routing: Ask gossipd to resolve channel_id and forward HTLCs

Since we now use the short_channel_id to identify the next hop we need
to resolve the channel_id to the pubkey of the next hop. This is done
by calling out to `gossipd` and stuffing the necessary information
into `htlc_end` and recovering it from there once we receive a reply.

lightningd/channel/channel.c

@@ -636,7 +636,6 @@ static void their_htlc_locked(const struct htlc *htlc, struct peer *peer)
 		goto remove_htlc;
 	}
 
-	u8 dummy_next_hop[20]; memset(dummy_next_hop, 0, 20);
 	/* Tell master to deal with it. */
 	msg = towire_channel_accepted_htlc(tmpctx, htlc->id, htlc->msatoshi,
 					   abs_locktime_to_blocks(&htlc->expiry),
@@ -646,7 +645,7 @@ static void their_htlc_locked(const struct htlc *htlc, struct peer *peer)
 					   rs->nextcase == ONION_FORWARD,
 					   rs->hop_data.amt_forward,
 					   rs->hop_data.outgoing_cltv,
-					   dummy_next_hop);
+					   &rs->hop_data.channel_id);
 	daemon_conn_send(&peer->master, take(msg));
 	tal_free(tmpctx);
 	return;

lightningd/channel/channel_wire.csv

@@ -85,7 +85,7 @@ channel_accepted_htlc,0,next_onion,1366*u8
 channel_accepted_htlc,0,forward,bool
 channel_accepted_htlc,0,amt_to_forward,u64
 channel_accepted_htlc,0,outgoing_cltv_value,u32
-channel_accepted_htlc,0,nexthop,20*u8
+channel_accepted_htlc,0,next_channel,struct short_channel_id
 
 # FIXME: Add code to commit current channel state!
 

lightningd/gossip/gossip.c

@@ -633,6 +633,34 @@ static struct io_plan *gossip_init(struct daemon_conn *master,
 	return daemon_conn_read_next(master->conn, master);
 }
 
+static struct io_plan *resolve_channel_req(struct io_conn *conn,
+					   struct daemon *daemon, const u8 *msg)
+{
+	struct short_channel_id scid;
+	struct node_connection *nc;
+	u8 *reply;
+	struct pubkey *nullkey = talz(msg, struct pubkey);
+	if (!fromwire_gossip_resolve_channel_request(msg, NULL, &scid)) {
+		status_trace("Unable to parse resolver request");
+		reply = towire_gossip_resolve_channel_reply(msg, 1, nullkey,
+							    nullkey);
+	} else {
+		status_trace("Attempting to resolce channel %d/%d/%d",
+			     scid.blocknum, scid.txnum, scid.outnum);
+
+		nc = get_connection_by_scid(daemon->rstate, &scid, 0);
+		if (!nc) {
+			reply = towire_gossip_resolve_channel_reply(
+			    msg, 2, nullkey, nullkey);
+		} else {
+			reply = towire_gossip_resolve_channel_reply(
+			    msg, 0, &nc->src->id, &nc->dst->id);
+		}
+	}
+	daemon_conn_send(&daemon->master, reply);
+	return daemon_conn_read_next(conn, &daemon->master);
+}
+
 static struct io_plan *recv_req(struct io_conn *conn, struct daemon_conn *master)
 {
 	struct daemon *daemon = container_of(master, struct daemon, master);
@@ -662,11 +690,15 @@ 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_RESOLVE_CHANNEL_REQUEST:
+		return resolve_channel_req(conn, daemon, daemon->master.msg_in);
+
 	case WIRE_GOSSIPCTL_RELEASE_PEER_REPLY:
 	case WIRE_GOSSIP_GETNODES_REPLY:
 	case WIRE_GOSSIP_GETROUTE_REPLY:
 	case WIRE_GOSSIP_GETCHANNELS_REPLY:
 	case WIRE_GOSSIP_PING_REPLY:
+	case WIRE_GOSSIP_RESOLVE_CHANNEL_REPLY:
 	case WIRE_GOSSIPSTATUS_INIT_FAILED:
 	case WIRE_GOSSIPSTATUS_BAD_NEW_PEER_REQUEST:
 	case WIRE_GOSSIPSTATUS_BAD_RELEASE_REQUEST:

lightningd/gossip/gossip_wire.csv

@@ -91,3 +91,11 @@ gossip_ping,0,len,u16
 gossip_ping_reply,108
 gossip_ping_reply,0,totlen,u16
 
