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Merged
merged 2 commits into from
Nov 9, 2025
Merged

Allow counterparty tx_abort before handling initial commitment signed #4204

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0cdcf54
Support capturing `tx_abort` send within channel reestablish tests
wpaulino Nov 3, 2025
d282a47
Allow counterparty tx_abort before handling initial commitment signed
wpaulino Nov 3, 2025
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104 changes: 72 additions & 32 deletions lightning/src/ln/channel.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1654,7 +1654,7 @@ where
}
chan.context.channel_state.clear_local_stfu_sent();
chan.context.channel_state.clear_remote_stfu_sent();
if chan.should_reset_pending_splice_state() {
if chan.should_reset_pending_splice_state(false) {
// If there was a pending splice negotiation that failed due to disconnecting, we
// also take the opportunity to clean up our state.
let splice_funding_failed = chan.reset_pending_splice_state();
Expand Down Expand Up @@ -1775,7 +1775,7 @@ where
None
},
ChannelPhase::Funded(funded_channel) => {
if funded_channel.should_reset_pending_splice_state() {
if funded_channel.should_reset_pending_splice_state(false) {
funded_channel.reset_pending_splice_state()
} else {
debug_assert!(false, "We should never fail an interactive funding negotiation once we're exchanging tx_signatures");
Expand Down Expand Up @@ -1932,12 +1932,24 @@ where
(had_constructor, None)
},
ChannelPhase::Funded(funded_channel) => {
if funded_channel.has_pending_splice_awaiting_signatures() {
if funded_channel.has_pending_splice_awaiting_signatures()
&& funded_channel
.context()
.interactive_tx_signing_session
.as_ref()
.expect("We have a pending splice awaiting signatures")
.has_received_commitment_signed()
{
// We only force close once the counterparty tries to abort after committing to
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@TheBlueMatt TheBlueMatt Nov 9, 2025

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This implies that this is somehow a limitation in LDK, but it isn't, its a rather fundamental limitation of the protocol - if we have received the CS, the peer cannot know whether we have provided them with funding signatures, at which point cancelling the splice would be unsafe no matter the implementation in LDK.

// the splice via their initial `commitment_signed`. This is because our monitor
// state is updated with the post-splice commitment transaction upon receiving
// their `commitment_signed`, so we would need another monitor update to abandon
// it, which we don't currently support.
return Err(ChannelError::close(
"Received tx_abort while awaiting tx_signatures exchange".to_owned(),
));
}
if funded_channel.should_reset_pending_splice_state() {
if funded_channel.should_reset_pending_splice_state(true) {
let has_funding_negotiation = funded_channel
.pending_splice
.as_ref()
Expand Down Expand Up @@ -2681,19 +2693,6 @@ impl FundingNegotiation {
}

impl PendingFunding {
fn can_abandon_state(&self) -> bool {
self.funding_negotiation
.as_ref()
.map(|funding_negotiation| {
!matches!(funding_negotiation, FundingNegotiation::AwaitingSignatures { .. })
})
.unwrap_or_else(|| {
let has_negotiated_candidates = !self.negotiated_candidates.is_empty();
debug_assert!(has_negotiated_candidates);
!has_negotiated_candidates
})
}

fn check_get_splice_locked<SP: Deref>(
&mut self, context: &ChannelContext<SP>, confirmed_funding_index: usize, height: u32,
) -> Option<msgs::SpliceLocked>
Expand Down Expand Up @@ -6873,7 +6872,7 @@ pub struct SpliceFundingFailed {
}

macro_rules! maybe_create_splice_funding_failed {
($pending_splice: expr, $get: ident, $contributed_inputs_and_outputs: ident) => {{
($funded_channel: expr, $pending_splice: expr, $get: ident, $contributed_inputs_and_outputs: ident) => {{
$pending_splice
.and_then(|pending_splice| pending_splice.funding_negotiation.$get())
.filter(|funding_negotiation| funding_negotiation.is_initiator())
Expand All @@ -6895,10 +6894,12 @@ macro_rules! maybe_create_splice_funding_failed {
interactive_tx_constructor,
..
} => interactive_tx_constructor.$contributed_inputs_and_outputs(),
FundingNegotiation::AwaitingSignatures { .. } => {
debug_assert!(false);
(Vec::new(), Vec::new())
},
FundingNegotiation::AwaitingSignatures { .. } => $funded_channel
.context
.interactive_tx_signing_session
.$get()
.expect("We have a pending splice awaiting signatures")
.$contributed_inputs_and_outputs(),
};

