Merge pull request #4373 from TheBlueMatt/2026-02-partial-mpp-payments

Support payments for less than the total MPP value

Author: TheBlueMatt

fuzz/src/chanmon_consistency.rs

@@ -613,7 +613,7 @@ fn send_payment(
 		}],
 		route_params: Some(route_params.clone()),
 	};
-	let onion = RecipientOnionFields::secret_only(payment_secret);
+	let onion = RecipientOnionFields::secret_only(payment_secret, amt);
 	let res = source.send_payment_with_route(route, payment_hash, onion, payment_id);
 	match res {
 		Err(err) => {
@@ -683,7 +683,7 @@ fn send_hop_payment(
 		}],
 		route_params: Some(route_params.clone()),
 	};
-	let onion = RecipientOnionFields::secret_only(payment_secret);
+	let onion = RecipientOnionFields::secret_only(payment_secret, amt);
 	let res = source.send_payment_with_route(route, payment_hash, onion, payment_id);
 	match res {
 		Err(err) => {
@@ -748,7 +748,7 @@ fn send_mpp_payment(
 		amt,
 	);
 	let route = Route { paths, route_params: Some(route_params) };
-	let onion = RecipientOnionFields::secret_only(payment_secret);
+	let onion = RecipientOnionFields::secret_only(payment_secret, amt);
 	let res = source.send_payment_with_route(route, payment_hash, onion, payment_id);
 	match res {
 		Err(_) => false,
@@ -844,7 +844,7 @@ fn send_mpp_hop_payment(
 		amt,
 	);
 	let route = Route { paths, route_params: Some(route_params) };
-	let onion = RecipientOnionFields::secret_only(payment_secret);
+	let onion = RecipientOnionFields::secret_only(payment_secret, amt);
 	let res = source.send_payment_with_route(route, payment_hash, onion, payment_id);
 	match res {
 		Err(_) => false,

fuzz/src/full_stack.rs

@@ -743,7 +743,7 @@ pub fn do_test(mut data: &[u8], logger: &Arc<dyn Logger + MaybeSend + MaybeSync>
 				payments_sent += 1;
 				let _ = channelmanager.send_payment(
 					payment_hash,
-					RecipientOnionFields::spontaneous_empty(),
+					RecipientOnionFields::spontaneous_empty(final_value_msat),
 					PaymentId(payment_hash.0),
 					params,
 					Retry::Attempts(2),
@@ -765,7 +765,7 @@ pub fn do_test(mut data: &[u8], logger: &Arc<dyn Logger + MaybeSend + MaybeSync>
 				payments_sent += 1;
 				let _ = channelmanager.send_payment(
 					payment_hash,
-					RecipientOnionFields::secret_only(payment_secret),
+					RecipientOnionFields::secret_only(payment_secret, final_value_msat),
 					PaymentId(payment_hash.0),
 					params,
 					Retry::Attempts(2),

lightning/src/chain/channelmonitor.rs

@@ -6850,7 +6850,7 @@ mod tests {
 		// the update through to the ChannelMonitor which will refuse it (as the channel is closed).
 		let (route, payment_hash, _, payment_secret) = get_route_and_payment_hash!(nodes[1], nodes[0], 100_000);
 		nodes[1].node.send_payment_with_route(route, payment_hash,
-			RecipientOnionFields::secret_only(payment_secret), PaymentId(payment_hash.0)
+			RecipientOnionFields::secret_only(payment_secret, 100_000), PaymentId(payment_hash.0)
 		).unwrap();
 		check_added_monitors(&nodes[1], 1);
 

lightning/src/events/mod.rs

@@ -41,8 +41,8 @@ use crate::types::payment::{PaymentHash, PaymentPreimage, PaymentSecret};
 use crate::types::string::UntrustedString;
 use crate::util::errors::APIError;
 use crate::util::ser::{
-	BigSize, FixedLengthReader, MaybeReadable, Readable, RequiredWrapper, UpgradableRequired,
-	WithoutLength, Writeable, Writer,
+	BigSize, FixedLengthReader, MaybeReadable, Readable, ReadableArgs, RequiredWrapper,
+	UpgradableRequired, WithoutLength, Writeable, Writer,
 };
 
 use crate::io;
@@ -2378,7 +2378,7 @@ impl MaybeReadable for Event {
 						(6, _user_payment_id, option),
 						(7, claim_deadline, option),
 						(8, payment_preimage, option),
-						(9, onion_fields, option),
+						(9, onion_fields, (option: ReadableArgs, amount_msat)),
 						(10, counterparty_skimmed_fee_msat_opt, option),
 						(11, payment_context, option),
 						(13, payment_id, option),
@@ -2710,7 +2710,8 @@ impl MaybeReadable for Event {
 						(4, amount_msat, required),
 						(5, htlcs, optional_vec),
 						(7, sender_intended_total_msat, option),
-						(9, onion_fields, option),
+						(9, onion_fields, (option: ReadableArgs,
+							sender_intended_total_msat.unwrap_or(amount_msat))),
 						(11, payment_id, option),
 					});
 					Ok(Some(Event::PaymentClaimed {

lightning/src/ln/accountable_tests.rs

@@ -32,7 +32,7 @@ fn test_accountable_forwarding_with_override(
 		PaymentParameters::from_node_id(nodes[2].node.get_our_node_id(), TEST_FINAL_CLTV),
 		100_000,
 	);
-	let onion_fields = RecipientOnionFields::secret_only(payment_secret);
+	let onion_fields = RecipientOnionFields::secret_only(payment_secret, 100_000);
 	let payment_id = PaymentId(payment_hash.0);
 	nodes[0]
 		.node

lightning/src/ln/async_payments_tests.rs

@@ -615,7 +615,7 @@ fn invalid_keysend_payment_secret() {
 		.node
 		.send_spontaneous_payment(
 			Some(keysend_preimage),
-			RecipientOnionFields::spontaneous_empty(),
+			RecipientOnionFields::spontaneous_empty(amt_msat),
 			PaymentId(keysend_preimage.0),
 			route_params,
 			Retry::Attempts(0),

lightning/src/ln/async_signer_tests.rs

@@ -296,7 +296,7 @@ fn do_test_async_commitment_signature_for_commitment_signed_revoke_and_ack(
 
 	let (route, our_payment_hash, _our_payment_preimage, our_payment_secret) =
 		get_route_and_payment_hash!(src, dst, 8000000);
-	let recipient_fields = RecipientOnionFields::secret_only(our_payment_secret);
+	let recipient_fields = RecipientOnionFields::secret_only(our_payment_secret, 8000000);
 	let payment_id = PaymentId(our_payment_hash.0);
 	src.node
 		.send_payment_with_route(route, our_payment_hash, recipient_fields, payment_id)
@@ -520,7 +520,7 @@ fn do_test_async_raa_peer_disconnect(
 
 	let (route, our_payment_hash, _our_payment_preimage, our_payment_secret) =
 		get_route_and_payment_hash!(src, dst, 8000000);
-	let recipient_fields = RecipientOnionFields::secret_only(our_payment_secret);
+	let recipient_fields = RecipientOnionFields::secret_only(our_payment_secret, 8000000);
 	let payment_id = PaymentId(our_payment_hash.0);
 	src.node
 		.send_payment_with_route(route, our_payment_hash, recipient_fields, payment_id)
@@ -669,7 +669,7 @@ fn do_test_async_commitment_signature_peer_disconnect(
 
 	let (route, our_payment_hash, _our_payment_preimage, our_payment_secret) =
 		get_route_and_payment_hash!(src, dst, 8000000);
-	let recipient_fields = RecipientOnionFields::secret_only(our_payment_secret);
+	let recipient_fields = RecipientOnionFields::secret_only(our_payment_secret, 8000000);
 	let payment_id = PaymentId(our_payment_hash.0);
 	src.node
 		.send_payment_with_route(route, our_payment_hash, recipient_fields, payment_id)
@@ -804,7 +804,7 @@ fn do_test_async_commitment_signature_ordering(monitor_update_failure: bool) {
 	// to the peer.
 	let (route, payment_hash_2, payment_preimage_2, payment_secret_2) =
 		get_route_and_payment_hash!(nodes[0], nodes[1], 1000000);
-	let recipient_fields = RecipientOnionFields::secret_only(payment_secret_2);
+	let recipient_fields = RecipientOnionFields::secret_only(payment_secret_2, 1000000);
 	let payment_id = PaymentId(payment_hash_2.0);
 	nodes[0]
 		.node
@@ -1343,14 +1343,14 @@ fn test_no_disconnect_while_async_revoke_and_ack_expecting_remote_commitment_sig
 	// We'll send a payment from both nodes to each other.
 	let (route1, payment_hash1, _, payment_secret1) =
 		get_route_and_payment_hash!(&nodes[0], &nodes[1], payment_amount);
-	let onion1 = RecipientOnionFields::secret_only(payment_secret1);
+	let onion1 = RecipientOnionFields::secret_only(payment_secret1, payment_amount);
 	let payment_id1 = PaymentId(payment_hash1.0);
 	nodes[0].node.send_payment_with_route(route1, payment_hash1, onion1, payment_id1).unwrap();
 	check_added_monitors(&nodes[0], 1);
 
 	let (route2, payment_hash2, _, payment_secret2) =
 		get_route_and_payment_hash!(&nodes[1], &nodes[0], payment_amount);
-	let onion2 = RecipientOnionFields::secret_only(payment_secret2);
+	let onion2 = RecipientOnionFields::secret_only(payment_secret2, payment_amount);
 	let payment_id2 = PaymentId(payment_hash2.0);
 	nodes[1].node.send_payment_with_route(route2, payment_hash2, onion2, payment_id2).unwrap();
 	check_added_monitors(&nodes[1], 1);