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fix: SCID preference for outbound payments on spliced channel #4376

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fix: SCID preference for outbound payments on spliced channel #4376

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b7a50a6
test: use route SCID instead of channel announcement SCID
okekefrancis112 Feb 5, 2026
a153dbe
fix: prefer outbound SCID alias over real SCID for spliced channels
okekefrancis112 Feb 5, 2026
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6 changes: 3 additions & 3 deletions lightning/src/ln/channel_state.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -499,12 +499,12 @@ impl ChannelDetails {
/// This should be used in [`Route`]s to describe the first hop or in other contexts where
/// we're sending or forwarding a payment outbound over this channel.
///
/// This is either the [`ChannelDetails::short_channel_id`], if set, or the
/// [`ChannelDetails::outbound_scid_alias`]. See those for more information.
/// This is either the [`ChannelDetails::outbound_scid_alias`], if set, or the
/// [`ChannelDetails::short_channel_id`]. See those for more information.
///
/// [`Route`]: crate::routing::router::Route
pub fn get_outbound_payment_scid(&self) -> Option<u64> {
self.short_channel_id.or(self.outbound_scid_alias)
self.outbound_scid_alias.or(self.short_channel_id)
}

/// Gets the funding output for this channel, if available.
Expand Down
38 changes: 19 additions & 19 deletions lightning/src/ln/onion_route_tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -419,7 +419,7 @@ fn test_fee_failures() {
// malleated the payment before forwarding, taking funds when they shouldn't have. However,
// because we ignore channel update contents, we will still blame the 2nd channel.
let (_, payment_hash, payment_secret) = get_payment_preimage_hash!(nodes[2]);
let short_channel_id = channels[1].0.contents.short_channel_id;
let short_channel_id = route.paths[0].hops[1].short_channel_id;
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@TheBlueMatt TheBlueMatt Feb 9, 2026

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Rather than pulling the expected scid value out of the route, can you instead pull the value out of the channel list?

run_onion_failure_test(
"fee_insufficient",
100,
Expand Down Expand Up @@ -510,7 +510,7 @@ fn test_onion_failure() {
};

// intermediate node failure
let short_channel_id = channels[1].0.contents.short_channel_id;
let short_channel_id = route.paths[0].hops[1].short_channel_id;
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@joostjager joostjager Feb 5, 2026

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I think there is some independent refactoring/correctness improvement here that could go in a separate commit?

The commit that makes the actual change can then also contain the test changes/additions that it requires.

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@okekefrancis112 okekefrancis112 Feb 5, 2026

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Alright, I will work on it and get back to you. @joostjager

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@okekefrancis112 okekefrancis112 Feb 5, 2026

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Hi @joostjager, I have made the fix and pushed. Can you help me review?

run_onion_failure_test(
"invalid_realm",
0,
Expand Down Expand Up @@ -552,7 +552,7 @@ fn test_onion_failure() {
);

// final node failure
let short_channel_id = channels[1].0.contents.short_channel_id;
let short_channel_id = route.paths[0].hops[1].short_channel_id;
run_onion_failure_test(
"invalid_realm",
3,
Expand Down Expand Up @@ -815,7 +815,7 @@ fn test_onion_failure() {

// Our immediate peer sent UpdateFailMalformedHTLC because it couldn't understand the onion in
// the UpdateAddHTLC that we sent.
let short_channel_id = channels[0].0.contents.short_channel_id;
let short_channel_id = route.paths[0].hops[0].short_channel_id;
run_onion_failure_test(
"invalid_onion_version",
0,
Expand Down Expand Up @@ -870,7 +870,7 @@ fn test_onion_failure() {
Some(HTLCHandlingFailureType::InvalidOnion),
);

let short_channel_id = channels[1].0.contents.short_channel_id;
let short_channel_id = route.paths[0].hops[1].short_channel_id;
let chan_update = ChannelUpdate::dummy(short_channel_id);

let mut err_data = Vec::new();
Expand Down Expand Up @@ -941,7 +941,7 @@ fn test_onion_failure() {
Some(next_hop_failure.clone()),
);

let short_channel_id = channels[1].0.contents.short_channel_id;
let short_channel_id = route.paths[0].hops[1].short_channel_id;
run_onion_failure_test_with_fail_intercept(
"permanent_channel_failure",
100,
Expand Down Expand Up @@ -974,7 +974,7 @@ fn test_onion_failure() {
Some(next_hop_failure.clone()),
);

let short_channel_id = channels[1].0.contents.short_channel_id;
let short_channel_id = route.paths[0].hops[1].short_channel_id;
run_onion_failure_test_with_fail_intercept(
"required_channel_feature_missing",
100,
Expand Down Expand Up @@ -1026,7 +1026,7 @@ fn test_onion_failure() {
Some(HTLCHandlingFailureType::InvalidForward { requested_forward_scid: short_channel_id }),
);

let short_channel_id = channels[1].0.contents.short_channel_id;
let short_channel_id = route.paths[0].hops[1].short_channel_id;
let amt_to_forward = {
let (per_peer_state, mut peer_state);
let chan = get_channel_ref!(nodes[1], nodes[2], per_peer_state, peer_state, channels[1].2);
Expand Down Expand Up @@ -1064,7 +1064,7 @@ fn test_onion_failure() {

