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Reorg return values of ChannelContext::build_commitment_transaction
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We choose to include in `CommitmentStats` only fields that will be
calculated or constructed by transaction builders.

The other fields are created by channel, and placed in a new struct
we call `CommitmentData`.
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@tankyleo
tankyleo committed Mar 9, 2025
1 parent a983014 commit 1b5bcb0
Showing 1 changed file with 77 additions and 44 deletions.
121 changes: 77 additions & 44 deletions lightning/src/ln/channel.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -877,15 +877,20 @@ struct HTLCStats {
on_holder_tx_outbound_holding_cell_htlcs_count: u32, // dust HTLCs *non*-included
}

/// An enum gathering stats on commitment transaction, either local or remote.
struct CommitmentStats<'a> {
/// A struct gathering data on a commitment, either local or remote.
struct CommitmentData<'a> {
stats: CommitmentStats,
htlcs_included: Vec<(HTLCOutputInCommitment, Option<&'a HTLCSource>)>, // the list of HTLCs (dust HTLCs *included*) which were not ignored when building the transaction
outbound_htlc_preimages: Vec<PaymentPreimage>, // preimages for successful offered HTLCs since last commitment
inbound_htlc_preimages: Vec<PaymentPreimage>, // preimages for successful received HTLCs since last commitment
}

/// A struct gathering stats on a commitment transaction, either local or remote.
struct CommitmentStats {
tx: CommitmentTransaction, // the transaction info
total_fee_sat: u64, // the total fee included in the transaction
htlcs_included: Vec<(HTLCOutputInCommitment, Option<&'a HTLCSource>)>, // the list of HTLCs (dust HTLCs *included*) which were not ignored when building the transaction
local_balance_msat: u64, // local balance before fees *not* considering dust limits
remote_balance_msat: u64, // remote balance before fees *not* considering dust limits
outbound_htlc_preimages: Vec<PaymentPreimage>, // preimages for successful offered HTLCs since last commitment
inbound_htlc_preimages: Vec<PaymentPreimage>, // preimages for successful received HTLCs since last commitment
}

/// Used when calculating whether we or the remote can afford an additional HTLC.
Expand Down Expand Up @@ -2043,7 +2048,10 @@ trait InitialRemoteCommitmentReceiver<SP: Deref> where SP::Target: SignerProvide
) -> Result<CommitmentTransaction, ChannelError> where L::Target: Logger {
let funding_script = self.funding().get_funding_redeemscript();

let initial_commitment_tx = self.context().build_commitment_transaction(self.funding(), holder_commitment_point.transaction_number(), &holder_commitment_point.current_point(), true, false, logger).tx;
let commitment_data = self.context().build_commitment_transaction(self.funding(),
holder_commitment_point.transaction_number(), &holder_commitment_point.current_point(),
true, false, logger);
let initial_commitment_tx = commitment_data.stats.tx;
let trusted_tx = initial_commitment_tx.trust();
let initial_commitment_bitcoin_tx = trusted_tx.built_transaction();
let sighash = initial_commitment_bitcoin_tx.get_sighash_all(&funding_script, self.funding().get_value_satoshis());
Expand Down Expand Up @@ -2080,7 +2088,10 @@ trait InitialRemoteCommitmentReceiver<SP: Deref> where SP::Target: SignerProvide
}
};
let context = self.context();
let counterparty_initial_commitment_tx = context.build_commitment_transaction(self.funding(), context.cur_counterparty_commitment_transaction_number, &context.counterparty_cur_commitment_point.unwrap(), false, false, logger).tx;
let commitment_data = context.build_commitment_transaction(self.funding(),
context.cur_counterparty_commitment_transaction_number,
&context.counterparty_cur_commitment_point.unwrap(), false, false, logger);
let counterparty_initial_commitment_tx = commitment_data.stats.tx;
let counterparty_trusted_tx = counterparty_initial_commitment_tx.trust();
let counterparty_initial_bitcoin_tx = counterparty_trusted_tx.built_transaction();