SpliceFundingFailed {
Expand Down Expand Up @@ -6937,7 +6938,7 @@ where

fn maybe_fail_splice_negotiation(&mut self) -> Option<SpliceFundingFailed> {
if matches!(self.context.channel_state, ChannelState::ChannelReady(_)) {
if self.should_reset_pending_splice_state() {
if self.should_reset_pending_splice_state(false) {
self.reset_pending_splice_state()
} else {
match self.quiescent_action.take() {
Expand Down Expand Up @@ -7011,19 +7012,54 @@ where

/// Returns a boolean indicating whether we should reset the splice's
/// [`PendingFunding::funding_negotiation`].
fn should_reset_pending_splice_state(&self) -> bool {
fn should_reset_pending_splice_state(&self, counterparty_aborted: bool) -> bool {
self.pending_splice
.as_ref()
.map(|pending_splice| pending_splice.can_abandon_state())
.map(|pending_splice| {
pending_splice
.funding_negotiation
.as_ref()
.map(|funding_negotiation| {
let is_awaiting_signatures = matches!(
funding_negotiation,
FundingNegotiation::AwaitingSignatures { .. }
);
if counterparty_aborted {
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@jkczyz jkczyz Nov 5, 2025

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Why do we condition on counterparty_aborted? Would it be a problem if always do the new check?

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@wpaulino wpaulino Nov 6, 2025

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If we don't, then we would always reset the splice state when we haven't received their initial commitment_signed.

!is_awaiting_signatures
|| !self
.context()
.interactive_tx_signing_session
.as_ref()
.expect("We have a pending splice awaiting signatures")
.has_received_commitment_signed()
} else {
!is_awaiting_signatures
}
})
.unwrap_or_else(|| {
let has_negotiated_candidates =
!pending_splice.negotiated_candidates.is_empty();
debug_assert!(has_negotiated_candidates);
!has_negotiated_candidates
})
})
.unwrap_or(false)
}

fn reset_pending_splice_state(&mut self) -> Option<SpliceFundingFailed> {
debug_assert!(self.should_reset_pending_splice_state());
debug_assert!(self.context.interactive_tx_signing_session.is_none());
self.context.channel_state.clear_quiescent();
debug_assert!(self.should_reset_pending_splice_state(true));
debug_assert!(
self.context.interactive_tx_signing_session.is_none()
|| !self
.context
.interactive_tx_signing_session
.as_ref()
.expect("We have a pending splice awaiting signatures")
.has_received_commitment_signed()
);

let splice_funding_failed = maybe_create_splice_funding_failed!(
self,
self.pending_splice.as_mut(),
take,
into_contributed_inputs_and_outputs
Expand All @@ -7033,15 +7069,19 @@ where
self.pending_splice.take();
}

self.context.channel_state.clear_quiescent();
self.context.interactive_tx_signing_session.take();

splice_funding_failed
}

pub(super) fn maybe_splice_funding_failed(&self) -> Option<SpliceFundingFailed> {
if !self.should_reset_pending_splice_state() {
if !self.should_reset_pending_splice_state(false) {
return None;
}

maybe_create_splice_funding_failed!(
self,
self.pending_splice.as_ref(),
as_ref,
to_contributed_inputs_and_outputs
Expand Down Expand Up @@ -11996,7 +12036,7 @@ where
pub fn abandon_splice(
&mut self,
) -> Result<(msgs::TxAbort, Option<SpliceFundingFailed>), APIError> {
if self.should_reset_pending_splice_state() {
if self.should_reset_pending_splice_state(false) {
let tx_abort =
msgs::TxAbort { channel_id: self.context.channel_id(), data: Vec::new() };
let splice_funding_failed = self.reset_pending_splice_state();
Expand Down Expand Up @@ -14361,7 +14401,7 @@ where
}
channel_state.clear_local_stfu_sent();
channel_state.clear_remote_stfu_sent();
if self.should_reset_pending_splice_state()
if self.should_reset_pending_splice_state(false)
|| !self.has_pending_splice_awaiting_signatures()
{
// We shouldn't be quiescent anymore upon reconnecting if:
Expand Down Expand Up @@ -14735,7 +14775,7 @@ where
// We don't have to worry about resetting the pending `FundingNegotiation` because we
// can only read `FundingNegotiation::AwaitingSignatures` variants anyway.
let pending_splice =
self.pending_splice.as_ref().filter(|_| !self.should_reset_pending_splice_state());
self.pending_splice.as_ref().filter(|_| !self.should_reset_pending_splice_state(false));