// We ignore channel update contents in onion errors, so will blame the 2nd channel even though
// the first node is the one that messed up.
let short_channel_id = channels[1].0.contents.short_channel_id;
let short_channel_id = route.paths[0].hops[1].short_channel_id;
run_onion_failure_test(
"fee_insufficient",
100,
Expand All @@ -1083,7 +1083,7 @@ fn test_onion_failure() {
Some(next_hop_failure.clone()),
);

let short_channel_id = channels[1].0.contents.short_channel_id;
let short_channel_id = route.paths[0].hops[1].short_channel_id;
run_onion_failure_test(
"incorrect_cltv_expiry",
100,
Expand All @@ -1103,7 +1103,7 @@ fn test_onion_failure() {
Some(next_hop_failure.clone()),
);

let short_channel_id = channels[1].0.contents.short_channel_id;
let short_channel_id = route.paths[0].hops[1].short_channel_id;
run_onion_failure_test(
"expiry_too_soon",
100,
Expand Down Expand Up @@ -1190,7 +1190,7 @@ fn test_onion_failure() {
true,
Some(LocalHTLCFailureReason::FinalIncorrectCLTVExpiry),
None,
Some(channels[1].0.contents.short_channel_id),
Some(route.paths[0].hops[1].short_channel_id),
Some(HTLCHandlingFailureType::Receive { payment_hash }),
);

Expand Down Expand Up @@ -1220,11 +1220,11 @@ fn test_onion_failure() {
true,
Some(LocalHTLCFailureReason::FinalIncorrectHTLCAmount),
None,
Some(channels[1].0.contents.short_channel_id),
Some(route.paths[0].hops[1].short_channel_id),
Some(HTLCHandlingFailureType::Receive { payment_hash }),
);

let short_channel_id = channels[1].0.contents.short_channel_id;
let short_channel_id = route.paths[0].hops[1].short_channel_id;
run_onion_failure_test(
"channel_disabled",
100,
Expand Down Expand Up @@ -1386,7 +1386,7 @@ fn test_onion_failure() {
node_id: route.paths[0].hops[1].pubkey,
is_permanent: true,
}),
Some(channels[1].0.contents.short_channel_id),
Some(route.paths[0].hops[1].short_channel_id),
None,
);

Expand Down Expand Up @@ -1455,10 +1455,10 @@ fn test_onion_failure() {
true,
Some(LocalHTLCFailureReason::TemporaryChannelFailure),
Some(NetworkUpdate::ChannelFailure {
short_channel_id: channels[1].0.contents.short_channel_id,
short_channel_id: route.paths[0].hops[1].short_channel_id,
is_permanent: false,
}),
Some(channels[1].0.contents.short_channel_id),
Some(route.paths[0].hops[1].short_channel_id),
Some(next_hop_failure.clone()),
);
run_onion_failure_test_with_fail_intercept(
Expand Down Expand Up @@ -1505,10 +1505,10 @@ fn test_onion_failure() {
true,
Some(LocalHTLCFailureReason::TemporaryChannelFailure),
Some(NetworkUpdate::ChannelFailure {
short_channel_id: channels[1].0.contents.short_channel_id,
short_channel_id: route.paths[0].hops[1].short_channel_id,
is_permanent: false,
}),
Some(channels[1].0.contents.short_channel_id),
Some(route.paths[0].hops[1].short_channel_id),
None,
);
run_onion_failure_test(
Expand Down
122 changes: 70 additions & 52 deletions lightning/src/ln/payment_tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -247,12 +247,18 @@ fn mpp_retry_overpay() {
get_route_and_payment_hash!(nodes[0], nodes[3], payment_params, amt_msat, max_fee);

