webrtc: clarify that there is no reuseport functionality (#2652)

Co-authored-by: Marten Seemann <[email protected]>

Author: sukunrt

p2p/transport/webrtc/transport.go

@@ -177,6 +177,11 @@ func (t *WebRTCTransport) CanDial(addr ma.Multiaddr) bool {
 	return dialMatcher.Matches(addr)
 }
 
+// Listen returns a listener for addr.
+//
+// The IP, Port combination for addr must be exclusive to this listener as a WebRTC listener cannot
+// be multiplexed on the same port as other UDP based transports like QUIC and WebTransport.
+// See https://github.com/libp2p/go-libp2p/issues/2446 for details.
 func (t *WebRTCTransport) Listen(addr ma.Multiaddr) (tpt.Listener, error) {
 	addr, wrtcComponent := ma.SplitLast(addr)
 	isWebrtc := wrtcComponent.Equal(webrtcComponent)