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Enable decoding new incoming HTLC onions when fully committed
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This commit ensures all new incoming HTLCs going forward will have their
onion decoded when they become fully committed to decide how we should
proceed with each one. As a result, we'll obtain `HTLCHandlingFailed`
events for _any_ failed HTLC that comes across a channel.

We will now start writing channels with the new serialization version
(4), and we will still be able to downgrade back to the commit that
introduced it since reading version 4 is supported.

Note that existing pending inbound HTLCs may already have their
resolution if they were received in a previous version of LDK. We must
support those until we no longer allow downgrading beyond this commit.
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@wpaulino
wpaulino committed Mar 29, 2024
1 parent da7391f commit 11c18ec
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Showing 11 changed files with 327 additions and 273 deletions.
6 changes: 4 additions & 2 deletions lightning/src/events/mod.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1021,9 +1021,11 @@ pub enum Event {
/// * When an unknown SCID is requested for forwarding a payment.
/// * Expected MPP amount has already been reached
/// * The HTLC has timed out
/// * The HTLC failed to meet the forwarding requirements (i.e. insufficient fees paid, or a
/// CLTV that is too soon)
///
/// This event, however, does not get generated if an HTLC fails to meet the forwarding
/// requirements (i.e. insufficient fees paid, or a CLTV that is too soon).
/// The list above is not meant to cover all scenarios. This event should be expected for each
/// incoming HTLC that has been fully committed but we failed to handle.
HTLCHandlingFailed {
/// The channel over which the HTLC was received.
prev_channel_id: ChannelId,
Expand Down
64 changes: 54 additions & 10 deletions lightning/src/ln/blinded_payment_tests.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -274,8 +274,10 @@ fn do_forward_checks_failure(check: ForwardCheckFail, intro_fails: bool) {
// We need the session priv to construct a bogus onion packet later.
*nodes[0].keys_manager.override_random_bytes.lock().unwrap() = Some([3; 32]);
create_announced_chan_between_nodes_with_value(&nodes, 0, 1, 1_000_000, 0);
let chan_upd_1_2 = create_announced_chan_between_nodes_with_value(&nodes, 1, 2, 1_000_000, 0).0.contents;
let chan_upd_2_3 = create_announced_chan_between_nodes_with_value(&nodes, 2, 3, 1_000_000, 0).0.contents;
let chan_1_2 = create_announced_chan_between_nodes_with_value(&nodes, 1, 2, 1_000_000, 0);
let chan_upd_1_2 = chan_1_2.0.contents;
let chan_2_3 = create_announced_chan_between_nodes_with_value(&nodes, 2, 3, 1_000_000, 0);
let chan_upd_2_3 = chan_2_3.0.contents;

let amt_msat = 5000;
let (_, payment_hash, payment_secret) = get_payment_preimage_hash(&nodes[3], Some(amt_msat), None);
Expand Down Expand Up @@ -327,18 +329,27 @@ fn do_forward_checks_failure(check: ForwardCheckFail, intro_fails: bool) {
check_added_monitors!(nodes[1], 0);
do_commitment_signed_dance(&nodes[1], &nodes[0], &updates_0_1.commitment_signed, true, true);

expect_pending_htlcs_forwardable!(nodes[1]);
check_added_monitors!(nodes[1], 1);

if intro_fails {
let mut updates = get_htlc_update_msgs!(nodes[1], nodes[0].node.get_our_node_id());
nodes[0].node.handle_update_fail_htlc(&nodes[1].node.get_our_node_id(), &updates.update_fail_htlcs[0]);
do_commitment_signed_dance(&nodes[0], &nodes[1], &updates.commitment_signed, false, false);
let failed_destination = match check {
ForwardCheckFail::InboundOnionCheck => HTLCDestination::InvalidOnion,
ForwardCheckFail::ForwardPayloadEncodedAsReceive => HTLCDestination::FailedPayment { payment_hash },
ForwardCheckFail::OutboundChannelCheck =>
HTLCDestination::NextHopChannel { node_id: Some(nodes[2].node.get_our_node_id()), channel_id: chan_1_2.2 },
};
expect_htlc_handling_failed_destinations!(
nodes[1].node.get_and_clear_pending_events(), &[failed_destination.clone()]
);
expect_payment_failed_conditions(&nodes[0], payment_hash, false,
PaymentFailedConditions::new().expected_htlc_error_data(INVALID_ONION_BLINDING, &[0; 32]));
return
}

expect_pending_htlcs_forwardable!(nodes[1]);
check_added_monitors!(nodes[1], 1);

let mut updates_1_2 = get_htlc_update_msgs!(nodes[1], nodes[2].node.get_our_node_id());
let mut update_add = &mut updates_1_2.update_add_htlcs[0];