// Check we overpay on the second path which we're about to fail.
// Find which path goes through each node (paths may be in any order).
let (path_to_b_idx, path_to_c_idx) =
if route.paths[0].hops[0].pubkey == node_b_id { (0, 1) } else { (1, 0) };

assert_eq!(chan_1_update.contents.fee_proportional_millionths, 0);
let overpaid_amount_1 = route.paths[0].fee_msat() as u32 - chan_1_update.contents.fee_base_msat;
let overpaid_amount_1 =
route.paths[path_to_b_idx].fee_msat() as u32 - chan_1_update.contents.fee_base_msat;
assert_eq!(overpaid_amount_1, 0);

assert_eq!(chan_2_update.contents.fee_proportional_millionths, 0);
let overpaid_amount_2 = route.paths[1].fee_msat() as u32 - chan_2_update.contents.fee_base_msat;
let overpaid_amount_2 =
route.paths[path_to_c_idx].fee_msat() as u32 - chan_2_update.contents.fee_base_msat;

let total_overpaid_amount = overpaid_amount_1 + overpaid_amount_2;

Expand Down Expand Up @@ -301,11 +307,12 @@ fn mpp_retry_overpay() {
send_payment(&nodes[3], &[&nodes[2]], 38_000_000);

// Retry the second half of the payment and make sure it succeeds.
let first_path_value = route.paths[0].final_value_msat();
assert_eq!(first_path_value, 36_000_000);
// The path to node B (path_to_b_idx) succeeded with 36M; remove it so we retry only the C path.
let succeeded_path_value = route.paths[path_to_b_idx].final_value_msat();
assert_eq!(succeeded_path_value, 36_000_000);

route.paths.remove(0);
route_params.final_value_msat -= first_path_value;
route.paths.remove(path_to_b_idx);
route_params.final_value_msat -= succeeded_path_value;
let chan_4_scid = chan_4_update.contents.short_channel_id;
route_params.payment_params.previously_failed_channels.push(chan_4_scid);
// Check the remaining max total routing fee for the second attempt accounts only for 1_000 msat
Expand Down Expand Up @@ -1781,13 +1788,32 @@ fn preflight_probes_yield_event() {
.unwrap();

let recv_value = 50_000_000;
let route_params = RouteParameters::from_payment_params_and_value(payment_params, recv_value);
let res = nodes[0].node.send_preflight_probes(route_params, None).unwrap();
let route_params =
RouteParameters::from_payment_params_and_value(payment_params.clone(), recv_value);

// Compute the route first to determine path ordering (probe results follow route path order).
let node_0_id = nodes[0].node.get_our_node_id();
let node_1_id = nodes[1].node.get_our_node_id();
let usable_channels = nodes[0].node.list_usable_channels();
let first_hops = usable_channels.iter().collect::<Vec<_>>();
let inflight_htlcs = nodes[0].node.compute_inflight_htlcs();
let route = nodes[0]
.router
.router
.find_route(&node_0_id, &route_params, Some(&first_hops), inflight_htlcs)
.unwrap();

let expected_route: &[(&[&Node], PaymentHash)] =
&[(&[&nodes[1], &nodes[3]], res[0].0), (&[&nodes[2], &nodes[3]], res[1].0)];
// Determine which path index goes to node 1 vs node 2
let (path_to_1_idx, path_to_2_idx) =
if route.paths[0].hops[0].pubkey == node_1_id { (0, 1) } else { (1, 0) };

assert_eq!(res.len(), expected_route.len());
let res = nodes[0].node.send_preflight_probes(route_params, None).unwrap();
assert_eq!(res.len(), 2);

let expected_route: &[(&[&Node], PaymentHash)] = &[
(&[&nodes[1], &nodes[3]], res[path_to_1_idx].0),
(&[&nodes[2], &nodes[3]], res[path_to_2_idx].0),
];

send_probe_along_route(&nodes[0], expected_route);

Expand Down Expand Up @@ -2029,29 +2055,40 @@ fn test_trivial_inflight_htlc_tracking() {
// Send and claim the payment. Inflight HTLCs should be empty.
let (_, payment_hash, _, payment_id) = send_payment(&nodes[0], &[&nodes[1], &nodes[2]], 500000);
let inflight_htlcs = node_chanmgrs[0].compute_inflight_htlcs();
{
let mut per_peer_lock;
let mut peer_state_lock;
let channel_1 =
get_channel_ref!(&nodes[0], nodes[1], per_peer_lock, peer_state_lock, chan_1_id);

// Inflight HTLCs are tracked by the SCID used in routes:
// - First hop uses alias via get_outbound_payment_scid()
// - Subsequent hops use the real SCID from gossip/network graph
let chan_1_scid = nodes[0]
.node
.list_channels()
.iter()
.find(|c| c.channel_id == chan_1_id)
.unwrap()
.get_outbound_payment_scid()
.unwrap();
let chan_2_scid = nodes[1]
.node
.list_channels()
.iter()
.find(|c| c.channel_id == chan_2_id)
.unwrap()
.short_channel_id
.unwrap();

