add xpay user layers

doc/lightningd-config.5.md

@@ -563,6 +563,10 @@ command, so they invoices can also be paid onchain.
 
   Setting this makes `xpay` wait until all parts have failed/succeeded before returning.  Usually this is unnecessary, as xpay will return on the first success (we have the preimage, if they don't take all the parts that's their problem) or failure (the destination could succeed another part, but it would mean it was only partially paid).  The default is `false`.
 
+* **xpay-user-layer**=*name* [plugin `xpay`]
+
+  Specify the name of a layer `xpay` shall use always for every payment.  This is specially useful when combined with `xpay-handle-pay` since the `layers` parameter is not available in the `pay` interface.  This can be specified multiple times to add more layers.
+
 * **askrene-timeout**=*SECONDS* [plugin `askrene`, *dynamic*]
 
   This option makes the `getroutes` call fail if it takes more than this many seconds.  Setting it to zero is a fun way to ensure your node never makes payments.

plugins/libplugin.c

@@ -1688,6 +1688,14 @@ char *charp_option(struct command *cmd, const char *arg, bool check_only, char *
 	return NULL;
 }
 
+char *multi_string_option(struct command *cmd, const char *arg, bool check_only,
+			  const char ***arr)
+{
+	if (!check_only)
+		tal_arr_expand(arr, tal_strdup(*arr, arg));
+	return NULL;
+}
+
 bool u64_jsonfmt(struct command *cmd, struct json_stream *js, const char *fieldname, u64 *i)
 {
 	json_add_u64(js, fieldname, *i);
@@ -1720,6 +1728,18 @@ bool charp_jsonfmt(struct command *cmd, struct json_stream *js, const char *fiel
 	return true;
 }
 
+bool string_array_jsonfmt(struct command *cmd, struct json_stream *js,
+			  const char *fieldname, const char ***arr)
+{
+	if (tal_count(*arr) == 0)
+		return false;
+	json_array_start(js, fieldname);
+	for (size_t i = 0; i < tal_count(*arr); i++)
+		json_add_string(js, NULL, (*arr)[i]);
+	json_array_end(js);
+	return true;
+}
+
 bool flag_jsonfmt(struct command *cmd, struct json_stream *js, const char *fieldname, bool *i)
 {
 	/* Don't print if the default (false) */

plugins/libplugin.h

@@ -638,6 +638,8 @@ char *u32_option(struct command *cmd, const char *arg, bool check_only, u32 *i);
 char *u16_option(struct command *cmd, const char *arg, bool check_only, u16 *i);
 char *bool_option(struct command *cmd, const char *arg, bool check_only, bool *i);
 char *charp_option(struct command *cmd, const char *arg, bool check_only, char **p);
+char *multi_string_option(struct command *cmd, const char *arg, bool check_only,
+			  const char ***arr);
 char *flag_option(struct command *cmd, const char *arg, bool check_only, bool *i);
 
 bool u64_jsonfmt(struct command *cmd, struct json_stream *js, const char *fieldname,
@@ -650,6 +652,8 @@ bool bool_jsonfmt(struct command *cmd, struct json_stream *js, const char *field
 		  bool *i);
 bool charp_jsonfmt(struct command *cmd, struct json_stream *js, const char *fieldname,
 		   char **p);
+bool string_array_jsonfmt(struct command *cmd, struct json_stream *js,
+			  const char *fieldname, const char ***arr);
 
 /* Usually equivalent to NULL, since flag must default to false be useful! */
 bool flag_jsonfmt(struct command *cmd, struct json_stream *js, const char *fieldname,

plugins/xpay/xpay.c

@@ -43,6 +43,7 @@ struct xpay {
 	bool slow_mode;
 	/* Suppress calls to askrene-age */
 	bool dev_no_age;
+	const char **user_layers;
 };
 
 static struct xpay *xpay_of(struct plugin *plugin)
@@ -1467,6 +1468,8 @@ static struct command_result *getroutes_for(struct command *aux_cmd,
 	/* Add user-specified layers */
 	for (size_t i = 0; i < tal_count(payment->layers); i++)
 		json_add_string(req->js, NULL, payment->layers[i]);
+	for (size_t i = 0; i < tal_count(xpay->user_layers); i++)
+		json_add_string(req->js, NULL, xpay->user_layers[i]);
 	if (payment->disable_mpp)
 		json_add_string(req->js, NULL, "auto.no_mpp_support");
 	json_array_end(req->js);
@@ -2534,6 +2537,7 @@ int main(int argc, char *argv[])
 	xpay->take_over_pay = false;
 	xpay->slow_mode = false;
 	xpay->dev_no_age = false;
+	xpay->user_layers = tal_arr(xpay, const char *, 0);
 	plugin_main(argv, init, take(xpay),
 		    PLUGIN_RESTARTABLE, true, NULL,
 		    commands, ARRAY_SIZE(commands),
@@ -2546,6 +2550,9 @@ int main(int argc, char *argv[])
 		    plugin_option_dynamic("xpay-slow-mode", "bool",
 					  "Wait until all parts have completed before returning success or failure",
 					  bool_option, bool_jsonfmt, &xpay->slow_mode),
+		    plugin_option_multi("xpay-user-layer", "string",
+					"Add a layer that will be used for every payment",
+					multi_string_option, string_array_jsonfmt, &xpay->user_layers),
 		    plugin_option_dev("dev-xpay-no-age", "flag",
 				      "Don't call askrene-age",
 				      flag_option, flag_jsonfmt, &xpay->dev_no_age),

