fix(relay/client): only try to forward handler events once

We currently try to forward pending handler events in the relay client behavior twice: in `handle_established_{in, out}bound_connection` and in `on_swarm_event()` (introduced in #3328).
This is redundant because by the second time we try to forward it there won't be any pending event anymore.
This PR removes the duplicated logic from `on_swarm_event`. Forwarding it in `handle_established_{in, out}bound_connection` is more convenient as we still have direct access to the handler there and don't need to go through the swarm.

However, it requires that in `handle_established_{in, out}bound_connection` the event is also removed when the connection is relayed, in which case the event is simply discarded because the commands are only valid on direct connections.

Pull-Request: #5765.

Cargo.toml

@@ -94,7 +94,7 @@ libp2p-ping = { version = "0.46.0", path = "protocols/ping" }
 libp2p-plaintext = { version = "0.43.0", path = "transports/plaintext" }
 libp2p-pnet = { version = "0.26.0", path = "transports/pnet" }
 libp2p-quic = { version = "0.12.0", path = "transports/quic" }
-libp2p-relay = { version = "0.19.0", path = "protocols/relay" }
+libp2p-relay = { version = "0.19.1", path = "protocols/relay" }
 libp2p-rendezvous = { version = "0.16.0", path = "protocols/rendezvous" }
 libp2p-request-response = { version = "0.28.0", path = "protocols/request-response" }
 libp2p-server = { version = "0.12.6", path = "misc/server" }

protocols/relay/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.19.1
+
+- Remove duplicated forwarding of pending events to connection handler.
+
 ## 0.19.0
 
 - Deprecate `void` crate.

protocols/relay/Cargo.toml

@@ -3,7 +3,7 @@ name = "libp2p-relay"
 edition = "2021"
 rust-version = { workspace = true }
 description = "Communications relaying for libp2p"
-version = "0.19.0"
+version = "0.19.1"
 authors = ["Parity Technologies <[email protected]>", "Max Inden <[email protected]>"]
 license = "MIT"
 repository = "https://github.com/libp2p/rust-libp2p"

protocols/relay/src/priv_client.rs

@@ -168,12 +168,14 @@ impl NetworkBehaviour for Behaviour {
         local_addr: &Multiaddr,
         remote_addr: &Multiaddr,
     ) -> Result<THandler<Self>, ConnectionDenied> {
+        let pending_handler_command = self.pending_handler_commands.remove(&connection_id);
+
         if local_addr.is_relayed() {
             return Ok(Either::Right(dummy::ConnectionHandler));
         }
         let mut handler = Handler::new(self.local_peer_id, peer, remote_addr.clone());
 
-        if let Some(event) = self.pending_handler_commands.remove(&connection_id) {
+        if let Some(event) = pending_handler_command {
             handler.on_behaviour_event(event)
         }
 
@@ -188,13 +190,15 @@ impl NetworkBehaviour for Behaviour {
         _: Endpoint,
         _: PortUse,
     ) -> Result<THandler<Self>, ConnectionDenied> {
+        let pending_handler_command = self.pending_handler_commands.remove(&connection_id);
+
         if addr.is_relayed() {
             return Ok(Either::Right(dummy::ConnectionHandler));
         }
 
         let mut handler = Handler::new(self.local_peer_id, peer, addr.clone());
 
-        if let Some(event) = self.pending_handler_commands.remove(&connection_id) {
+        if let Some(event) = pending_handler_command {
             handler.on_behaviour_event(event)
         }
 
@@ -208,21 +212,11 @@ impl NetworkBehaviour for Behaviour {
                 connection_id,
                 endpoint,
                 ..
-            }) => {
-                if !endpoint.is_relayed() {
-                    self.directly_connected_peers
-                        .entry(peer_id)
-                        .or_default()
-                        .push(connection_id);
-                }
-
-                if let Some(event) = self.pending_handler_commands.remove(&connection_id) {
-                    self.queued_actions.push_back(ToSwarm::NotifyHandler {
-                        peer_id,
-                        handler: NotifyHandler::One(connection_id),
-                        event: Either::Left(event),
-                    })
-                }
+            }) if !endpoint.is_relayed() => {
+                self.directly_connected_peers
+                    .entry(peer_id)
+                    .or_default()
+                    .push(connection_id);
             }
             FromSwarm::ConnectionClosed(connection_closed) => {
                 self.on_connection_closed(connection_closed)