) = crate::network::remove_nat(&state.config.subnet, &iface).await {
+                        warn!("Failed to remove NAT rules: {}", e);
+                    }
+                }
+            }
+        }
+
         if let Some(tx) = self.shutdown_tx.take() {
             let _ = tx.send(()).await;
         }
@@ -736,6 +859,56 @@ async fn run_quic_listener(
     Ok(())
 }
 
+/// TUN reader task: reads IP packets from the TUN device and dispatches them
+/// to the correct client via the routing table.
+async fn run_tun_reader(
+    state: Arc<ServerState>,
+    mut tun_reader: tokio::io::ReadHalf<tun::AsyncDevice>,
+    mut shutdown_rx: mpsc::Receiver<()>,
+) -> Result<()> {
+    use tokio::io::AsyncReadExt;
+
+    let mut buf = vec![0u8; 65536];
+
+    loop {
+        tokio::select! {
+            result = tun_reader.read(&mut buf) => {
+                let n = match result {
+                    Ok(0) => {
+                        info!("TUN reader: device closed");
+                        break;
+                    }
+                    Ok(n) => n,
+                    Err(e) => {
+                        error!("TUN reader error: {}", e);
+                        break;
+                    }
+                };
+
+                // Extract destination IP from the raw IP packet
+                let dst_ip = match tunnel::extract_dst_ip(&buf[..n]) {
+                    Some(std::net::IpAddr::V4(v4)) => v4,
+                    _ => continue, // IPv6 or malformed — skip
+                };
+
+                // Look up client by destination IP
+                let routes = state.tun_routes.read().await;
+                if let Some(sender) = routes.get(&dst_ip) {
+                    if sender.try_send(buf[..n].to_vec()).is_err() {
+                        // Channel full or closed — drop packet (correct for IP best-effort)
+                    }
+                }
+            }
+            _ = shutdown_rx.recv() => {
+                info!("TUN reader shutting down");
+                break;
+            }
+        }
+    }
+
+    Ok(())
+}
+
 /// Transport-agnostic client handler. Performs the Noise IK handshake, authenticates
 /// the client against the registry, and runs the main packet forwarding loop.
 async fn handle_client_connection(
@@ -846,6 +1019,14 @@ async fn handle_client_connection(
     // Allocate IP
     let assigned_ip = state.ip_pool.lock().await.allocate(&client_id)?;
 
+    // Create return-packet channel for forwarding engine -> client
+    let (tun_return_tx, mut tun_return_rx) = mpsc::channel::<Vec<u8>>(256);
+    let fwd_mode = state.config.forwarding_mode.as_deref().unwrap_or("testing");
+    let forwarding_active = fwd_mode == "tun" || fwd_mode == "socket";
+    if forwarding_active {
+        state.tun_routes.write().await.insert(assigned_ip, tun_return_tx);
+    }
+
     // Determine rate limits: per-client security overrides server defaults
     let (rate_limit, burst) = if let Some(ref sec) = client_security {
         if let Some(ref rl) = sec.rate_limit {
@@ -973,6 +1154,24 @@ async fn handle_client_connection(
                                             if let Some(info) = clients.get_mut(&client_id) {
                                                 info.bytes_received += len as u64;
                                             }
+                                            drop(clients);
+
+                                            // Forward decrypted packet via the active engine
+                                            {
+                                                let mut engine = state.forwarding_engine.lock().await;
+                                                match &mut *engine {
+                                                    ForwardingEngine::Tun(writer) => {
+                                                        use tokio::io::AsyncWriteExt;
+                                                        if let Err(e) = writer.write_all(&buf[..len]).await {
+                                                            warn!("TUN write error for client {}: {}", client_id, e);
+                                                        }
+                                                    }
+                                                    ForwardingEngine::Socket(sender) => {
+                                                        let _ = sender.try_send(buf[..len].to_vec());
+                                                    }
+                                                    ForwardingEngine::Testing => {}
+                                                }
+                                            }
                                         }
                                         Err(e) => {
                                             warn!("Decrypt error from {}: {}", client_id, e);
@@ -1029,6 +1228,37 @@ async fn handle_client_connection(
                     }
                 }
             }
+            // Return packets from TUN device destined for this client
+            Some(packet) = tun_return_rx.recv() => {
+                let pkt_len = packet.len();
+                match noise_transport.write_message(&packet, &mut buf) {
+                    Ok(len) => {
+                        let frame = Frame {
+                            packet_type: PacketType::IpPacket,
+                            payload: buf[..len].to_vec(),
+                        };
+                        let mut frame_bytes = BytesMut::new();
+                        <FrameCodec as tokio_util::codec::Encoder<Frame>>::encode(
+                            &mut FrameCodec, frame, &mut frame_bytes
+                        )?;
+                        sink.send_reliable(frame_bytes.to_vec()).await?;
+
+                        // Update stats
+                        let mut stats = state.stats.write().await;
+                        stats.bytes_sent += pkt_len as u64;
+                        stats.packets_sent += 1;
+                        drop(stats);
+                        let mut clients = state.clients.write().await;
+                        if let Some(info) = clients.get_mut(&client_id) {
+                            info.bytes_sent += pkt_len as u64;
+                        }
+                    }
+                    Err(e) => {
+                        warn!("Noise encrypt error for return packet to {}: {}", client_id, e);
+                        break;
+                    }
+                }
+            }
             _ = tokio::time::sleep_until(last_activity + DEAD_PEER_TIMEOUT) => {
                 warn!("Client {} dead-peer timeout ({}s inactivity)", client_id, DEAD_PEER_TIMEOUT.as_secs());
                 break;
@@ -1037,6 +1267,9 @@ async fn handle_client_connection(
     }
 
