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Introduce FundingContributionBuilder API #4516

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b4b3bfb
Remove wallet argument from FundingTemplate::splice_out
wpaulino Mar 19, 2026
b643ed9
Make holder_balance argument optional throughout FundingTemplate methods
wpaulino Apr 2, 2026
bfc21bb
Derive FundingContribution::net_value implicitly
wpaulino Apr 3, 2026
231d555
Introduce FundingBuilder for splice requests
wpaulino Apr 3, 2026
de4ccfb
Replace FundingTemplate contribution methods with FundingBuilder
wpaulino Apr 3, 2026
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20 changes: 5 additions & 15 deletions fuzz/src/chanmon_consistency.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1504,7 +1504,6 @@ pub fn do_test<Out: Output + MaybeSend + MaybeSync>(data: &[u8], out: Out) {
counterparty_node_id: &PublicKey,
channel_id: &ChannelId,
wallet: &TestWalletSource,
logger: Arc<dyn Logger + MaybeSend + MaybeSync>,
funding_feerate_sat_per_kw: FeeRate| {
// We conditionally splice out `MAX_STD_OUTPUT_DUST_LIMIT_SATOSHIS` only when the node
// has double the balance required to send a payment upon a `0xff` byte. We do this to
Expand All @@ -1524,12 +1523,7 @@ pub fn do_test<Out: Output + MaybeSend + MaybeSync>(data: &[u8], out: Out) {
value: Amount::from_sat(MAX_STD_OUTPUT_DUST_LIMIT_SATOSHIS),
script_pubkey: wallet.get_change_script().unwrap(),
}];
funding_template.splice_out_sync(
outputs,
feerate,
FeeRate::MAX,
&WalletSync::new(wallet, logger.clone()),
)
funding_template.splice_out(outputs, feerate, FeeRate::MAX)
});
};

Expand Down Expand Up @@ -2450,30 +2444,26 @@ pub fn do_test<Out: Output + MaybeSend + MaybeSync>(data: &[u8], out: Out) {
0xa4 => {
let cp_node_id = nodes[1].get_our_node_id();
let wallet = &wallets[0];
let logger = Arc::clone(&loggers[0]);
let feerate_sat_per_kw = fee_estimators[0].feerate_sat_per_kw();
splice_out(&nodes[0], &cp_node_id, &chan_a_id, wallet, logger, feerate_sat_per_kw);
splice_out(&nodes[0], &cp_node_id, &chan_a_id, wallet, feerate_sat_per_kw);
},
0xa5 => {
let cp_node_id = nodes[0].get_our_node_id();
let wallet = &wallets[1];
let logger = Arc::clone(&loggers[1]);
let feerate_sat_per_kw = fee_estimators[1].feerate_sat_per_kw();
splice_out(&nodes[1], &cp_node_id, &chan_a_id, wallet, logger, feerate_sat_per_kw);
splice_out(&nodes[1], &cp_node_id, &chan_a_id, wallet, feerate_sat_per_kw);
},
0xa6 => {
let cp_node_id = nodes[2].get_our_node_id();
let wallet = &wallets[1];
let logger = Arc::clone(&loggers[1]);
let feerate_sat_per_kw = fee_estimators[1].feerate_sat_per_kw();
splice_out(&nodes[1], &cp_node_id, &chan_b_id, wallet, logger, feerate_sat_per_kw);
splice_out(&nodes[1], &cp_node_id, &chan_b_id, wallet, feerate_sat_per_kw);
},
0xa7 => {
let cp_node_id = nodes[1].get_our_node_id();
let wallet = &wallets[2];
let logger = Arc::clone(&loggers[2]);
let feerate_sat_per_kw = fee_estimators[2].feerate_sat_per_kw();
splice_out(&nodes[2], &cp_node_id, &chan_b_id, wallet, logger, feerate_sat_per_kw);
splice_out(&nodes[2], &cp_node_id, &chan_b_id, wallet, feerate_sat_per_kw);
},

// Sync node by 1 block to cover confirmation of a transaction.
Expand Down
28 changes: 12 additions & 16 deletions fuzz/src/full_stack.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1083,13 +1083,9 @@ pub fn do_test(mut data: &[u8], logger: &Arc<dyn Logger + MaybeSend + MaybeSync>
value: Amount::from_sat(splice_out_sats),
script_pubkey: wallet.get_change_script().unwrap(),
}];
let wallet_sync = WalletSync::new(&wallet, Arc::clone(&logger));
if let Ok(contribution) = funding_template.splice_out_sync(
outputs,
feerate,
FeeRate::MAX,
&wallet_sync,
) {
if let Ok(contribution) =
funding_template.splice_out(outputs, feerate, FeeRate::MAX)
{
let _ = channelmanager.funding_contributed(
&chan_id,
&counterparty,
Expand Down Expand Up @@ -1890,8 +1886,8 @@ fn splice_seed() -> Vec<u8> {
// CommitmentSigned message with proper signature (r=f7, s=01...) and funding_txid TLV
// signature r encodes sighash first byte f7, s follows the pattern from funding_created
// TLV type 1 (odd/optional) for funding_txid as per impl_writeable_msg!(CommitmentSigned, ...)
// Note: txid is encoded in reverse byte order (Bitcoin standard), so to get display 0000...0033, encode 3300...0000
ext_from_hex("0084 c000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000000000f7 0100000000000000000000000000000000000000000000000000000000000000 0000 01 20 3300000000000000000000000000000000000000000000000000000000000000 03000000000000000000000000000000", &mut test);
// Note: txid is encoded in reverse byte order (Bitcoin standard), so to get display 0000...0031, encode 3100...0000
ext_from_hex("0084 c000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000000000f7 0100000000000000000000000000000000000000000000000000000000000000 0000 01 20 3100000000000000000000000000000000000000000000000000000000000000 03000000000000000000000000000000", &mut test);