Expand Down Expand Up @@ -3483,9 +3494,11 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider {
{
let funding_script = funding.get_funding_redeemscript();

let commitment_stats = self.build_commitment_transaction(funding, holder_commitment_point.transaction_number(), &holder_commitment_point.current_point(), true, false, logger);
let commitment_data = self.build_commitment_transaction(funding,
holder_commitment_point.transaction_number(), &holder_commitment_point.current_point(),
true, false, logger);
let commitment_txid = {
let trusted_tx = commitment_stats.tx.trust();
let trusted_tx = commitment_data.stats.tx.trust();
let bitcoin_tx = trusted_tx.built_transaction();
let sighash = bitcoin_tx.get_sighash_all(&funding_script, funding.get_value_satoshis());

Expand All @@ -3498,7 +3511,7 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider {
}
bitcoin_tx.txid
};
let mut htlcs_cloned: Vec<_> = commitment_stats.htlcs_included.iter().map(|htlc| (htlc.0.clone(), htlc.1.map(|h| h.clone()))).collect();
let mut htlcs_cloned: Vec<_> = commitment_data.htlcs_included.iter().map(|htlc| (htlc.0.clone(), htlc.1.map(|h| h.clone()))).collect();

// If our counterparty updated the channel fee in this commitment transaction, check that
// they can actually afford the new fee now.
Expand All @@ -3508,7 +3521,7 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider {
if update_fee {
debug_assert!(!funding.is_outbound());
let counterparty_reserve_we_require_msat = funding.holder_selected_channel_reserve_satoshis * 1000;
if commitment_stats.remote_balance_msat < commitment_stats.total_fee_sat * 1000 + counterparty_reserve_we_require_msat {
if commitment_data.stats.remote_balance_msat < commitment_data.stats.total_fee_sat * 1000 + counterparty_reserve_we_require_msat {
return Err(ChannelError::close("Funding remote cannot afford proposed new fee".to_owned()));
}
}
Expand All @@ -3524,14 +3537,14 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider {
&& info.next_holder_htlc_id == self.next_holder_htlc_id
&& info.next_counterparty_htlc_id == self.next_counterparty_htlc_id
&& info.feerate == self.feerate_per_kw {
assert_eq!(commitment_stats.total_fee_sat, info.fee / 1000);
assert_eq!(commitment_data.stats.total_fee_sat, info.fee / 1000);
}
}
}
}

if msg.htlc_signatures.len() != commitment_stats.tx.htlcs().len() {
return Err(ChannelError::close(format!("Got wrong number of HTLC signatures ({}) from remote. It must be {}", msg.htlc_signatures.len(), commitment_stats.tx.htlcs().len())));
if msg.htlc_signatures.len() != commitment_data.stats.tx.htlcs().len() {
return Err(ChannelError::close(format!("Got wrong number of HTLC signatures ({}) from remote. It must be {}", msg.htlc_signatures.len(), commitment_data.stats.tx.htlcs().len())));
}

// Up to LDK 0.0.115, HTLC information was required to be duplicated in the
Expand All @@ -3551,10 +3564,10 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider {

let mut nondust_htlc_sources = Vec::with_capacity(htlcs_cloned.len());
let mut htlcs_and_sigs = Vec::with_capacity(htlcs_cloned.len());
let holder_keys = commitment_stats.tx.trust().keys();
let holder_keys = commitment_data.stats.tx.trust().keys();
for (idx, (htlc, mut source_opt)) in htlcs_cloned.drain(..).enumerate() {
if let Some(_) = htlc.transaction_output_index {
let htlc_tx = chan_utils::build_htlc_transaction(&commitment_txid, commitment_stats.tx.feerate_per_kw(),
let htlc_tx = chan_utils::build_htlc_transaction(&commitment_txid, commitment_data.stats.tx.feerate_per_kw(),
funding.get_counterparty_selected_contest_delay().unwrap(), &htlc, &self.channel_type,
&holder_keys.broadcaster_delayed_payment_key, &holder_keys.revocation_key);

Expand Down Expand Up @@ -3582,14 +3595,14 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider {
}

let holder_commitment_tx = HolderCommitmentTransaction::new(
commitment_stats.tx,
commitment_data.stats.tx,
msg.signature,
msg.htlc_signatures.clone(),
&funding.get_holder_pubkeys().funding_pubkey,
funding.counterparty_funding_pubkey()
);

self.holder_signer.as_ref().validate_holder_commitment(&holder_commitment_tx, commitment_stats.outbound_htlc_preimages)
self.holder_signer.as_ref().validate_holder_commitment(&holder_commitment_tx, commitment_data.outbound_htlc_preimages)
.map_err(|_| ChannelError::close("Failed to validate our commitment".to_owned()))?;

