lightingd: do a local short_channel_id lookup for forwarding.

Even without optimization, it's faster to walk all the channels than
ping another daemon and wait for the response.

Changelog-Changed: Forwarding messages is now much faster (less inter-daemon traffic)
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

gossipd/gossip_wire.csv

@@ -73,15 +73,6 @@ msgdata,gossip_ping_reply,totlen,u16,
 msgtype,gossip_dev_set_max_scids_encode_size,3030
 msgdata,gossip_dev_set_max_scids_encode_size,max,u32,
 
-# Given a short_channel_id, return the other endpoint (or none if DNE)
-msgtype,gossip_get_channel_peer,3009
-msgdata,gossip_get_channel_peer,channel_id,short_channel_id,
-
-msgtype,gossip_get_channel_peer_reply,3109
-msgdata,gossip_get_channel_peer_reply,peer_id,?node_id,
-msgdata,gossip_get_channel_peer_reply,stripped_update_len,u16,
-msgdata,gossip_get_channel_peer_reply,stripped_update,u8,stripped_update_len
-
 # Given a short_channel_id, return the latest (stripped) update for error msg.
 msgtype,gossip_get_stripped_cupdate,3010
 msgdata,gossip_get_stripped_cupdate,channel_id,short_channel_id,

gossipd/gossipd.c

@@ -1335,48 +1335,6 @@ static struct io_plan *dev_gossip_set_time(struct io_conn *conn,
 }
 #endif /* DEVELOPER */
 
-/*~ lightningd: so, tell me about this channel, so we can forward to it. */
-static struct io_plan *get_channel_peer(struct io_conn *conn,
-					struct daemon *daemon, const u8 *msg)
-{
-	struct short_channel_id scid;
-	struct local_chan *local_chan;
-	const struct node_id *key;
-	const u8 *stripped_update;
-
-	if (!fromwire_gossip_get_channel_peer(msg, &scid))
-		master_badmsg(WIRE_GOSSIP_GET_CHANNEL_PEER, msg);
-
-	local_chan = local_chan_map_get(&daemon->rstate->local_chan_map, &scid);
-	if (!local_chan) {
-		status_debug("Failed to resolve local channel %s",
-			     type_to_string(tmpctx, struct short_channel_id, &scid));
-		key = NULL;
-		stripped_update = NULL;
-	} else {
-		const struct half_chan *hc;
-
-		key = &local_chan->chan->nodes[!local_chan->direction]->id;
-		/* Since we're going to use it, make sure it's up-to-date. */
-		refresh_local_channel(daemon, local_chan, false);
-
-		hc = &local_chan->chan->half[local_chan->direction];
-		if (is_halfchan_defined(hc)) {
-			const u8 *update;
-
-			update = gossip_store_get(tmpctx, daemon->rstate->gs,
-						  hc->bcast.index);
-			stripped_update = tal_dup_arr(tmpctx, u8, update + 2,
-						      tal_count(update) - 2, 0);
-		} else
-			stripped_update = NULL;
-	}
-	daemon_conn_send(daemon->master,
-			 take(towire_gossip_get_channel_peer_reply(NULL, key,
-							   stripped_update)));
-	return daemon_conn_read_next(conn, daemon->master);
-}
-
 /*~ lightningd: so, get me the latest update for this local channel,
  *  so I can include it in an error message. */
 static struct io_plan *get_stripped_cupdate(struct io_conn *conn,
@@ -1611,9 +1569,6 @@ static struct io_plan *recv_req(struct io_conn *conn,
 	case WIRE_GOSSIP_GETCHANNELS_REQUEST:
 		return getchannels_req(conn, daemon, msg);
 
-	case WIRE_GOSSIP_GET_CHANNEL_PEER:
-		return get_channel_peer(conn, daemon, msg);
-
 	case WIRE_GOSSIP_GET_STRIPPED_CUPDATE:
 		return get_stripped_cupdate(conn, daemon, msg);
 
@@ -1663,7 +1618,6 @@ static struct io_plan *recv_req(struct io_conn *conn,
 	case WIRE_GOSSIP_GETROUTE_REPLY:
 	case WIRE_GOSSIP_GETCHANNELS_REPLY:
 	case WIRE_GOSSIP_PING_REPLY:
-	case WIRE_GOSSIP_GET_CHANNEL_PEER_REPLY:
 	case WIRE_GOSSIP_GET_STRIPPED_CUPDATE_REPLY:
 	case WIRE_GOSSIP_GET_INCOMING_CHANNELS_REPLY:
 	case WIRE_GOSSIP_GET_TXOUT:

lightningd/channel.c

@@ -328,6 +328,22 @@ struct channel *active_channel_by_id(struct lightningd *ld,
 	return peer_active_channel(peer);
 }
 
