simplify peer disconnect detection logic to ensure a single outgoing stream

comm.go

@@ -66,12 +66,29 @@ func (p *PubSub) handleNewPeer(ctx context.Context, pid peer.ID, outgoing <-chan
 	}
 
 	go p.handleSendingMessages(ctx, s, outgoing)
+	go p.handlePeerEOF(ctx, s)
 	select {
 	case p.newPeerStream <- s:
 	case <-ctx.Done():
 	}
 }
 
+func (p *PubSub) handlePeerEOF(ctx context.Context, s inet.Stream) {
+	r := ggio.NewDelimitedReader(s, 1<<20)
+	rpc := new(RPC)
+	for {
+		err := r.ReadMsg(&rpc.RPC)
+		if err != nil {
+			select {
+			case p.peerDead <- s.Conn().RemotePeer():
+			case <-ctx.Done():
+			}
+			return
+		}
+		log.Warning("unexpected message from ", s.Conn().RemotePeer())
+	}
+}
+
 func (p *PubSub) handleSendingMessages(ctx context.Context, s inet.Stream, outgoing <-chan *RPC) {
 	bufw := bufio.NewWriter(s)
 	wc := ggio.NewDelimitedWriter(bufw)

notify.go

@@ -25,12 +25,6 @@ func (p *PubSubNotif) Connected(n inet.Network, c inet.Conn) {
 }
 
 func (p *PubSubNotif) Disconnected(n inet.Network, c inet.Conn) {
-	go func() {
-		select {
-		case p.peerDead <- c.RemotePeer():
-		case <-p.ctx.Done():
-		}
-	}()
 }
 
 func (p *PubSubNotif) Listen(n inet.Network, _ ma.Multiaddr) {

pubsub.go

@@ -318,8 +318,7 @@ func (p *PubSub) processLoop(ctx context.Context) {
 
 			if p.host.Network().Connectedness(pid) == inet.Connected {
 				// still connected, must be a duplicate connection being closed.
-				// we respawn the writer as we need to ensure there is at leat one active
-				// at worst we can end with two writers pushing messages from the same channel.
+				// we respawn the writer as we need to ensure there is a stream active
 				log.Warning("peer declared dead but still connected; respawning writer: ", pid)
 				go p.handleNewPeer(ctx, pid, ch)
 				continue