     // Cleanup
+    if forwarding_active {
+        state.tun_routes.write().await.remove(&assigned_ip);
+    }
     state.clients.write().await.remove(&client_id);
     state.ip_pool.lock().await.release(&assigned_ip);
     state.rate_limiters.lock().await.remove(&client_id);

rust/src/tunnel.rs

@@ -1,5 +1,5 @@
 use anyhow::Result;
-use std::net::Ipv4Addr;
+use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
 use tracing::info;
 
 /// Configuration for creating a TUN device.
@@ -80,6 +80,26 @@ pub fn check_tun_mtu(packet: &[u8], mtu_config: &crate::mtu::MtuConfig) -> TunMt
     }
 }
 
+/// Extract destination IP from a raw IP packet header.
+pub fn extract_dst_ip(packet: &[u8]) -> Option<IpAddr> {
+    if packet.is_empty() {
+        return None;
+    }
+    let version = packet[0] >> 4;
+    match version {
+        4 if packet.len() >= 20 => {
+            let dst = Ipv4Addr::new(packet[16], packet[17], packet[18], packet[19]);
+            Some(IpAddr::V4(dst))
+        }
+        6 if packet.len() >= 40 => {
+            let mut octets = [0u8; 16];
+            octets.copy_from_slice(&packet[24..40]);
+            Some(IpAddr::V6(Ipv6Addr::from(octets)))
+        }
+        _ => None,
+    }
+}
+
 /// Remove a route.
 pub async fn remove_route(subnet: &str, device_name: &str) -> Result<()> {
     let output = tokio::process::Command::new("ip")