Expand All @@ -348,6 +359,17 @@ fn do_forward_checks_failure(check: ForwardCheckFail, intro_fails: bool) {
check_added_monitors!(nodes[2], 0);
do_commitment_signed_dance(&nodes[2], &nodes[1], &updates_1_2.commitment_signed, true, true);

expect_pending_htlcs_forwardable!(nodes[2]);
let failed_destination = match check {
ForwardCheckFail::InboundOnionCheck|ForwardCheckFail::ForwardPayloadEncodedAsReceive => HTLCDestination::InvalidOnion,
ForwardCheckFail::OutboundChannelCheck =>
HTLCDestination::NextHopChannel { node_id: Some(nodes[3].node.get_our_node_id()), channel_id: chan_2_3.2 },
};
expect_htlc_handling_failed_destinations!(
nodes[2].node.get_and_clear_pending_events(), &[failed_destination.clone()]
);
check_added_monitors!(nodes[2], 1);

let mut updates = get_htlc_update_msgs!(nodes[2], nodes[1].node.get_our_node_id());
let update_malformed = &mut updates.update_fail_malformed_htlcs[0];
assert_eq!(update_malformed.failure_code, INVALID_ONION_BLINDING);
Expand Down Expand Up @@ -407,7 +429,10 @@ fn failed_backwards_to_intro_node() {
nodes[2].node.handle_update_add_htlc(&nodes[1].node.get_our_node_id(), &payment_event.msgs[0]);
check_added_monitors!(nodes[2], 0);
do_commitment_signed_dance(&nodes[2], &nodes[1], &payment_event.commitment_msg, true, true);
nodes[2].node.process_pending_htlc_forwards();

expect_pending_htlcs_forwardable!(nodes[2]);
expect_htlc_handling_failed_destinations!(nodes[2].node.get_and_clear_pending_events(), &[HTLCDestination::InvalidOnion]);
check_added_monitors(&nodes[2], 1);

let mut updates = get_htlc_update_msgs!(nodes[2], nodes[1].node.get_our_node_id());
let mut update_malformed = &mut updates.update_fail_malformed_htlcs[0];
Expand Down Expand Up @@ -483,7 +508,7 @@ fn do_forward_fail_in_process_pending_htlc_fwds(check: ProcessPendingHTLCsCheck,
// intro node will error backwards.
$curr_node.node.peer_disconnected(&$next_node.node.get_our_node_id());
expect_pending_htlcs_forwardable!($curr_node);
expect_pending_htlcs_forwardable_and_htlc_handling_failed_ignore!($curr_node,
expect_htlc_handling_failed_destinations!($curr_node.node.get_and_clear_pending_events(),
vec![HTLCDestination::NextHopChannel { node_id: Some($next_node.node.get_our_node_id()), channel_id: $failed_chan_id }]);
},
ProcessPendingHTLCsCheck::FwdChannelClosed => {
Expand All @@ -499,12 +524,12 @@ fn do_forward_fail_in_process_pending_htlc_fwds(check: ProcessPendingHTLCsCheck,
crate::events::Event::ChannelClosed { .. } => {},
_ => panic!("Unexpected event {:?}", events),
}
check_closed_broadcast(&$curr_node, 1, true);
check_added_monitors!($curr_node, 1);