tests/plugins/test_libplugin.c

@@ -372,25 +372,6 @@ static const struct plugin_notification notifs[] = { {
 	}
 };
 
-static char *set_multi_string_option(struct command *cmd,
-				     const char *arg,
-				     bool check_only,
-				     const char ***arr)
-{
-	if (!check_only)
-		tal_arr_expand(arr, tal_strdup(*arr, arg));
-	return NULL;
-}
-
-static bool multi_string_jsonfmt(struct command *cmd, struct json_stream *js, const char *fieldname, const char ***arr)
-{
-	json_array_start(js, fieldname);
-	for (size_t i = 0; i < tal_count(*arr); i++)
-		json_add_string(js, NULL, (*arr)[i]);
-	json_array_end(js);
-	return true;
-}
-
 int main(int argc, char *argv[])
 {
 	setup_locale();
@@ -436,8 +417,8 @@ int main(int argc, char *argv[])
 		    plugin_option_multi("multiopt",
 					"string",
 					"Set me multiple times!",
-					set_multi_string_option,
-					multi_string_jsonfmt,
+					multi_string_option,
+					string_array_jsonfmt,
 					&tlp->strarr),
 		    NULL);
 }

tests/test_xpay.py

@@ -1081,3 +1081,59 @@ def mock_getblockhash(req):
     # Now let it catch up, and it will retry, and succeed.
     l1.daemon.rpcproxy.mock_rpc('getblockhash')
     fut.result(TIMEOUT)
+
+
+def test_xpay_user_layers(node_factory):
+    l1, l2, l3, l4 = node_factory.get_nodes(
+        4, opts={"may_reconnect": True, "xpay-handle-pay": True}
+    )
+    node_factory.join_nodes([l1, l2, l3], wait_for_announce=True)
+    node_factory.join_nodes([l2, l4], wait_for_announce=True)
+
+    layer = "disable-chan23"
+    l1.rpc.askrene_create_layer(layer=layer, persistent=True)
+    scid = l2.rpc.listpeerchannels(l3.info["id"])["channels"][0]["short_channel_id"]
+    direction = l2.rpc.listpeerchannels(l3.info["id"])["channels"][0]["direction"]
+    l1.rpc.askrene_update_channel(
+        layer=layer, enabled=False, short_channel_id_dir=f"{scid}/{direction}"
+    )
+
+    layer = "disable-chan24"
+    l1.rpc.askrene_create_layer(layer=layer, persistent=True)
+    scid = l2.rpc.listpeerchannels(l4.info["id"])["channels"][0]["short_channel_id"]
+    direction = l2.rpc.listpeerchannels(l4.info["id"])["channels"][0]["direction"]
+    l1.rpc.askrene_update_channel(
+        layer=layer, enabled=False, short_channel_id_dir=f"{scid}/{direction}"
+    )
+
+    # Let us load these layers as user layers in xpay. Both payments should fail
+    l1.stop()
+    l1.daemon.opts["xpay-user-layer"] = ["disable-chan23", "disable-chan24"]
+    l1.start()
+    l1.rpc.connect(l2.info["id"], "localhost", l2.port)
+    l1.daemon.wait_for_log(f"channeld.*: billboard: Channel ready for use")
+    inv3 = l3.rpc.invoice(1000, "test-xpay-user-layer", "test-xpay-user-layer")[
+        "bolt11"
+    ]
+    with pytest.raises(
+        RpcError,
+        match="We could not find a usable set of paths.  The destination has disabled 1 of 1 channels",
+    ):
+        l1.rpc.pay(inv3)
+    inv4 = l4.rpc.invoice(1000, "test-xpay-user-layer", "test-xpay-user-layer")[
+        "bolt11"
+    ]
+    with pytest.raises(
+        RpcError,
+        match="We could not find a usable set of paths.  The destination has disabled 1 of 1 channels",
+    ):
+        l1.rpc.pay(inv4)
+
+    # Without those layers, the same payments should go through
+    l1.stop()
+    del l1.daemon.opts["xpay-user-layer"]
+    l1.start()
+    l1.rpc.connect(l2.info["id"], "localhost", l2.port)
+    l1.daemon.wait_for_log(f"channeld.*: billboard: Channel ready for use")
+    l1.rpc.pay(inv3)
+    l1.rpc.pay(inv4)