rust/src/userspace_nat.rs

@@ -0,0 +1,640 @@
+use std::collections::{HashMap, VecDeque};
+use std::net::{Ipv4Addr, SocketAddr};
+use std::sync::Arc;
+use std::time::Duration;
+
+use anyhow::Result;
+use smoltcp::iface::{Config, Interface, SocketHandle, SocketSet};
+use smoltcp::phy::{self, Device, DeviceCapabilities, Medium};
+use smoltcp::socket::{tcp, udp};
+use smoltcp::wire::{HardwareAddress, IpAddress, IpCidr, IpEndpoint};
+use tokio::io::{AsyncReadExt, AsyncWriteExt};
+use tokio::net::{TcpStream, UdpSocket};
+use tokio::sync::mpsc;
+use tracing::{debug, info, warn};
+
+use crate::server::ServerState;
+use crate::tunnel;
+
+// ============================================================================
+// Virtual IP device for smoltcp
+// ============================================================================
+
+pub struct VirtualIpDevice {
+    rx_queue: VecDeque<Vec<u8>>,
+    tx_queue: VecDeque<Vec<u8>>,
+    mtu: usize,
+}
+
+impl VirtualIpDevice {
+    pub fn new(mtu: usize) -> Self {
+        Self {
+            rx_queue: VecDeque::new(),
+            tx_queue: VecDeque::new(),
+            mtu,
+        }
+    }
+
+    pub fn inject_packet(&mut self, packet: Vec<u8>) {
+        self.rx_queue.push_back(packet);
+    }
+
+    pub fn drain_tx(&mut self) -> impl Iterator<Item = Vec<u8>> + '_ {
+        self.tx_queue.drain(..)
+    }
+}
+
+pub struct VirtualRxToken {
+    buffer: Vec<u8>,
+}
+
+impl phy::RxToken for VirtualRxToken {
+    fn consume<R, F>(self, f: F) -> R
+    where
+        F: FnOnce(&[u8]) -> R,
+    {
+        f(&self.buffer)
+    }
+}
+
+pub struct VirtualTxToken<'a> {
+    queue: &'a mut VecDeque<Vec<u8>>,
+}
+
+impl<'a> phy::TxToken for VirtualTxToken<'a> {
+    fn consume<R, F>(self, len: usize, f: F) -> R
+    where
+        F: FnOnce(&mut [u8]) -> R,
+    {
+        let mut buffer = vec![0u8; len];
+        let result = f(&mut buffer);
+        self.queue.push_back(buffer);
+        result
+    }
+}
+
+impl Device for VirtualIpDevice {
+    type RxToken<'a> = VirtualRxToken;
+    type TxToken<'a> = VirtualTxToken<'a>;
+
+    fn receive(
+        &mut self,
+        _timestamp: smoltcp::time::Instant,
+    ) -> Option<(Self::RxToken<'_>, Self::TxToken<'_>)> {
+        self.rx_queue.pop_front().map(|buffer| {
+            let rx = VirtualRxToken { buffer };
+            let tx = VirtualTxToken {
+                queue: &mut self.tx_queue,
+            };
+            (rx, tx)
+        })
+    }
+
+    fn transmit(&mut self, _timestamp: smoltcp::time::Instant) -> Option<Self::TxToken<'_>> {
+        Some(VirtualTxToken {
+            queue: &mut self.tx_queue,
+        })
+    }
+
+    fn capabilities(&self) -> DeviceCapabilities {
+        let mut caps = DeviceCapabilities::default();
+        caps.medium = Medium::Ip;
+        caps.max_transmission_unit = self.mtu;
+        caps.max_burst_size = Some(1);
+        caps
+    }
+}
+
+// ============================================================================
+// Session tracking
+// ============================================================================
+
+#[derive(Debug, Clone, Hash, Eq, PartialEq)]
+struct SessionKey {
+    src_ip: Ipv4Addr,
+    src_port: u16,
+    dst_ip: Ipv4Addr,
+    dst_port: u16,
+    protocol: u8,
+}
+
+struct TcpSession {
+    smoltcp_handle: SocketHandle,
+    bridge_data_tx: mpsc::Sender<Vec<u8>>,
+    #[allow(dead_code)]
+    client_ip: Ipv4Addr,
+}
+
+struct UdpSession {
+    smoltcp_handle: SocketHandle,
+    bridge_data_tx: mpsc::Sender<Vec<u8>>,
+    #[allow(dead_code)]
+    client_ip: Ipv4Addr,
+    last_activity: tokio::time::Instant,
+}
+
+enum BridgeMessage {
+    TcpData { key: SessionKey, data: Vec<u8> },
+    TcpClosed { key: SessionKey },
+    UdpData { key: SessionKey, data: Vec<u8> },
+}
+
+// ============================================================================
+// IP packet parsing helpers
+// ============================================================================
+
+fn parse_ipv4_header(packet: &[u8]) -> Option<(u8, Ipv4Addr, Ipv4Addr, u8)> {
+    if packet.len() < 20 {
+        return None;
+    }
+    let version = packet[0] >> 4;
+    if version != 4 {
