Include input weight in splice_channel; test util to return weight as well

Author: optout21

lightning/src/ln/channel.rs

@@ -54,7 +54,9 @@ use crate::chain::chaininterface::{FeeEstimator, ConfirmationTarget, LowerBounde
 use crate::chain::channelmonitor::{ChannelMonitor, ChannelMonitorUpdate, ChannelMonitorUpdateStep, LATENCY_GRACE_PERIOD_BLOCKS};
 use crate::chain::transaction::{OutPoint, TransactionData};
 use crate::sign::ecdsa::EcdsaChannelSigner;
-use crate::sign::{EntropySource, ChannelSigner, SignerProvider, NodeSigner, Recipient, P2WPKH_WITNESS_WEIGHT};
+use crate::sign::{EntropySource, ChannelSigner, SignerProvider, NodeSigner, Recipient};
+#[cfg(splicing)]
+use crate::sign::P2WPKH_WITNESS_WEIGHT;
 use crate::events::{ClosureReason, Event};
 use crate::events::bump_transaction::BASE_INPUT_WEIGHT;
 use crate::routing::gossip::NodeId;
@@ -8216,10 +8218,12 @@ impl<SP: Deref> FundedChannel<SP> where
 		}
 	}
 
-	/// Initiate splicing
+	/// Initiate splicing.
+	/// - witness_weight: The witness weight for contributed inputs.
 	#[cfg(splicing)]
 	pub fn splice_channel(&mut self, our_funding_contribution_satoshis: i64,
-		our_funding_inputs: Vec<(TxIn, Transaction)>, funding_feerate_per_kw: u32, locktime: u32,
+		our_funding_inputs: Vec<(TxIn, Transaction)>, witness_weight: Weight,
+		funding_feerate_per_kw: u32, locktime: u32,
 	) -> Result<msgs::SpliceInit, ChannelError> {
 		// Check if a splice has been initiated already.
 		// Note: only a single outstanding splice is supported (per spec)
@@ -8262,10 +8266,10 @@ impl<SP: Deref> FundedChannel<SP> where
 
 		// The +1 is to include the input of the old funding
 		let funding_input_count = our_funding_inputs.len() + 1;
-		// Add weight for inputs (estimated as P2WPKH) *and* spending old funding
+		// Input witness weight, extended with weight for spending old funding
 		let total_witness_weight = Weight::from_wu(
-			our_funding_inputs.len() as u64 * P2WPKH_WITNESS_WEIGHT +
-			2 * P2WPKH_WITNESS_WEIGHT
+			witness_weight.to_wu()
+				.saturating_add(2 * P2WPKH_WITNESS_WEIGHT)
 		);
 		let estimated_fee = estimate_funding_transaction_fee(true, funding_input_count, total_witness_weight, funding_feerate_per_kw);
 		let available_input = sum_input.saturating_sub(estimated_fee);

lightning/src/ln/channelmanager.rs

@@ -4238,10 +4238,12 @@ where
 	/// Note: Currently only splice-in is supported (increase in channel capacity), splice-out is not.
 	/// - our_funding_contribution_satoshis: the amount contributed by us to the channel. This will increase our channel balance.
 	/// - our_funding_inputs: the funding inputs provided by us. If our contribution is positive, our funding inputs must cover at least that amount.
+	/// - witness_weight: The witness weight for contributed inputs.
 	#[cfg(splicing)]
 	pub fn splice_channel(
 		&self, channel_id: &ChannelId, counterparty_node_id: &PublicKey, our_funding_contribution_satoshis: i64,
-		our_funding_inputs: Vec<(TxIn, Transaction)>, funding_feerate_per_kw: u32, locktime: u32,
+		our_funding_inputs: Vec<(TxIn, Transaction)>, witness_weight: Weight,
+		funding_feerate_per_kw: u32, locktime: u32,
 	) -> Result<(), APIError> {
 		let per_peer_state = self.per_peer_state.read().unwrap();
 
@@ -4255,7 +4257,7 @@ where
 		match peer_state.channel_by_id.entry(*channel_id) {
 			hash_map::Entry::Occupied(mut chan_phase_entry) => {
 				if let Some(chan) = chan_phase_entry.get_mut().as_funded_mut() {
-					let msg = chan.splice_channel(our_funding_contribution_satoshis, our_funding_inputs, funding_feerate_per_kw, locktime)
+					let msg = chan.splice_channel(our_funding_contribution_satoshis, our_funding_inputs, witness_weight, funding_feerate_per_kw, locktime)
 						.map_err(|err| APIError::APIMisuseError {
 							err: format!(
 								"Cannot initiate Splicing, {}, channel ID {}", err, channel_id

lightning/src/ln/dual_funding_tests.rs

@@ -51,7 +51,7 @@ fn do_test_v2_channel_establishment(
 	let logger_a = test_utils::TestLogger::with_id("node a".to_owned());
 
