gossipd: add request to connect to new gossip peer

Gossipd uses this to ask lightningd -> connectd to initiate
a connection to a new gossip peer.  This can be used when
there are insufficient peers already connected to gossip with.

Changelog-Changed: Gossipd can now request connections to additional nodes for improved gossip sync

gossipd/gossipd.c

@@ -636,6 +636,7 @@ static struct io_plan *recv_req(struct io_conn *conn,
 	case WIRE_GOSSIPD_NEW_BLOCKHEIGHT_REPLY:
 	case WIRE_GOSSIPD_GET_ADDRS_REPLY:
 	case WIRE_GOSSIPD_REMOTE_CHANNEL_UPDATE:
+	case WIRE_GOSSIPD_CONNECT_TO_PEER:
 		break;
 	}
 

gossipd/gossipd_wire.csv

@@ -90,3 +90,9 @@ subtypedata,peer_update,htlc_maximum_msat,amount_msat,
 msgtype,gossipd_remote_channel_update,3010
 msgdata,gossipd_remote_channel_update,source_node,?node_id,
 msgdata,gossipd_remote_channel_update,peer_update,peer_update,
+
+# Ask lightningd to connect to a peer.
+msgtype,gossipd_connect_to_peer,3011
+msgdata,gossipd_connect_to_peer,id,node_id,
+msgdata,gossipd_connect_to_peer,num,u16,
+msgdata,gossipd_connect_to_peer,addrs,wireaddr,num,

gossipd/seeker.c

@@ -963,6 +963,20 @@ static bool seek_any_unknown_nodes(struct seeker *seeker)
 	return true;
 }
 
+/* Ask lightningd for more peers if we're short on gossip streamers. */
+static void maybe_get_new_peer(struct seeker *seeker)
+{
+	size_t connected_peers = peer_node_id_map_count(seeker->daemon->peers);
+	if (connected_peers < ARRAY_SIZE(seeker->gossiper)) {
+		status_debug("seeker: have only %zu connected peers."
+			     " Should connect to more.",
+			     connected_peers);
+
+	}
+	/* TODO: find random node announcement, see if we can connect,
+	 * ask lightningd to connect via towire_gossipd_connect_to_peer. */
+}
+
 /* Periodic timer to see how our gossip is going. */
 static void seeker_check(struct seeker *seeker)
 {
@@ -988,6 +1002,7 @@ static void seeker_check(struct seeker *seeker)
 		break;
 	case NORMAL:
 		/* FIXME: maybe_get_more_peers(seeker); */
+		maybe_get_new_peer(seeker);
 		maybe_rotate_gossipers(seeker);
 		if (!seek_any_unknown_scids(seeker)
 		    && !seek_any_stale_scids(seeker))

lightningd/gossip_control.c

@@ -167,6 +167,20 @@ static void handle_peer_update_data(struct lightningd *ld, const u8 *msg)
 	channel_gossip_set_remote_update(ld, &update, source);
 }
 
+/* gossipd would like a connection to this peer for more gossiping. */
+static void handle_connect_to_peer(struct subd *gossip, const u8 *msg)
+{
+	struct node_id *id = tal(tmpctx, struct node_id);
+	struct wireaddr *addrs;
+	if (!fromwire_gossipd_connect_to_peer(tmpctx, msg, id, &addrs))
+		log_broken(gossip->ld->log, "malformed peer connect request"
+			   " from gossipd %s", tal_hex(msg, msg));
+	else
+		log_debug(gossip->ld->log, "asked to connect to %s",
+			  fmt_node_id(msg, &id));
+	/* TODO: send node_id and address to connectd. */
+}
+
 static unsigned gossip_msg(struct subd *gossip, const u8 *msg, const int *fds)
 {
 	enum gossipd_wire t = fromwire_peektype(msg);
@@ -203,6 +217,9 @@ static unsigned gossip_msg(struct subd *gossip, const u8 *msg, const int *fds)
 		handle_peer_update_data(gossip->ld, msg);
 		tal_free(msg);
 		break;
+	case WIRE_GOSSIPD_CONNECT_TO_PEER:
+		/* Please try connecting to this peer for more gossip. */
+		handle_connect_to_peer(gossip, msg);
 	}
 	return 0;
 }