$curr_node.node.process_pending_htlc_forwards();
expect_pending_htlcs_forwardable_and_htlc_handling_failed_ignore!($curr_node,
expect_htlc_handling_failed_destinations!($curr_node.node.get_and_clear_pending_events(),
vec![HTLCDestination::UnknownNextHop { requested_forward_scid: $failed_scid }]);
check_closed_broadcast(&$curr_node, 1, true);
check_added_monitors!($curr_node, 1);
$curr_node.node.process_pending_htlc_forwards();
},
}
Expand Down Expand Up @@ -590,6 +615,7 @@ fn do_blinded_intercept_payment(intercept_node_fails: bool) {
};
nodes[1].node.handle_update_add_htlc(&nodes[0].node.get_our_node_id(), &payment_event.msgs[0]);
commitment_signed_dance!(nodes[1], nodes[0], &payment_event.commitment_msg, false, true);
expect_pending_htlcs_forwardable!(nodes[1]);

let events = nodes[1].node.get_and_clear_pending_events();
assert_eq!(events.len(), 1);
Expand Down Expand Up @@ -891,13 +917,19 @@ fn do_multi_hop_receiver_fail(check: ReceiveCheckFail) {
nodes[2].node.handle_update_add_htlc(&nodes[1].node.get_our_node_id(), update_add);
check_added_monitors!(nodes[2], 0);
do_commitment_signed_dance(&nodes[2], &nodes[1], &payment_event_1_2.commitment_msg, true, true);
expect_pending_htlcs_forwardable!(nodes[2]);
expect_htlc_handling_failed_destinations!(nodes[2].node.get_and_clear_pending_events(), &[HTLCDestination::InvalidOnion]);
check_added_monitors(&nodes[2], 1);
},
ReceiveCheckFail::ReceiveRequirements => {
let update_add = &mut payment_event_1_2.msgs[0];
update_add.amount_msat -= 1;
nodes[2].node.handle_update_add_htlc(&nodes[1].node.get_our_node_id(), update_add);
check_added_monitors!(nodes[2], 0);
do_commitment_signed_dance(&nodes[2], &nodes[1], &payment_event_1_2.commitment_msg, true, true);
expect_pending_htlcs_forwardable!(nodes[2]);
expect_htlc_handling_failed_destinations!(nodes[2].node.get_and_clear_pending_events(), &[HTLCDestination::FailedPayment { payment_hash }]);
check_added_monitors(&nodes[2], 1);
},
ReceiveCheckFail::ChannelCheck => {
nodes[2].node.close_channel(&chan_id_1_2, &nodes[1].node.get_our_node_id()).unwrap();
Expand All @@ -911,6 +943,9 @@ fn do_multi_hop_receiver_fail(check: ReceiveCheckFail) {

nodes[2].node.handle_shutdown(&nodes[1].node.get_our_node_id(), &node_1_shutdown);
commitment_signed_dance!(nodes[2], nodes[1], (), false, true, false, false);
expect_pending_htlcs_forwardable!(nodes[2]);
expect_htlc_handling_failed_destinations!(nodes[2].node.get_and_clear_pending_events(), &[HTLCDestination::FailedPayment { payment_hash }]);
check_added_monitors(&nodes[2], 1);
},
ReceiveCheckFail::ProcessPendingHTLCsCheck => {
assert_eq!(payment_event_1_2.msgs[0].cltv_expiry, nodes[0].best_block_info().1 + 1 + excess_final_cltv_delta_opt.unwrap() as u32 + TEST_FINAL_CLTV);
Expand All @@ -926,6 +961,9 @@ fn do_multi_hop_receiver_fail(check: ReceiveCheckFail) {
nodes[2].node.handle_update_add_htlc(&nodes[1].node.get_our_node_id(), &payment_event_1_2.msgs[0]);
check_added_monitors!(nodes[2], 0);
do_commitment_signed_dance(&nodes[2], &nodes[1], &payment_event_1_2.commitment_msg, true, true);
expect_pending_htlcs_forwardable!(nodes[2]);
expect_htlc_handling_failed_destinations!(nodes[2].node.get_and_clear_pending_events(), &[HTLCDestination::FailedPayment { payment_hash }]);
check_added_monitors(&nodes[2], 1);
}
}

