fix(upnp): don't panic when gateway is dropped

There seems to be a situation when the `Behaviour` and therefore it's `Gateway` is dropped leaving the `tokio` loop to panic.  It has been reported on  sigp/lighthouse#5498, this attempts to fix it.
Cc @dariusc93 can you review this please Darius? Thanks!

Pull-Request: #5273.

Cargo.toml

@@ -107,7 +107,7 @@ libp2p-swarm-test = { version = "0.3.0", path = "swarm-test" }
 libp2p-tcp = { version = "0.41.0", path = "transports/tcp" }
 libp2p-tls = { version = "0.3.0", path = "transports/tls" }
 libp2p-uds = { version = "0.40.0", path = "transports/uds" }
-libp2p-upnp = { version = "0.2.1", path = "protocols/upnp" }
+libp2p-upnp = { version = "0.2.2", path = "protocols/upnp" }
 libp2p-webrtc = { version = "0.7.1-alpha", path = "transports/webrtc" }
 libp2p-webrtc-utils = { version = "0.2.0", path = "misc/webrtc-utils" }
 libp2p-webrtc-websys = { version = "0.3.0-alpha", path = "transports/webrtc-websys" }

protocols/upnp/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 0.2.2
+- Fix a panic caused when `upnp::Gateway` is dropped and its events queue receiver is no longer
+available.
+  See [PR 5273](https://github.com/libp2p/rust-libp2p/pull/5273).
+
 ## 0.2.1
 - Fix a panic caused when dropping `upnp::Behaviour` such as when used together with `Toggle`.
   See [PR 5096](https://github.com/libp2p/rust-libp2p/pull/5096).

protocols/upnp/Cargo.toml

@@ -3,7 +3,7 @@ name = "libp2p-upnp"
 edition = "2021"
 rust-version = "1.60.0"
 description = "UPnP support for libp2p transports"
-version = "0.2.1"
+version = "0.2.2"
 license = "MIT"
 repository = "https://github.com/libp2p/rust-libp2p"
 keywords = ["peer-to-peer", "libp2p", "networking"]

protocols/upnp/src/tokio.rs

@@ -158,10 +158,10 @@ pub(crate) fn search_gateway() -> oneshot::Receiver<Result<Gateway, Box<dyn Erro
                     }
                 }
             };
-            task_sender
-                .send(event)
-                .await
-                .expect("receiver should be available");
+            // Gateway was dropped.
+            if task_sender.send(event).await.is_err() {
+                return;
+            }
         }
     });