switch to gossip broadcast for topology updates

router/gossip.go

@@ -269,6 +269,7 @@ func (c *GossipChannel) relayBroadcast(srcName PeerName, update GossipData) erro
 }
 
 func (c *GossipChannel) sendBroadcast(srcName PeerName, update GossipData) {
+	c.ourself.Router.Routes.EnsureRecalculated()
 	nextHops := c.ourself.Router.Routes.BroadcastAll(srcName)
 	if len(nextHops) == 0 {
 		return

router/local_peer.go

@@ -241,14 +241,7 @@ func (peer *LocalPeer) handleDeleteConnection(conn Connection) {
 
 func (peer *LocalPeer) broadcastPeerUpdate(peers ...*Peer) {
 	peer.Router.Routes.Recalculate()
-	// TODO We should just be invoking TopologyGossip.GossipBroadcast
-	// here, but route calculation is asynchronous and in this
-	// particular case would likely result in the broadcast not
-	// reaching all peers. So instead we slightly break the Gossip
-	// abstraction (hence the cast) and send a regular update. This is
-	// less efficient though since it will almost certainly reach
-	// peers more than once.
-	peer.Router.TopologyGossip.(*GossipChannel).Send(NewTopologyGossipData(peer.Router.Peers, append(peers, peer.Peer)...))
+	peer.Router.TopologyGossip.GossipBroadcast(NewTopologyGossipData(peer.Router.Peers, append(peers, peer.Peer)...))
 }
 
 func (peer *LocalPeer) checkConnectionLimit() error {

router/protocol.go

@@ -2,7 +2,7 @@ package router
 
 const (
 	Protocol        = "weave"
-	ProtocolVersion = 14
+	ProtocolVersion = 15
 )
 
 type ProtocolTag byte

router/router.go

@@ -378,7 +378,11 @@ func (router *Router) OnGossipUnicast(sender PeerName, msg []byte) error {
 }
 
 func (router *Router) OnGossipBroadcast(update []byte) (GossipData, error) {
-	return nil, fmt.Errorf("unexpected topology gossip broadcast: %v", update)
+	origUpdate, _, err := router.applyTopologyUpdate(update)
+	if err != nil || len(origUpdate) == 0 {
+		return nil, err
+	}
+	return &TopologyGossipData{peers: router.Peers, update: origUpdate}, nil
 }
 
 func (router *Router) Gossip() GossipData {