In splice_channel() check if provided inputs are sufficient

Author: optout21

lightning/src/ln/channel.rs

@@ -8517,7 +8517,7 @@ impl<SP: Deref> FundedChannel<SP> where
 	/// Initiate splicing
 	#[cfg(splicing)]
 	pub fn splice_channel(&mut self, our_funding_contribution_satoshis: i64,
-		funding_feerate_perkw: u32, locktime: u32,
+		our_funding_inputs: Vec<(TxIn, Transaction)>, funding_feerate_perkw: u32, locktime: u32,
 	) -> Result<msgs::SpliceInit, ChannelError> {
 		// Check if a splice has been initiated already.
 		// Note: this could be handled more nicely, and support multiple outstanding splice's, the incoming splice_ack matters anyways.
@@ -8550,6 +8550,17 @@ impl<SP: Deref> FundedChannel<SP> where
 		// Note: post-splice channel value is not yet known at this point, counterpary contribution is not known
 		// (Cannot test for miminum required post-splice channel value)
 
+		// Check that inputs are sufficient to cover our contribution
+		let sum_input: i64 = our_funding_inputs.into_iter().fold(0, |acc, i|
+			acc + i.1.output.get(i.0.previous_output.vout as usize).map(|tx| tx.value.to_sat() as i64).unwrap_or(0)
+		);
+		if sum_input < our_funding_contribution_satoshis {
+			return Err(ChannelError::Warn(format!(
+				"Provided inputs are insufficient for our contribution, {} {}",
+				sum_input, our_funding_contribution_satoshis,
+			)));
+		}
+
 		self.pending_splice_pre = Some(PendingSpliceInfoPre {
 			our_funding_contribution: our_funding_contribution_satoshis,
 		});

lightning/src/ln/channelmanager.rs

@@ -4290,7 +4290,7 @@ where
 	#[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_perkw: u32, locktime: u32,
+		our_funding_inputs: Vec<(TxIn, Transaction)>, funding_feerate_perkw: u32, locktime: u32,
 	) -> Result<(), APIError> {
 		let per_peer_state = self.per_peer_state.read().unwrap();
 
@@ -4304,7 +4304,7 @@ 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, funding_feerate_perkw, locktime)
+					let msg = chan.splice_channel(our_funding_contribution_satoshis, our_funding_inputs, funding_feerate_perkw, locktime)
 						.map_err(|err| APIError::APIMisuseError {
 							err: format!(
 								"Cannot initiate Splicing, {}, channel ID {}", err, channel_id

lightning/src/ln/functional_tests_splice.rs

@@ -229,14 +229,17 @@ fn test_v1_splice_in() {
 	let funding_feerate_perkw = 1024; // TODO
 	let locktime = 0; // TODO
 
+	// Create additional inputs
+	let extra_splice_funding_input_sats = 35_000;
+	let funding_inputs = create_dual_funding_utxos_with_prev_txs(&initiator_node, &[extra_splice_funding_input_sats]);
 	// Initiate splice-in (on initiator_node)
 	let _res = initiator_node
 		.node
 		.splice_channel(
 			&channel_id2,
 			&acceptor_node.node.get_our_node_id(),
 			splice_in_sats as i64,
-			Vec::new(),
+			funding_inputs,
 			funding_feerate_perkw,
 			locktime,
 		)