+struct channel *active_channel_by_scid(struct lightningd *ld,
+				       const struct short_channel_id *scid)
+{
+	struct peer *p;
+	struct channel *chan;
+	list_for_each(&ld->peers, p, list) {
+		list_for_each(&p->channels, chan, list) {
+			if (channel_active(chan)
+			    && chan->scid
+			    && short_channel_id_eq(scid, chan->scid))
+				return chan;
+		}
+	}
+	return NULL;
+}
+
 struct channel *channel_by_dbid(struct lightningd *ld, const u64 dbid)
 {
 	struct peer *p;

lightningd/channel.h

@@ -214,6 +214,9 @@ struct channel *active_channel_by_id(struct lightningd *ld,
 
 struct channel *channel_by_dbid(struct lightningd *ld, const u64 dbid);
 
+struct channel *active_channel_by_scid(struct lightningd *ld,
+				       const struct short_channel_id *scid);
+
 void channel_set_last_tx(struct channel *channel,
 			 struct bitcoin_tx *tx,
 			 const struct bitcoin_signature *sig,

lightningd/gossip_control.c

@@ -138,7 +138,6 @@ static unsigned gossip_msg(struct subd *gossip, const u8 *msg, const int *fds)
 	case WIRE_GOSSIP_GETROUTE_REQUEST:
 	case WIRE_GOSSIP_GETCHANNELS_REQUEST:
 	case WIRE_GOSSIP_PING:
-	case WIRE_GOSSIP_GET_CHANNEL_PEER:
 	case WIRE_GOSSIP_GET_STRIPPED_CUPDATE:
 	case WIRE_GOSSIP_GET_TXOUT_REPLY:
 	case WIRE_GOSSIP_OUTPOINT_SPENT:
@@ -155,7 +154,6 @@ static unsigned gossip_msg(struct subd *gossip, const u8 *msg, const int *fds)
 	case WIRE_GOSSIP_GETNODES_REPLY:
 	case WIRE_GOSSIP_GETROUTE_REPLY:
 	case WIRE_GOSSIP_GETCHANNELS_REPLY:
-	case WIRE_GOSSIP_GET_CHANNEL_PEER_REPLY:
 	case WIRE_GOSSIP_GET_INCOMING_CHANNELS_REPLY:
 	case WIRE_GOSSIP_DEV_MEMLEAK_REPLY:
 	case WIRE_GOSSIP_DEV_COMPACT_STORE_REPLY:

lightningd/peer_control.c

@@ -1199,14 +1199,10 @@ command_find_channel(struct command *cmd,
 				    tok->end - tok->start,
 				    buffer + tok->start);
 	} else if (json_to_short_channel_id(buffer, tok, &scid)) {
-		list_for_each(&ld->peers, peer, list) {
-			*channel = peer_active_channel(peer);
-			if (!*channel)
-				continue;
-			if ((*channel)->scid
-			    && (*channel)->scid->u64 == scid.u64)
-				return NULL;
-		}
+		*channel = active_channel_by_scid(ld, &scid);
+		if (*channel)
+			return NULL;
+
 		return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
 				    "Short channel ID not found: '%.*s'",
 				    tok->end - tok->start,

lightningd/peer_htlcs.c

@@ -657,13 +657,13 @@ static void forward_htlc(struct htlc_in *hin,
 			 u32 cltv_expiry,
 			 struct amount_msat amt_to_forward,
 			 u32 outgoing_cltv_value,
-			 const struct node_id *next_hop,
+			 const struct short_channel_id *scid,
 			 const u8 next_onion[TOTAL_PACKET_SIZE])
 {
 	const u8 *failmsg;
 	struct amount_msat fee;
 	struct lightningd *ld = hin->key.channel->peer->ld;
-	struct channel *next = active_channel_by_id(ld, next_hop, NULL);
+	struct channel *next = active_channel_by_scid(ld, scid);
 	struct htlc_out *hout = NULL;
 	bool needs_update_appended;
 
@@ -769,50 +769,6 @@ static void forward_htlc(struct htlc_in *hin,
 				 fromwire_peektype(failmsg));
 }
 
