feat: add non-blocking handshakes and tunnel health monitoring (#13)

src-tauri/src/commands/session.rs

@@ -189,7 +189,16 @@ fn build_connect_link(dest: &str, ik_hex: &str, spk_hex: &str) -> String {
 }
 
 /// Accept loop: waits for incoming I2P stream connections for this session.
+/// Implements non-blocking handshakes with timeout and tunnel health monitoring.
 async fn accept_loop(app: AppHandle, session_id: String, sam_addr: String) {
+    // Spawn health monitoring task
+    let app_health = app.clone();
+    let session_id_health = session_id.clone();
+    let sam_addr_health = sam_addr.clone();
+    tauri::async_runtime::spawn(async move {
+        tunnel_health_monitor(app_health, session_id_health, sam_addr_health).await;
+    });
+
     loop {
         // Exit if the session was replaced or dropped (e.g. after panic_wipe)
         let should_continue = {
@@ -203,11 +212,31 @@ async fn accept_loop(app: AppHandle, session_id: String, sam_addr: String) {
 
         match accept_once_raw(&session_id, &sam_addr).await {
             Ok((peer_dest, tunnel)) => {
-                if let Err(e) = handle_incoming(&app, peer_dest, tunnel).await {
-                    #[cfg(debug_assertions)]
-                    log::warn!("incoming session error: {}", e);
-                    let _ = e;
-                }
+                // Spawn handshake in a separate task with timeout to avoid blocking
+                let app_clone = app.clone();
+                tauri::async_runtime::spawn(async move {
+                    // 60s timeout for handshake to prevent indefinite blocking
+                    let result = tokio::time::timeout(
+                        tokio::time::Duration::from_secs(60),
+                        handle_incoming(&app_clone, peer_dest, tunnel)
+                    ).await;
+
+                    match result {
+                        Ok(Ok(())) => {
+                            // Handshake successful
+                        },
+                        Ok(Err(e)) => {
+                            #[cfg(debug_assertions)]
+                            log::warn!("incoming session handshake error: {}", e);
+                            let _ = e;
+                        },
+                        Err(_) => {
+                            #[cfg(debug_assertions)]
+                            log::warn!("incoming session handshake timeout (60s)");
+                            let _ = app_clone.emit("connection_error", "Incoming handshake timeout - peer unresponsive");
+                        }
+                    }
+                });
             }
             Err(e) => {
                 #[cfg(debug_assertions)]
@@ -218,6 +247,53 @@ async fn accept_loop(app: AppHandle, session_id: String, sam_addr: String) {
     }
 }
 
+/// Monitor tunnel health and emit status events.
+/// Periodically checks if the SAM session is still responsive.
+async fn tunnel_health_monitor(app: AppHandle, session_id: String, sam_addr: String) {
+    loop {
+        // Check if session is still valid
+        let should_continue = {
+            let state = app.state::<AppState>();
+            let i2p = state.i2p.lock().await;
+            i2p.as_ref().map_or(false, |s| s.session_id == session_id)
+        };
+        if !should_continue {
+            break;
+        }
+
+        // Check tunnel health by attempting a quick SAM status check
+        let is_healthy = check_tunnel_health(&sam_addr).await;
+
+        if is_healthy {
+            let _ = app.emit("tunnel_healthy", ());
+        } else {
+            #[cfg(debug_assertions)]
+            log::warn!("Tunnel health check failed");
+            let _ = app.emit("tunnel_degraded", ());
+        }
+
+        // Check every 30 seconds
+        tokio::time::sleep(tokio::time::Duration::from_secs(30)).await;
+    }
+}
+
+/// Quick health check for the I2P tunnel.
+/// Attempts to connect to SAM and verify session is still valid.
+async fn check_tunnel_health(sam_addr: &str) -> bool {
+    match tokio::net::TcpStream::connect(sam_addr).await {
+        Ok(mut stream) => {
+            use tokio::io::AsyncWriteExt;
+            if stream.write_all(b"HELLO VERSION MIN=3.1 MAX=3.3\n").await.is_ok() {
+                // If we can connect and send HELLO, tunnel is healthy
+                true
+            } else {
+                false
+            }
+        }
+        Err(_) => false,
+    }
+}
+
 async fn accept_once_raw(
     session_id: &str,
     sam_addr: &str,