Support sending blinded MPP payments

lightning/src/ln/blinded_payment_tests.rs

@@ -11,13 +11,15 @@ use bitcoin::secp256k1::Secp256k1;
 use crate::blinded_path::BlindedPath;
 use crate::blinded_path::payment::{ForwardTlvs, PaymentConstraints, PaymentRelay, ReceiveTlvs};
 use crate::events::MessageSendEventsProvider;
+use crate::ln::channelmanager;
 use crate::ln::channelmanager::{PaymentId, RecipientOnionFields, RetryableSendFailure};
-use crate::ln::features::BlindedHopFeatures;
+use crate::ln::features::{BlindedHopFeatures, Bolt12InvoiceFeatures};
 use crate::ln::functional_test_utils::*;
 use crate::ln::msgs::ChannelMessageHandler;
 use crate::ln::outbound_payment::Retry;
 use crate::prelude::*;
 use crate::routing::router::{PaymentParameters, RouteParameters};
+use crate::util::config::UserConfig;
 
 #[test]
 fn simple_blinded_payment() {
@@ -70,6 +72,74 @@ fn simple_blinded_payment() {
 	claim_payment(&nodes[0], &[&nodes[1], &nodes[2], &nodes[3]], payment_preimage);
 }
 
+#[test]
+fn blinded_mpp() {
+	let chanmon_cfgs = create_chanmon_cfgs(4);
+	let node_cfgs = create_node_cfgs(4, &chanmon_cfgs);
+	let node_chanmgrs = create_node_chanmgrs(4, &node_cfgs, &[None, None, None, None]);
+	let nodes = create_network(4, &node_cfgs, &node_chanmgrs);
+	let mut secp_ctx = Secp256k1::new();
+
+	create_announced_chan_between_nodes(&nodes, 0, 1);
+	create_announced_chan_between_nodes(&nodes, 0, 2);
+	let chan_upd_1_3 = create_announced_chan_between_nodes(&nodes, 1, 3).0.contents;
+	let chan_upd_2_3 = create_announced_chan_between_nodes(&nodes, 2, 3).0.contents;
+
+	let amt_msat = 15_000_000;
+	let (payment_preimage, payment_hash, payment_secret) = get_payment_preimage_hash(&nodes[3], Some(amt_msat), None);
+	let mut blinded_paths = Vec::new();
+	for (idx, chan_upd) in [chan_upd_1_3, chan_upd_2_3].iter().enumerate() {
+		let intermediate_nodes = vec![(nodes[idx + 1].node.get_our_node_id(), ForwardTlvs {
+			short_channel_id: chan_upd.short_channel_id,
+			payment_relay: PaymentRelay {
+				cltv_expiry_delta: chan_upd.cltv_expiry_delta,
+				fee_proportional_millionths: chan_upd.fee_proportional_millionths,
+				fee_base_msat: chan_upd.fee_base_msat,
+			},
+			payment_constraints: PaymentConstraints {
+				max_cltv_expiry: u32::max_value(),
+				htlc_minimum_msat: chan_upd.htlc_minimum_msat,
+			},
+			features: BlindedHopFeatures::empty(),
+		})];
+		let payee_tlvs = ReceiveTlvs {
+			payment_secret,
+			payment_constraints: PaymentConstraints {
+				max_cltv_expiry: u32::max_value(),
+				htlc_minimum_msat: chan_upd.htlc_minimum_msat,
+			},
+		};
+		let blinded_path = BlindedPath::new_for_payment(
+			&intermediate_nodes[..], nodes[3].node.get_our_node_id(), payee_tlvs,
+			chan_upd.htlc_maximum_msat, &chanmon_cfgs[3].keys_manager, &secp_ctx
+		).unwrap();
+		blinded_paths.push(blinded_path);
+	}
+
+	let bolt12_features: Bolt12InvoiceFeatures =
+		channelmanager::provided_invoice_features(&UserConfig::default()).to_context();
+	let route_params = RouteParameters {
+		payment_params: PaymentParameters::blinded(blinded_paths)
+			.with_bolt12_features(bolt12_features).unwrap(),
+		final_value_msat: amt_msat,
+	};
+	nodes[0].node.send_payment(payment_hash, RecipientOnionFields::spontaneous_empty(), PaymentId(payment_hash.0), route_params, Retry::Attempts(0)).unwrap();
+	check_added_monitors(&nodes[0], 2);
+
+	let expected_route: &[&[&Node]] = &[&[&nodes[1], &nodes[3]], &[&nodes[2], &nodes[3]]];
+	let mut events = nodes[0].node.get_and_clear_pending_msg_events();
+	assert_eq!(events.len(), 2);
+
+	let ev = remove_first_msg_event_to_node(&nodes[1].node.get_our_node_id(), &mut events);
+	pass_along_path(&nodes[0], expected_route[0], amt_msat, payment_hash.clone(),
+		Some(payment_secret), ev.clone(), false, None);
+
+	let ev = remove_first_msg_event_to_node(&nodes[2].node.get_our_node_id(), &mut events);
+	pass_along_path(&nodes[0], expected_route[1], amt_msat, payment_hash.clone(),
+		Some(payment_secret), ev.clone(), true, None);
+	claim_payment_along_route(&nodes[0], expected_route, false, payment_preimage);
+}
+
 #[test]
 fn blinded_intercept_payment() {
 	let chanmon_cfgs = create_chanmon_cfgs(3);

lightning/src/ln/outbound_payment.rs

@@ -1064,7 +1064,9 @@ impl OutboundPayments {
 		if route.paths.len() < 1 {
 			return Err(PaymentSendFailure::ParameterError(APIError::InvalidRoute{err: "There must be at least one path to send over".to_owned()}));
 		}
-		if recipient_onion.payment_secret.is_none() && route.paths.len() > 1 {
+		if recipient_onion.payment_secret.is_none() && route.paths.len() > 1
+			&& !route.paths.iter().any(|p| p.blinded_tail.is_some())
+		{
 			return Err(PaymentSendFailure::ParameterError(APIError::APIMisuseError{err: "Payment secret is required for multi-path payments".to_owned()}));
 		}
 		let mut total_value = 0;