gossipd: allow an array of excluded channels for getroute_request.

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

gossipd/gossip_wire.csv

@@ -32,6 +32,9 @@ gossip_getroute_request,,msatoshi,u64
 gossip_getroute_request,,riskfactor,u16
 gossip_getroute_request,,final_cltv,u32
 gossip_getroute_request,,fuzz,double
+gossip_getroute_request,,num_excluded,u16
+gossip_getroute_request,,excluded,num_excluded*struct short_channel_id
+gossip_getroute_request,,excluded_dir,num_excluded*bool
 
 gossip_getroute_reply,3106
 gossip_getroute_reply,,num_hops,u16

gossipd/gossipd.c

@@ -1870,6 +1870,8 @@ static struct io_plan *getroute_req(struct io_conn *conn, struct daemon *daemon,
 	u8 *out;
 	struct route_hop *hops;
 	double fuzz;
+	struct short_channel_id *excluded;
+	bool *excluded_dir;
 
 	/* To choose between variations, we need to know how much we're
 	 * sending (eliminates too-small channels, and also effects the fees
@@ -1877,10 +1879,11 @@ static struct io_plan *getroute_req(struct io_conn *conn, struct daemon *daemon,
 	 * much cltv we need a the final node to give exact values for each
 	 * intermediate hop, as well as how much random fuzz to inject to
 	 * avoid being too predictable. */
-	if (!fromwire_gossip_getroute_request(msg,
+	if (!fromwire_gossip_getroute_request(msg, msg,
 					      &source, &destination,
 					      &msatoshi, &riskfactor,
-					      &final_cltv, &fuzz))
+					      &final_cltv, &fuzz,
+					      &excluded, &excluded_dir))
 		master_badmsg(WIRE_GOSSIP_GETROUTE_REQUEST, msg);
 
 	status_trace("Trying to find a route from %s to %s for %"PRIu64" msatoshi",
@@ -1890,7 +1893,7 @@ static struct io_plan *getroute_req(struct io_conn *conn, struct daemon *daemon,
 	/* routing.c does all the hard work; can return NULL. */
 	hops = get_route(tmpctx, daemon->rstate, &source, &destination,
 			 msatoshi, riskfactor, final_cltv,
-			 fuzz, siphash_seed());
+			 fuzz, siphash_seed(), excluded, excluded_dir);
 
 	out = towire_gossip_getroute_reply(NULL, hops);
 	daemon_conn_send(daemon->master, take(out));

gossipd/routing.c

@@ -1496,20 +1496,44 @@ struct route_hop *get_route(const tal_t *ctx, struct routing_state *rstate,
 			    const struct pubkey *destination,
 			    const u64 msatoshi, double riskfactor,
 			    u32 final_cltv,
-			    double fuzz, const struct siphash_seed *base_seed)
+			    double fuzz, const struct siphash_seed *base_seed,
+			    const struct short_channel_id *excluded,
+			    const bool *excluded_dir)
 {
 	struct chan **route;
 	u64 total_amount;
 	unsigned int total_delay;
 	u64 fee;
 	struct route_hop *hops;
-	int i;
 	struct node *n;
+	u64 *saved_capacity;
+
+	assert(tal_count(excluded) == tal_count(excluded_dir));
+	saved_capacity = tal_arr(tmpctx, u64, tal_count(excluded));
+
+	/* Temporarily set excluded channels' capacity to zero. */
+	for (size_t i = 0; i < tal_count(excluded); i++) {
+		struct chan *chan = get_channel(rstate, &excluded[i]);
+		if (!chan)
+			continue;
+		saved_capacity[i]
+			= chan->half[excluded_dir[i]].htlc_maximum_msat;
+		chan->half[excluded_dir[i]].htlc_maximum_msat = 0;
+	}
 
 	route = find_route(ctx, rstate, source, destination, msatoshi,
 			   riskfactor / BLOCKS_PER_YEAR / 10000,
 			   fuzz, base_seed, &fee);
 
+	/* Now restore the capacity. */
+	for (size_t i = 0; i < tal_count(excluded); i++) {
+		struct chan *chan = get_channel(rstate, &excluded[i]);
+		if (!chan)
+			continue;
+		chan->half[excluded_dir[i]].htlc_maximum_msat
+			= saved_capacity[i];
+	}
+
 	if (!route) {
 		return NULL;
 	}
@@ -1521,7 +1545,7 @@ struct route_hop *get_route(const tal_t *ctx, struct routing_state *rstate,
 
 	/* Start at destination node. */
 	n = get_node(rstate, destination);
-	for (i = tal_count(route) - 1; i >= 0; i--) {
+	for (int i = tal_count(route) - 1; i >= 0; i--) {
 		const struct half_chan *c;
 		int idx = half_chan_to(n, route[i]);
 		c = &route[i]->half[idx];

gossipd/routing.h

@@ -267,7 +267,9 @@ struct route_hop *get_route(const tal_t *ctx, struct routing_state *rstate,
 			    const u64 msatoshi, double riskfactor,
 			    u32 final_cltv,
 			    double fuzz,
-			    const struct siphash_seed *base_seed);
+			    const struct siphash_seed *base_seed,
+			    const struct short_channel_id *excluded,
+			    const bool *excluded_dir);
 /* Disable channel(s) based on the given routing failure. */
 void routing_failure(struct routing_state *rstate,
 		     const struct pubkey *erring_node,

lightningd/gossip_control.c

@@ -325,7 +325,8 @@ static struct command_result *json_getroute(struct command *cmd,
 
 	u8 *req = towire_gossip_getroute_request(cmd, source, destination,
 						 *msatoshi, *riskfactor * 1000,
-						 *cltv, fuzz);
+						 *cltv, fuzz,
+						 NULL, NULL);
 	subd_req(ld->gossip, ld->gossip, req, -1, 0, json_getroute_reply, cmd);
 	return command_still_pending(cmd);
 }

lightningd/payalgo.c

@@ -557,7 +557,7 @@ static struct command_result *json_pay_try(struct pay *pay)
 					     pay->msatoshi + overpayment,
 					     pay->riskfactor,
 					     pay->min_final_cltv_expiry,
-					     &pay->fuzz);
+					     &pay->fuzz, NULL, NULL);
 	subd_req(pay->try_parent, cmd->ld->gossip, req, -1, 0, json_pay_getroute_reply, pay);
 
 	return NULL;