// After commitment_signed exchange, we need to exchange tx_signatures.
// Message type IDs: TxSignatures = 71 (0x0047)
Expand All @@ -1904,19 +1900,19 @@ fn splice_seed() -> Vec<u8> {
// inbound read from peer id 0 of len 150 (134 message + 16 MAC)
ext_from_hex("030096", &mut test);
// TxSignatures message with shared_input_signature TLV (type 0)
// txid must match the splice funding txid (0x33 in reverse byte order)
// txid must match the splice funding txid (0x31 in reverse byte order)
// shared_input_signature: 64-byte fuzz signature for the shared input
ext_from_hex("0047 c000000000000000000000000000000000000000000000000000000000000000 3300000000000000000000000000000000000000000000000000000000000000 0000 00 40 00000000000000000000000000000000000000000000000000000000000000dc 0100000000000000000000000000000000000000000000000000000000000000 03000000000000000000000000000000", &mut test);
ext_from_hex("0047 c000000000000000000000000000000000000000000000000000000000000000 3100000000000000000000000000000000000000000000000000000000000000 0000 00 40 00000000000000000000000000000000000000000000000000000000000000dc 0100000000000000000000000000000000000000000000000000000000000000 03000000000000000000000000000000", &mut test);

// Connect a block with the splice funding transaction to confirm it
// The splice funding tx: version(4) + input_count(1) + txid(32) + vout(4) + script_len(1) + sequence(4)
// + output_count(1) + value(8) + script_len(1) + script(34) + locktime(4) = 94 bytes = 0x5e
// Transaction structure from FundingTransactionReadyForSigning:
// - Input: spending c000...00:0 with sequence 0xfffffffd
// - Output: 115536 sats to OP_0 PUSH32 6e00...00
// - Output: 115538 sats to OP_0 PUSH32 6e00...00
// - Locktime: 13
ext_from_hex("0c005e", &mut test);
ext_from_hex("02000000 01 c000000000000000000000000000000000000000000000000000000000000000 00000000 00 fdffffff 01 50c3010000000000 22 00206e00000000000000000000000000000000000000000000000000000000000000 0d000000", &mut test);
ext_from_hex("02000000 01 c000000000000000000000000000000000000000000000000000000000000000 00000000 00 fdffffff 01 52c3010000000000 22 00206e00000000000000000000000000000000000000000000000000000000000000 0d000000", &mut test);

// Connect additional blocks to reach minimum_depth confirmations
for _ in 0..5 {
Expand All @@ -1933,8 +1929,8 @@ fn splice_seed() -> Vec<u8> {
// inbound read from peer id 0 of len 82 (66 message + 16 MAC)
ext_from_hex("030052", &mut test);
// SpliceLocked message (type 77 = 0x004d): channel_id + splice_txid + mac
// splice_txid must match the splice funding txid (0x33 in reverse byte order)
ext_from_hex("004d c000000000000000000000000000000000000000000000000000000000000000 3300000000000000000000000000000000000000000000000000000000000000 03000000000000000000000000000000", &mut test);
// splice_txid must match the splice funding txid (0x31 in reverse byte order)
ext_from_hex("004d c000000000000000000000000000000000000000000000000000000000000000 3100000000000000000000000000000000000000000000000000000000000000 03000000000000000000000000000000", &mut test);

test
}
Expand Down Expand Up @@ -2064,6 +2060,6 @@ mod tests {

// Splice locked
assert_eq!(log_entries.get(&("lightning::ln::peer_handler".to_string(), "Handling SendSpliceLocked event in peer_handler for node 030000000000000000000000000000000000000000000000000000000000000002 for channel c000000000000000000000000000000000000000000000000000000000000000".to_string())), Some(&1));
assert_eq!(log_entries.get(&("lightning::ln::channel".to_string(), "Promoting splice funding txid 0000000000000000000000000000000000000000000000000000000000000033".to_string())), Some(&1));
assert_eq!(log_entries.get(&("lightning::ln::channel".to_string(), "Promoting splice funding txid 0000000000000000000000000000000000000000000000000000000000000031".to_string())), Some(&1));
}
}
74 changes: 32 additions & 42 deletions lightning/src/ln/channel.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -12441,7 +12441,7 @@ where
};

if let Err(e) =
contribution.net_value_for_initiator_at_feerate(min_rbf_feerate, holder_balance)
contribution.net_value_for_initiator_at_feerate(min_rbf_feerate, Some(holder_balance))
{
log_info!(
logger,
Expand All @@ -12462,7 +12462,7 @@ where
min_rbf_feerate,
);
contribution
.for_initiator_at_feerate(min_rbf_feerate, holder_balance)
.for_initiator_at_feerate(min_rbf_feerate, Some(holder_balance))
.expect("feerate compatibility already checked")
}

