gossipd: prepare for internally-generated short-channel-id queries.

Up until now we only generated these in dev mode for testing.  Hoist
into common code, turn counter into a flag (we're only allowed one!)
and note if query is internal or not.

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

gossipd/gossipd.c

@@ -132,7 +132,7 @@ struct peer {
 	/* The two features gossip cares about (so far) */
 	bool gossip_queries_feature, initial_routing_sync_feature;
 
-	/* Are there outstanding queries on short_channel_ids? */
+	/* Are there outstanding responses for queries on short_channel_ids? */
 	const struct short_channel_id *scid_queries;
 	size_t scid_query_idx;
 
@@ -140,8 +140,9 @@ struct peer {
 	struct node_id *scid_query_nodes;
 	size_t scid_query_nodes_idx;
 
-	/* How many query responses are we expecting? */
+	/* Do we have an scid_query outstanding?  Was it internal? */
-	size_t num_scid_queries_outstanding;
+	bool scid_query_outstanding;
+	bool scid_query_was_internal;
 
 	/* How many pongs are we expecting? */
 	size_t num_pings_outstanding;
@@ -516,6 +517,61 @@ static void maybe_send_own_node_announce(struct daemon *daemon)
 	daemon->rstate->local_channel_announced = false;
 }
 
+/* Query this peer for these short-channel-ids. */
+static bool query_short_channel_ids(struct daemon *daemon,
+				    struct peer *peer,
+				    const struct short_channel_id *scids,
+				    bool internal)
+{
+	u8 *encoded, *msg;
+
+	/* BOLT #7:
+	 *
+	 * 1. type: 261 (`query_short_channel_ids`) (`gossip_queries`)
+	 * 2. data:
+	 *     * [`32`:`chain_hash`]
+	 *     * [`2`:`len`]
+	 *     * [`len`:`encoded_short_ids`]
+	 */
+	const size_t reply_overhead = 32 + 2;
+	const size_t max_encoded_bytes = 65535 - 2 - reply_overhead;
+
+	/* Can't query if they don't have gossip_queries_feature */
+	if (!peer->gossip_queries_feature)
+		return false;
+
+	/* BOLT #7:
+	 *
+	 * The sender:
+	 *  - MUST NOT send `query_short_channel_ids` if it has sent a previous
+	 *   `query_short_channel_ids` to this peer and not received
+	 *   `reply_short_channel_ids_end`.
+	 */
+	if (peer->scid_query_outstanding)
+		return false;
+
+	encoded = encode_short_channel_ids_start(tmpctx);
+	for (size_t i = 0; i < tal_count(scids); i++)
+		encode_add_short_channel_id(&encoded, &scids[i]);
+
+	if (!encode_short_channel_ids_end(&encoded, max_encoded_bytes)) {
+		status_broken("query_short_channel_ids: %zu is too many",
+			      tal_count(scids));
+		return false;
+	}
+
+	msg = towire_query_short_channel_ids(NULL, &daemon->chain_hash,
+					     encoded);
+	queue_peer_msg(peer, take(msg));
+	peer->scid_query_outstanding = true;
+	peer->scid_query_was_internal = internal;
+
+	status_trace("%s: sending query for %zu scids",
+		     type_to_string(tmpctx, struct node_id, &peer->id),
+		     tal_count(scids));
+	return true;
+}
+
 /*~Routines to handle gossip messages from peer, forwarded by subdaemons.
  *-----------------------------------------------------------------------
  *
@@ -981,17 +1037,22 @@ static u8 *handle_reply_short_channel_ids_end(struct peer *peer, const u8 *msg)
 				       tal_hex(tmpctx, msg));
 	}
 
-	if (peer->num_scid_queries_outstanding == 0) {
+	if (!peer->scid_query_outstanding) {
 		return towire_errorfmt(peer, NULL,
 				       "unexpected reply_short_channel_ids_end: %s",
 				       tal_hex(tmpctx, msg));
 	}
 
