discovery: add new option to toggle gossip rate limiting

In this commit, we add a new option to toggle gossip rate limiting. This
new option can be useful in contexts that require near instant
propagation of gossip messages like integration tests.

discovery/gossiper.go

@@ -228,6 +228,11 @@ type Config struct {
 	// This prevents ranges with old start times from causing us to dump the
 	// graph on connect.
 	IgnoreHistoricalFilters bool
+
+	// GossipUpdateThrottle if true, then the gossiper will throttle
+	// gossip updates to once per RebroadcastInterval for any keep-alive
+	// updates, and once per block for other types of updates.
+	GossipUpdateThrottle bool
 }
 
 // AuthenticatedGossiper is a subsystem which is responsible for receiving
@@ -1965,8 +1970,9 @@ func (d *AuthenticatedGossiper) processNetworkAnnouncement(
 
 		// If we have a previous version of the edge being updated,
 		// we'll want to rate limit its updates to prevent spam
-		// throughout the network.
-		if nMsg.isRemote && edgeToUpdate != nil {
+		// throughout the network if we're currently throttling such
+		// updates.
+		if d.cfg.GossipUpdateThrottle && nMsg.isRemote && edgeToUpdate != nil {
 			// If it's a keep-alive update, we'll only propagate one
 			// if it's been a day since the previous. This follows
 			// our own heuristic of sending keep-alive updates after

discovery/gossiper_test.go

@@ -3957,6 +3957,7 @@ func TestRateLimitChannelUpdates(t *testing.T) {
 	}
 	defer cleanup()
 	ctx.gossiper.cfg.RebroadcastInterval = time.Hour
+	ctx.gossiper.cfg.GossipUpdateThrottle = true
 
 	// The graph should start empty.
 	require.Empty(t, ctx.router.infos)

server.go

@@ -804,6 +804,7 @@ func newServer(cfg *Config, listenAddrs []net.Addr,
 		MinimumBatchSize:        10,
 		SubBatchDelay:           time.Second * 5,
 		IgnoreHistoricalFilters: cfg.IgnoreHistoricalGossipFilters,
+		GossipUpdateThrottle:    !cfg.ProtocolOptions.NoGossipThrottle(),
 	},
 		s.identityECDH.PubKey(),
 	)