gossip: Make the broadcast interval configurable

Adds a new command line flag `--dev-broadcast-interval=<ms>` that
allows us to specify how often the staggered broadcast should
trigger. The value is passed down to `gossipd` via an init message.

This is mainly useful for integration tests, since we do not want to
wait forever for gossip to propagate.

lightningd/gossip/gossip.c

@@ -44,6 +44,8 @@ struct daemon {
 	struct routing_state *rstate;
 
 	struct timers timers;
+
+	u32 broadcast_interval;
 };
 
 struct peer {
@@ -285,7 +287,8 @@ static struct io_plan *peer_msgin(struct io_conn *conn,
 static void wake_pkt_out(struct peer *peer)
 {
 	peer->gossip_sync = true;
-	new_reltimer(&peer->daemon->timers, peer, time_from_sec(30),
+	new_reltimer(&peer->daemon->timers, peer,
+		     time_from_msec(peer->daemon->broadcast_interval),
 		     wake_pkt_out, peer);
 	/* Notify the peer-write loop */
 	msg_wake(&peer->peer_out);
@@ -617,6 +620,19 @@ static struct io_plan *ping_req(struct io_conn *conn, struct daemon *daemon,
 	return daemon_conn_read_next(conn, &daemon->master);
 }
 
+/* Parse an incoming gossip init message and assign config variables
+ * to the daemon.
+ */
+static struct io_plan *gossip_init(struct daemon_conn *master,
+				   struct daemon *daemon, u8 *msg)
+{
+	if (!fromwire_gossipctl_init(msg, NULL, &daemon->broadcast_interval)) {
+		status_failed(WIRE_GOSSIPSTATUS_INIT_FAILED,
+			      "Unable to parse init message");
+	}
+	return daemon_conn_read_next(master->conn, master);
+}
+
 static struct io_plan *recv_req(struct io_conn *conn, struct daemon_conn *master)
 {
 	struct daemon *daemon = container_of(master, struct daemon, master);
@@ -626,6 +642,9 @@ static struct io_plan *recv_req(struct io_conn *conn, struct daemon_conn *master
 		     gossip_wire_type_name(t), tal_count(master->msg_in));
 
 	switch (t) {
+	case WIRE_GOSSIPCTL_INIT:
+		return gossip_init(master, daemon, master->msg_in);
+
 	case WIRE_GOSSIPCTL_NEW_PEER:
 		return new_peer(conn, daemon, master->msg_in);
 	case WIRE_GOSSIPCTL_RELEASE_PEER:
@@ -690,6 +709,7 @@ int main(int argc, char *argv[])
 	daemon->rstate = new_routing_state(daemon, base_log);
 	list_head_init(&daemon->peers);
 	timers_init(&daemon->timers, time_mono());
+	daemon->broadcast_interval = 30000;
 
 	/* stdin == control */
 	daemon_conn_init(daemon, &daemon->master, STDIN_FILENO, recv_req);

lightningd/gossip/gossip_wire.csv

@@ -19,6 +19,10 @@ gossipstatus_peer_failed,10,err,len*u8
 
 #include <lightningd/cryptomsg.h>
 
+# Initialize the gossip daemon
+gossipctl_init,0
+gossipctl_init,0,broadcast_interval,4
+
 # These take an fd, but have no response
 # (if it is to move onto a channel, we get a status msg).
 gossipctl_new_peer,1

lightningd/gossip_control.c

@@ -140,6 +140,7 @@ static int gossip_msg(struct subd *gossip, const u8 *msg, const int *fds)
 	case WIRE_GOSSIPSTATUS_FDPASS_FAILED:
 	case WIRE_GOSSIPSTATUS_BAD_RELEASE_REQUEST:
 	/* These are messages we send, not them. */
+	case WIRE_GOSSIPCTL_INIT:
 	case WIRE_GOSSIPCTL_NEW_PEER:
 	case WIRE_GOSSIPCTL_RELEASE_PEER:
 	case WIRE_GOSSIP_GETNODES_REQUEST:
@@ -171,13 +172,21 @@ static int gossip_msg(struct subd *gossip, const u8 *msg, const int *fds)
 	return 0;
 }
 
+/* Create the `gossipd` subdaemon and send the initialization
+ * message */
 void gossip_init(struct lightningd *ld)
 {
+	tal_t *tmpctx = tal_tmpctx(ld);
+	u8 *init;
 	ld->gossip = new_subd(ld, ld, "lightningd_gossip", NULL,
 			      gossip_wire_type_name,
 			      gossip_msg, gossip_finished, -1);
 	if (!ld->gossip)
 		err(1, "Could not subdaemon gossip");
+
+	init = towire_gossipctl_init(tmpctx, ld->broadcast_interval);
+	subd_send_msg(ld->gossip, init);
+	tal_free(tmpctx);
 }
 
 static bool json_getnodes_reply(struct subd *gossip, const u8 *reply,

lightningd/lightningd.c

@@ -228,6 +228,14 @@ int main(int argc, char *argv[])
 	opt_register_arg("--dev-debugger=<subdaemon>", opt_subd_debug, NULL,
 			 ld, "Wait for gdb attach at start of <subdaemon>");
 
+	opt_register_arg("--dev-broadcast-interval=<ms>", opt_set_uintval,
+			 opt_show_uintval, &ld->broadcast_interval,
+			 "Time between gossip broadcasts in milliseconds (default: 30000)");
+
+	/* FIXME: move to option initialization once we drop the
+	 * legacy daemon */
+	ld->broadcast_interval = 30000;
+
 	/* Handle options and config; move to .lightningd */
 	newdir = handle_opts(&ld->dstate, argc, argv);
 

lightningd/lightningd.h

@@ -55,6 +55,8 @@ struct lightningd {
 
 	/* HTLCs in flight. */
 	struct htlc_end_map htlc_ends;
+
+	u32 broadcast_interval;
 };
 
 void derive_peer_seed(struct lightningd *ld, struct privkey *peer_seed,