+        return None;
+    }
+    let ihl = (packet[0] & 0x0F) as usize * 4;
+    let protocol = packet[9];
+    let src = Ipv4Addr::new(packet[12], packet[13], packet[14], packet[15]);
+    let dst = Ipv4Addr::new(packet[16], packet[17], packet[18], packet[19]);
+    Some((ihl as u8, src, dst, protocol))
+}
+
+fn parse_tcp_ports(packet: &[u8], ihl: usize) -> Option<(u16, u16, u8)> {
+    if packet.len() < ihl + 14 {
+        return None;
+    }
+    let src_port = u16::from_be_bytes([packet[ihl], packet[ihl + 1]]);
+    let dst_port = u16::from_be_bytes([packet[ihl + 2], packet[ihl + 3]]);
+    let flags = packet[ihl + 13];
+    Some((src_port, dst_port, flags))
+}
+
+fn parse_udp_ports(packet: &[u8], ihl: usize) -> Option<(u16, u16)> {
+    if packet.len() < ihl + 4 {
+        return None;
+    }
+    let src_port = u16::from_be_bytes([packet[ihl], packet[ihl + 1]]);
+    let dst_port = u16::from_be_bytes([packet[ihl + 2], packet[ihl + 3]]);
+    Some((src_port, dst_port))
+}
+
+// ============================================================================
+// NAT Engine
+// ============================================================================
+
+pub struct NatEngine {
+    device: VirtualIpDevice,
+    iface: Interface,
+    sockets: SocketSet<'static>,
+    tcp_sessions: HashMap<SessionKey, TcpSession>,
+    udp_sessions: HashMap<SessionKey, UdpSession>,
+    state: Arc<ServerState>,
+    bridge_rx: mpsc::Receiver<BridgeMessage>,
+    bridge_tx: mpsc::Sender<BridgeMessage>,
+    start_time: std::time::Instant,
+}
+
+impl NatEngine {
+    pub fn new(gateway_ip: Ipv4Addr, mtu: usize, state: Arc<ServerState>) -> Self {
+        let mut device = VirtualIpDevice::new(mtu);
+        let config = Config::new(HardwareAddress::Ip);
+        let now = smoltcp::time::Instant::from_millis(0);
+        let mut iface = Interface::new(config, &mut device, now);
+
+        // Accept packets to ANY destination IP (essential for NAT)
+        iface.set_any_ip(true);
+
+        // Assign the gateway IP as the interface address
+        iface.update_ip_addrs(|addrs| {
+            addrs
+                .push(IpCidr::new(IpAddress::Ipv4(gateway_ip.into()), 24))
+                .unwrap();
+        });
+
+        // Add a default route so smoltcp knows where to send packets
+        iface.routes_mut().add_default_ipv4_route(gateway_ip.into()).unwrap();
+
+        let sockets = SocketSet::new(Vec::with_capacity(256));
+        let (bridge_tx, bridge_rx) = mpsc::channel(4096);
+
+        Self {
+            device,
+            iface,
+            sockets,
+            tcp_sessions: HashMap::new(),
+            udp_sessions: HashMap::new(),
+            state,
+            bridge_rx,
+            bridge_tx,
+            start_time: std::time::Instant::now(),
+        }
+    }
+
+    fn smoltcp_now(&self) -> smoltcp::time::Instant {
+        smoltcp::time::Instant::from_millis(self.start_time.elapsed().as_millis() as i64)
+    }
+
+    /// Inject a raw IP packet from a VPN client and handle new session creation.
+    fn inject_packet(&mut self, packet: Vec<u8>) {
+        let Some((ihl, src_ip, dst_ip, protocol)) = parse_ipv4_header(&packet) else {
+            return;
+        };
+        let ihl = ihl as usize;
+
+        match protocol {
+            6 => {
+                // TCP
+                let Some((src_port, dst_port, flags)) = parse_tcp_ports(&packet, ihl) else {
+                    return;
+                };
+                let key = SessionKey {
+                    src_ip,
+                    src_port,
+                    dst_ip,
+                    dst_port,
+                    protocol: 6,
+                };
+
+                // SYN without ACK = new connection
+                let is_syn = (flags & 0x02) != 0 && (flags & 0x10) == 0;
+                if is_syn && !self.tcp_sessions.contains_key(&key) {
+                    self.create_tcp_session(&key);
+                }
+            }
+            17 => {
+                // UDP
+                let Some((src_port, dst_port)) = parse_udp_ports(&packet, ihl) else {
+                    return;
+                };