+# Given a short_channel_id, return the endpoints
+gossip_resolve_channel_request,9
+gossip_resolve_channel_request,0,channel_id,struct short_channel_id
+
+gossip_resolve_channel_reply,109
+gossip_resolve_channel_reply,0,error,u8
+gossip_resolve_channel_reply,1,node_id_1,struct pubkey
+gossip_resolve_channel_reply,34,node_id_2,struct pubkey

lightningd/gossip_control.c

@@ -147,12 +147,14 @@ static int 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_RESOLVE_CHANNEL_REQUEST:
 	/* This is a reply, so never gets through to here. */
 	case WIRE_GOSSIPCTL_RELEASE_PEER_REPLY:
 	case WIRE_GOSSIP_GETNODES_REPLY:
 	case WIRE_GOSSIP_GETROUTE_REPLY:
 	case WIRE_GOSSIP_GETCHANNELS_REPLY:
 	case WIRE_GOSSIP_PING_REPLY:
+	case WIRE_GOSSIP_RESOLVE_CHANNEL_REPLY:
 		break;
 	case WIRE_GOSSIPSTATUS_PEER_BAD_MSG:
 		peer_bad_message(gossip, msg);

lightningd/htlc_end.h

@@ -3,6 +3,7 @@
 #include "config.h"
 #include <ccan/htable/htable_type.h>
 #include <ccan/short_types/short_types.h>
+#include <lightningd/sphinx.h>
 
 /* A HTLC has a source and destination: if other is NULL, it's this node.
  *
@@ -14,11 +15,19 @@ struct htlc_end {
 	enum htlc_end_type which_end;
 	struct peer *peer;
 	u64 htlc_id;
-	u64 msatoshis;
+	u32 msatoshis;
 
 	struct htlc_end *other_end;
 	/* If this is driven by a command. */
 	struct pay_command *pay_command;
+
+	/* Temporary information, while we resolve the next hop */
+	u8 next_onion[TOTAL_PACKET_SIZE];
+	struct short_channel_id next_channel;
+	u64 amt_to_forward;
+	u32 outgoing_cltv_value;
+	u32 cltv_expiry;
+	struct sha256 payment_hash;
 };
 
 static inline const struct htlc_end *keyof_htlc_end(const struct htlc_end *e)

lightningd/peer_control.c

@@ -875,14 +875,11 @@ fail:
 	tal_free(hend);
 }
 
-static struct peer *peer_by_pkhash(struct lightningd *ld, const u8 pkhash[20])
+static struct peer *peer_by_pubkey(struct lightningd *ld, const struct pubkey *id)
 {
 	struct peer *peer;
-	u8 addr[20];
-
 	list_for_each(&ld->peers, peer, list) {
-		pubkey_hash160(addr, peer->id);
-		if (memcmp(addr, pkhash, sizeof(addr)) == 0)
+		if (pubkey_cmp(id, peer->id) == 0)
 			return peer;
 	}
 	return NULL;
@@ -945,13 +942,13 @@ static void forward_htlc(struct htlc_end *hend,
 			 const struct sha256 *payment_hash,
 			 u64 amt_to_forward,
 			 u32 outgoing_cltv_value,
-			 const u8 next_hop[20],
+			 const struct pubkey *next_hop,
 			 const u8 next_onion[TOTAL_PACKET_SIZE])
 {
 	u8 *err, *msg;
 	u64 fee;
 	struct lightningd *ld = hend->peer->ld;
-	struct peer *next = peer_by_pkhash(ld, next_hop);
+	struct peer *next = peer_by_pubkey(ld, next_hop);
 
 	if (!next) {
 		err = towire_unknown_next_peer(hend);
@@ -1035,44 +1032,63 @@ fail:
 	tal_free(hend);
 }
 
