common/onion: handle payment by node_id.

In a blinded path, you can specify node_id instead of scid.  Handle
that case.

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

common/onion.c

@@ -159,14 +159,16 @@ static bool handle_blinded_forward(struct onion_payload *p,
 		return false;
 	}
 
-	/* FIXME: handle fwd-by-node-id */
+	if (enc->short_channel_id) {
-	if (!enc->short_channel_id) {
-		*failtlvtype = TLV_TLV_PAYLOAD_ENCRYPTED_RECIPIENT_DATA;
-		return false;
-	}
-
 		p->forward_channel = tal_dup(p, struct short_channel_id,
 					     enc->short_channel_id);
+		p->forward_node_id = NULL;
+	} else {
+		p->forward_channel = NULL;
+		p->forward_node_id = tal_dup(p, struct pubkey,
+					     enc->next_node_id);
+	}
+
 	p->total_msat = NULL;
 
 	/* BOLT-route-blinding #4:
@@ -231,6 +233,8 @@ static bool handle_blinded_terminal(struct onion_payload *p,
 	p->outgoing_cltv = *tlv->outgoing_cltv_value;
 
 	p->forward_channel = NULL;
+	p->forward_node_id = NULL;
+
 	if (tlv->total_amount_msat) {
 		p->total_msat = tal(p, struct amount_msat);
 		*p->total_msat = amount_msat(*tlv->total_amount_msat);
@@ -454,6 +458,9 @@ struct onion_payload *onion_decode(const tal_t *ctx,
 					&p->amt_to_forward);
 	}
 
+	/* Non-blinded is (currently) always by scid */
+	p->forward_node_id = NULL;
+
 	p->payment_secret = NULL;
 	if (p->tlv->payment_data) {
 		p->payment_secret = tal_dup(p, struct secret,

common/onion.h

@@ -11,7 +11,11 @@ struct onion_payload {
 	struct amount_msat amt_to_forward;
 	u32 outgoing_cltv;
 	struct amount_msat *total_msat;
+
+	/* One of these is set */
 	struct short_channel_id *forward_channel;
+	struct pubkey *forward_node_id;
+
 	struct secret *payment_secret;
 	u8 *payment_metadata;
 

lightningd/peer_htlcs.c

@@ -1077,6 +1077,9 @@ static void htlc_accepted_hook_serialize(struct htlc_accepted_hook_payload *p,
 		if (p->payload->forward_channel)
 			json_add_short_channel_id(s, "short_channel_id",
 						  p->payload->forward_channel);
+		if (p->payload->forward_node_id)
+			json_add_pubkey(s, "next_node_id",
+					p->payload->forward_node_id);
 		if (deprecated_apis)
 			json_add_string(s, "forward_amount",
 					fmt_amount_msat(tmpctx,
@@ -1202,20 +1205,42 @@ static struct channel_id *calc_forwarding_channel(struct lightningd *ld,
 						  const struct route_step *rs)
 {
 	const struct onion_payload *p = hp->payload;
+	struct peer *peer;
 	struct channel *c, *best;
 
 	if (rs->nextcase != ONION_FORWARD)
 		return NULL;
 
-	if (!p || !p->forward_channel)
+	if (!p)
 		return NULL;
 
+	if (p->forward_channel) {
 		c = any_channel_by_scid(ld, p->forward_channel, false);
 		if (!c)
 			return NULL;
+		peer = c->peer;
+	} else {
+		struct node_id id;
+		if (!p->forward_node_id)
+			return NULL;
+		node_id_from_pubkey(&id, p->forward_node_id);
+		peer = peer_by_id(ld, &id);
+		if (!peer)
+			return NULL;
+		c = NULL;
+	}
 
-	best = best_channel(ld, c->peer, p->amt_to_forward, c);
+	best = best_channel(ld, peer, p->amt_to_forward, c);
-	if (best != c) {
+	if (!c) {
+		if (!best)
+			return NULL;
+		log_debug(hp->channel->log,
+			  "Chose channel %s for peer %s",
+			  type_to_string(tmpctx, struct short_channel_id,
+					 channel_scid_or_local_alias(best)),
+			  type_to_string(tmpctx, struct node_id,
+					 &peer->id));
+	} else if (best != c) {
 		log_debug(hp->channel->log,
 			  "Chose a better channel than %s: %s",
 			  type_to_string(tmpctx, struct short_channel_id,

wallet/test/run-wallet.c

@@ -347,6 +347,11 @@ void json_add_node_id(struct json_stream *response UNNEEDED,
 void json_add_num(struct json_stream *result UNNEEDED, const char *fieldname UNNEEDED,
 		  unsigned int value UNNEEDED)
 { fprintf(stderr, "json_add_num called!\n"); abort(); }
+/* Generated stub for json_add_pubkey */
+void json_add_pubkey(struct json_stream *response UNNEEDED,
+		     const char *fieldname UNNEEDED,
+		     const struct pubkey *key UNNEEDED)
+{ fprintf(stderr, "json_add_pubkey called!\n"); abort(); }
 /* Generated stub for json_add_s32 */
 void json_add_s32(struct json_stream *result UNNEEDED, const char *fieldname UNNEEDED,
 		  int32_t value UNNEEDED)