daemon_conn: simplify msg_queue_cleared_cb.

Now it just returns true if it queued something.  This allows it
to queue multiple packets, and lets it share code paths with other code
in future patches.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

common/daemon_conn.c

@@ -16,7 +16,10 @@ struct io_plan *daemon_conn_read_next(struct io_conn *conn,
 struct io_plan *daemon_conn_write_next(struct io_conn *conn,
 				       struct daemon_conn *dc)
 {
-	const u8 *msg = msg_dequeue(&dc->out);
+	const u8 *msg;
+
+again:
+	msg = msg_dequeue(&dc->out);
 	if (msg) {
 		int fd = msg_extract_fd(msg);
 		if (fd >= 0)
@@ -25,11 +28,10 @@ struct io_plan *daemon_conn_write_next(struct io_conn *conn,
 		return io_write_wire(conn, take(msg), daemon_conn_write_next,
 				     dc);
 	} else if (dc->msg_queue_cleared_cb) {
-		return dc->msg_queue_cleared_cb(conn, dc);
+		if (dc->msg_queue_cleared_cb(conn, dc))
-	} else {
+			goto again;
-		return msg_queue_wait(conn, &dc->out,
-				      daemon_conn_write_next, dc);
 	}
+	return msg_queue_wait(conn, &dc->out, daemon_conn_write_next, dc);
 }
 
 bool daemon_conn_sync_flush(struct daemon_conn *dc)

common/daemon_conn.h

@@ -24,10 +24,9 @@ struct daemon_conn {
 	struct io_plan *(*daemon_conn_recv)(struct io_conn *conn,
 					    struct daemon_conn *);
 
-	/* Called whenever we've cleared the msg_out queue. Used to
+	/* Called whenever we've cleared the msg_out queue. If it returns
-	 * inject things into the write loop */
+	 * true, it has added packets to msg_out queue. */
-	struct io_plan *(*msg_queue_cleared_cb)(struct io_conn *conn,
+	bool (*msg_queue_cleared_cb)(struct io_conn *, struct daemon_conn *);
-						struct daemon_conn *);
 };
 
 /**

gossipd/gossip.c

@@ -423,8 +423,7 @@ static struct io_plan *init_new_peer(struct io_conn *conn,
 
 static struct io_plan *owner_msg_in(struct io_conn *conn,
 				    struct daemon_conn *dc);
-static struct io_plan *nonlocal_dump_gossip(struct io_conn *conn,
+static bool nonlocal_dump_gossip(struct io_conn *conn, struct daemon_conn *dc);
-					    struct daemon_conn *dc);
 
 /* Create a node_announcement with the given signature. It may be NULL
  * in the case we need to create a provisional announcement for the
@@ -914,7 +913,7 @@ static bool send_peer_with_fds(struct peer *peer, const u8 *msg)
  *
  * Registered as `msg_queue_cleared_cb` by the `peer->remote`.
  */
-static struct io_plan *nonlocal_dump_gossip(struct io_conn *conn, struct daemon_conn *dc)
+static bool nonlocal_dump_gossip(struct io_conn *conn, struct daemon_conn *dc)
 {
 	struct queued_message *next;
 	struct peer *peer = dc->ctx;
@@ -925,22 +924,20 @@ static struct io_plan *nonlocal_dump_gossip(struct io_conn *conn, struct daemon_
 
 	/* Nothing to do if we're not gossiping */
 	if (!peer->gossip_sync)
-		return msg_queue_wait(conn, &peer->remote->out,
+		return false;
-				      daemon_conn_write_next, dc);
 
 	next = next_broadcast_message(peer->daemon->rstate->broadcasts,
 				      &peer->broadcast_index);
 
 	if (!next) {
 		peer->gossip_sync = false;
-		return msg_queue_wait(conn, &peer->remote->out,
+		return false;
-				      daemon_conn_write_next, dc);
 	} else {
 		u8 *msg = towire_gossip_send_gossip(conn,
 						    peer->broadcast_index,
 						    next->payload);
-		return io_write_wire(conn, take(msg),
+		daemon_conn_send(peer->remote, take(msg));
-				     nonlocal_dump_gossip, dc);
+		return true;
 	}
 }