-/* Temporary information, while we resolve the next hop */
-struct gossip_resolve {
-	struct short_channel_id next_channel;
-	struct amount_msat amt_to_forward;
-	struct amount_msat total_msat;
-	/* Only set if TLV specifies it */
-	const struct secret *payment_secret;
-	u32 outgoing_cltv_value;
-	u8 *next_onion;
-	struct htlc_in *hin;
-};
-
-/* We received a resolver reply, which gives us the node_ids of the
- * channel we want to forward over */
-static void channel_resolve_reply(struct subd *gossip, const u8 *msg,
-				  const int *fds UNUSED, struct gossip_resolve *gr)
-{
-	struct node_id *peer_id;
-	u8 *stripped_update;
-
-	if (!fromwire_gossip_get_channel_peer_reply(msg, msg, &peer_id,
-						    &stripped_update)) {
-		log_broken(gossip->log,
-			   "bad fromwire_gossip_get_channel_peer_reply %s",
-			   tal_hex(msg, msg));
-		return;
-	}
-
-	if (!peer_id) {
-		local_fail_in_htlc(gr->hin, take(towire_unknown_next_peer(NULL)));
-		wallet_forwarded_payment_add(gr->hin->key.channel->peer->ld->wallet,
-					 gr->hin, &gr->next_channel, NULL,
-					 FORWARD_LOCAL_FAILED,
-					 WIRE_UNKNOWN_NEXT_PEER);
-		tal_free(gr);
-		return;
-	}
-
-	forward_htlc(gr->hin, gr->hin->cltv_expiry,
-		     gr->amt_to_forward, gr->outgoing_cltv_value, peer_id,
-		     gr->next_onion);
-	tal_free(gr);
-}
-
 /**
  * Data passed to the plugin, and as the context for the hook callback
  */
@@ -1014,7 +970,6 @@ htlc_accepted_hook_callback(struct htlc_accepted_hook_payload *request,
 	struct channel *channel = request->channel;
 	struct lightningd *ld = request->ld;
 	struct preimage payment_preimage;
-	u8 *req;
 	enum htlc_accepted_result result;
 	const u8 *failmsg;
 	result = htlc_accepted_hook_deserialize(request, ld, buffer, toks, &payment_preimage, &failmsg);
@@ -1027,20 +982,11 @@ htlc_accepted_hook_callback(struct htlc_accepted_hook_payload *request,
 			local_fail_in_htlc_badonion(hin,
 						    WIRE_INVALID_ONION_PAYLOAD);
 		} else if (rs->nextcase == ONION_FORWARD) {
-			struct gossip_resolve *gr = tal(ld, struct gossip_resolve);
-
-			gr->next_onion = serialize_onionpacket(gr, rs->next);
-			gr->next_channel = *request->payload->forward_channel;
-			gr->amt_to_forward = request->payload->amt_to_forward;
-			gr->outgoing_cltv_value = request->payload->outgoing_cltv;
-			gr->hin = hin;
-
-			req = towire_gossip_get_channel_peer(tmpctx, &gr->next_channel);
-			log_debug(channel->log, "Asking gossip to resolve channel %s",
-				  type_to_string(tmpctx, struct short_channel_id,
-						 &gr->next_channel));
-			subd_req(hin, ld->gossip, req, -1, 0,
-				 channel_resolve_reply, gr);
+			forward_htlc(hin, hin->cltv_expiry,
+				     request->payload->amt_to_forward,
+				     request->payload->outgoing_cltv,
+				     request->payload->forward_channel,
+				     serialize_onionpacket(tmpctx, rs->next));
 		} else
 			handle_localpay(hin,
 					request->payload->amt_to_forward,

wallet/test/run-wallet.c

@@ -120,9 +120,6 @@ bool fromwire_connect_peer_connected(const tal_t *ctx UNNEEDED, const void *p UN
 /* Generated stub for fromwire_custommsg_in */
 bool fromwire_custommsg_in(const tal_t *ctx UNNEEDED, const void *p UNNEEDED, u8 **msg UNNEEDED)
 { fprintf(stderr, "fromwire_custommsg_in called!\n"); abort(); }
-/* Generated stub for fromwire_gossip_get_channel_peer_reply */
-bool fromwire_gossip_get_channel_peer_reply(const tal_t *ctx UNNEEDED, const void *p UNNEEDED, struct node_id **peer_id UNNEEDED, u8 **stripped_update UNNEEDED)
-{ fprintf(stderr, "fromwire_gossip_get_channel_peer_reply called!\n"); abort(); }
 /* Generated stub for fromwire_gossip_get_stripped_cupdate_reply */
 bool fromwire_gossip_get_stripped_cupdate_reply(const tal_t *ctx UNNEEDED, const void *p UNNEEDED, u8 **stripped_update UNNEEDED)
 { fprintf(stderr, "fromwire_gossip_get_stripped_cupdate_reply called!\n"); abort(); }
@@ -642,9 +639,6 @@ u8 *towire_final_incorrect_cltv_expiry(const tal_t *ctx UNNEEDED, u32 cltv_expir
 /* Generated stub for towire_final_incorrect_htlc_amount */
 u8 *towire_final_incorrect_htlc_amount(const tal_t *ctx UNNEEDED, struct amount_msat incoming_htlc_amt UNNEEDED)
 { fprintf(stderr, "towire_final_incorrect_htlc_amount called!\n"); abort(); }
-/* Generated stub for towire_gossip_get_channel_peer */
-u8 *towire_gossip_get_channel_peer(const tal_t *ctx UNNEEDED, const struct short_channel_id *channel_id UNNEEDED)
-{ fprintf(stderr, "towire_gossip_get_channel_peer called!\n"); abort(); }
 /* Generated stub for towire_gossip_get_stripped_cupdate */
 u8 *towire_gossip_get_stripped_cupdate(const tal_t *ctx UNNEEDED, const struct short_channel_id *channel_id UNNEEDED)
 { fprintf(stderr, "towire_gossip_get_stripped_cupdate called!\n"); abort(); }