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Merge pull request #2703 from wpaulino/retryable-commitment-broadcast
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Refactor commitment broadcast to always go through OnchainTxHandler
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@TheBlueMatt
TheBlueMatt committed Dec 13, 2023
2 parents 2b04f19 + 60bb39a commit 0dbf17b
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Showing 7 changed files with 361 additions and 136 deletions.
166 changes: 112 additions & 54 deletions lightning/src/chain/channelmonitor.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2666,18 +2666,59 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitorImpl<Signer> {
}
}

fn broadcast_latest_holder_commitment_txn<B: Deref, L: Deref>(&mut self, broadcaster: &B, logger: &WithChannelMonitor<L>)
where B::Target: BroadcasterInterface,
L::Target: Logger,
{
let commit_txs = self.get_latest_holder_commitment_txn(logger);
let mut txs = vec![];
for tx in commit_txs.iter() {
log_info!(logger, "Broadcasting local {}", log_tx!(tx));
txs.push(tx);
}
broadcaster.broadcast_transactions(&txs);
fn generate_claimable_outpoints_and_watch_outputs(&mut self) -> (Vec<PackageTemplate>, Vec<TransactionOutputs>) {
let funding_outp = HolderFundingOutput::build(
self.funding_redeemscript.clone(),
self.channel_value_satoshis,
self.onchain_tx_handler.channel_type_features().clone()
);
let commitment_package = PackageTemplate::build_package(
self.funding_info.0.txid.clone(), self.funding_info.0.index as u32,
PackageSolvingData::HolderFundingOutput(funding_outp),
self.best_block.height(), self.best_block.height()
);
let mut claimable_outpoints = vec![commitment_package];
self.pending_monitor_events.push(MonitorEvent::HolderForceClosed(self.funding_info.0));
// Although we aren't signing the transaction directly here, the transaction will be signed
// in the claim that is queued to OnchainTxHandler. We set holder_tx_signed here to reject
// new channel updates.
self.holder_tx_signed = true;
let mut watch_outputs = Vec::new();
// We can't broadcast our HTLC transactions while the commitment transaction is
// unconfirmed. We'll delay doing so until we detect the confirmed commitment in
// `transactions_confirmed`.
if !self.onchain_tx_handler.channel_type_features().supports_anchors_zero_fee_htlc_tx() {
// Because we're broadcasting a commitment transaction, we should construct the package
// assuming it gets confirmed in the next block. Sadly, we have code which considers
// "not yet confirmed" things as discardable, so we cannot do that here.
let (mut new_outpoints, _) = self.get_broadcasted_holder_claims(
&self.current_holder_commitment_tx, self.best_block.height()
);
let unsigned_commitment_tx = self.onchain_tx_handler.get_unsigned_holder_commitment_tx();
let new_outputs = self.get_broadcasted_holder_watch_outputs(
&self.current_holder_commitment_tx, &unsigned_commitment_tx
);
if !new_outputs.is_empty() {
watch_outputs.push((self.current_holder_commitment_tx.txid.clone(), new_outputs));
}
claimable_outpoints.append(&mut new_outpoints);
}
(claimable_outpoints, watch_outputs)
}

pub(crate) fn queue_latest_holder_commitment_txn_for_broadcast<B: Deref, F: Deref, L: Deref>(
&mut self, broadcaster: &B, fee_estimator: &LowerBoundedFeeEstimator<F>, logger: &WithChannelMonitor<L>
)
where
B::Target: BroadcasterInterface,
F::Target: FeeEstimator,
L::Target: Logger,
{
let (claimable_outpoints, _) = self.generate_claimable_outpoints_and_watch_outputs();
self.onchain_tx_handler.update_claims_view_from_requests(
claimable_outpoints, self.best_block.height(), self.best_block.height(), broadcaster,
fee_estimator, logger
);
}

