discovery: prevent broadcast of anns received during initial graph sync

discovery/gossiper.go

@@ -913,6 +913,12 @@ func (d *AuthenticatedGossiper) networkHandler() {
 			policyUpdate.errResp <- nil
 
 		case announcement := <-d.networkMsgs:
+			// We should only broadcast this message forward if it
+			// originated from us or it wasn't received as part of
+			// our initial historical sync.
+			shouldBroadcast := !announcement.isRemote ||
+				d.syncMgr.IsGraphSynced()
+
 			switch announcement.msg.(type) {
 			// Channel announcement signatures are amongst the only
 			// messages that we'll process serially.
@@ -981,12 +987,16 @@ func (d *AuthenticatedGossiper) networkHandler() {
 				// the emitted announcements to our announce
 				// batch to be broadcast once the trickle timer
 				// ticks gain.
-				if emittedAnnouncements != nil {
+				if emittedAnnouncements != nil && shouldBroadcast {
 					// TODO(roasbeef): exclude peer that
 					// sent.
 					announcements.AddMsgs(
 						emittedAnnouncements...,
 					)
+				} else if emittedAnnouncements != nil {
+					log.Trace("Skipping broadcast of " +
+						"announcements received " +
+						"during initial graph sync")
 				}
 
 			}()

discovery/gossiper_test.go

@@ -763,6 +763,10 @@ func createTestCtx(startHeight uint32) (*testCtx, func(), error) {
 		return nil, nil, fmt.Errorf("unable to start router: %v", err)
 	}
 
+	// Mark the graph as synced in order to allow the announcements to be
+	// broadcast.
+	gossiper.syncMgr.markGraphSynced()
+
 	cleanUp := func() {
 		gossiper.Stop()
 		cleanUpDb()
@@ -1512,6 +1516,10 @@ func TestSignatureAnnouncementRetryAtStartup(t *testing.T) {
 	}
 	defer gossiper.Stop()
 
+	// Mark the graph as synced in order to allow the announcements to be
+	// broadcast.
+	gossiper.syncMgr.markGraphSynced()
+
 	ctx.gossiper = gossiper
 	remotePeer.quit = ctx.gossiper.quit
 
@@ -3649,3 +3657,86 @@ func TestCalculateCorrectSubBatchSizesDifferentDelay(t *testing.T) {
 		assertCorrectSubBatchSize(t, expectedBatchSize, actualSubBatchSize)
 	}
 }
+
+// TestBroadcastAnnsAfterGraphSynced ensures that we only broadcast
+// announcements after the graph has been considered as synced, i.e., after our
+// initial historical sync has completed.
+func TestBroadcastAnnsAfterGraphSynced(t *testing.T) {
+	t.Parallel()
+
+	ctx, cleanup, err := createTestCtx(10)
+	if err != nil {
+		t.Fatalf("can't create context: %v", err)
+	}
+	defer cleanup()
+
+	// We'll mark the graph as not synced. This should prevent us from
+	// broadcasting any messages we've received as part of our initial
+	// historical sync.
+	ctx.gossiper.syncMgr.markGraphSyncing()
+
+	assertBroadcast := func(msg lnwire.Message, isRemote bool,
+		shouldBroadcast bool) {
+
+		t.Helper()
+
+		nodePeer := &mockPeer{nodeKeyPriv1.PubKey(), nil, nil}
+		var errChan chan error
+		if isRemote {
+			errChan = ctx.gossiper.ProcessRemoteAnnouncement(
+				msg, nodePeer,
+			)
+		} else {
+			errChan = ctx.gossiper.ProcessLocalAnnouncement(
+				msg, nodePeer.pk,
+			)
+		}
+
+		select {
+		case err := <-errChan:
+			if err != nil {
+				t.Fatalf("unable to process gossip message: %v",
+					err)
+			}
+		case <-time.After(2 * time.Second):
+			t.Fatal("gossip message not processed")
+		}
+
+		select {
+		case <-ctx.broadcastedMessage:
+			if !shouldBroadcast {
+				t.Fatal("gossip message was broadcast")
+			}
+		case <-time.After(2 * trickleDelay):
+			if shouldBroadcast {
+				t.Fatal("gossip message wasn't broadcast")
+			}
+		}
+	}
+
+	// A remote channel announcement should not be broadcast since the graph
+	// has not yet been synced.
+	chanAnn1, err := createRemoteChannelAnnouncement(0)
+	if err != nil {
+		t.Fatalf("unable to create channel announcement: %v", err)
+	}
+	assertBroadcast(chanAnn1, true, false)
+
+	// A local channel announcement should be broadcast though, regardless
+	// of whether we've synced our graph or not.
+	chanUpd, err := createUpdateAnnouncement(0, 0, nodeKeyPriv1, 1)
+	if err != nil {
+		t.Fatalf("unable to create channel announcement: %v", err)
+	}
+	assertBroadcast(chanUpd, false, true)
+
+	// Mark the graph as synced, which should allow the channel announcement
+	// should to be broadcast.
+	ctx.gossiper.syncMgr.markGraphSynced()
+
+	chanAnn2, err := createRemoteChannelAnnouncement(1)
+	if err != nil {
+		t.Fatalf("unable to create channel announcement: %v", err)
+	}
+	assertBroadcast(chanAnn2, true, true)
+}