+                let key = SessionKey {
+                    src_ip,
+                    src_port,
+                    dst_ip,
+                    dst_port,
+                    protocol: 17,
+                };
+
+                if !self.udp_sessions.contains_key(&key) {
+                    self.create_udp_session(&key);
+                }
+
+                // Update last_activity for existing sessions
+                if let Some(session) = self.udp_sessions.get_mut(&key) {
+                    session.last_activity = tokio::time::Instant::now();
+                }
+            }
+            _ => {
+                // ICMP and other protocols — not forwarded in socket mode
+                return;
+            }
+        }
+
+        self.device.inject_packet(packet);
+    }
+
+    fn create_tcp_session(&mut self, key: &SessionKey) {
+        // Create smoltcp TCP socket
+        let tcp_rx_buf = tcp::SocketBuffer::new(vec![0u8; 65535]);
+        let tcp_tx_buf = tcp::SocketBuffer::new(vec![0u8; 65535]);
+        let mut socket = tcp::Socket::new(tcp_rx_buf, tcp_tx_buf);
+
+        // Listen on the destination address so smoltcp accepts the SYN
+        let endpoint = IpEndpoint::new(
+            IpAddress::Ipv4(key.dst_ip.into()),
+            key.dst_port,
+        );
+        if socket.listen(endpoint).is_err() {
+            warn!("NAT: failed to listen on {:?}", endpoint);
+            return;
+        }
+
+        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 session = TcpSession {
+            smoltcp_handle: handle,
+            bridge_data_tx: data_tx,
+            client_ip: key.src_ip,
+        };
+        self.tcp_sessions.insert(key.clone(), session);
+
+        // Spawn bridge task that connects to the real destination
+        let bridge_tx = self.bridge_tx.clone();
+        let key_clone = key.clone();
+        tokio::spawn(async move {
+            tcp_bridge_task(key_clone, data_rx, bridge_tx).await;
+        });
+
+        debug!(
+            "NAT: new TCP session {}:{} -> {}:{}",
+            key.src_ip, key.src_port, key.dst_ip, key.dst_port
+        );
+    }
+
+    fn create_udp_session(&mut self, key: &SessionKey) {
+        // Create smoltcp UDP socket
+        let udp_rx_buf = udp::PacketBuffer::new(
+            vec![udp::PacketMetadata::EMPTY; 32],
+            vec![0u8; 65535],
+        );
+        let udp_tx_buf = udp::PacketBuffer::new(
+            vec![udp::PacketMetadata::EMPTY; 32],
+            vec![0u8; 65535],
+        );
+        let mut socket = udp::Socket::new(udp_rx_buf, udp_tx_buf);
+
+        let endpoint = IpEndpoint::new(
+            IpAddress::Ipv4(key.dst_ip.into()),
+            key.dst_port,
+        );
+        if socket.bind(endpoint).is_err() {
+            warn!("NAT: failed to bind UDP on {:?}", endpoint);
+            return;
+        }
+
+        let handle = self.sockets.add(socket);
+
+        let (data_tx, data_rx) = mpsc::channel::<Vec<u8>>(256);
+
+        let session = UdpSession {
+            smoltcp_handle: handle,
+            bridge_data_tx: data_tx,
+            client_ip: key.src_ip,
+            last_activity: tokio::time::Instant::now(),
+        };
+        self.udp_sessions.insert(key.clone(), session);
+
+        let bridge_tx = self.bridge_tx.clone();
+        let key_clone = key.clone();
+        tokio::spawn(async move {
+            udp_bridge_task(key_clone, data_rx, bridge_tx).await;
+        });
+
+        debug!(
+            "NAT: new UDP session {}:{} -> {}:{}",
+            key.src_ip, key.src_port, key.dst_ip, key.dst_port
+        );
+    }
+
+    /// Poll smoltcp, bridge data between smoltcp sockets and bridge tasks,
+    /// and dispatch outgoing packets to VPN clients.
+    async fn process(&mut self) {
+        let now = self.smoltcp_now();
+        self.iface
+            .poll(now, &mut self.device, &mut self.sockets);
+
+        // Bridge: read data from smoltcp TCP sockets → send to bridge tasks
+        let mut closed_tcp: Vec<SessionKey> = Vec::new();
+        for (key, session) in &self.tcp_sessions {
+            let socket = self.sockets.get_mut::<tcp::Socket>(session.smoltcp_handle);