write_tlv_fields!(writer, {
(0, self.context.announcement_sigs, option),
Expand Down
34 changes: 34 additions & 0 deletions lightning/src/ln/interactivetxs.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -350,6 +350,36 @@ impl ConstructedTransaction {
NegotiationError { reason, contributed_inputs, contributed_outputs }
}

fn to_contributed_inputs_and_outputs(&self) -> (Vec<BitcoinOutPoint>, Vec<TxOut>) {
let contributed_inputs = self
.tx
.input
.iter()
.zip(self.input_metadata.iter())
.enumerate()
.filter(|(_, (_, input))| input.is_local(self.holder_is_initiator))
.filter(|(index, _)| {
self.shared_input_index
.map(|shared_index| *index != shared_index as usize)
.unwrap_or(true)
})
.map(|(_, (txin, _))| txin.previous_output)
.collect();

let contributed_outputs = self
.tx
.output
.iter()
.zip(self.output_metadata.iter())
.enumerate()
.filter(|(_, (_, output))| output.is_local(self.holder_is_initiator))
.filter(|(index, _)| *index != self.shared_output_index as usize)
.map(|(_, (txout, _))| txout.clone())
.collect();

(contributed_inputs, contributed_outputs)
}

fn into_contributed_inputs_and_outputs(self) -> (Vec<BitcoinOutPoint>, Vec<TxOut>) {
let contributed_inputs = self
.tx
Expand Down Expand Up @@ -859,6 +889,10 @@ impl InteractiveTxSigningSession {
self.unsigned_tx.into_negotiation_error(reason)
}

pub(super) fn to_contributed_inputs_and_outputs(&self) -> (Vec<BitcoinOutPoint>, Vec<TxOut>) {
self.unsigned_tx.to_contributed_inputs_and_outputs()
}

pub(super) fn into_contributed_inputs_and_outputs(self) -> (Vec<BitcoinOutPoint>, Vec<TxOut>) {
self.unsigned_tx.into_contributed_inputs_and_outputs()
}
Expand Down
106 changes: 101 additions & 5 deletions lightning/src/ln/splicing_tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -395,17 +395,28 @@ fn do_test_splice_state_reset_on_disconnect(reload: bool) {
// retry later.
let chanmon_cfgs = create_chanmon_cfgs(2);
let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
let (persister_0a, persister_0b, persister_0c, persister_1a, persister_1b, persister_1c);
let (
persister_0a,
persister_0b,
persister_0c,
persister_0d,
persister_1a,
persister_1b,
persister_1c,
persister_1d,
);
let (
chain_monitor_0a,
chain_monitor_0b,
chain_monitor_0c,
chain_monitor_0d,
chain_monitor_1a,
chain_monitor_1b,
chain_monitor_1c,
chain_monitor_1d,
);
let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
let (node_0a, node_0b, node_0c, node_1a, node_1b, node_1c);
let (node_0a, node_0b, node_0c, node_0d, node_1a, node_1b, node_1c, node_1d);
let mut nodes = create_network(2, &node_cfgs, &node_chanmgrs);

let node_id_0 = nodes[0].node.get_our_node_id();
Expand Down Expand Up @@ -533,9 +544,56 @@ fn do_test_splice_state_reset_on_disconnect(reload: bool) {
reconnect_args.send_announcement_sigs = (true, true);
reconnect_nodes(reconnect_args);

// Attempt a splice negotiation that completes, (i.e. `tx_signatures` are exchanged). Reconnecting
// should not abort the negotiation or reset the splice state.
let splice_tx = splice_channel(&nodes[0], &nodes[1], channel_id, contribution);
nodes[0]
.node
.splice_channel(
&channel_id,
&node_id_1,
contribution.clone(),
FEERATE_FLOOR_SATS_PER_KW,
None,
)
.unwrap();

