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Introduce RenegotiatedFundingLocked monitor update variant #3894

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Merged
merged 2 commits into from
Jul 22, 2025
Merged

Introduce RenegotiatedFundingLocked monitor update variant #3894

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07c2eb5
Introduce RenegotiatedFundingLocked monitor update variant
wpaulino Jun 26, 2025
22d5428
Rename ChannelMonitor::first_confirmed_funding_txo
wpaulino Jul 16, 2025
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65 changes: 55 additions & 10 deletions lightning/src/chain/channelmonitor.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -676,6 +676,9 @@ pub(crate) enum ChannelMonitorUpdateStep {
holder_commitment_tx: HolderCommitmentTransaction,
counterparty_commitment_tx: CommitmentTransaction,
},
RenegotiatedFundingLocked {
funding_txid: Txid,
},
}

impl ChannelMonitorUpdateStep {
Expand All @@ -690,6 +693,7 @@ impl ChannelMonitorUpdateStep {
ChannelMonitorUpdateStep::ChannelForceClosed { .. } => "ChannelForceClosed",
ChannelMonitorUpdateStep::ShutdownScript { .. } => "ShutdownScript",
ChannelMonitorUpdateStep::RenegotiatedFunding { .. } => "RenegotiatedFunding",
ChannelMonitorUpdateStep::RenegotiatedFundingLocked { .. } => "RenegotiatedFundingLocked",
}
}
}
Expand Down Expand Up @@ -733,6 +737,9 @@ impl_writeable_tlv_based_enum_upgradable!(ChannelMonitorUpdateStep,
(3, holder_commitment_tx, required),
(5, counterparty_commitment_tx, required),
},
(12, RenegotiatedFundingLocked) => {
(1, funding_txid, required),
},
);

/// Indicates whether the balance is derived from a cooperative close, a force-close
Expand Down Expand Up @@ -1075,6 +1082,10 @@ impl FundingScope {
fn funding_txid(&self) -> Txid {
self.funding_outpoint().txid
}

fn is_splice(&self) -> bool {
self.channel_parameters.splice_parent_funding_txid.is_some()
}
}

impl Writeable for FundingScope {
Expand Down Expand Up @@ -1141,7 +1152,7 @@ pub(crate) struct ChannelMonitorImpl<Signer: EcdsaChannelSigner> {
channel_keys_id: [u8; 32],
holder_revocation_basepoint: RevocationBasepoint,
channel_id: ChannelId,
first_confirmed_funding_txo: OutPoint,
first_negotiated_funding_txo: OutPoint,

counterparty_commitment_params: CounterpartyCommitmentParameters,

Expand Down Expand Up @@ -1209,8 +1220,6 @@ pub(crate) struct ChannelMonitorImpl<Signer: EcdsaChannelSigner> {
// interface knows about the TXOs that we want to be notified of spends of. We could probably
// be smart and derive them from the above storage fields, but its much simpler and more
// Obviously Correct (tm) if we just keep track of them explicitly.
//
// TODO: Remove entries for stale funding transactions on `splice_locked`.
outputs_to_watch: HashMap<Txid, Vec<(u32, ScriptBuf)>>,

#[cfg(any(test, feature = "_test_utils"))]
Expand Down Expand Up @@ -1566,7 +1575,7 @@ impl<Signer: EcdsaChannelSigner> Writeable for ChannelMonitorImpl<Signer> {
(21, self.balances_empty_height, option),
(23, self.holder_pays_commitment_tx_fee, option),
(25, self.payment_preimages, required),
(27, self.first_confirmed_funding_txo, required),
(27, self.first_negotiated_funding_txo, required),
(29, self.initial_counterparty_commitment_tx, option),
(31, self.funding.channel_parameters, required),
(32, self.pending_funding, optional_vec),
Expand Down Expand Up @@ -1752,7 +1761,7 @@ impl<Signer: EcdsaChannelSigner> ChannelMonitor<Signer> {
channel_keys_id,
holder_revocation_basepoint,
channel_id,
first_confirmed_funding_txo: funding_outpoint,
first_negotiated_funding_txo: funding_outpoint,

counterparty_commitment_params,
their_cur_per_commitment_points: None,
Expand Down Expand Up @@ -1811,7 +1820,7 @@ impl<Signer: EcdsaChannelSigner> ChannelMonitor<Signer> {
/// [`Persist`]: crate::chain::chainmonitor::Persist
pub fn persistence_key(&self) -> MonitorName {
let inner = self.inner.lock().unwrap();
let funding_outpoint = inner.first_confirmed_funding_txo;
let funding_outpoint = inner.first_negotiated_funding_txo;
let channel_id = inner.channel_id;
if ChannelId::v1_from_funding_outpoint(funding_outpoint) == channel_id {
MonitorName::V1Channel(funding_outpoint)
Expand Down Expand Up @@ -3670,6 +3679,10 @@ impl<Signer: EcdsaChannelSigner> ChannelMonitorImpl<Signer> {
);
return Err(());
}
} else if self.funding.is_splice() {
// If we've already spliced at least once, we're no longer able to RBF the original
// funding transaction.
return Err(());
}

self.outputs_to_watch.insert(
Expand All @@ -3681,6 +3694,30 @@ impl<Signer: EcdsaChannelSigner> ChannelMonitorImpl<Signer> {
Ok(())
}

fn promote_funding(&mut self, new_funding_txid: Txid) -> Result<(), ()> {
let new_funding = self
.pending_funding
.iter_mut()
.find(|funding| funding.funding_txid() == new_funding_txid);
if new_funding.is_none() {
return Err(());
}
let mut new_funding = new_funding.unwrap();

mem::swap(&mut self.funding, &mut new_funding);
self.onchain_tx_handler.update_after_renegotiated_funding_locked(
self.funding.current_holder_commitment_tx.clone(),
self.funding.prev_holder_commitment_tx.clone(),
);