Ok(LatestHolderCommitmentTXInfo {
Expand All @@ -3613,7 +3626,7 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider {
/// generated by the peer which proposed adding the HTLCs, and thus we need to understand both
/// which peer generated this transaction and "to whom" this transaction flows.
#[inline]
fn build_commitment_transaction<L: Deref>(&self, funding: &FundingScope, commitment_number: u64, per_commitment_point: &PublicKey, local: bool, generated_by_local: bool, logger: &L) -> CommitmentStats
fn build_commitment_transaction<L: Deref>(&self, funding: &FundingScope, commitment_number: u64, per_commitment_point: &PublicKey, local: bool, generated_by_local: bool, logger: &L) -> CommitmentData
where L::Target: Logger
{
let mut included_dust_htlcs: Vec<(HTLCOutputInCommitment, Option<&HTLCSource>)> = Vec::new();
Expand Down Expand Up @@ -3820,12 +3833,16 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider {
htlcs_included.sort_unstable_by_key(|h| h.0.transaction_output_index.unwrap());
htlcs_included.append(&mut included_dust_htlcs);

CommitmentStats {
let stats = CommitmentStats {
tx,
total_fee_sat,
htlcs_included,
local_balance_msat: value_to_self_msat,
remote_balance_msat: value_to_remote_msat,
};

CommitmentData {
stats,
htlcs_included,
inbound_htlc_preimages,
outbound_htlc_preimages,
}
Expand Down Expand Up @@ -4613,8 +4630,10 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider {
SP::Target: SignerProvider,
L::Target: Logger
{
let counterparty_initial_commitment_tx = self.build_commitment_transaction(
funding, self.cur_counterparty_commitment_transaction_number, &self.counterparty_cur_commitment_point.unwrap(), false, false, logger).tx;
let commitment_data = self.build_commitment_transaction(funding,
self.cur_counterparty_commitment_transaction_number,
&self.counterparty_cur_commitment_point.unwrap(), false, false, logger);
let counterparty_initial_commitment_tx = commitment_data.stats.tx;
match self.holder_signer {
// TODO (taproot|arik): move match into calling method for Taproot
ChannelSignerType::Ecdsa(ref ecdsa) => {
Expand Down Expand Up @@ -6328,9 +6347,11 @@ impl<SP: Deref> FundedChannel<SP> where
// Before proposing a feerate update, check that we can actually afford the new fee.
let dust_exposure_limiting_feerate = self.context.get_dust_exposure_limiting_feerate(&fee_estimator);
let htlc_stats = self.context.get_pending_htlc_stats(Some(feerate_per_kw), dust_exposure_limiting_feerate);
let commitment_stats = self.context.build_commitment_transaction(&self.funding, self.holder_commitment_point.transaction_number(), &self.holder_commitment_point.current_point(), true, true, logger);
let buffer_fee_msat = commit_tx_fee_sat(feerate_per_kw, commitment_stats.tx.htlcs().len() + htlc_stats.on_holder_tx_outbound_holding_cell_htlcs_count as usize + CONCURRENT_INBOUND_HTLC_FEE_BUFFER as usize, self.context.get_channel_type()) * 1000;
let holder_balance_msat = commitment_stats.local_balance_msat - htlc_stats.outbound_holding_cell_msat;
let commitment_data = self.context.build_commitment_transaction(&self.funding,
self.holder_commitment_point.transaction_number(),
&self.holder_commitment_point.current_point(), true, true, logger);
let buffer_fee_msat = commit_tx_fee_sat(feerate_per_kw, commitment_data.stats.tx.htlcs().len() + htlc_stats.on_holder_tx_outbound_holding_cell_htlcs_count as usize + CONCURRENT_INBOUND_HTLC_FEE_BUFFER as usize, self.context.get_channel_type()) * 1000;
let holder_balance_msat = commitment_data.stats.local_balance_msat - htlc_stats.outbound_holding_cell_msat;
if holder_balance_msat < buffer_fee_msat + self.funding.counterparty_selected_channel_reserve_satoshis.unwrap() * 1000 {
//TODO: auto-close after a number of failures?
log_debug!(logger, "Cannot afford to send new feerate at {}", feerate_per_kw);
Expand Down Expand Up @@ -6641,7 +6662,10 @@ impl<SP: Deref> FundedChannel<SP> where
self.holder_commitment_point.try_resolve_pending(&self.context.holder_signer, &self.context.secp_ctx, logger);
}
let funding_signed = if self.context.signer_pending_funding && !self.funding.is_outbound() {
let counterparty_initial_commitment_tx = self.context.build_commitment_transaction(&self.funding, self.context.cur_counterparty_commitment_transaction_number + 1, &self.context.counterparty_cur_commitment_point.unwrap(), false, false, logger).tx;
let commitment_data = self.context.build_commitment_transaction(&self.funding,
self.context.cur_counterparty_commitment_transaction_number + 1,
&self.context.counterparty_cur_commitment_point.unwrap(), false, false, logger);
let counterparty_initial_commitment_tx = commitment_data.stats.tx;
self.context.get_funding_signed_msg(&self.funding.channel_transaction_parameters, logger, counterparty_initial_commitment_tx)
} else { None };
// Provide a `channel_ready` message if we need to, but only if we're _not_ still pending
Expand Down Expand Up @@ -8712,8 +8736,10 @@ impl<SP: Deref> FundedChannel<SP> where
-> (Vec<(HTLCOutputInCommitment, Option<&HTLCSource>)>, CommitmentTransaction)
where L::Target: Logger
{
let commitment_stats = self.context.build_commitment_transaction(&self.funding, self.context.cur_counterparty_commitment_transaction_number, &self.context.counterparty_cur_commitment_point.unwrap(), false, true, logger);
let counterparty_commitment_tx = commitment_stats.tx;
let commitment_data = self.context.build_commitment_transaction(&self.funding,
self.context.cur_counterparty_commitment_transaction_number,
&self.context.counterparty_cur_commitment_point.unwrap(), false, true, logger);
let counterparty_commitment_tx = commitment_data.stats.tx;