// Attempt a splice negotiation that ends before the initial `commitment_signed` messages are
// exchanged. The node missing the other's `commitment_signed` upon reconnecting should
// implicitly abort the negotiation and reset the splice state such that we're able to retry
// another splice later.
let stfu = get_event_msg!(nodes[0], MessageSendEvent::SendStfu, node_id_1);
nodes[1].node.handle_stfu(node_id_0, &stfu);
let stfu = get_event_msg!(nodes[1], MessageSendEvent::SendStfu, node_id_0);
nodes[0].node.handle_stfu(node_id_1, &stfu);

let splice_init = get_event_msg!(nodes[0], MessageSendEvent::SendSpliceInit, node_id_1);
nodes[1].node.handle_splice_init(node_id_0, &splice_init);
let splice_ack = get_event_msg!(nodes[1], MessageSendEvent::SendSpliceAck, node_id_0);
nodes[0].node.handle_splice_ack(node_id_1, &splice_ack);

let tx_add_input = get_event_msg!(nodes[0], MessageSendEvent::SendTxAddInput, node_id_1);
nodes[1].node.handle_tx_add_input(node_id_0, &tx_add_input);
let tx_complete = get_event_msg!(nodes[1], MessageSendEvent::SendTxComplete, node_id_0);
nodes[0].node.handle_tx_complete(node_id_1, &tx_complete);

let tx_add_output = get_event_msg!(nodes[0], MessageSendEvent::SendTxAddOutput, node_id_1);
nodes[1].node.handle_tx_add_output(node_id_0, &tx_add_output);
let tx_complete = get_event_msg!(nodes[1], MessageSendEvent::SendTxComplete, node_id_0);
nodes[0].node.handle_tx_complete(node_id_1, &tx_complete);

let tx_add_output = get_event_msg!(nodes[0], MessageSendEvent::SendTxAddOutput, node_id_1);
nodes[1].node.handle_tx_add_output(node_id_0, &tx_add_output);
let tx_complete = get_event_msg!(nodes[1], MessageSendEvent::SendTxComplete, node_id_0);
nodes[0].node.handle_tx_complete(node_id_1, &tx_complete);

let msg_events = nodes[0].node.get_and_clear_pending_msg_events();
assert_eq!(msg_events.len(), 2);
if let MessageSendEvent::SendTxComplete { .. } = &msg_events[0] {
} else {
panic!("Unexpected event");
}
if let MessageSendEvent::UpdateHTLCs { .. } = &msg_events[1] {
} else {
panic!("Unexpected event");
}

if reload {
let encoded_monitor_0 = get_monitor!(nodes[0], channel_id).encode();
Expand All @@ -561,6 +619,44 @@ fn do_test_splice_state_reset_on_disconnect(reload: bool) {
nodes[1].node.peer_disconnected(node_id_0);
}

let mut reconnect_args = ReconnectArgs::new(&nodes[0], &nodes[1]);
reconnect_args.send_channel_ready = (true, false);
reconnect_args.send_announcement_sigs = (true, true);
reconnect_args.send_tx_abort = (true, false);
reconnect_nodes(reconnect_args);

let tx_abort = get_event_msg!(nodes[0], MessageSendEvent::SendTxAbort, node_id_1);
nodes[1].node.handle_tx_abort(node_id_0, &tx_abort);
let _event = get_event!(nodes[0], Event::SpliceFailed);

// Attempt a splice negotiation that completes, (i.e. `tx_signatures` are exchanged). Reconnecting
// should not abort the negotiation or reset the splice state.
let splice_tx = splice_channel(&nodes[0], &nodes[1], channel_id, contribution);

if reload {
let encoded_monitor_0 = get_monitor!(nodes[0], channel_id).encode();
reload_node!(
nodes[0],
&nodes[0].node.encode(),
&[&encoded_monitor_0],
persister_0d,
chain_monitor_0d,
node_0d
);
let encoded_monitor_1 = get_monitor!(nodes[1], channel_id).encode();
reload_node!(
nodes[1],
&nodes[1].node.encode(),
&[&encoded_monitor_1],
persister_1d,
chain_monitor_1d,
node_1d
);
} else {
nodes[0].node.peer_disconnected(node_id_1);
nodes[1].node.peer_disconnected(node_id_0);
}

let mut reconnect_args = ReconnectArgs::new(&nodes[0], &nodes[1]);
reconnect_args.send_announcement_sigs = (true, true);
reconnect_nodes(reconnect_args);
Expand Down
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