// The swap above places the previous `FundingScope` into `pending_funding`.
for funding in self.pending_funding.drain(..) {
self.outputs_to_watch.remove(&funding.funding_txid());
}

Ok(())
}

#[rustfmt::skip]
fn update_monitor<B: Deref, F: Deref, L: Deref>(
&mut self, updates: &ChannelMonitorUpdate, broadcaster: &B, fee_estimator: &F, logger: &WithChannelMonitor<L>
Expand Down Expand Up @@ -3771,6 +3808,13 @@ impl<Signer: EcdsaChannelSigner> ChannelMonitorImpl<Signer> {
ret = Err(());
}
},
ChannelMonitorUpdateStep::RenegotiatedFundingLocked { funding_txid } => {
log_trace!(logger, "Updating ChannelMonitor with locked renegotiated funding txid {}", funding_txid);
if let Err(_) = self.promote_funding(*funding_txid) {
log_error!(logger, "Unknown funding with txid {} became locked", funding_txid);
ret = Err(());
}
},
ChannelMonitorUpdateStep::ChannelForceClosed { should_broadcast } => {
log_trace!(logger, "Updating ChannelMonitor: channel force closed, should broadcast: {}", should_broadcast);
self.lockdown_from_offchain = true;
Expand Down Expand Up @@ -3823,7 +3867,8 @@ impl<Signer: EcdsaChannelSigner> ChannelMonitorImpl<Signer> {
|ChannelMonitorUpdateStep::LatestCounterpartyCommitmentTX { .. }
|ChannelMonitorUpdateStep::ShutdownScript { .. }
|ChannelMonitorUpdateStep::CommitmentSecret { .. }
|ChannelMonitorUpdateStep::RenegotiatedFunding { .. } =>
|ChannelMonitorUpdateStep::RenegotiatedFunding { .. }
|ChannelMonitorUpdateStep::RenegotiatedFundingLocked { .. } =>
is_pre_close_update = true,
// After a channel is closed, we don't communicate with our peer about it, so the
// only things we will update is getting a new preimage (from a different channel)
Expand Down Expand Up @@ -5679,7 +5724,7 @@ impl<'a, 'b, ES: EntropySource, SP: SignerProvider> ReadableArgs<(&'a ES, &'b SP
let mut channel_id = None;
let mut holder_pays_commitment_tx_fee = None;
let mut payment_preimages_with_info: Option<HashMap<_, _>> = None;
let mut first_confirmed_funding_txo = RequiredWrapper(None);
let mut first_negotiated_funding_txo = RequiredWrapper(None);
let mut channel_parameters = None;
let mut pending_funding = None;
read_tlv_fields!(reader, {
Expand All @@ -5696,7 +5741,7 @@ impl<'a, 'b, ES: EntropySource, SP: SignerProvider> ReadableArgs<(&'a ES, &'b SP
(21, balances_empty_height, option),
(23, holder_pays_commitment_tx_fee, option),
(25, payment_preimages_with_info, option),
(27, first_confirmed_funding_txo, (default_value, outpoint)),
(27, first_negotiated_funding_txo, (default_value, outpoint)),
(29, initial_counterparty_commitment_tx, option),
(31, channel_parameters, (option: ReadableArgs, None)),
(32, pending_funding, optional_vec),
Expand Down Expand Up @@ -5828,7 +5873,7 @@ impl<'a, 'b, ES: EntropySource, SP: SignerProvider> ReadableArgs<(&'a ES, &'b SP
channel_keys_id,
holder_revocation_basepoint,
channel_id,
first_confirmed_funding_txo: first_confirmed_funding_txo.0.unwrap(),
first_negotiated_funding_txo: first_negotiated_funding_txo.0.unwrap(),

counterparty_commitment_params,
their_cur_per_commitment_points,
Expand Down
9 changes: 9 additions & 0 deletions lightning/src/chain/onchaintx.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1216,6 +1216,15 @@ impl<ChannelSigner: EcdsaChannelSigner> OnchainTxHandler<ChannelSigner> {
self.prev_holder_commitment = Some(replace(&mut self.holder_commitment, tx));
}

/// Replaces the current/prev holder commitment transactions spending the currently confirmed
/// funding outpoint with those spending the new funding outpoint.
pub(crate) fn update_after_renegotiated_funding_locked(
&mut self, current: HolderCommitmentTransaction, prev: Option<HolderCommitmentTransaction>,
) {
self.holder_commitment = current;
self.prev_holder_commitment = prev;
}

// Deprecated as of 0.2, only use in cases where it was not previously available.
pub(crate) fn channel_parameters(&self) -> &ChannelTransactionParameters {
&self.channel_transaction_parameters
Expand Down
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