 	// Create a funding input for the new channel along with its previous transaction.
-	let initiator_funding_inputs: Vec<_> = create_dual_funding_utxos_with_prev_txs(
+	let (initiator_funding_inputs, total_weight) = create_dual_funding_utxos_with_prev_txs(
 		&nodes[0],
 		&[session.initiator_input_value_satoshis],
 	)
@@ -66,7 +66,7 @@ fn do_test_v2_channel_establishment(
 	let funding_satoshis = calculate_our_funding_satoshis(
 		true,
 		&initiator_funding_inputs[..],
-		Weight::from_wu(P2WPKH_WITNESS_WEIGHT),
+		total_weight,
 		funding_feerate,
 		MIN_CHAN_DUST_LIMIT_SATOSHIS,
 	)

lightning/src/ln/functional_test_utils.rs

@@ -38,7 +38,7 @@ use crate::util::test_utils;
 use crate::util::test_utils::{TestChainMonitor, TestScorer, TestKeysInterface};
 use crate::util::ser::{ReadableArgs, Writeable};
 
-use bitcoin::WPubkeyHash;
+use bitcoin::{Weight, WPubkeyHash};
 use bitcoin::amount::Amount;
 use bitcoin::block::{Block, Header, Version as BlockVersion};
 use bitcoin::locktime::absolute::{LockTime, LOCK_TIME_THRESHOLD};
@@ -60,6 +60,7 @@ use core::mem;
 use core::ops::Deref;
 use crate::io;
 use crate::prelude::*;
+use crate::sign::P2WPKH_WITNESS_WEIGHT;
 use crate::sync::{Arc, Mutex, LockTestExt, RwLock};
 
 pub const CHAN_CONFIRM_DEPTH: u32 = 10;
@@ -1245,9 +1246,11 @@ fn internal_create_funding_transaction<'a, 'b, 'c>(node: &Node<'a, 'b, 'c>,
 	}
 }
 
+/// Create test inputs for a funding transaction.
+/// Return the inputs (with prev tx), and the total witness weight for these inputs
 pub fn create_dual_funding_utxos_with_prev_txs(
 	node: &Node<'_, '_, '_>, utxo_values_in_satoshis: &[u64],
-) -> Vec<(TxIn, Transaction)> {
+) -> (Vec<(TxIn, Transaction)>, Weight) {
 	// Ensure we have unique transactions per node by using the locktime.
 	let tx = Transaction {
 		version: TxVersion::TWO,
@@ -1260,9 +1263,9 @@ pub fn create_dual_funding_utxos_with_prev_txs(
 		}).collect()
 	};
 
-	let mut result = vec![];
+	let mut inputs = vec![];
 	for i in 0..utxo_values_in_satoshis.len() {
-		result.push(
+		inputs.push(
 			(TxIn {
 				previous_output: OutPoint {
 					txid: tx.compute_txid(),
@@ -1273,7 +1276,9 @@ pub fn create_dual_funding_utxos_with_prev_txs(
 				witness: Witness::new(),
 			}, tx.clone()));
 	}
-	result
+	let total_weight = Weight::from_wu(utxo_values_in_satoshis.len() as u64 * P2WPKH_WITNESS_WEIGHT);
+
+	(inputs, total_weight)
 }
 
 pub fn sign_funding_transaction<'a, 'b, 'c>(node_a: &Node<'a, 'b, 'c>, node_b: &Node<'a, 'b, 'c>, channel_value: u64, expected_temporary_channel_id: ChannelId) -> Transaction {

lightning/src/ln/functional_tests_splice.rs

@@ -231,7 +231,7 @@ fn test_v1_splice_in() {
 
 	// Create additional inputs
 	let extra_splice_funding_input_sats = 35_000;
-	let funding_inputs = create_dual_funding_utxos_with_prev_txs(
+	let (funding_inputs, total_weight) = create_dual_funding_utxos_with_prev_txs(
 		&initiator_node,
 		&[extra_splice_funding_input_sats],
 	);
@@ -243,6 +243,7 @@ fn test_v1_splice_in() {
 			&acceptor_node.node.get_our_node_id(),
 			splice_in_sats as i64,
 			funding_inputs,
+			total_weight,
 			funding_feerate_per_kw,
 			locktime,
 		)