{
let chan_1_used_liquidity = inflight_htlcs.used_liquidity_msat(
&NodeId::from_pubkey(&node_a_id),
&NodeId::from_pubkey(&node_b_id),
channel_1.funding().get_short_channel_id().unwrap(),
chan_1_scid,
);
assert_eq!(chan_1_used_liquidity, None);
}
{
let mut per_peer_lock;
let mut peer_state_lock;
let channel_2 =
get_channel_ref!(&nodes[1], nodes[2], per_peer_lock, peer_state_lock, chan_2_id);

let chan_2_used_liquidity = inflight_htlcs.used_liquidity_msat(
&NodeId::from_pubkey(&node_b_id),
&NodeId::from_pubkey(&node_c_id),
channel_2.funding().get_short_channel_id().unwrap(),
chan_2_scid,
);

assert_eq!(chan_2_used_liquidity, None);
Expand All @@ -2071,29 +2108,19 @@ fn test_trivial_inflight_htlc_tracking() {
route_payment(&nodes[0], &[&nodes[1], &nodes[2]], 500000);
let inflight_htlcs = node_chanmgrs[0].compute_inflight_htlcs();
{
let mut per_peer_lock;
let mut peer_state_lock;
let channel_1 =
get_channel_ref!(&nodes[0], nodes[1], per_peer_lock, peer_state_lock, chan_1_id);

let chan_1_used_liquidity = inflight_htlcs.used_liquidity_msat(
&NodeId::from_pubkey(&node_a_id),
&NodeId::from_pubkey(&node_b_id),
channel_1.funding().get_short_channel_id().unwrap(),
chan_1_scid,
);
// First hop accounts for expected 1000 msat fee
assert_eq!(chan_1_used_liquidity, Some(501000));
}
{
let mut per_peer_lock;
let mut peer_state_lock;
let channel_2 =
get_channel_ref!(&nodes[1], nodes[2], per_peer_lock, peer_state_lock, chan_2_id);

let chan_2_used_liquidity = inflight_htlcs.used_liquidity_msat(
&NodeId::from_pubkey(&node_b_id),
&NodeId::from_pubkey(&node_c_id),
channel_2.funding().get_short_channel_id().unwrap(),
chan_2_scid,
);

assert_eq!(chan_2_used_liquidity, Some(500000));
Expand All @@ -2113,28 +2140,18 @@ fn test_trivial_inflight_htlc_tracking() {

let inflight_htlcs = node_chanmgrs[0].compute_inflight_htlcs();
{
let mut per_peer_lock;
let mut peer_state_lock;
let channel_1 =
get_channel_ref!(&nodes[0], nodes[1], per_peer_lock, peer_state_lock, chan_1_id);

let chan_1_used_liquidity = inflight_htlcs.used_liquidity_msat(
&NodeId::from_pubkey(&node_a_id),
&NodeId::from_pubkey(&node_b_id),
channel_1.funding().get_short_channel_id().unwrap(),
chan_1_scid,
);
assert_eq!(chan_1_used_liquidity, None);
}
{
let mut per_peer_lock;
let mut peer_state_lock;
let channel_2 =
get_channel_ref!(&nodes[1], nodes[2], per_peer_lock, peer_state_lock, chan_2_id);

let chan_2_used_liquidity = inflight_htlcs.used_liquidity_msat(
&NodeId::from_pubkey(&node_b_id),
&NodeId::from_pubkey(&node_c_id),
channel_2.funding().get_short_channel_id().unwrap(),
chan_2_scid,
);
assert_eq!(chan_2_used_liquidity, None);
}
Expand Down Expand Up @@ -2176,15 +2193,16 @@ fn test_holding_cell_inflight_htlcs() {
let inflight_htlcs = node_chanmgrs[0].compute_inflight_htlcs();

{
let mut per_peer_lock;
let mut peer_state_lock;
let channel =
get_channel_ref!(&nodes[0], nodes[1], per_peer_lock, peer_state_lock, channel_id);
// Inflight HTLCs are tracked by the SCID used in routes, which is now the alias.
// Use the route's SCID (from get_outbound_payment_scid) to query inflight liquidity.
let chan_details =
nodes[0].node.list_channels().into_iter().find(|c| c.channel_id == channel_id).unwrap();
let route_scid = chan_details.get_outbound_payment_scid().unwrap();

let used_liquidity = inflight_htlcs.used_liquidity_msat(
&NodeId::from_pubkey(&node_a_id),
&NodeId::from_pubkey(&node_b_id),
channel.funding().get_short_channel_id().unwrap(),
route_scid,
);

assert_eq!(used_liquidity, Some(2000000));
Expand Down
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