+/* We received a resolver reply, which gives us the node_ids of the
+ * channel we want to forward over */
+static bool channel_resolve_reply(struct subd *gossip, const u8 *msg,
+				  const int *fds, struct htlc_end *hend)
+{
+	struct pubkey node_id_1, node_id_2, peer_id;
+	u8 error;
+	fromwire_gossip_resolve_channel_reply(msg, NULL, &error, &node_id_1,
+					      &node_id_2);
+
+	/* Get the other peer matching the id that is not us */
+	if (pubkey_cmp(&node_id_1, &gossip->ld->dstate.id) == 0) {
+		peer_id = node_id_2;
+	} else {
+		peer_id = node_id_1;
+	}
+
+	forward_htlc(hend, hend->cltv_expiry, &hend->payment_hash,
+		     hend->amt_to_forward, hend->outgoing_cltv_value, &peer_id,
+		     hend->next_onion);
+	/* FIXME(cdecker) Cleanup things we stuffed into hend before (maybe?) */
+	return true;
+}
+
 static int peer_accepted_htlc(struct peer *peer, const u8 *msg)
 {
-	u64 id;
-	u32 cltv_expiry, amount_msat;
-	struct sha256 payment_hash;
-	u8 next_onion[TOTAL_PACKET_SIZE];
-	u8 next_hop[20];
 	bool forward;
-	u64 amt_to_forward;
-	u32 outgoing_cltv_value;
 	struct htlc_end *hend;
-
-	if (!fromwire_channel_accepted_htlc(msg, NULL, &id, &amount_msat,
-					    &cltv_expiry, &payment_hash,
-					    next_onion, &forward,
-					    &amt_to_forward,
-					    &outgoing_cltv_value,
-					    next_hop)) {
+	u8 *req;
+
+	hend = tal(msg, struct htlc_end);
+	if (!fromwire_channel_accepted_htlc(msg, NULL,
+					    &hend->htlc_id, &hend->msatoshis,
+					    &hend->cltv_expiry, &hend->payment_hash,
+					    hend->next_onion, &forward,
+					    &hend->amt_to_forward,
+					    &hend->outgoing_cltv_value,
+					    &hend->next_channel)) {
 		log_broken(peer->log, "bad fromwire_channel_accepted_htlc %s",
 			   tal_hex(peer, msg));
 		return -1;
 	}
 
-	hend = tal(peer, struct htlc_end);
+	tal_steal(peer, hend);
 	hend->which_end = HTLC_SRC;
 	hend->peer = peer;
-	hend->htlc_id = id;
 	hend->other_end = NULL;
 	hend->pay_command = NULL;
-	hend->msatoshis = amount_msat;
 
-	if (forward)
-		forward_htlc(hend, cltv_expiry, &payment_hash,
-			     amt_to_forward, outgoing_cltv_value,
-			     next_hop, next_onion);
-	else
-		handle_localpay(hend, cltv_expiry, &payment_hash,
-				amt_to_forward, outgoing_cltv_value);
+	if (forward) {
+		req = towire_gossip_resolve_channel_request(msg, &hend->next_channel);
+		log_broken(peer->log, "Asking gossip to resolve channel %d/%d/%d", hend->next_channel.blocknum, hend->next_channel.txnum, hend->next_channel.outnum);
+		subd_req(hend, peer->ld->gossip, req, -1, 0, channel_resolve_reply, hend);
+		/* FIXME(cdecker) Stuff all this info into hend */
+	} else
+		handle_localpay(hend, hend->cltv_expiry, &hend->payment_hash,
+				hend->amt_to_forward, hend->outgoing_cltv_value);
 	return 0;
 }