gossipd: routine to get route_info for known incoming channels.

For routeboost, we want to select from all our enabled channels with
sufficient incoming capacity.  Gossipd knows which are enabled (ie. we
have received a `channel_update` from the peer), but doesn't know the
current incoming capacity.

So we get gossipd to give us all the candidates, and lightningd
selects from those.

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

gossipd/gossip_wire.csv

@@ -165,3 +165,13 @@ gossip_outpoint_spent,,short_channel_id,struct short_channel_id
 
 # master -> gossipd: stop gossip timers.
 gossip_dev_suppress,3032
+
+#include <common/bolt11.h>
+
+# master -> gossipd: get route_info for our incoming channels
+gossip_get_incoming_channels,3025
+
+# gossipd -> master: here they are.
+gossip_get_incoming_channels_reply,3125
+gossip_get_incoming_channels_reply,,num,u16
+gossip_get_incoming_channels_reply,,route_info,num*struct route_info

gossipd/gossipd.c

@@ -1492,6 +1492,43 @@ out:
 	return daemon_conn_read_next(conn, &daemon->master);
 }
 
+static struct io_plan *get_incoming_channels(struct io_conn *conn,
+					     struct daemon *daemon,
+					     const u8 *msg)
+{
+	struct node *node;
+	struct route_info *r = tal_arr(tmpctx, struct route_info, 0);
+
+	if (!fromwire_gossip_get_incoming_channels(msg))
+		master_badmsg(WIRE_GOSSIP_GET_INCOMING_CHANNELS, msg);
+
+	node = get_node(daemon->rstate, &daemon->rstate->local_id);
+	if (node) {
+		for (size_t i = 0; i < tal_count(node->chans); i++) {
+			const struct chan *c = node->chans[i];
+			const struct half_chan *hc;
+			struct route_info *ri;
+
+			hc = &c->half[half_chan_to(node, c)];
+
+			if (!is_halfchan_enabled(hc))
+				continue;
+
+			ri = tal_arr_expand(&r);
+			ri->pubkey = other_node(node, c)->id;
+			ri->short_channel_id = c->scid;
+			ri->fee_base_msat = hc->base_fee;
+			ri->fee_proportional_millionths = hc->proportional_fee;
+			ri->cltv_expiry_delta = hc->delay;
+		}
+	}
+
+	msg = towire_gossip_get_incoming_channels_reply(NULL, r);
+	daemon_conn_send(&daemon->master, take(msg));
+
+	return daemon_conn_read_next(conn, &daemon->master);
+}
+
 #if DEVELOPER
 static struct io_plan *query_scids_req(struct io_conn *conn,
 				       struct daemon *daemon,
@@ -1948,6 +1985,10 @@ static struct io_plan *recv_req(struct io_conn *conn, struct daemon_conn *master
 	case WIRE_GOSSIP_PING:
 		return ping_req(conn, daemon, daemon->master.msg_in);
 
+	case WIRE_GOSSIP_GET_INCOMING_CHANNELS:
+		return get_incoming_channels(conn, daemon,
+					     daemon->master.msg_in);
+
 #if DEVELOPER
 	case WIRE_GOSSIP_QUERY_SCIDS:
 		return query_scids_req(conn, daemon, daemon->master.msg_in);
@@ -1981,6 +2022,7 @@ static struct io_plan *recv_req(struct io_conn *conn, struct daemon_conn *master
 	case WIRE_GOSSIP_SCIDS_REPLY:
 	case WIRE_GOSSIP_QUERY_CHANNEL_RANGE_REPLY:
 	case WIRE_GOSSIP_RESOLVE_CHANNEL_REPLY:
+	case WIRE_GOSSIP_GET_INCOMING_CHANNELS_REPLY:
 	case WIRE_GOSSIP_GET_UPDATE:
 	case WIRE_GOSSIP_GET_UPDATE_REPLY:
 	case WIRE_GOSSIP_SEND_GOSSIP:

lightningd/gossip_control.c

@@ -116,6 +116,7 @@ static unsigned gossip_msg(struct subd *gossip, const u8 *msg, const int *fds)
 	case WIRE_GOSSIP_QUERY_SCIDS:
 	case WIRE_GOSSIP_QUERY_CHANNEL_RANGE:
 	case WIRE_GOSSIP_SEND_TIMESTAMP_FILTER:
+	case WIRE_GOSSIP_GET_INCOMING_CHANNELS:
 	case WIRE_GOSSIP_DEV_SET_MAX_SCIDS_ENCODE_SIZE:
 	case WIRE_GOSSIP_DEV_SUPPRESS:
 	/* This is a reply, so never gets through to here. */
@@ -126,6 +127,7 @@ static unsigned gossip_msg(struct subd *gossip, const u8 *msg, const int *fds)
 	case WIRE_GOSSIP_SCIDS_REPLY:
 	case WIRE_GOSSIP_QUERY_CHANNEL_RANGE_REPLY:
 	case WIRE_GOSSIP_RESOLVE_CHANNEL_REPLY:
+	case WIRE_GOSSIP_GET_INCOMING_CHANNELS_REPLY:
 	/* These are inter-daemon messages, not received by us */
 	case WIRE_GOSSIP_LOCAL_ADD_CHANNEL:
 	case WIRE_GOSSIP_LOCAL_CHANNEL_UPDATE: