fetchinvoice: include send in path, use pubkeys.

We had sent->path be a list of node_ids, but it makes more sense as
pubkeys so we can avoid conversion.  Also, I find it easier to think
about (especially creating backwards paths) if we include *ourselves*
as the first element in the path.

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

Author: rustyrussell

plugins/fetchinvoice.c

@@ -20,7 +20,7 @@
 #include <sodium.h>
 
 static struct gossmap *global_gossmap;
-static struct node_id local_id;
+static struct pubkey local_id;
 static bool disable_connect = false;
 static LIST_HEAD(sent_list);
 
@@ -33,8 +33,8 @@ struct sent {
 	struct command *cmd;
 	/* The offer we are trying to get an invoice/payment for. */
 	struct tlv_offer *offer;
-	/* Path to use. */
-	struct node_id *path;
+	/* Path to use (including self) */
+	struct pubkey *path;
 
 	/* The invreq we sent, OR the invoice we sent */
 	struct tlv_invoice_request *invreq;
@@ -567,18 +567,21 @@ static void node_id_from_pubkey32(struct node_id *nid,
 					 &node32_id->pubkey);
 }
 
-/* Create path to node which can carry onion messages; if it can't find
- * one, returns NULL.  Fills in nodeid_parity for 33rd nodeid byte. */
-static struct node_id *path_to_node(const tal_t *ctx,
-				    struct gossmap *gossmap,
-				    const struct pubkey32 *node32_id,
-				    enum nodeid_parity *parity)
+/* Create path to node which can carry onion messages (including
+ * self); if it can't find one, returns NULL.  Fills in nodeid_parity
+ * for 33rd nodeid byte. */
+static struct pubkey *path_to_node(const tal_t *ctx,
+				   struct plugin *plugin,
+				   const struct pubkey32 *node32_id,
+				   enum nodeid_parity *parity)
 {
 	struct route_hop *r;
 	const struct dijkstra *dij;
 	const struct gossmap_node *src;
 	const struct gossmap_node *dst;
-	struct node_id *nodes, dstid;
+	struct node_id dstid, local_nodeid;
+	struct pubkey *nodes;
+	struct gossmap *gossmap = get_gossmap(plugin);
 
 	/* We try both parities. */
 	*parity = nodeid_parity_even;
@@ -597,7 +600,8 @@ static struct node_id *path_to_node(const tal_t *ctx,
 	*parity = node_parity(gossmap, dst);
 
 	/* If we don't exist in gossip, routing can't happen. */
-	src = gossmap_find_node(gossmap, &local_id);
+	node_id_from_pubkey(&local_nodeid, &local_id);
+	src = gossmap_find_node(gossmap, &local_nodeid);
 	if (!src)
 		return NULL;
 
@@ -608,9 +612,15 @@ static struct node_id *path_to_node(const tal_t *ctx,
 	if (!r)
 		return NULL;
 
-	nodes = tal_arr(ctx, struct node_id, tal_count(r));
-	for (size_t i = 0; i < tal_count(r); i++)
-		nodes[i] = r[i].node_id;
+	nodes = tal_arr(ctx, struct pubkey, tal_count(r) + 1);
+	nodes[0] = local_id;
+	for (size_t i = 0; i < tal_count(r); i++) {
+		if (!pubkey_from_node_id(&nodes[i+1], &r[i].node_id)) {
+			plugin_err(plugin, "Could not convert nodeid %s",
+				   type_to_string(tmpctx, struct node_id,
+						  &r[i].node_id));
+		}
+	}
 	return nodes;
 }
 
@@ -631,19 +641,14 @@ static struct command_result *send_message(struct command *cmd,
 	struct out_req *req;
 
 	/* FIXME: Maybe we should allow this? */
-	if (tal_bytelen(sent->path) == 0)
+	if (tal_count(sent->path) == 1)
 		return command_fail(cmd, PAY_ROUTE_NOT_FOUND,
 				    "Refusing to talk to ourselves");
 
-	/* Reverse path is offset by one: we are the final node. */
-	backwards = tal_arr(tmpctx, struct pubkey, tal_count(sent->path));
-	for (size_t i = 0; i < tal_count(sent->path) - 1; i++) {
-		if (!pubkey_from_node_id(&backwards[tal_count(sent->path)-2-i],
-					 &sent->path[i]))
-			abort();
-	}
-	if (!pubkey_from_node_id(&backwards[tal_count(sent->path)-1], &local_id))
-		abort();
+	/* Reverse path is offset by one. */
+	backwards = tal_arr(tmpctx, struct pubkey, tal_count(sent->path) - 1);
+	for (size_t i = 0; i < tal_count(backwards); i++)
+		backwards[tal_count(backwards)-1-i] = sent->path[i];
 
