Include witness weights in FundingNegotiationContext

ChannelManager::splice_channel takes witness weights with the funding
inputs. Storing these in FundingNegotiationContext allows us to use them
when calculating the change output and include them in a common struct
used for initiating a splice-in.

In preparation for having ChannelManager::splice_channel take
FundingTxContributions, add a weight to the
FundingTxContributions::InputsOnly, which supports the splice-in use
case.

Author: jkczyz

lightning/src/ln/channel.rs

@@ -5977,7 +5977,7 @@ pub(super) struct FundingNegotiationContext {
 	pub shared_funding_input: Option<SharedOwnedInput>,
 	/// The funding inputs we will be contributing to the channel.
 	#[allow(dead_code)] // TODO(dual_funding): Remove once contribution to V2 channels is enabled.
-	pub our_funding_inputs: Vec<(TxIn, Transaction)>,
+	pub our_funding_inputs: Vec<(TxIn, Transaction, Weight)>,
 	/// The change output script. This will be used if needed or -- if not set -- generated using
 	/// `SignerProvider::get_destination_script`.
 	#[allow(dead_code)] // TODO(splicing): Remove once splicing is enabled.
@@ -6049,6 +6049,9 @@ impl FundingNegotiationContext {
 			}
 		}
 
+		let funding_inputs =
+			self.our_funding_inputs.into_iter().map(|(txin, tx, _)| (txin, tx)).collect();
+
 		let constructor_args = InteractiveTxConstructorArgs {
 			entropy_source,
 			holder_node_id,
@@ -6057,7 +6060,7 @@ impl FundingNegotiationContext {
 			feerate_sat_per_kw: self.funding_feerate_sat_per_1000_weight,
 			is_initiator: self.is_initiator,
 			funding_tx_locktime: self.funding_tx_locktime,
-			inputs_to_contribute: self.our_funding_inputs,
+			inputs_to_contribute: funding_inputs,
 			shared_funding_input: self.shared_funding_input,
 			shared_funding_output: SharedOwnedOutput::new(
 				shared_funding_output,
@@ -10674,9 +10677,8 @@ where
 				err,
 			),
 		})?;
-		// Convert inputs
-		let mut funding_inputs = Vec::new();
-		for (txin, tx, _) in our_funding_inputs.into_iter() {
+
+		for (_, tx, _) in our_funding_inputs.iter() {
 			const MESSAGE_TEMPLATE: msgs::TxAddInput = msgs::TxAddInput {
 				channel_id: ChannelId([0; 32]),
 				serial_id: 0,
@@ -10694,8 +10696,6 @@ where
 					),
 				});
 			}
-
-			funding_inputs.push((txin, tx));
 		}
 
 		let prev_funding_input = self.funding.to_splice_funding_input();
@@ -10705,7 +10705,7 @@ where
 			funding_tx_locktime: LockTime::from_consensus(locktime),
 			funding_feerate_sat_per_1000_weight: funding_feerate_per_kw,
 			shared_funding_input: Some(prev_funding_input),
-			our_funding_inputs: funding_inputs,
+			our_funding_inputs,
 			change_script,
 		};
 
@@ -12472,7 +12472,7 @@ where
 	pub fn new_outbound<ES: Deref, F: Deref, L: Deref>(
 		fee_estimator: &LowerBoundedFeeEstimator<F>, entropy_source: &ES, signer_provider: &SP,
 		counterparty_node_id: PublicKey, their_features: &InitFeatures, funding_satoshis: u64,
-		funding_inputs: Vec<(TxIn, Transaction)>, user_id: u128, config: &UserConfig,
+		funding_inputs: Vec<(TxIn, Transaction, Weight)>, user_id: u128, config: &UserConfig,
 		current_chain_height: u32, outbound_scid_alias: u64, funding_confirmation_target: ConfirmationTarget,
 		logger: L,
 	) -> Result<Self, APIError>
@@ -12686,6 +12686,8 @@ where
 			value: Amount::from_sat(funding.get_value_satoshis()),
 			script_pubkey: funding.get_funding_redeemscript().to_p2wsh(),
 		};
+		let inputs_to_contribute =
+			our_funding_inputs.into_iter().map(|(txin, tx, _)| (txin, tx)).collect();
 
 		let interactive_tx_constructor = Some(InteractiveTxConstructor::new(
 			InteractiveTxConstructorArgs {
@@ -12696,7 +12698,7 @@ where
 				feerate_sat_per_kw: funding_negotiation_context.funding_feerate_sat_per_1000_weight,
 				funding_tx_locktime: funding_negotiation_context.funding_tx_locktime,
 				is_initiator: false,
-				inputs_to_contribute: our_funding_inputs,
+				inputs_to_contribute,
 				shared_funding_input: None,
 				shared_funding_output: SharedOwnedOutput::new(shared_funding_output, our_funding_contribution_sats),
 				outputs_to_contribute: Vec::new(),

lightning/src/ln/dual_funding_tests.rs

@@ -48,10 +48,7 @@ fn do_test_v2_channel_establishment(session: V2ChannelEstablishmentTestSession)
 	let initiator_funding_inputs: Vec<_> = create_dual_funding_utxos_with_prev_txs(
 		&nodes[0],
 		&[session.initiator_input_value_satoshis],
-	)
-	.into_iter()
-	.map(|(txin, tx, _)| (txin, tx))
-	.collect();
+	);
 
 	// Alice creates a dual-funded channel as initiator.
 	let funding_satoshis = session.funding_input_sats;

lightning/src/ln/interactivetxs.rs

@@ -1884,7 +1884,7 @@ pub(super) fn calculate_change_output_value(
 
 	let mut total_input_satoshis = 0u64;
 	let mut our_funding_inputs_weight = 0u64;
-	for (txin, tx) in context.our_funding_inputs.iter() {
+	for (txin, tx, _) in context.our_funding_inputs.iter() {
 		let txid = tx.compute_txid();
 		if txin.previous_output.txid != txid {
 			return Err(AbortReason::PrevTxOutInvalid);
@@ -1894,6 +1894,7 @@ pub(super) fn calculate_change_output_value(
 			.get(txin.previous_output.vout as usize)
 			.ok_or(AbortReason::PrevTxOutInvalid)?;
 		total_input_satoshis = total_input_satoshis.saturating_add(output.value.to_sat());
+		// FIXME: Can we use the Weight from context.our_funding_inputs?
 		let weight = estimate_input_weight(output).to_wu();
 		our_funding_inputs_weight = our_funding_inputs_weight.saturating_add(weight);
 	}
@@ -1956,7 +1957,7 @@ mod tests {
 	use bitcoin::transaction::Version;
 	use bitcoin::{
 		OutPoint, PubkeyHash, ScriptBuf, Sequence, SignedAmount, Transaction, TxIn, TxOut,
-		WPubkeyHash, Witness,
+		WPubkeyHash, Weight, Witness,
 	};
 	use core::ops::Deref;
 
@@ -2967,9 +2968,10 @@ mod tests {
 					sequence: Sequence::ZERO,
 					witness: Witness::new(),
 				};
-				(txin, tx)
+				let weight = Weight::ZERO;
+				(txin, tx, weight)
 			})
-			.collect::<Vec<(TxIn, Transaction)>>();
+			.collect::<Vec<(TxIn, Transaction, Weight)>>();
 		let our_contributed = 110_000;
 		let txout = TxOut { value: Amount::from_sat(10_000), script_pubkey: ScriptBuf::new() };
 		let outputs = vec![txout];