+            if socket.can_recv() {
+                let _ = socket.recv(|data| {
+                    let _ = session.bridge_data_tx.try_send(data.to_vec());
+                    (data.len(), ())
+                });
+            }
+            // Detect closed connections
+            if !socket.is_open() && !socket.is_listening() {
+                closed_tcp.push(key.clone());
+            }
+        }
+
+        // Clean up closed TCP sessions
+        for key in closed_tcp {
+            if let Some(session) = self.tcp_sessions.remove(&key) {
+                self.sockets.remove(session.smoltcp_handle);
+                debug!("NAT: TCP session closed {}:{} -> {}:{}", key.src_ip, key.src_port, key.dst_ip, key.dst_port);
+            }
+        }
+
+        // Bridge: read data from smoltcp UDP sockets → send to bridge tasks
+        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());
+            }
+        }
+
+        // Dispatch outgoing packets from smoltcp to VPN clients
+        let routes = self.state.tun_routes.read().await;
+        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);
+                }
+            }
+        }
+    }
+
+    fn handle_bridge_message(&mut self, msg: BridgeMessage) {
+        match msg {
+            BridgeMessage::TcpData { key, data } => {
+                if let Some(session) = self.tcp_sessions.get(&key) {
+                    let socket =
+                        self.sockets.get_mut::<tcp::Socket>(session.smoltcp_handle);
+                    if socket.can_send() {
+                        let _ = socket.send_slice(&data);
+                    }
+                }
+            }
+            BridgeMessage::TcpClosed { key } => {
+                if let Some(session) = self.tcp_sessions.remove(&key) {
+                    let socket =
+                        self.sockets.get_mut::<tcp::Socket>(session.smoltcp_handle);
+                    socket.close();
+                    // 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 } => {
+                if let Some(session) = self.udp_sessions.get_mut(&key) {
+                    session.last_activity = tokio::time::Instant::now();
+                    let socket =
+                        self.sockets.get_mut::<udp::Socket>(session.smoltcp_handle);
+                    let dst_endpoint = IpEndpoint::new(
+                        IpAddress::Ipv4(key.src_ip.into()),
+                        key.src_port,
+                    );
+                    // Send response: from the "server" (dst) back to the "client" (src)
+                    let _ = socket.send_slice(&data, dst_endpoint);
+                }
+            }
+        }
+    }
+
+    fn cleanup_idle_udp_sessions(&mut self) {
+        let timeout = Duration::from_secs(60);
+        let now = tokio::time::Instant::now();
+        let expired: Vec<SessionKey> = self
+            .udp_sessions
+            .iter()
+            .filter(|(_, s)| now.duration_since(s.last_activity) > timeout)
+            .map(|(k, _)| k.clone())
+            .collect();
+
+        for key in expired {
+            if let Some(session) = self.udp_sessions.remove(&key) {
+                self.sockets.remove(session.smoltcp_handle);
+                debug!(
+                    "NAT: UDP session timed out {}:{} -> {}:{}",
+                    key.src_ip, key.src_port, key.dst_ip, key.dst_port
+                );
+            }
+        }
+    }
+
+    /// Main async event loop for the NAT engine.
+    pub async fn run(
+        mut self,
+        mut packet_rx: mpsc::Receiver<Vec<u8>>,
+        mut shutdown_rx: mpsc::Receiver<()>,
+    ) -> Result<()> {
+        info!("Userspace NAT engine started");
+        let mut timer = tokio::time::interval(Duration::from_millis(50));
+        let mut cleanup_timer = tokio::time::interval(Duration::from_secs(10));
+
+        loop {
+            tokio::select! {
+                Some(packet) = packet_rx.recv() => {
+                    self.inject_packet(packet);
+                    self.process().await;
+                }
+                Some(msg) = self.bridge_rx.recv() => {
+                    self.handle_bridge_message(msg);
