gossip: Add timer and normal queue for messages

The peer is woken up every 30 seconds to deliver the backlog of
messages. Additionally I added the normal message queue to be able to
send non-gossip message to the peer.

lightningd/gossip/gossip.c

@@ -59,6 +59,7 @@ struct peer {
 
 	/* High water mark for the staggered broadcast */
 	u64 broadcast_index;
+	u8 **msg_out;
 };
 
 static void destroy_peer(struct peer *peer)
@@ -79,6 +80,7 @@ static struct peer *setup_new_peer(struct daemon *daemon, const u8 *msg)
 	peer->cs->peer = peer;
 	peer->daemon = daemon;
 	peer->error = NULL;
+	peer->msg_out = tal_arr(peer, u8*, 0);
 	list_add_tail(&daemon->peers, &peer->list);
 	tal_add_destructor(peer, destroy_peer);
 	return peer;
@@ -154,6 +156,16 @@ static struct io_plan *peer_msgin(struct io_conn *conn,
  * queued gossip messages and processes them. */
 static struct io_plan *pkt_out(struct io_conn *conn, struct peer *peer);
 
+/* Wake up the outgoing direction of the connection and write any
+ * queued messages. Needed since the `io_wake` method signature does
+ * not allow us to specify it as the callback for `new_reltimer`.
+ */
+static void wake_pkt_out(struct peer *peer)
+{
+	/*  */
+	io_wake(peer);
+}
+
 /* Loop through the backlog of channel_{announcements,updates} and
  * node_announcements, writing out one on each iteration. Once we are
  * through wait for the broadcast interval and start again. */
@@ -164,7 +176,8 @@ static struct io_plan *peer_dump_gossip(struct io_conn *conn, struct peer *peer)
 		peer->daemon->rstate->broadcasts, &peer->broadcast_index);
 
 	if (!next) {
-		//FIXME(cdecker) Add wakeup timer once timers are refactored.
+		new_reltimer(&peer->daemon->timers, peer, time_from_sec(30), wake_pkt_out, peer);
+		/* Going to wake up in pkt_out since we mix time based and message based wakeups */
 		return io_out_wait(conn, peer, pkt_out, peer);
 	} else {
 		return peer_write_message(conn, peer->cs, next->payload, peer_dump_gossip);
@@ -173,8 +186,17 @@ static struct io_plan *peer_dump_gossip(struct io_conn *conn, struct peer *peer)
 
 static struct io_plan *pkt_out(struct io_conn *conn, struct peer *peer)
 {
-	//FIXME(cdecker) Add logic to enable sending of non-broadcast messages
-	/* Send any queued up messages */
+	/* First we process queued packets, if any */
+	u8 *out;
+	size_t n = tal_count(peer->msg_out);
+	if (n > 0) {
+		out = peer->msg_out[0];
+		memmove(peer->msg_out, peer->msg_out + 1, (sizeof(*peer->msg_out)*(n-1)));
+		tal_resize(&peer->msg_out, n-1);
+		return peer_write_message(conn, peer->cs, out, pkt_out);
+	}
+
+	/* Send any queued up broadcast messages */
 	return peer_dump_gossip(conn, peer);
 }