Merge pull request #404 from G8XSU/payment-forwarded-event

Start publishing PaymentForwarded events.

bindings/ldk_node.udl

@@ -277,6 +277,7 @@ interface Event {
 	PaymentFailed(PaymentId? payment_id, PaymentHash? payment_hash, PaymentFailureReason? reason);
 	PaymentReceived(PaymentId? payment_id, PaymentHash payment_hash, u64 amount_msat);
 	PaymentClaimable(PaymentId payment_id, PaymentHash payment_hash, u64 claimable_amount_msat, u32? claim_deadline);
+	PaymentForwarded(ChannelId prev_channel_id, ChannelId next_channel_id, UserChannelId? prev_user_channel_id, UserChannelId? next_user_channel_id, u64? total_fee_earned_msat, u64? skimmed_fee_msat, boolean claim_from_onchain_tx, u64? outbound_amount_forwarded_msat);
 	ChannelPending(ChannelId channel_id, UserChannelId user_channel_id, ChannelId former_temporary_channel_id, PublicKey counterparty_node_id, OutPoint funding_txo);
 	ChannelReady(ChannelId channel_id, UserChannelId user_channel_id, PublicKey? counterparty_node_id);
 	ChannelClosed(ChannelId channel_id, UserChannelId user_channel_id, PublicKey? counterparty_node_id, ClosureReason? reason);

src/event.rs

@@ -103,6 +103,50 @@ pub enum Event {
 		/// The value, in thousandths of a satoshi, that has been received.
 		amount_msat: u64,
 	},
+	/// A payment has been forwarded.
+	PaymentForwarded {
+		/// The channel id of the incoming channel between the previous node and us.
+		prev_channel_id: ChannelId,
+		/// The channel id of the outgoing channel between the next node and us.
+		next_channel_id: ChannelId,
+		/// The `user_channel_id` of the incoming channel between the previous node and us.
+		///
+		/// Will only be `None` for events serialized with LDK Node v0.3.0 or prior.
+		prev_user_channel_id: Option<UserChannelId>,
+		/// The `user_channel_id` of the outgoing channel between the next node and us.
+		///
+		/// This will be `None` if the payment was settled via an on-chain transaction. See the
+		/// caveat described for the `total_fee_earned_msat` field.
+		next_user_channel_id: Option<UserChannelId>,
+		/// The total fee, in milli-satoshis, which was earned as a result of the payment.
+		///
+		/// Note that if we force-closed the channel over which we forwarded an HTLC while the HTLC
+		/// was pending, the amount the next hop claimed will have been rounded down to the nearest
+		/// whole satoshi. Thus, the fee calculated here may be higher than expected as we still
+		/// claimed the full value in millisatoshis from the source. In this case,
+		/// `claim_from_onchain_tx` will be set.
+		///
+		/// If the channel which sent us the payment has been force-closed, we will claim the funds
+		/// via an on-chain transaction. In that case we do not yet know the on-chain transaction
+		/// fees which we will spend and will instead set this to `None`.
+		total_fee_earned_msat: Option<u64>,
+		/// The share of the total fee, in milli-satoshis, which was withheld in addition to the
+		/// forwarding fee.
+		///
+		/// This will only be `Some` if we forwarded an intercepted HTLC with less than the
+		/// expected amount. This means our counterparty accepted to receive less than the invoice
+		/// amount.
+		///
+		/// The caveat described above the `total_fee_earned_msat` field applies here as well.
+		skimmed_fee_msat: Option<u64>,
+		/// 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 `total_fee_earned_msat` field applies here as well.
+		outbound_amount_forwarded_msat: Option<u64>,
+	},
 	/// A payment for a previously-registered payment hash has been received.
 	///
 	/// This needs to be manually claimed by supplying the correct preimage to [`claim_for_hash`].
@@ -204,6 +248,16 @@ impl_writeable_tlv_based_enum!(Event,
 		(2, payment_id, required),
 		(4, claimable_amount_msat, required),
 		(6, claim_deadline, option),
+	},
+	(7, PaymentForwarded) => {
+		(0, prev_channel_id, required),
+		(2, next_channel_id, required),
+		(4, prev_user_channel_id, option),
+		(6, next_user_channel_id, option),
+		(8, total_fee_earned_msat, option),
+		(10, skimmed_fee_msat, option),
+		(12, claim_from_onchain_tx, required),
+		(14, outbound_amount_forwarded_msat, option),
 	}
 );
 
@@ -1068,11 +1122,28 @@ where
 			LdkEvent::PaymentForwarded {
 				prev_channel_id,
 				next_channel_id,
+				prev_user_channel_id,
+				next_user_channel_id,
 				total_fee_earned_msat,
+				skimmed_fee_msat,
 				claim_from_onchain_tx,
 				outbound_amount_forwarded_msat,
-				..
 			} => {
+				let event = Event::PaymentForwarded {
+					prev_channel_id: prev_channel_id.expect("prev_channel_id expected for events generated by LDK versions greater than 0.0.107."),
+					next_channel_id: next_channel_id.expect("next_channel_id expected for events generated by LDK versions greater than 0.0.107."),
+					prev_user_channel_id: prev_user_channel_id.map(UserChannelId),
+					next_user_channel_id: next_user_channel_id.map(UserChannelId),
+					total_fee_earned_msat,
+					skimmed_fee_msat,
+					claim_from_onchain_tx,
+					outbound_amount_forwarded_msat,
+				};
+				self.event_queue.add_event(event).map_err(|e| {
+					log_error!(self.logger, "Failed to push to event queue: {}", e);
+					ReplayEvent()
+				})?;
+
 				let read_only_network_graph = self.network_graph.read_only();
 				let nodes = read_only_network_graph.nodes();
 				let channels = self.channel_manager.list_channels();

tests/integration_tests_rust.rs

@@ -192,6 +192,9 @@ fn multi_hop_sending() {
 	let invoice = nodes[4].bolt11_payment().receive(2_500_000, &"asdf", 9217).unwrap();
 	nodes[0].bolt11_payment().send(&invoice, Some(sending_params)).unwrap();
 
+	expect_event!(nodes[1], PaymentForwarded);
+	expect_event!(nodes[2], PaymentForwarded);
+
 	let payment_id = expect_payment_received_event!(&nodes[4], 2_500_000);
 	let fee_paid_msat = Some(2000);
 	expect_payment_successful_event!(nodes[0], payment_id, Some(fee_paid_msat));