Pre-build CommitmentTransaction

reduces CPU and memory allocation effort involved in bitcoin tx construction and txid derivation

Author: devrandom

lightning/src/chain/channelmonitor.rs

@@ -251,6 +251,7 @@ pub(crate) const ANTI_REORG_DELAY: u32 = 6;
 /// end up force-closing the channel on us to claim it.
 pub(crate) const HTLC_FAIL_BACK_BUFFER: u32 = CLTV_CLAIM_BUFFER + LATENCY_GRACE_PERIOD_BLOCKS;
 
+// TODO(devrandom) replace this with HolderCommitmentTransaction
 #[derive(Clone, PartialEq)]
 struct HolderSignedTx {
 	/// txid of the transaction in tx, just used to make comparison faster
@@ -968,8 +969,7 @@ impl<ChanSigner: ChannelKeys> ChannelMonitor<ChanSigner> {
 
 		let secp_ctx = Secp256k1::new();
 
-		let directed_channel_parameters = channel_parameters.to_directed(true);
-		let txid = initial_holder_commitment_tx.calculate_txid(&directed_channel_parameters, &secp_ctx);
+		let txid = initial_holder_commitment_tx.trust_txid();
 
 		// block for Rust 1.34 compat
 		let (holder_commitment_tx, current_holder_commitment_number) = {
@@ -1146,7 +1146,7 @@ impl<ChanSigner: ChannelKeys> ChannelMonitor<ChanSigner> {
 	/// up-to-date as our holder commitment transaction is updated.
 	/// Panics if set_on_holder_tx_csv has never been called.
 	fn provide_latest_holder_commitment_tx(&mut self, holder_commitment_tx: HolderCommitmentTransaction, htlc_outputs: Vec<(HTLCOutputInCommitment, Option<Signature>, Option<HTLCSource>)>) -> Result<(), MonitorUpdateError> {
-		let txid = holder_commitment_tx.calculate_txid(&self.onchain_tx_handler.channel_transaction_parameters.to_directed(true), &self.secp_ctx);
+		let txid = holder_commitment_tx.trust_txid();
 
 		// block for Rust 1.34 compat
 		let mut new_holder_commitment_tx = {

lightning/src/chain/keysinterface.rs

@@ -486,11 +486,10 @@ impl ChannelKeys for InMemoryChannelKeys {
 		let funding_pubkey = PublicKey::from_secret_key(secp_ctx, &self.funding_key);
 		let channel_funding_redeemscript = make_funding_redeemscript(&funding_pubkey, &self.counterparty_pubkeys().funding_pubkey);
 
-		let channel_parameters = self.make_channel_parameters();
-		let directed_channel_parameters = channel_parameters.to_directed(false);
-		let commitment_sig = commitment_tx.get_signature(&directed_channel_parameters, &self.funding_key, &channel_funding_redeemscript, self.channel_value_satoshis, secp_ctx);
+		let built_tx = &commitment_tx.built;
+		let commitment_sig = built_tx.get_signature(&self.funding_key, &channel_funding_redeemscript, self.channel_value_satoshis, secp_ctx);
 
-		let commitment_txid = commitment_tx.calculate_txid(&directed_channel_parameters, secp_ctx);
+		let commitment_txid = commitment_tx.trust_txid();
 
 		let mut htlc_sigs = Vec::with_capacity(commitment_tx.htlcs.len());
 		for htlc in &commitment_tx.htlcs {
@@ -511,9 +510,8 @@ impl ChannelKeys for InMemoryChannelKeys {
 		let funding_pubkey = PublicKey::from_secret_key(secp_ctx, &self.funding_key);
 		let funding_redeemscript = make_funding_redeemscript(&funding_pubkey, &self.counterparty_pubkeys().funding_pubkey);
 
-		let channel_parameters = self.make_channel_parameters();
-		let channel_paramters = channel_parameters.to_directed(true);
-		let sig = commitment_tx.inner.get_signature(&channel_paramters, &self.funding_key, &funding_redeemscript, self.channel_value_satoshis, secp_ctx);
+		let built_tx = &commitment_tx.inner.built;
+		let sig = built_tx.get_signature(&self.funding_key, &funding_redeemscript, self.channel_value_satoshis, secp_ctx);
 		let htlc_sigs_o = self.sign_holder_commitment_htlc_transactions(&commitment_tx, secp_ctx)?;
 		let htlc_sigs = htlc_sigs_o.iter().map(|o| o.unwrap()).collect();
 
@@ -524,10 +522,9 @@ impl ChannelKeys for InMemoryChannelKeys {
 	fn unsafe_sign_holder_commitment<T: secp256k1::Signing + secp256k1::Verification>(&self, holder_commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()> {
 		let funding_pubkey = PublicKey::from_secret_key(secp_ctx, &self.funding_key);
 		let channel_funding_redeemscript = make_funding_redeemscript(&funding_pubkey, &self.counterparty_pubkeys().funding_pubkey);
-		let channel_parameters = self.make_channel_parameters();
-		let channel_parameters = channel_parameters.to_directed(true);
 
-		Ok(holder_commitment_tx.inner.get_signature(&channel_parameters, &self.funding_key, &channel_funding_redeemscript, self.channel_value_satoshis, secp_ctx))
+		let built_tx = &holder_commitment_tx.inner.built;
+		Ok(built_tx.get_signature(&self.funding_key, &channel_funding_redeemscript, self.channel_value_satoshis, secp_ctx))
 	}
 
 	fn sign_holder_commitment_htlc_transactions<T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<T>) -> Result<Vec<Option<Signature>>, ()> {