Merge pull request #2136 from marctyndel/2023-03-paymentforwarded-expose-amount-forwarded

Expose amount forwarded in `PaymentForwarded` event

Author: TheBlueMatt

lightning/src/events/mod.rs

@@ -603,6 +603,10 @@ pub enum Event {
 		/// If this is `true`, the forwarded HTLC was claimed by our counterparty via an on-chain
 		/// transaction.
 		claim_from_onchain_tx: bool,
+		/// The final amount forwarded, in milli-satoshis, after the fee is deducted.
+		///
+		/// The caveat described above the `fee_earned_msat` field applies here as well.
+		outbound_amount_forwarded_msat: Option<u64>,
 	},
 	/// Used to indicate that a channel with the given `channel_id` is ready to
 	/// be used. This event is emitted either when the funding transaction has been confirmed
@@ -820,13 +824,17 @@ impl Writeable for Event {
 					(8, expected_outbound_amount_msat, required),
 				});
 			}
-			&Event::PaymentForwarded { fee_earned_msat, prev_channel_id, claim_from_onchain_tx, next_channel_id } => {
+			&Event::PaymentForwarded {
+				fee_earned_msat, prev_channel_id, claim_from_onchain_tx,
+				next_channel_id, outbound_amount_forwarded_msat
+			} => {
 				7u8.write(writer)?;
 				write_tlv_fields!(writer, {
 					(0, fee_earned_msat, option),
 					(1, prev_channel_id, option),
 					(2, claim_from_onchain_tx, required),
 					(3, next_channel_id, option),
+					(5, outbound_amount_forwarded_msat, option),
 				});
 			},
 			&Event::ChannelClosed { ref channel_id, ref user_channel_id, ref reason } => {
@@ -1078,13 +1086,18 @@ impl MaybeReadable for Event {
 					let mut prev_channel_id = None;
 					let mut claim_from_onchain_tx = false;
 					let mut next_channel_id = None;
+					let mut outbound_amount_forwarded_msat = None;
 					read_tlv_fields!(reader, {
 						(0, fee_earned_msat, option),
 						(1, prev_channel_id, option),
 						(2, claim_from_onchain_tx, required),
 						(3, next_channel_id, option),
+						(5, outbound_amount_forwarded_msat, option),
 					});
-					Ok(Some(Event::PaymentForwarded { fee_earned_msat, prev_channel_id, claim_from_onchain_tx, next_channel_id }))
+					Ok(Some(Event::PaymentForwarded {
+						fee_earned_msat, prev_channel_id, claim_from_onchain_tx, next_channel_id,
+						outbound_amount_forwarded_msat
+					}))
 				};
 				f()
 			},

lightning/src/ln/channelmanager.rs

@@ -4184,6 +4184,7 @@ where
 								claim_from_onchain_tx: from_onchain,
 								prev_channel_id,
 								next_channel_id,
+								outbound_amount_forwarded_msat: forwarded_htlc_value_msat,
 							}})
 						} else { None }
 					});

lightning/src/ln/functional_test_utils.rs

@@ -1780,7 +1780,10 @@ macro_rules! expect_payment_forwarded {
 		let events = $node.node.get_and_clear_pending_events();
 		assert_eq!(events.len(), 1);
 		match events[0] {
-			Event::PaymentForwarded { fee_earned_msat, prev_channel_id, claim_from_onchain_tx, next_channel_id } => {
+			Event::PaymentForwarded {
+				fee_earned_msat, prev_channel_id, claim_from_onchain_tx, next_channel_id,
+				outbound_amount_forwarded_msat: _
+			} => {
 				assert_eq!(fee_earned_msat, $expected_fee);
 				if fee_earned_msat.is_some() {
 					// Is the event prev_channel_id in one of the channels between the two nodes?

lightning/src/ln/functional_tests.rs

@@ -2731,20 +2731,22 @@ fn test_htlc_on_chain_success() {
 	}
 	let chan_id = Some(chan_1.2);
 	match forwarded_events[1] {
-		Event::PaymentForwarded { fee_earned_msat, prev_channel_id, claim_from_onchain_tx, next_channel_id } => {
+		Event::PaymentForwarded { fee_earned_msat, prev_channel_id, claim_from_onchain_tx, next_channel_id, outbound_amount_forwarded_msat } => {
 			assert_eq!(fee_earned_msat, Some(1000));
 			assert_eq!(prev_channel_id, chan_id);
 			assert_eq!(claim_from_onchain_tx, true);
 			assert_eq!(next_channel_id, Some(chan_2.2));
+			assert_eq!(outbound_amount_forwarded_msat, Some(3000000));
 		},
 		_ => panic!()
 	}
 	match forwarded_events[2] {
-		Event::PaymentForwarded { fee_earned_msat, prev_channel_id, claim_from_onchain_tx, next_channel_id } => {
+		Event::PaymentForwarded { fee_earned_msat, prev_channel_id, claim_from_onchain_tx, next_channel_id, outbound_amount_forwarded_msat } => {
 			assert_eq!(fee_earned_msat, Some(1000));
 			assert_eq!(prev_channel_id, chan_id);
 			assert_eq!(claim_from_onchain_tx, true);
 			assert_eq!(next_channel_id, Some(chan_2.2));
+			assert_eq!(outbound_amount_forwarded_msat, Some(3000000));
 		},
 		_ => panic!()
 	}
@@ -4653,11 +4655,12 @@ fn test_onchain_to_onchain_claim() {
 		_ => panic!("Unexpected event"),
 	}
 	match events[1] {
-		Event::PaymentForwarded { fee_earned_msat, prev_channel_id, claim_from_onchain_tx, next_channel_id } => {
+		Event::PaymentForwarded { fee_earned_msat, prev_channel_id, claim_from_onchain_tx, next_channel_id, outbound_amount_forwarded_msat } => {
 			assert_eq!(fee_earned_msat, Some(1000));
 			assert_eq!(prev_channel_id, Some(chan_1.2));
 			assert_eq!(claim_from_onchain_tx, true);
 			assert_eq!(next_channel_id, Some(chan_2.2));
+			assert_eq!(outbound_amount_forwarded_msat, Some(3000000));
 		},
 		_ => panic!("Unexpected event"),
 	}