-	peer->num_scid_queries_outstanding--;
+	peer->scid_query_outstanding = false;
-	/* We tell lightningd: this is because we currently only ask for
+
-	 * query_short_channel_ids when lightningd asks. */
+	/* If it wasn't generated by us, it's the dev interface from lightningd
-	msg = towire_gossip_scids_reply(msg, true, complete);
+	 */
-	daemon_conn_send(peer->daemon->master, take(msg));
+	if (!peer->scid_query_was_internal) {
+		msg = towire_gossip_scids_reply(msg, true, complete);
+		daemon_conn_send(peer->daemon->master, take(msg));
+	}
+
+	/* All good, no error. */
 	return NULL;
 }
 
@@ -1625,7 +1686,7 @@ static struct io_plan *connectd_new_peer(struct io_conn *conn,
 	peer->scid_query_idx = 0;
 	peer->scid_query_nodes = NULL;
 	peer->scid_query_nodes_idx = 0;
-	peer->num_scid_queries_outstanding = 0;
+	peer->scid_query_outstanding = false;
 	peer->query_channel_blocks = NULL;
 	peer->num_pings_outstanding = 0;
 
@@ -2280,8 +2341,6 @@ static struct io_plan *get_incoming_channels(struct io_conn *conn,
 }
 
 #if DEVELOPER
-/* FIXME: One day this will be called internally; for now it's just for
- * testing with dev_query_scids. */
 static struct io_plan *query_scids_req(struct io_conn *conn,
 				       struct daemon *daemon,
 				       const u8 *msg)
@@ -2289,17 +2348,6 @@ static struct io_plan *query_scids_req(struct io_conn *conn,
 	struct node_id id;
 	struct short_channel_id *scids;
 	struct peer *peer;
-	u8 *encoded;
-	/* BOLT #7:
-	 *
-	 * 1. type: 261 (`query_short_channel_ids`) (`gossip_queries`)
-	 * 2. data:
-	 *     * [`32`:`chain_hash`]
-	 *     * [`2`:`len`]
-	 *     * [`len`:`encoded_short_ids`]
-	 */
-	const size_t reply_overhead = 32 + 2;
-	const size_t max_encoded_bytes = 65535 - 2 - reply_overhead;
 
 	if (!fromwire_gossip_query_scids(msg, msg, &id, &scids))
 		master_badmsg(WIRE_GOSSIP_QUERY_SCIDS, msg);
@@ -2308,40 +2356,14 @@ static struct io_plan *query_scids_req(struct io_conn *conn,
 	if (!peer) {
 		status_broken("query_scids: unknown peer %s",
 			      type_to_string(tmpctx, struct node_id, &id));
-		goto fail;
+		daemon_conn_send(daemon->master,
-	}
+				 take(towire_gossip_scids_reply(NULL,
-
+								false, false)));
-	if (!peer->gossip_queries_feature) {
+	} else if (!query_short_channel_ids(daemon, peer, scids, false))
-		status_broken("query_scids: no gossip_query support in peer %s",
+		daemon_conn_send(daemon->master,
-			      type_to_string(tmpctx, struct node_id, &id));
+				 take(towire_gossip_scids_reply(NULL,
-		goto fail;
+								false, false)));
-	}
-
-	encoded = encode_short_channel_ids_start(tmpctx);
-	for (size_t i = 0; i < tal_count(scids); i++)
-		encode_add_short_channel_id(&encoded, &scids[i]);
-
-	/* Because this is a dev command, we simply say this case is
-	 * "too hard". */
-	if (!encode_short_channel_ids_end(&encoded, max_encoded_bytes)) {
-		status_broken("query_short_channel_ids: %zu is too many",
-			      tal_count(scids));
-		goto fail;
-	}
-
-	msg = towire_query_short_channel_ids(NULL, &daemon->chain_hash,
-					     encoded);
-	queue_peer_msg(peer, take(msg));
-	peer->num_scid_queries_outstanding++;
-
-	status_trace("sending query for %zu scids", tal_count(scids));
-out:
 	return daemon_conn_read_next(conn, daemon->master);
-
-fail:
-	daemon_conn_send(daemon->master,
-			 take(towire_gossip_scids_reply(NULL, false, false)));
-	goto out;
 }
 
 /* BOLT #7: