Add FinalOnionHopData to ReceiveKeysend

This is needed to communicate `total_msat` to the recipient so they
know to wait for more payment parts before claiming.

Author: alecchendev

lightning/src/ln/channelmanager.rs

@@ -110,6 +110,7 @@ pub(super) enum PendingHTLCRouting {
 		phantom_shared_secret: Option<[u8; 32]>,
 	},
 	ReceiveKeysend {
+		payment_data: Option<msgs::FinalOnionHopData>,
 		payment_preimage: PaymentPreimage,
 		incoming_cltv_expiry: u32, // Used to track when we should expire pending HTLCs that go unclaimed
 	},
@@ -2155,19 +2156,7 @@ where
 				});
 			},
 			msgs::OnionHopDataFormat::FinalNode { payment_data, keysend_preimage } => {
-				if payment_data.is_some() && keysend_preimage.is_some() {
-					return Err(ReceiveError {
-						err_code: 0x4000|22,
-						err_data: Vec::new(),
-						msg: "We don't support MPP keysend payments",
-					});
-				} else if let Some(data) = payment_data {
-					PendingHTLCRouting::Receive {
-						payment_data: data,
-						incoming_cltv_expiry: hop_data.outgoing_cltv_value,
-						phantom_shared_secret,
-					}
-				} else if let Some(payment_preimage) = keysend_preimage {
+				if let Some(payment_preimage) = keysend_preimage {
 					// We need to check that the sender knows the keysend preimage before processing this
 					// payment further. Otherwise, an intermediary routing hop forwarding non-keysend-HTLC X
 					// could discover the final destination of X, by probing the adjacent nodes on the route
@@ -2183,9 +2172,16 @@ where
 					}
 
 					PendingHTLCRouting::ReceiveKeysend {
+						payment_data,
 						payment_preimage,
 						incoming_cltv_expiry: hop_data.outgoing_cltv_value,
 					}
+				} else if let Some(data) = payment_data {
+					PendingHTLCRouting::Receive {
+						payment_data: data,
+						incoming_cltv_expiry: hop_data.outgoing_cltv_value,
+						phantom_shared_secret,
+					}
 				} else {
 					return Err(ReceiveError {
 						err_code: 0x4000|0x2000|3,
@@ -3288,8 +3284,8 @@ where
 										let _legacy_hop_data = Some(payment_data.clone());
 										(incoming_cltv_expiry, OnionPayload::Invoice { _legacy_hop_data }, Some(payment_data), phantom_shared_secret)
 									},
-									PendingHTLCRouting::ReceiveKeysend { payment_preimage, incoming_cltv_expiry } =>
-										(incoming_cltv_expiry, OnionPayload::Spontaneous(payment_preimage), None, None),
+									PendingHTLCRouting::ReceiveKeysend { payment_data, payment_preimage, incoming_cltv_expiry } =>
+										(incoming_cltv_expiry, OnionPayload::Spontaneous(payment_preimage), payment_data, None),
 									_ => {
 										panic!("short_channel_id == 0 should imply any pending_forward entries are of type Receive");
 									}
@@ -6724,6 +6720,7 @@ impl_writeable_tlv_based_enum!(PendingHTLCRouting,
 	},
 	(2, ReceiveKeysend) => {
 		(0, payment_preimage, required),
+		(1, payment_data, option),
 		(2, incoming_cltv_expiry, required),
 	},
 ;);
@@ -8283,49 +8280,6 @@ mod tests {
 		nodes[1].logger.assert_log_contains("lightning::ln::channelmanager", "Payment preimage didn't match payment hash", 1);
 	}
 
-	#[test]
-	fn test_keysend_msg_with_secret_err() {
-		// Test that we error as expected if we receive a keysend payment that includes a payment secret.
-		let chanmon_cfgs = create_chanmon_cfgs(2);
-		let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
-		let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
-		let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
-
-		let payer_pubkey = nodes[0].node.get_our_node_id();
-		let payee_pubkey = nodes[1].node.get_our_node_id();
-
-		let _chan = create_chan_between_nodes(&nodes[0], &nodes[1]);
-		let route_params = RouteParameters {
-			payment_params: PaymentParameters::for_keysend(payee_pubkey, 40),
-			final_value_msat: 10_000,
-		};
-		let network_graph = nodes[0].network_graph.clone();
-		let first_hops = nodes[0].node.list_usable_channels();
-		let scorer = test_utils::TestScorer::new();
-		let random_seed_bytes = chanmon_cfgs[1].keys_manager.get_secure_random_bytes();
-		let route = find_route(
-			&payer_pubkey, &route_params, &network_graph, Some(&first_hops.iter().collect::<Vec<_>>()),
-			nodes[0].logger, &scorer, &random_seed_bytes
-		).unwrap();
-
-		let test_preimage = PaymentPreimage([42; 32]);
-		let test_secret = PaymentSecret([43; 32]);
-		let payment_hash = PaymentHash(Sha256::hash(&test_preimage.0).into_inner());
-		let session_privs = nodes[0].node.test_add_new_pending_payment(payment_hash, Some(test_secret), PaymentId(payment_hash.0), &route).unwrap();
-		nodes[0].node.test_send_payment_internal(&route, payment_hash, &Some(test_secret), Some(test_preimage), PaymentId(payment_hash.0), None, session_privs).unwrap();
-		check_added_monitors!(nodes[0], 1);
-
-		let updates = get_htlc_update_msgs!(nodes[0], nodes[1].node.get_our_node_id());
-		assert_eq!(updates.update_add_htlcs.len(), 1);
-		assert!(updates.update_fulfill_htlcs.is_empty());
-		assert!(updates.update_fail_htlcs.is_empty());
-		assert!(updates.update_fail_malformed_htlcs.is_empty());
-		assert!(updates.update_fee.is_none());
-		nodes[1].node.handle_update_add_htlc(&nodes[0].node.get_our_node_id(), &updates.update_add_htlcs[0]);
-
-		nodes[1].logger.assert_log_contains("lightning::ln::channelmanager", "We don't support MPP keysend payments", 1);
-	}
-
 	#[test]
 	fn test_multi_hop_missing_secret() {
 		let chanmon_cfgs = create_chanmon_cfgs(4);

lightning/src/ln/onion_utils.rs

@@ -169,7 +169,12 @@ pub(super) fn build_onion_payloads(path: &Vec<RouteHop>, total_msat: u64, paymen
 							payment_secret: payment_secret.clone(),
 							total_msat,
 						})
-					} else { None },
+					} else if keysend_preimage.is_some() && value_msat < total_msat {
+						Some(msgs::FinalOnionHopData {
+							payment_secret: PaymentSecret([0u8; 32]),
+							total_msat,
+						})
+					} else { None }, // For probing
 					keysend_preimage: *keysend_preimage,
 				}
 			} else {