fix(mdns): don't suspend task forever upon reading non-mDNS packet

Fixes: #4860.

Pull-Request: #4861.

protocols/mdns/CHANGELOG.md

@@ -2,6 +2,8 @@
 
 - Ensure `Multiaddr` handled and returned by `Behaviour` are `/p2p` terminated.
   See [PR 4596](https://github.com/libp2p/rust-libp2p/pull/4596).
+- Fix a bug in the `Behaviour::poll` method causing missed mdns packets.
+  See [PR 4861](https://github.com/libp2p/rust-libp2p/pull/4861).
 
 ## 0.45.0
 

protocols/mdns/src/behaviour/iface.rs

@@ -312,14 +312,18 @@ where
                 }
                 Poll::Ready(Err(err)) if err.kind() == std::io::ErrorKind::WouldBlock => {
                     // No more bytes available on the socket to read
+                    continue;
                 }
                 Poll::Ready(Err(err)) => {
                     tracing::error!("failed reading datagram: {}", err);
+                    return Poll::Ready(());
                 }
                 Poll::Ready(Ok(Err(err))) => {
                     tracing::debug!("Parsing mdns packet failed: {:?}", err);
+                    continue;
                 }
-                Poll::Ready(Ok(Ok(None))) | Poll::Pending => {}
+                Poll::Ready(Ok(Ok(None))) => continue,
+                Poll::Pending => {}
             }
 
             return Poll::Pending;