fn update_monitor<B: Deref, F: Deref, L: Deref>(
Expand Down Expand Up @@ -2767,26 +2808,7 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitorImpl<Signer> {
log_trace!(logger, "Avoiding commitment broadcast, already detected confirmed spend onchain");
continue;
}
self.broadcast_latest_holder_commitment_txn(broadcaster, logger);
// If the channel supports anchor outputs, we'll need to emit an external
// event to be consumed such that a child transaction is broadcast with a
// high enough feerate for the parent commitment transaction to confirm.
if self.onchain_tx_handler.channel_type_features().supports_anchors_zero_fee_htlc_tx() {
let funding_output = HolderFundingOutput::build(
self.funding_redeemscript.clone(), self.channel_value_satoshis,
self.onchain_tx_handler.channel_type_features().clone(),
);
let best_block_height = self.best_block.height();
let commitment_package = PackageTemplate::build_package(
self.funding_info.0.txid.clone(), self.funding_info.0.index as u32,
PackageSolvingData::HolderFundingOutput(funding_output),
best_block_height, best_block_height
);
self.onchain_tx_handler.update_claims_view_from_requests(
vec![commitment_package], best_block_height, best_block_height,
broadcaster, &bounded_fee_estimator, logger,
);
}
self.queue_latest_holder_commitment_txn_for_broadcast(broadcaster, &bounded_fee_estimator, logger);
} else if !self.holder_tx_signed {
log_error!(logger, "WARNING: You have a potentially-unsafe holder commitment transaction available to broadcast");
log_error!(logger, " in channel monitor for channel {}!", &self.funding_info.0.to_channel_id());
Expand Down Expand Up @@ -3363,6 +3385,58 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitorImpl<Signer> {
}
}

/// Cancels any existing pending claims for a commitment that previously confirmed and has now
/// been replaced by another.
pub fn cancel_prev_commitment_claims<L: Deref>(
&mut self, logger: &L, confirmed_commitment_txid: &Txid
) where L::Target: Logger {
for (counterparty_commitment_txid, _) in &self.counterparty_commitment_txn_on_chain {
// Cancel any pending claims for counterparty commitments we've seen confirm.
if counterparty_commitment_txid == confirmed_commitment_txid {
continue;
}
for (htlc, _) in self.counterparty_claimable_outpoints.get(counterparty_commitment_txid).unwrap_or(&vec![]) {
log_trace!(logger, "Canceling claims for previously confirmed counterparty commitment {}",
counterparty_commitment_txid);
let mut outpoint = BitcoinOutPoint { txid: *counterparty_commitment_txid, vout: 0 };
if let Some(vout) = htlc.transaction_output_index {
outpoint.vout = vout;
self.onchain_tx_handler.abandon_claim(&outpoint);
}
}
}
if self.holder_tx_signed {
// If we've signed, we may have broadcast either commitment (prev or current), and
// attempted to claim from it immediately without waiting for a confirmation.
if self.current_holder_commitment_tx.txid != *confirmed_commitment_txid {
log_trace!(logger, "Canceling claims for previously broadcast holder commitment {}",
self.current_holder_commitment_tx.txid);
let mut outpoint = BitcoinOutPoint { txid: self.current_holder_commitment_tx.txid, vout: 0 };
for (htlc, _, _) in &self.current_holder_commitment_tx.htlc_outputs {
if let Some(vout) = htlc.transaction_output_index {
outpoint.vout = vout;
self.onchain_tx_handler.abandon_claim(&outpoint);
}
}
}
if let Some(prev_holder_commitment_tx) = &self.prev_holder_signed_commitment_tx {
if prev_holder_commitment_tx.txid != *confirmed_commitment_txid {
log_trace!(logger, "Canceling claims for previously broadcast holder commitment {}",
prev_holder_commitment_tx.txid);
let mut outpoint = BitcoinOutPoint { txid: prev_holder_commitment_tx.txid, vout: 0 };
for (htlc, _, _) in &prev_holder_commitment_tx.htlc_outputs {
if let Some(vout) = htlc.transaction_output_index {
outpoint.vout = vout;
self.onchain_tx_handler.abandon_claim(&outpoint);
}
}
}
}
} else {
// No previous claim.
}
}