Expand Down Expand Up @@ -12532,14 +12532,12 @@ where
};
}

if let Err(e) = contribution.validate().and_then(|()| {
// For splice-out, our_funding_contribution is adjusted to cover fees if there
// aren't any inputs.
let our_funding_contribution = contribution.net_value();
let our_funding_contribution = contribution.net_value();

if let Err(e) =
self.validate_splice_contributions(our_funding_contribution, SignedAmount::ZERO)
}) {
{
log_error!(logger, "Channel {} cannot be funded: {}", self.context.channel_id(), e);

return Err(QuiescentError::FailSplice(self.splice_funding_failed_for(contribution)));
}

Expand Down Expand Up @@ -12863,23 +12861,21 @@ where
.ok();

let net_value = match holder_balance.and_then(|_| self.queued_funding_contribution()) {
Some(c) => {
match c.net_value_for_acceptor_at_feerate(feerate, holder_balance.unwrap()) {
Ok(net_value) => Some(net_value),
Err(FeeRateAdjustmentError::FeeRateTooHigh { .. }) => {
return Err(ChannelError::Abort(AbortReason::FeeRateTooHigh));
},
Err(e) => {
log_info!(
logger,
"Cannot accommodate initiator's feerate ({}) for channel {}: {}",
feerate,
self.context.channel_id(),
e,
);
None
},
}
Some(c) => match c.net_value_for_acceptor_at_feerate(feerate, holder_balance) {
Ok(net_value) => Some(net_value),
Err(FeeRateAdjustmentError::FeeRateTooHigh { .. }) => {
return Err(ChannelError::Abort(AbortReason::FeeRateTooHigh));
},
Err(e) => {
log_info!(
logger,
"Cannot accommodate initiator's feerate ({}) for channel {}: {}",
feerate,
self.context.channel_id(),
e,
);
None
},
},
None => None,
};
Expand All @@ -12904,7 +12900,7 @@ where
let adjusted_contribution = self
.take_queued_funding_contribution()
.expect("queued_funding_contribution was Some")
.for_acceptor_at_feerate(feerate, holder_balance.unwrap())
.for_acceptor_at_feerate(feerate, holder_balance)
.expect("feerate compatibility already checked");
let (inputs, outputs) = adjusted_contribution.clone().into_tx_parts();
(Some(adjusted_contribution), inputs, outputs)
Expand Down Expand Up @@ -13062,13 +13058,9 @@ where
.as_ref()
.and_then(|pending_splice| pending_splice.contributions.last())
{
let net_value = holder_balance
.ok_or_else(|| ChannelError::Abort(AbortReason::InsufficientRbfFeerate))
.and_then(|holder_balance| {
prior
.net_value_for_acceptor_at_feerate(feerate, holder_balance)
.map_err(|_| ChannelError::Abort(AbortReason::InsufficientRbfFeerate))
})?;
let net_value = prior
.net_value_for_acceptor_at_feerate(feerate, holder_balance)
.map_err(|_| ChannelError::Abort(AbortReason::InsufficientRbfFeerate))?;
Some(net_value)
} else {
None
Expand All @@ -13087,7 +13079,7 @@ where
let adjusted_contribution = self
.take_queued_funding_contribution()
.expect("queued_funding_contribution was Some")
.for_acceptor_at_feerate(feerate, holder_balance.unwrap())
.for_acceptor_at_feerate(feerate, holder_balance)
.expect("feerate compatibility already checked");
self.pending_splice
.as_mut()
Expand All @@ -13105,7 +13097,7 @@ where
.expect("prior_net_value was Some")
.clone();
let adjusted_contribution = prior_contribution
.for_acceptor_at_feerate(feerate, holder_balance.unwrap())
.for_acceptor_at_feerate(feerate, holder_balance)
.expect("feerate compatibility already checked");
self.pending_splice
.as_mut()
Expand Down Expand Up @@ -14101,13 +14093,11 @@ where
// funding_contributed and quiescence, reducing the holder's
// balance. If invalid, disconnect and return the contribution so
// the user can reclaim their inputs.
if let Err(e) = contribution.validate().and_then(|()| {
let our_funding_contribution = contribution.net_value();
self.validate_splice_contributions(
our_funding_contribution,
SignedAmount::ZERO,
)
}) {
let our_funding_contribution = contribution.net_value();
if let Err(e) = self.validate_splice_contributions(
our_funding_contribution,
SignedAmount::ZERO,
) {
let failed = self.splice_funding_failed_for(contribution);
return Err((
ChannelError::WarnAndDisconnect(format!(
Expand Down
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