+                    self.process().await;
+                }
+                _ = timer.tick() => {
+                    // Periodic poll for smoltcp maintenance (TCP retransmit, etc.)
+                    self.process().await;
+                }
+                _ = cleanup_timer.tick() => {
+                    self.cleanup_idle_udp_sessions();
+                }
+                _ = shutdown_rx.recv() => {
+                    info!("Userspace NAT engine shutting down");
+                    break;
+                }
+            }
+        }
+
+        Ok(())
+    }
+}
+
+// ============================================================================
+// Bridge tasks
+// ============================================================================
+
+async fn tcp_bridge_task(
+    key: SessionKey,
+    mut data_rx: mpsc::Receiver<Vec<u8>>,
+    bridge_tx: mpsc::Sender<BridgeMessage>,
+) {
+    let addr = SocketAddr::new(key.dst_ip.into(), key.dst_port);
+
+    // Connect to real destination with timeout
+    let stream = match tokio::time::timeout(Duration::from_secs(30), TcpStream::connect(addr)).await
+    {
+        Ok(Ok(s)) => s,
+        Ok(Err(e)) => {
+            debug!("NAT TCP connect to {} failed: {}", addr, e);
+            let _ = bridge_tx.send(BridgeMessage::TcpClosed { key }).await;
+            return;
+        }
+        Err(_) => {
+            debug!("NAT TCP connect to {} timed out", addr);
+            let _ = bridge_tx.send(BridgeMessage::TcpClosed { key }).await;
+            return;
+        }
+    };
+
+    let (mut reader, mut writer) = stream.into_split();
+
+    // Read from real socket → send to NAT engine
+    let bridge_tx2 = bridge_tx.clone();
+    let key2 = key.clone();
+    let read_task = tokio::spawn(async move {
+        let mut buf = vec![0u8; 65536];
+        loop {
+            match reader.read(&mut buf).await {
+                Ok(0) => break,
+                Ok(n) => {
+                    if bridge_tx2
+                        .send(BridgeMessage::TcpData {
+                            key: key2.clone(),
+                            data: buf[..n].to_vec(),
+                        })
+                        .await
+                        .is_err()
+                    {
+                        break;
+                    }
+                }
+                Err(_) => break,
+            }
+        }
+        let _ = bridge_tx2
+            .send(BridgeMessage::TcpClosed { key: key2 })
+            .await;
+    });
+
+    // Receive from NAT engine → write to real socket
+    while let Some(data) = data_rx.recv().await {
+        if writer.write_all(&data).await.is_err() {
+            break;
+        }
+    }
+
+    read_task.abort();
+}
+
+async fn udp_bridge_task(
+    key: SessionKey,
+    mut data_rx: mpsc::Receiver<Vec<u8>>,
+    bridge_tx: mpsc::Sender<BridgeMessage>,
+) {
+    let socket = match UdpSocket::bind("0.0.0.0:0").await {
+        Ok(s) => s,
+        Err(e) => {
+            warn!("NAT UDP bind failed: {}", e);
+            return;
+        }
+    };
+    let dest = SocketAddr::new(key.dst_ip.into(), key.dst_port);
+
+    let socket = Arc::new(socket);
+    let socket2 = socket.clone();
+    let bridge_tx2 = bridge_tx.clone();
+    let key2 = key.clone();
+
+    // Read responses from real socket
+    let read_task = tokio::spawn(async move {
+        let mut buf = vec![0u8; 65536];
+        loop {
+            match socket2.recv_from(&mut buf).await {
+                Ok((n, _src)) => {
+                    if bridge_tx2
+                        .send(BridgeMessage::UdpData {
+                            key: key2.clone(),
+                            data: buf[..n].to_vec(),
+                        })
+                        .await
+                        .is_err()
+                    {
+                        break;
+                    }
+                }
+                Err(_) => break,
+            }
+        }
+    });
+
+    // Forward data from NAT engine to real socket
+    while let Some(data) = data_rx.recv().await {
+        let _ = socket.send_to(&data, dest).await;
+    }
+
+    read_task.abort();
+}

