fix(remoteingress-core): guard tunnel frame sends with cancellation to prevent async send deadlocks

rust/crates/remoteingress-core/src/edge.rs

@@ -739,7 +739,11 @@ async fn handle_client_connection(
     // Send OPEN frame with PROXY v1 header via control channel
     let proxy_header = build_proxy_v1_header(&client_ip, edge_ip, client_port, dest_port);
     let open_frame = encode_frame(stream_id, FRAME_OPEN, proxy_header.as_bytes());
-    if tunnel_ctrl_tx.send(open_frame).await.is_err() {
+    let send_ok = tokio::select! {
+        result = tunnel_ctrl_tx.send(open_frame) => result.is_ok(),
+        _ = client_token.cancelled() => false,
+    };
+    if !send_ok {
         return;
     }
 
@@ -814,7 +818,10 @@ async fn handle_client_connection(
         // Send final window update for any remaining consumed bytes
         if consumed_since_update > 0 {
             let frame = encode_window_update(stream_id, FRAME_WINDOW_UPDATE, consumed_since_update);
-            let _ = wu_tx.send(frame).await;
+            tokio::select! {
+                _ = wu_tx.send(frame) => {}
+                _ = hub_to_client_token.cancelled() => {}
+            }
         }
         let _ = client_write.shutdown().await;
     });
@@ -890,9 +897,13 @@ async fn handle_client_connection(
     ).await;
 
     // NOW send CLOSE — the response has been fully delivered (or timed out).
+    // select! with cancellation guard prevents indefinite blocking if tunnel dies.
     if !client_token.is_cancelled() {
         let close_frame = encode_frame(stream_id, FRAME_CLOSE, &[]);
-        let _ = tunnel_data_tx.send(close_frame).await;
+        tokio::select! {
+            _ = tunnel_data_tx.send(close_frame) => {}
+            _ = client_token.cancelled() => {}
+        }
     }
 
     // Clean up