f include remote_value to account for splice outs by counterparty

Author: dunxen

lightning/src/ln/interactivetxs.rs

@@ -84,6 +84,7 @@ struct NegotiationContext {
 	outputs: HashMap<SerialId, TxOut>,
 	tx_locktime: AbsoluteLockTime,
 	feerate_sat_per_kw: u32,
+	to_remote_value: u64,
 }
 
 impl NegotiationContext {
@@ -314,7 +315,11 @@ impl NegotiationContext {
 		for output in self.counterparty_outputs_contributed() {
 			counterparty_outputs_value = counterparty_outputs_value.saturating_add(output.value);
 		}
-		if counterparty_inputs_value < counterparty_outputs_value {
+		// ...actually the counterparty might be splicing out, so that their balance also contributes
+		// to the total input value.
+		if counterparty_inputs_value.saturating_add(self.to_remote_value)
+			< counterparty_outputs_value
+		{
 			return Err(AbortReason::OutputsValueExceedsInputsValue);
 		}
 
@@ -549,7 +554,10 @@ macro_rules! define_state_machine_transitions {
 }
 
 impl StateMachine {
-	fn new(feerate_sat_per_kw: u32, is_initiator: bool, tx_locktime: AbsoluteLockTime) -> Self {
+	fn new(
+		feerate_sat_per_kw: u32, is_initiator: bool, tx_locktime: AbsoluteLockTime,
+		to_remote_value: u64,
+	) -> Self {
 		let context = NegotiationContext {
 			tx_locktime,
 			holder_is_initiator: is_initiator,
@@ -559,6 +567,7 @@ impl StateMachine {
 			prevtx_outpoints: new_hash_set(),
 			outputs: new_hash_map(),
 			feerate_sat_per_kw,
+			to_remote_value,
 		};
 		if is_initiator {
 			Self::RemoteChange(RemoteChange(context))
@@ -643,12 +652,13 @@ impl InteractiveTxConstructor {
 	pub fn new<ES: Deref>(
 		entropy_source: &ES, channel_id: ChannelId, feerate_sat_per_kw: u32, is_initiator: bool,
 		tx_locktime: AbsoluteLockTime, inputs_to_contribute: Vec<(TxIn, TransactionU16LenLimited)>,
-		outputs_to_contribute: Vec<TxOut>,
+		outputs_to_contribute: Vec<TxOut>, to_remote_value: u64,
 	) -> (Self, Option<InteractiveTxMessageSend>)
 	where
 		ES::Target: EntropySource,
 	{
-		let state_machine = StateMachine::new(feerate_sat_per_kw, is_initiator, tx_locktime);
+		let state_machine =
+			StateMachine::new(feerate_sat_per_kw, is_initiator, tx_locktime, to_remote_value);
 		let inputs_to_contribute = inputs_to_contribute
 			.into_iter()
 			.map(|(input, tx)| {
@@ -813,6 +823,7 @@ mod tests {
 			tx_locktime,
 			session.inputs_a,
 			session.outputs_a,
+			0,
 		);
 		let (mut constructor_b, first_message_b) = InteractiveTxConstructor::new(
 			&&entropy_source,
@@ -822,6 +833,7 @@ mod tests {
 			tx_locktime,
 			session.inputs_b,
 			session.outputs_b,
+			0,
 		);
 
 		let handle_message_send =