comment on why we lock when handling (dis)connect notifs

notif.go

@@ -26,6 +26,9 @@ func (nn *netNotifiee) Connected(n inet.Network, v inet.Conn) {
 	p := v.RemotePeer()
 	protos, err := dht.peerstore.SupportsProtocols(p, dhtProtocols...)
 	if err == nil && len(protos) != 0 {
+		// We lock here for consistency with the lock in testConnection.
+		// This probably isn't necessary because (dis)connect
+		// notifications are serialized but it's nice to be consistent.
 		dht.plk.Lock()
 		defer dht.plk.Unlock()
 		if dht.host.Network().Connectedness(p) == inet.Connected {
@@ -62,9 +65,11 @@ func (nn *netNotifiee) testConnection(v inet.Conn) {
 	// Remember this choice (makes subsequent negotiations faster)
 	dht.peerstore.AddProtocols(p, selected)
 
+	// We lock here as we race with disconnect. If we didn't lock, we could
+	// finish processing a connect after handling the associated disconnect
+	// event and add the peer to the routing table after removing it.
 	dht.plk.Lock()
 	defer dht.plk.Unlock()
-	// Make sure we're still connected under the lock (race with disconnect)
 	if dht.host.Network().Connectedness(p) == inet.Connected {
 		dht.Update(dht.Context(), p)
 	}
@@ -80,6 +85,8 @@ func (nn *netNotifiee) Disconnected(n inet.Network, v inet.Conn) {
 
 	p := v.RemotePeer()
 
+	// Lock and check to see if we're still connected. We lock to make sure
+	// we don't concurrently process a connect event.
 	dht.plk.Lock()
 	defer dht.plk.Unlock()
 	if dht.host.Network().Connectedness(p) == inet.Connected {