#[cfg(any(test, fuzzing))]
{
Expand All @@ -8733,7 +8759,7 @@ impl<SP: Deref> FundedChannel<SP> where
}
}

(commitment_stats.htlcs_included, counterparty_commitment_tx)
(commitment_data.htlcs_included, counterparty_commitment_tx)
}

/// Only fails in case of signer rejection. Used for channel_reestablish commitment_signed
Expand All @@ -8743,8 +8769,10 @@ impl<SP: Deref> FundedChannel<SP> where
#[cfg(any(test, fuzzing))]
self.build_commitment_no_state_update(logger);

let commitment_stats = self.context.build_commitment_transaction(&self.funding, self.context.cur_counterparty_commitment_transaction_number, &self.context.counterparty_cur_commitment_point.unwrap(), false, true, logger);
let counterparty_commitment_txid = commitment_stats.tx.trust().txid();
let commitment_data = self.context.build_commitment_transaction(&self.funding,
self.context.cur_counterparty_commitment_transaction_number,
&self.context.counterparty_cur_commitment_point.unwrap(), false, true, logger);
let counterparty_commitment_tx = commitment_data.stats.tx;

match &self.context.holder_signer {
ChannelSignerType::Ecdsa(ecdsa) => {
Expand All @@ -8753,24 +8781,25 @@ impl<SP: Deref> FundedChannel<SP> where
{
let res = ecdsa.sign_counterparty_commitment(
&self.funding.channel_transaction_parameters,
&commitment_stats.tx,
commitment_stats.inbound_htlc_preimages,
commitment_stats.outbound_htlc_preimages,
&counterparty_commitment_tx,
commitment_data.inbound_htlc_preimages,
commitment_data.outbound_htlc_preimages,
&self.context.secp_ctx,
).map_err(|_| ChannelError::Ignore("Failed to get signatures for new commitment_signed".to_owned()))?;
signature = res.0;
htlc_signatures = res.1;

