renepay: handle non-MPP invoices

Changelog-Fixed: renepay: Now able to handle invoices that don't support Multi-Path-Payments.

Signed-off-by: Lagrang3 <[email protected]>

Author: Lagrang3

plugins/renepay/json.c

@@ -277,7 +277,8 @@ void json_add_payment(struct json_stream *s, const struct payment *payment)
 
 	json_add_timeabs(s, "created_at", pinfo->start_time);
 	json_add_u64(s, "groupid", payment->groupid);
-	json_add_u64(s, "parts", payment->next_partid);
+	// all tried parts, not all successful parts
+	json_add_u64(s, "parts", payment_parts(payment));
 
 	switch (payment->status) {
 	case PAYMENT_SUCCESS:

plugins/renepay/mods.c

@@ -587,6 +587,8 @@ static struct command_result *getroutes_cb(struct payment *payment)
 	json_add_string(req->js, NULL, "auto.sourcefree");
 	json_add_string(req->js, NULL, payment->payment_layer);
 	json_add_string(req->js, NULL, RENEPAY_LAYER);
+	if (!payment->payment_info.use_mpp)
+		json_add_string(req->js, NULL, "auto.no_mpp_support");
 	json_array_end(req->js);
 	// FIXME: add further constraints here if necessary when they become
 	// available in getroutes

plugins/renepay/payment.c

@@ -108,7 +108,8 @@ bool payment_set_constraints(
 		u64 min_prob_success_millionths,
 		u64 base_prob_success_millionths,
 		bool use_shadow,
-		const struct route_exclusion **exclusions)
+		const struct route_exclusion **exclusions,
+		bool mpp_enabled)
 {
 	// FIXME: add exclusions to a layer
 	assert(p);
@@ -129,6 +130,7 @@ bool payment_set_constraints(
 	pinfo->min_prob_success = min_prob_success_millionths / 1e6;
 	pinfo->base_prob_success = base_prob_success_millionths / 1e6;
 	pinfo->use_shadow = use_shadow;
+	pinfo->use_mpp = mpp_enabled;
 
 	return true;
 }

plugins/renepay/payment.h

@@ -122,7 +122,8 @@ bool payment_set_constraints(
 		u64 min_prob_success_millionths,
 		u64 base_prob_success_millionths,
 		bool use_shadow,
-		const struct route_exclusion **exclusions);
+		const struct route_exclusion **exclusions,
+		bool mpp_enabled);
 
 bool payment_refresh(struct payment *p);
 

plugins/renepay/payment_info.h

@@ -86,6 +86,9 @@ struct payment_info {
 
 	/* --developer allows disabling shadow route */
 	bool use_shadow;
+
+	/* Use Multi-Path-Payments feature. */
+	bool use_mpp;
 };
 
 #endif /* LIGHTNING_PLUGINS_RENEPAY_PAYMENT_INFO_H */

plugins/renepay/renepay.c

@@ -181,6 +181,7 @@ static struct command_result *json_renepay(struct command *cmd, const char *buf,
 	const char *description;
 	const char *label;
 	struct route_exclusion **exclusions;
+	bool mpp_enabled = true;
 
 	// dev options
 	bool *use_shadow;
@@ -262,6 +263,8 @@ static struct command_result *json_renepay(struct command *cmd, const char *buf,
 			*inv_msat = amount_msat(*b12->invoice_amount);
 		}
 		payment_hash = b12->invoice_payment_hash;
+		mpp_enabled =
+		    feature_offered(b12->invoice_features, OPT_BASIC_MPP);
 	} else {
 		b11 = bolt11_decode(tmpctx, invstr,
 				    plugin_feature_set(cmd->plugin),
@@ -280,6 +283,7 @@ static struct command_result *json_renepay(struct command *cmd, const char *buf,
 		inv_msat = b11->msat;
 		invexpiry = b11->timestamp + b11->expiry;
 		payment_hash = &b11->payment_hash;
+		mpp_enabled = feature_offered(b11->features, OPT_BASIC_MPP);
 	}
 
 	/* === Set default values for non-trivial constraints  === */
@@ -396,7 +400,8 @@ static struct command_result *json_renepay(struct command *cmd, const char *buf,
 			*min_prob_success_millionths,
 			*base_prob_success_millionths, use_shadow,
 			cast_const2(const struct route_exclusion **,
-				    exclusions)) ||
+				    exclusions),
+			mpp_enabled) ||
 		    !payment_refresh(payment))
 			return command_fail(
 			    cmd, PLUGIN_ERROR,
@@ -431,7 +436,8 @@ static struct command_result *json_renepay(struct command *cmd, const char *buf,
 			*min_prob_success_millionths,
 			*base_prob_success_millionths, use_shadow,
 			cast_const2(const struct route_exclusion **,
-				    exclusions)) ||
+				    exclusions),
+			mpp_enabled) ||
 		    !payment_refresh(payment))
 			return command_fail(
 			    cmd, PLUGIN_ERROR,

tests/test_renepay.py

@@ -863,3 +863,60 @@ def test_unannounced(node_factory):
     b12 = l1.rpc.fetchinvoice(offer, "21sat")["invoice"]
     ret = l1.rpc.call("renepay", {"invstring": b12})
     assert ret["status"] == "complete"
+
+
+def test_renepay_no_mpp(node_factory, chainparams):
+    """Renepay should produce single route solutions for invoices that don't
+    signal their support for MPP."""
+    def test_bit(features, bit_pos):
+        return (features[bit_pos // 8] & (1 << (bit_pos % 8))) != 0
+
+    # l4 does not support MPP
+    l1, l2, l3, l4 = node_factory.get_nodes(
+        4, opts=[{}, {}, {}, {"dev-force-features": -17}]
+    )
+
+    # make it so such that it would be convenient to use MPP, eg. higher
+    # probability of success
+    amount = "900000sat"
+    start_channels(
+        [(l1, l2, 1000_000), (l2, l4, 1000_000), (l1, l3, 1000_000), (l3, l4, 1000_000)]
+    )
+
+    # a normal call to getroutes returns two routes
+    routes = l1.rpc.getroutes(
+        source=l1.info["id"],
+        destination=l4.info["id"],
+        amount_msat=amount,
+        layers=[],
+        maxfee_msat="1000sat",
+        final_cltv=0,
+    )["routes"]
+    assert len(routes) == 2
+
+    inv = l4.rpc.invoice(amount, "test_no_mpp", "test_no_mpp")["bolt11"]
+
+    # check that MPP feature is not present
+    features = bytearray.fromhex(l1.rpc.decode(inv)["features"])
+    features.reverse()
+    # var_onion_optin is compulsory
+    assert test_bit(features, 8)
+    # payment_secret is compulsory
+    assert test_bit(features, 14)
+    # basic_mpp should not be present
+    assert not test_bit(features, 16)
+    assert not test_bit(features, 17)
+
+    # pay with renepay
+    ret = l1.rpc.call("renepay", {"invstring": inv})
+    l1.wait_for_htlcs()
+
+    # check that payment succeed
+    # FIXME: lightningd on l4 will accept the MPP HTLCs (>1 routes) even if we
+    # have disabled the feature.
+    assert ret["status"] == "complete"
+    # check that number of parts was 1
+    assert ret["parts"] == 1
+    # check that destination received the payment
+    receipt = only_one(l4.rpc.listinvoices("test_no_mpp")["invoices"])
+    assert receipt["amount_received_msat"] == Millisatoshi(amount)