rust/src/wireguard.rs

@@ -1,5 +1,5 @@
 use std::collections::HashMap;
-use std::net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr};
+use std::net::{IpAddr, Ipv4Addr, SocketAddr};
 use std::sync::atomic::{AtomicU32, Ordering};
 use std::sync::Arc;
 use std::time::Instant;
@@ -18,6 +18,7 @@ use tokio::sync::{mpsc, oneshot, RwLock};
 use tracing::{debug, error, info, warn};
 
 use crate::network;
+use crate::tunnel::extract_dst_ip;
 use crate::tunnel::{self, TunConfig};
 
 // ============================================================================
@@ -228,26 +229,6 @@ impl AllowedIp {
     }
 }
 
-/// Extract destination IP from an IP packet header.
-fn extract_dst_ip(packet: &[u8]) -> Option<IpAddr> {
-    if packet.is_empty() {
-        return None;
-    }
-    let version = packet[0] >> 4;
-    match version {
-        4 if packet.len() >= 20 => {
-            let dst = Ipv4Addr::new(packet[16], packet[17], packet[18], packet[19]);
-            Some(IpAddr::V4(dst))
-        }
-        6 if packet.len() >= 40 => {
-            let mut octets = [0u8; 16];
-            octets.copy_from_slice(&packet[24..40]);
-            Some(IpAddr::V6(Ipv6Addr::from(octets)))
-        }
-        _ => None,
-    }
-}
-
 // ============================================================================
 // Dynamic peer management commands
 // ============================================================================
@@ -1096,6 +1077,7 @@ fn chrono_now() -> String {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use std::net::Ipv6Addr;
 
     #[test]
     fn test_generate_wg_keypair() {

ts/00_commitinfo_data.ts

@@ -3,6 +3,6 @@
  */
 export const commitinfo = {
   name: '@push.rocks/smartvpn',
-  version: '1.9.0',
+  version: '1.10.0',
   description: 'A VPN solution with TypeScript control plane and Rust data plane daemon'
 }

ts/smartvpn.interfaces.ts

@@ -40,6 +40,9 @@ export interface IVpnClientConfig {
   transport?: 'auto' | 'websocket' | 'quic' | 'wireguard';
   /** For QUIC: SHA-256 hash of server certificate (base64) for cert pinning */
   serverCertHash?: string;
+  /** Forwarding mode: 'tun' (TUN device, requires root) or 'testing' (no TUN).
+   *  Default: 'testing'. */
+  forwardingMode?: 'tun' | 'testing';
   /** WireGuard: client private key (base64, X25519) */
   wgPrivateKey?: string;
   /** WireGuard: client TUN address (e.g. 10.8.0.2) */
@@ -86,6 +89,9 @@ export interface IVpnServerConfig {
   keepaliveIntervalSecs?: number;
   /** Enable NAT/masquerade for client traffic */
   enableNat?: boolean;
+  /** Forwarding mode: 'tun' (kernel TUN, requires root), 'socket' (userspace NAT),
+   *  or 'testing' (monitoring only). Default: 'testing'. */
+  forwardingMode?: 'tun' | 'socket' | 'testing';
   /** Default rate limit for new clients (bytes/sec). Omit for unlimited. */
   defaultRateLimitBytesPerSec?: number;
   /** Default burst size for new clients (bytes). Omit for unlimited. */