let trusted_tx = counterparty_commitment_tx.trust();
log_trace!(logger, "Signed remote commitment tx {} (txid {}) with redeemscript {} -> {} in channel {}",
encode::serialize_hex(&commitment_stats.tx.trust().built_transaction().transaction),
&counterparty_commitment_txid, encode::serialize_hex(&self.funding.get_funding_redeemscript()),
encode::serialize_hex(&trusted_tx.built_transaction().transaction),
&trusted_tx.txid(), encode::serialize_hex(&self.funding.get_funding_redeemscript()),
log_bytes!(signature.serialize_compact()[..]), &self.context.channel_id());

let counterparty_keys = commitment_stats.tx.trust().keys();
debug_assert_eq!(htlc_signatures.len(), commitment_stats.tx.htlcs().len());
for (ref htlc_sig, ref htlc) in htlc_signatures.iter().zip(commitment_stats.tx.htlcs()) {
let counterparty_keys = trusted_tx.keys();
debug_assert_eq!(htlc_signatures.len(), trusted_tx.htlcs().len());
for (ref htlc_sig, ref htlc) in htlc_signatures.iter().zip(trusted_tx.htlcs()) {
log_trace!(logger, "Signed remote HTLC tx {} with redeemscript {} with pubkey {} -> {} in channel {}",
encode::serialize_hex(&chan_utils::build_htlc_transaction(&counterparty_commitment_txid, commitment_stats.tx.feerate_per_kw(), self.funding.get_holder_selected_contest_delay(), htlc, &self.context.channel_type, &counterparty_keys.broadcaster_delayed_payment_key, &counterparty_keys.revocation_key)),
encode::serialize_hex(&chan_utils::build_htlc_transaction(&trusted_tx.txid(), trusted_tx.feerate_per_kw(), self.funding.get_holder_selected_contest_delay(), htlc, &self.context.channel_type, &counterparty_keys.broadcaster_delayed_payment_key, &counterparty_keys.revocation_key)),
encode::serialize_hex(&chan_utils::get_htlc_redeemscript(&htlc, &self.context.channel_type, &counterparty_keys)),
log_bytes!(counterparty_keys.broadcaster_htlc_key.to_public_key().serialize()),
log_bytes!(htlc_sig.serialize_compact()[..]), &self.context.channel_id());
Expand Down Expand Up @@ -9224,7 +9253,10 @@ impl<SP: Deref> OutboundV1Channel<SP> where SP::Target: SignerProvider {

/// Only allowed after [`FundingScope::channel_transaction_parameters`] is set.
fn get_funding_created_msg<L: Deref>(&mut self, logger: &L) -> Option<msgs::FundingCreated> where L::Target: Logger {
let counterparty_initial_commitment_tx = self.context.build_commitment_transaction(&self.funding, self.context.cur_counterparty_commitment_transaction_number, &self.context.counterparty_cur_commitment_point.unwrap(), false, false, logger).tx;
let commitment_data = self.context.build_commitment_transaction(&self.funding,
self.context.cur_counterparty_commitment_transaction_number,
&self.context.counterparty_cur_commitment_point.unwrap(), false, false, logger);
let counterparty_initial_commitment_tx = commitment_data.stats.tx;
let signature = match &self.context.holder_signer {
// TODO (taproot|arik): move match into calling method for Taproot
ChannelSignerType::Ecdsa(ecdsa) => {
Expand Down Expand Up @@ -11857,8 +11889,9 @@ mod tests {
( $counterparty_sig_hex: expr, $sig_hex: expr, $tx_hex: expr, $opt_anchors: expr, {
$( { $htlc_idx: expr, $counterparty_htlc_sig_hex: expr, $htlc_sig_hex: expr, $htlc_tx_hex: expr } ), *
} ) => { {
let commitment_stats = chan.context.build_commitment_transaction(&chan.funding, 0xffffffffffff - 42, &per_commitment_point, true, false, &logger);
let commitment_tx = commitment_stats.tx;
let commitment_data = chan.context.build_commitment_transaction(&chan.funding,
0xffffffffffff - 42, &per_commitment_point, true, false, &logger);
let commitment_tx = commitment_data.stats.tx;
let trusted_tx = commitment_tx.trust();
let unsigned_tx = trusted_tx.built_transaction();
let redeemscript = chan.funding.get_funding_redeemscript();
Expand Down

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