fix(iroh-gossip): do not drop existing peer connection when we get in…

…coming one

iroh-gossip/src/net.rs

@@ -616,12 +616,20 @@ async fn connection_loop(
     };
     let mut send_buf = BytesMut::new();
     let mut recv_buf = BytesMut::new();
+    let mut tx_open = true;
     loop {
         tokio::select! {
             biased;
-            msg = send_rx.recv() => {
+            msg = send_rx.recv(), if tx_open => {
                 match msg {
-                    None => break,
+                    None => {
+                        // Channel is closed and is always ready to return None now,
+                        // stop polling it.
+                        // We are not going to use the connection for sending anymore,
+                        // but do not exit yet because the other side may
+                        // still want to use the connection to send data to us.
+                        tx_open = false;
+                    }
                     Some(msg) =>  write_message(&mut send, &mut send_buf, &msg).await?,
                 }
             }