fn get_latest_holder_commitment_txn<L: Deref>(
&mut self, logger: &WithChannelMonitor<L>,
) -> Vec<Transaction> where L::Target: Logger {
Expand Down Expand Up @@ -3578,6 +3652,10 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitorImpl<Signer> {
commitment_tx_to_counterparty_output,
},
});
// Now that we've detected a confirmed commitment transaction, attempt to cancel
// pending claims for any commitments that were previously confirmed such that
// we don't continue claiming inputs that no longer exist.
self.cancel_prev_commitment_claims(&logger, &txid);
}
}
if tx.input.len() >= 1 {
Expand Down Expand Up @@ -3643,29 +3721,9 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitorImpl<Signer> {

let should_broadcast = self.should_broadcast_holder_commitment_txn(logger);
if should_broadcast {
let funding_outp = HolderFundingOutput::build(self.funding_redeemscript.clone(), self.channel_value_satoshis, self.onchain_tx_handler.channel_type_features().clone());
let commitment_package = PackageTemplate::build_package(self.funding_info.0.txid.clone(), self.funding_info.0.index as u32, PackageSolvingData::HolderFundingOutput(funding_outp), self.best_block.height(), self.best_block.height());
claimable_outpoints.push(commitment_package);
self.pending_monitor_events.push(MonitorEvent::HolderForceClosed(self.funding_info.0));
// Although we aren't signing the transaction directly here, the transaction will be signed
// in the claim that is queued to OnchainTxHandler. We set holder_tx_signed here to reject
// new channel updates.
self.holder_tx_signed = true;
// We can't broadcast our HTLC transactions while the commitment transaction is
// unconfirmed. We'll delay doing so until we detect the confirmed commitment in
// `transactions_confirmed`.
if !self.onchain_tx_handler.channel_type_features().supports_anchors_zero_fee_htlc_tx() {
// Because we're broadcasting a commitment transaction, we should construct the package
// assuming it gets confirmed in the next block. Sadly, we have code which considers
// "not yet confirmed" things as discardable, so we cannot do that here.
let (mut new_outpoints, _) = self.get_broadcasted_holder_claims(&self.current_holder_commitment_tx, self.best_block.height());
let unsigned_commitment_tx = self.onchain_tx_handler.get_unsigned_holder_commitment_tx();
let new_outputs = self.get_broadcasted_holder_watch_outputs(&self.current_holder_commitment_tx, &unsigned_commitment_tx);
if !new_outputs.is_empty() {
watch_outputs.push((self.current_holder_commitment_tx.txid.clone(), new_outputs));
}
claimable_outpoints.append(&mut new_outpoints);
}
let (mut new_outpoints, mut new_outputs) = self.generate_claimable_outpoints_and_watch_outputs();
claimable_outpoints.append(&mut new_outpoints);
watch_outputs.append(&mut new_outputs);
}

// Find which on-chain events have reached their confirmation threshold.
Expand Down
19 changes: 19 additions & 0 deletions lightning/src/chain/onchaintx.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -676,6 +676,25 @@ impl<ChannelSigner: WriteableEcdsaChannelSigner> OnchainTxHandler<ChannelSigner>
None
}

pub fn abandon_claim(&mut self, outpoint: &BitcoinOutPoint) {
let claim_id = self.claimable_outpoints.get(outpoint).map(|(claim_id, _)| *claim_id)
.or_else(|| {
self.pending_claim_requests.iter()
.find(|(_, claim)| claim.outpoints().iter().any(|claim_outpoint| *claim_outpoint == outpoint))
.map(|(claim_id, _)| *claim_id)
});
if let Some(claim_id) = claim_id {
if let Some(claim) = self.pending_claim_requests.remove(&claim_id) {
for outpoint in claim.outpoints() {
self.claimable_outpoints.remove(&outpoint);
}
}
} else {
self.locktimed_packages.values_mut().for_each(|claims|
claims.retain(|claim| !claim.outpoints().iter().any(|claim_outpoint| *claim_outpoint == outpoint)));
}
}

/// Upon channelmonitor.block_connected(..) or upon provision of a preimage on the forward link
/// for this channel, provide new relevant on-chain transactions and/or new claim requests.
/// Together with `update_claims_view_from_matched_txn` this used to be named
Expand Down
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