Drop gossipsub stale messages when polling ConnectionHandler.

beacon_node/lighthouse_network/src/gossipsub/handler.rs

@@ -247,10 +247,6 @@ impl EnabledHandler {
             });
         }
 
-        // We may need to inform the behviour if we have a dropped a message. This gets set if that
-        // is the case.
-        let mut dropped_message = None;
-
         // process outbound stream
         loop {
             match std::mem::replace(
@@ -271,10 +267,11 @@ impl EnabledHandler {
                             } => {
                                 if Pin::new(timeout).poll(cx).is_ready() {
                                     // Inform the behaviour and end the poll.
-                                    dropped_message = Some(HandlerEvent::MessageDropped(message));
                                     self.outbound_substream =
                                         Some(OutboundSubstreamState::WaitingOutput(substream));
-                                    break;
+                                    return Poll::Ready(ConnectionHandlerEvent::NotifyBehaviour(
+                                        HandlerEvent::MessageDropped(message),
+                                    ));
                                 }
                             }
                             _ => {} // All other messages are not time-bound.
@@ -348,13 +345,7 @@ impl EnabledHandler {
             }
         }
 
-        // If there was a timeout in sending a message, inform the behaviour before restarting the
-        // poll
-        if let Some(handler_event) = dropped_message {
-            return Poll::Ready(ConnectionHandlerEvent::NotifyBehaviour(handler_event));
-        }
-
-        // Handle inbound messages
+        // Handle inbound messages.
         loop {
             match std::mem::replace(
                 &mut self.inbound_substream,
@@ -419,6 +410,32 @@ impl EnabledHandler {
             }
         }
 
+        // Drop the next message in queue if it's stale.
+        let mut peakable = self.send_queue.clone().peekable();
+        if let Poll::Ready(Some(mut message)) = peakable.poll_next_unpin(cx) {
+            match message {
+                RpcOut::Publish {
+                    message: _,
+                    ref mut timeout,
+                }
+                | RpcOut::Forward {
+                    message: _,
+                    ref mut timeout,
+                } => {
+                    if Pin::new(timeout).poll(cx).is_ready() {
+                        // Drop the message.
+                        let dropped = futures::ready!(self.send_queue.poll_next_unpin(cx))
+                            .expect("There should be a message");
+                        return Poll::Ready(ConnectionHandlerEvent::NotifyBehaviour(
+                            HandlerEvent::MessageDropped(dropped),
+                        ));
+                    }
+                }
+                // the next message in queue is not time bound.
+                _ => {}
+            }
+        }
+
         Poll::Pending
     }
 }