server: ensure unique addresses for node ann

Modifiers of the node announcement may add duplicate addresses, which we
remove here after the modifications were applied. This also ensures that
any previously added duplicate addresses are removed as well.

server.go

@@ -3399,6 +3399,18 @@ func (s *server) genNodeAnnouncement(features *lnwire.RawFeatureVector,
 		modifier(&newNodeAnn)
 	}
 
+	// The modifiers may have added duplicate addresses, so we need to
+	// de-duplicate them here.
+	uniqueAddrs := map[string]struct{}{}
+	dedupedAddrs := make([]net.Addr, 0)
+	for _, addr := range newNodeAnn.Addresses {
+		if _, ok := uniqueAddrs[addr.String()]; !ok {
+			uniqueAddrs[addr.String()] = struct{}{}
+			dedupedAddrs = append(dedupedAddrs, addr)
+		}
+	}
+	newNodeAnn.Addresses = dedupedAddrs
+
 	// Sign a new update after applying all of the passed modifiers.
 	err := netann.SignNodeAnnouncement(
 		s.nodeSigner, s.identityKeyLoc, &newNodeAnn,