Expand Down Expand Up @@ -1126,6 +1164,12 @@ fn min_htlc() {
nodes[1].node.handle_update_add_htlc(&nodes[0].node.get_our_node_id(), &payment_event_0_1.msgs[0]);
check_added_monitors!(nodes[1], 0);
do_commitment_signed_dance(&nodes[1], &nodes[0], &payment_event_0_1.commitment_msg, true, true);
expect_pending_htlcs_forwardable!(nodes[1]);
expect_htlc_handling_failed_destinations!(
nodes[1].node.get_and_clear_pending_events(),
&[HTLCDestination::NextHopChannel { node_id: Some(nodes[2].node.get_our_node_id()), channel_id: chan_1_2.2 }]
);
check_added_monitors(&nodes[1], 1);
let mut updates = get_htlc_update_msgs!(nodes[1], nodes[0].node.get_our_node_id());
nodes[0].node.handle_update_fail_htlc(&nodes[1].node.get_our_node_id(), &updates.update_fail_htlcs[0]);
do_commitment_signed_dance(&nodes[0], &nodes[1], &updates.commitment_signed, false, false);
Expand Down
55 changes: 10 additions & 45 deletions lightning/src/ln/channel.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -4121,9 +4121,7 @@ impl<SP: Deref> Channel<SP> where
Ok(self.get_announcement_sigs(node_signer, chain_hash, user_config, best_block.height, logger))
}

pub fn update_add_htlc(
&mut self, msg: &msgs::UpdateAddHTLC, pending_forward_status: PendingHTLCStatus,
) -> Result<(), ChannelError> {
pub fn update_add_htlc(&mut self, msg: &msgs::UpdateAddHTLC) -> Result<(), ChannelError> {
if !matches!(self.context.channel_state, ChannelState::ChannelReady(_)) {
return Err(ChannelError::Close("Got add HTLC message when channel was not in an operational state".to_owned()));
}
Expand Down Expand Up @@ -4221,21 +4219,15 @@ impl<SP: Deref> Channel<SP> where
return Err(ChannelError::Close("Remote provided CLTV expiry in seconds instead of block height".to_owned()));
}

if self.context.channel_state.is_local_shutdown_sent() {
if let PendingHTLCStatus::Forward(_) = pending_forward_status {
panic!("ChannelManager shouldn't be trying to add a forwardable HTLC after we've started closing");
}
}

// Now update local state:
self.context.next_counterparty_htlc_id += 1;
self.context.pending_inbound_htlcs.push(InboundHTLCOutput {
htlc_id: msg.htlc_id,
amount_msat: msg.amount_msat,
payment_hash: msg.payment_hash,
cltv_expiry: msg.cltv_expiry,
state: InboundHTLCState::RemoteAnnounced(InboundHTLCResolution::Resolved {
pending_htlc_status: pending_forward_status
state: InboundHTLCState::RemoteAnnounced(InboundHTLCResolution::Pending {
update_add_htlc: msg.clone(),
}),
});
Ok(())
Expand Down Expand Up @@ -6118,7 +6110,7 @@ impl<SP: Deref> Channel<SP> where
};
let exposure_dust_limit_timeout_sats = htlc_timeout_dust_limit + self.context.counterparty_dust_limit_satoshis;
if msg.amount_msat / 1000 < exposure_dust_limit_timeout_sats {
let on_counterparty_tx_dust_htlc_exposure_msat = inbound_stats.on_counterparty_tx_dust_exposure_msat + outbound_stats.on_counterparty_tx_dust_exposure_msat + msg.amount_msat;
let on_counterparty_tx_dust_htlc_exposure_msat = inbound_stats.on_counterparty_tx_dust_exposure_msat + outbound_stats.on_counterparty_tx_dust_exposure_msat;
if on_counterparty_tx_dust_htlc_exposure_msat > max_dust_htlc_exposure_msat {
log_info!(logger, "Cannot accept value that would put our exposure to dust HTLCs at {} over the limit {} on counterparty commitment tx",
on_counterparty_tx_dust_htlc_exposure_msat, max_dust_htlc_exposure_msat);
Expand All @@ -6128,7 +6120,7 @@ impl<SP: Deref> Channel<SP> where

