Add MPP receive timeout handling

Author: dunxen

lightning/src/ln/channelmanager.rs

@@ -441,6 +441,7 @@ struct ClaimableHTLC {
 	cltv_expiry: u32,
 	value: u64,
 	onion_payload: OnionPayload,
+	timer_ticks: u8,
 }
 
 /// A payment identifier used to uniquely identify a payment to LDK.
@@ -1148,6 +1149,9 @@ const CHECK_CLTV_EXPIRY_SANITY_2: u32 = MIN_CLTV_EXPIRY_DELTA as u32 - LATENCY_G
 /// pending HTLCs in flight.
 pub(crate) const PAYMENT_EXPIRY_BLOCKS: u32 = 3;
 
+/// The number of ticks of [`ChannelManager::timer_tick_occurred`] until expiry of incomplete MPPs
+pub(crate) const MPP_TIMEOUT_TICKS: u8 = 3;
+
 /// Information needed for constructing an invoice route hint for this channel.
 #[derive(Clone, Debug, PartialEq)]
 pub struct CounterpartyForwardingInfo {
@@ -3326,6 +3330,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 										phantom_shared_secret,
 									},
 									value: amt_to_forward,
+									timer_ticks: 0,
 									cltv_expiry,
 									onion_payload,
 								};
@@ -3620,6 +3625,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 			let new_feerate = self.fee_estimator.get_est_sat_per_1000_weight(ConfirmationTarget::Normal);
 
 			let mut handle_errors = Vec::new();
+			let mut timed_out_mpp_htlcs = Vec::new();
 			{
 				let mut channel_state_lock = self.channel_state.lock().unwrap();
 				let channel_state = &mut *channel_state_lock;
@@ -3668,6 +3674,28 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 
 					true
 				});
+
+				channel_state.claimable_htlcs.retain(|payment_hash, htlcs| {
+					if htlcs.is_empty() { return false }
+					if let OnionPayload::Invoice(ref final_hop_data) = htlcs[0].onion_payload {
+						// Check if we've received all the parts we need for an MPP (the value of the parts adds to total_msat).
+						// In this case we're not going to handle any timeouts of the parts here.
+						if final_hop_data.total_msat == htlcs.iter().fold(0, |total, htlc| total + htlc.value) {
+							return true;
+						} else if !htlcs.into_iter().all(|htlc| {
+							htlc.timer_ticks += 1;
+							return htlc.timer_ticks < MPP_TIMEOUT_TICKS
+						}) {
+							timed_out_mpp_htlcs.extend(htlcs.into_iter().map(|htlc| (htlc.prev_hop.clone(), payment_hash.clone())));
+							return false;
+						}
+					}
+					true
+				});
+			}
+
+			for htlc_source in timed_out_mpp_htlcs.drain(..) {
+				self.fail_htlc_backwards_internal(self.channel_state.lock().unwrap(), HTLCSource::PreviousHopData(htlc_source.0), &htlc_source.1, HTLCFailReason::Reason { failure_code: 23, data: Vec::new() });
 			}
 
 			for (err, counterparty_node_id) in handle_errors.drain(..) {
@@ -6233,6 +6261,7 @@ impl Readable for ClaimableHTLC {
 		};
 		Ok(Self {
 			prev_hop: prev_hop.0.unwrap(),
+			timer_ticks: 0,
 			value,
 			onion_payload,
 			cltv_expiry,

lightning/src/ln/functional_tests.rs

@@ -55,6 +55,8 @@ use sync::{Arc, Mutex};
 use ln::functional_test_utils::*;
 use ln::chan_utils::CommitmentTransaction;
 
+use crate::ln::channelmanager::MPP_TIMEOUT_TICKS;
+
 #[test]
 fn test_insane_channel_opens() {
 	// Stand up a network of 2 nodes
@@ -9689,3 +9691,46 @@ fn test_max_dust_htlc_exposure() {
 	do_test_max_dust_htlc_exposure(false, ExposureEvent::AtUpdateFeeOutbound, false);
 	do_test_max_dust_htlc_exposure(false, ExposureEvent::AtUpdateFeeOutbound, true);
 }
+
+#[test]
+fn test_mpp_receive_timeout() {
+	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 chan_id = create_announced_chan_between_nodes(&nodes, 0, 1, InitFeatures::known(), InitFeatures::known()).0.contents.short_channel_id;
+
+	let (mut route, payment_hash, _payment_preimage, payment_secret) = get_route_and_payment_hash!(&nodes[0], nodes[1], 100000);
+	let path = route.paths[0].clone();
+	route.paths.push(path);
+	route.paths[0][0].pubkey = nodes[1].node.get_our_node_id();
+	route.paths[0][0].short_channel_id = chan_id;
+
+	let cur_height = CHAN_CONFIRM_DEPTH + 1; // route_payment calls send_payment, which adds 1 to the current height. So we do the same here to match.
+	let payment_id = PaymentId([42; 32]);
+
+	nodes[0].node.send_payment_along_path(&route.paths[0], &route.payment_params, &payment_hash, &Some(payment_secret), 200000, cur_height, payment_id, &None).unwrap();
+	check_added_monitors!(nodes[0], 1);
+	let mut events = nodes[0].node.get_and_clear_pending_msg_events();
+	assert_eq!(events.len(), 1);
+
+	// Now do the relevant commitment_signed/RAA dances along the path, noting that the final
+	// hop should *not* yet generate any PaymentReceived event(s).
+	pass_along_path(&nodes[0], &[&nodes[1]], 100000, payment_hash, Some(payment_secret), events.drain(..).next().unwrap(), false, None);
+
+	for _ in 0..MPP_TIMEOUT_TICKS {
+		nodes[1].node.timer_tick_occurred();
+	}
+
+	expect_pending_htlcs_forwardable!(nodes[1]);
+
+	let htlc_fail_updates = get_htlc_update_msgs!(nodes[1], nodes[0].node.get_our_node_id());
+	assert_eq!(htlc_fail_updates.update_fail_htlcs.len(), 1);
+
+	nodes[0].node.handle_update_fail_htlc(&nodes[1].node.get_our_node_id(), &htlc_fail_updates.update_fail_htlcs[0]);
+	check_added_monitors!(nodes[1], 1);
+
+	commitment_signed_dance!(nodes[0], nodes[1], htlc_fail_updates.commitment_signed, true, true);
+	expect_payment_failed!(nodes[0], payment_hash, false, 23, &[][..]);
+}