 	/* Ok, now make reply for onion_message */
 	path = make_blindedpath(tmpctx, backwards, &blinding,
@@ -654,9 +659,9 @@ static struct command_result *send_message(struct command *cmd,
 				    forward_error,
 				    sent);
 	json_array_start(req->js, "hops");
-	for (size_t i = 0; i < tal_count(sent->path); i++) {
+	for (size_t i = 1; i < tal_count(sent->path); i++) {
 		json_object_start(req->js, NULL);
-		json_add_node_id(req->js, "id", &sent->path[i]);
+		json_add_pubkey(req->js, "id", &sent->path[i]);
 		if (i == tal_count(sent->path) - 1)
 			json_add_hex_talarr(req->js, msgfield, msgval);
 		json_object_end(req->js);
@@ -757,7 +762,17 @@ static struct command_result *try_other_parity(struct command *cmd,
 
 	/* Flip parity */
 	ca->node_id.k[0] = SECP256K1_TAG_PUBKEY_ODD;
-	ca->sent->path[0] = ca->node_id;
+	/* Path is us -> them, so they're second entry */
+	if (!pubkey_from_node_id(&ca->sent->path[1], &ca->node_id)) {
+		/* Should not happen!
+		 * Pieter Wuille points out:
+		 *   y^2 = x^3 + 7 mod p
+		 *   negating y doesn’t change the left hand side
+		 */
+		return command_done_err(cmd, LIGHTNINGD,
+					"Failed: could not convert inverted pubkey?",
+					NULL);
+	}
 	req = jsonrpc_request_start(cmd->plugin, cmd, "connect", connected,
 				    connect_failed, ca);
 	json_add_node_id(req->js, "id", &ca->node_id);
@@ -797,8 +812,14 @@ connect_direct(struct command *cmd,
 	}
 
 	/* Make a direct path -> dst. */
-	sent->path = tal_arr(sent, struct node_id, 1);
-	sent->path[0] = ca->node_id;
+	sent->path = tal_arr(sent, struct pubkey, 2);
+	sent->path[0] = local_id;
+	if (!pubkey_from_node_id(&sent->path[1], &ca->node_id)) {
+		/* Should not happen! */
+		return command_done_err(cmd, LIGHTNINGD,
+					"Failed: could not convert to pubkey?",
+					NULL);
+	}
 
 	if (disable_connect) {
 		/* FIXME: This means we will fail if parity is wrong! */
@@ -918,7 +939,7 @@ static struct command_result *invreq_done(struct command *cmd,
 		}
 	}
 
-	sent->path = path_to_node(sent, get_gossmap(cmd->plugin),
+	sent->path = path_to_node(sent, cmd->plugin,
 				  sent->offer->node_id,
 				  &parity);
 	if (!sent->path)
@@ -978,7 +999,7 @@ force_payer_secret(struct command *cmd,
 				    "Failed to sign with payer_secret");
 	}
 
-	sent->path = path_to_node(sent, get_gossmap(cmd->plugin),
+	sent->path = path_to_node(sent, cmd->plugin,
 				  sent->offer->node_id,
 				  &parity);
 	if (!sent->path)
@@ -1273,7 +1294,7 @@ static struct command_result *createinvoice_done(struct command *cmd,
 				    "Bad createinvoice response %s", fail);
 	}
 
-	sent->path = path_to_node(sent, get_gossmap(cmd->plugin),
+	sent->path = path_to_node(sent, cmd->plugin,
 				  sent->offer->node_id,
 				  &parity);
 	if (!sent->path)
@@ -1455,9 +1476,13 @@ static struct command_result *json_sendinvoice(struct command *cmd,
 	 *   - MUST set `description` the same as the offer.
 	 */
 	sent->inv->node_id = tal(sent->inv, struct pubkey32);
-	if (!pubkey32_from_node_id(sent->inv->node_id, &local_id))
-		plugin_err(cmd->plugin, "Invalid local_id %s?",
-			   type_to_string(tmpctx, struct node_id, &local_id));
+
+	/* This only fails if pubkey is invalid. */
+	if (!secp256k1_xonly_pubkey_from_pubkey(secp256k1_ctx,
+						&sent->inv->node_id->pubkey,
+						NULL,
+						&local_id.pubkey))
+		abort();
 
 	sent->inv->description
 		= tal_dup_talarr(sent->inv, char, sent->offer->description);
@@ -1633,7 +1658,7 @@ static struct command_result *json_rawrequest(struct command *cmd,
 	sent->cmd = cmd;
 	sent->offer = NULL;
 
-	sent->path = path_to_node(sent, get_gossmap(cmd->plugin),
+	sent->path = path_to_node(sent, cmd->plugin,
 				  &node_id32,
 				  &parity);
 	if (!sent->path) {
@@ -1680,7 +1705,7 @@ static const char *init(struct plugin *p, const char *buf UNUSED,
 
 	rpc_scan(p, "getinfo",
 		 take(json_out_obj(NULL, NULL, NULL)),
-		 "{id:%}", JSON_SCAN(json_to_node_id, &local_id));
+		 "{id:%}", JSON_SCAN(json_to_pubkey, &local_id));
 
 	rpc_scan(p, "listconfigs",
 		 take(json_out_obj(NULL, "config", "experimental-offers")),