let exposure_dust_limit_success_sats = htlc_success_dust_limit + self.context.holder_dust_limit_satoshis;
if msg.amount_msat / 1000 < exposure_dust_limit_success_sats {
let on_holder_tx_dust_htlc_exposure_msat = inbound_stats.on_holder_tx_dust_exposure_msat + outbound_stats.on_holder_tx_dust_exposure_msat + msg.amount_msat;
let on_holder_tx_dust_htlc_exposure_msat = inbound_stats.on_holder_tx_dust_exposure_msat + outbound_stats.on_holder_tx_dust_exposure_msat;
if on_holder_tx_dust_htlc_exposure_msat > max_dust_htlc_exposure_msat {
log_info!(logger, "Cannot accept value that would put our exposure to dust HTLCs at {} over the limit {} on holder commitment tx",
on_holder_tx_dust_htlc_exposure_msat, max_dust_htlc_exposure_msat);
Expand Down Expand Up @@ -6162,11 +6154,11 @@ impl<SP: Deref> Channel<SP> where
// side, only on the sender's. Note that with anchor outputs we are no longer as
// sensitive to fee spikes, so we need to account for them.
let htlc_candidate = HTLCCandidate::new(msg.amount_msat, HTLCInitiator::RemoteOffered);
let mut remote_fee_cost_incl_stuck_buffer_msat = self.context.next_remote_commit_tx_fee_msat(htlc_candidate, Some(()));
let mut remote_fee_cost_incl_stuck_buffer_msat = self.context.next_remote_commit_tx_fee_msat(htlc_candidate, None);
if !self.context.get_channel_type().supports_anchors_zero_fee_htlc_tx() {
remote_fee_cost_incl_stuck_buffer_msat *= FEE_SPIKE_BUFFER_FEE_INCREASE_MULTIPLE;
}
if pending_remote_value_msat.saturating_sub(msg.amount_msat).saturating_sub(self.context.holder_selected_channel_reserve_satoshis * 1000).saturating_sub(anchor_outputs_value_msat) < remote_fee_cost_incl_stuck_buffer_msat {
if pending_remote_value_msat.saturating_sub(self.context.holder_selected_channel_reserve_satoshis * 1000).saturating_sub(anchor_outputs_value_msat) < remote_fee_cost_incl_stuck_buffer_msat {
log_info!(logger, "Attempting to fail HTLC due to fee spike buffer violation in channel {}. Rebalancing is required.", &self.context.channel_id());
return Err(("Fee spike buffer violation", 0x1000|7));
}
Expand Down Expand Up @@ -8370,18 +8362,7 @@ impl<SP: Deref> Writeable for Channel<SP> where SP::Target: SignerProvider {
// Note that we write out as if remove_uncommitted_htlcs_and_mark_paused had just been
// called.

let version_to_write = if self.context.pending_inbound_htlcs.iter().any(|htlc| match htlc.state {
InboundHTLCState::AwaitingRemoteRevokeToAnnounce(ref htlc_resolution)|
InboundHTLCState::AwaitingAnnouncedRemoteRevoke(ref htlc_resolution) => {
matches!(htlc_resolution, InboundHTLCResolution::Pending { .. })
},
_ => false,
}) {
SERIALIZATION_VERSION
} else {
MIN_SERIALIZATION_VERSION
};
write_ver_prefix!(writer, version_to_write, MIN_SERIALIZATION_VERSION);
write_ver_prefix!(writer, SERIALIZATION_VERSION, MIN_SERIALIZATION_VERSION);

// `user_id` used to be a single u64 value. In order to remain backwards compatible with
// versions prior to 0.0.113, the u128 is serialized as two separate u64 values. We write
Expand Down Expand Up @@ -8439,27 +8420,11 @@ impl<SP: Deref> Writeable for Channel<SP> where SP::Target: SignerProvider {
&InboundHTLCState::RemoteAnnounced(_) => unreachable!(),
&InboundHTLCState::AwaitingRemoteRevokeToAnnounce(ref htlc_resolution) => {
1u8.write(writer)?;
if version_to_write <= 3 {
if let InboundHTLCResolution::Resolved { pending_htlc_status } = htlc_resolution {
pending_htlc_status.write(writer)?;
} else {
panic!();
}
} else {
htlc_resolution.write(writer)?;
}
htlc_resolution.write(writer)?;
},
&InboundHTLCState::AwaitingAnnouncedRemoteRevoke(ref htlc_resolution) => {
2u8.write(writer)?;
if version_to_write <= 3 {
if let InboundHTLCResolution::Resolved { pending_htlc_status } = htlc_resolution {
pending_htlc_status.write(writer)?;
} else {
panic!();
}
} else {
htlc_resolution.write(writer)?;
}
htlc_resolution.write(writer)?;
},
&InboundHTLCState::Committed => {
3u8.write(writer)?;
Expand Down
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