Merge pull request #4019 from TheBlueMatt/2025-08-splice-quiescent-real

Integrate Splicing with Quiescence

Author: TheBlueMatt

lightning/src/events/bump_transaction/mod.rs

@@ -264,6 +264,12 @@ pub struct Utxo {
 	pub satisfaction_weight: u64,
 }
 
+impl_writeable_tlv_based!(Utxo, {
+	(1, outpoint, required),
+	(3, output, required),
+	(5, satisfaction_weight, required),
+});
+
 impl Utxo {
 	/// Returns a `Utxo` with the `satisfaction_weight` estimate for a legacy P2PKH output.
 	pub fn new_p2pkh(outpoint: OutPoint, value: Amount, pubkey_hash: &PubkeyHash) -> Self {

lightning/src/ln/channel.rs

@@ -2463,13 +2463,46 @@ impl PendingSplice {
 	}
 }
 
+pub(crate) struct SpliceInstructions {
+	adjusted_funding_contribution: SignedAmount,
+	our_funding_inputs: Vec<FundingTxInput>,
+	our_funding_outputs: Vec<TxOut>,
+	change_script: Option<ScriptBuf>,
+	funding_feerate_per_kw: u32,
+	locktime: u32,
+	original_funding_txo: OutPoint,
+}
+
+impl_writeable_tlv_based!(SpliceInstructions, {
+	(1, adjusted_funding_contribution, required),
+	(3, our_funding_inputs, required_vec),
+	(5, our_funding_outputs, required_vec),
+	(7, change_script, option),
+	(9, funding_feerate_per_kw, required),
+	(11, locktime, required),
+	(13, original_funding_txo, required),
+});
+
 pub(crate) enum QuiescentAction {
-	// TODO: Make this test-only once we have another variant (as some code requires *a* variant).
+	Splice(SpliceInstructions),
+	#[cfg(any(test, fuzzing))]
 	DoNothing,
 }
 
+pub(crate) enum StfuResponse {
+	Stfu(msgs::Stfu),
+	#[cfg_attr(not(splicing), allow(unused))]
+	SpliceInit(msgs::SpliceInit),
+}
+
+#[cfg(any(test, fuzzing))]
 impl_writeable_tlv_based_enum_upgradable!(QuiescentAction,
-	(99, DoNothing) => {},
+	(0, DoNothing) => {},
+	{1, Splice} => (),
+);
+#[cfg(not(any(test, fuzzing)))]
+impl_writeable_tlv_based_enum_upgradable!(QuiescentAction,,
+	{1, Splice} => (),
 );
 
 /// Wrapper around a [`Transaction`] useful for caching the result of [`Transaction::compute_txid`].
@@ -6158,7 +6191,7 @@ fn get_v2_channel_reserve_satoshis(channel_value_satoshis: u64, dust_limit_satos
 fn check_splice_contribution_sufficient(
 	channel_balance: Amount, contribution: &SpliceContribution, is_initiator: bool,
 	funding_feerate: FeeRate,
-) -> Result<Amount, ChannelError> {
+) -> Result<Amount, String> {
 	let contribution_amount = contribution.value();
 	if contribution_amount < SignedAmount::ZERO {
 		let estimated_fee = Amount::from_sat(estimate_v2_funding_transaction_fee(
@@ -6172,10 +6205,10 @@ fn check_splice_contribution_sufficient(
 		if channel_balance >= contribution_amount.unsigned_abs() + estimated_fee {
 			Ok(estimated_fee)
 		} else {
-			Err(ChannelError::Warn(format!(
-				"Available channel balance {} is lower than needed for splicing out {}, considering fees of {}",
-				channel_balance, contribution_amount.unsigned_abs(), estimated_fee,
-			)))
+			Err(format!(
+				"Available channel balance {channel_balance} is lower than needed for splicing out {}, considering fees of {estimated_fee}",
+				contribution_amount.unsigned_abs(),
+			))
 		}
 	} else {
 		check_v2_funding_inputs_sufficient(
@@ -6242,7 +6275,7 @@ fn estimate_v2_funding_transaction_fee(
 fn check_v2_funding_inputs_sufficient(
 	contribution_amount: i64, funding_inputs: &[FundingTxInput], is_initiator: bool,
 	is_splice: bool, funding_feerate_sat_per_1000_weight: u32,
-) -> Result<u64, ChannelError> {
+) -> Result<u64, String> {
 	let estimated_fee = estimate_v2_funding_transaction_fee(
 		funding_inputs, &[], is_initiator, is_splice, funding_feerate_sat_per_1000_weight,
 	);
@@ -6265,10 +6298,9 @@ fn check_v2_funding_inputs_sufficient(
 
 	let minimal_input_amount_needed = contribution_amount.saturating_add(estimated_fee as i64);
 	if (total_input_sats as i64) < minimal_input_amount_needed {
-		Err(ChannelError::Warn(format!(
-			"Total input amount {} is lower than needed for contribution {}, considering fees of {}. Need more inputs.",
-			total_input_sats, contribution_amount, estimated_fee,
-		)))
+		Err(format!(
+			"Total input amount {total_input_sats} is lower than needed for contribution {contribution_amount}, considering fees of {estimated_fee}. Need more inputs.",
+		))
 	} else {
 		Ok(estimated_fee)
 	}
@@ -11022,9 +11054,13 @@ where
 	/// - `change_script`: an option change output script. If `None` and needed, one will be
 	///   generated by `SignerProvider::get_destination_script`.
 	#[cfg(splicing)]
-	pub fn splice_channel(
+	pub fn splice_channel<L: Deref>(
 		&mut self, contribution: SpliceContribution, funding_feerate_per_kw: u32, locktime: u32,
-	) -> Result<msgs::SpliceInit, APIError> {
+		logger: &L,
+	) -> Result<Option<msgs::Stfu>, APIError>
+	where
+		L::Target: Logger,
+	{
 		if self.holder_commitment_point.current_point().is_none() {
 			return Err(APIError::APIMisuseError {
 				err: format!(
@@ -11036,7 +11072,7 @@ where
 
 		// Check if a splice has been initiated already.
 		// Note: only a single outstanding splice is supported (per spec)
-		if self.pending_splice.is_some() {
+		if self.pending_splice.is_some() || self.quiescent_action.is_some() {
 			return Err(APIError::APIMisuseError {
 				err: format!(
 					"Channel {} cannot be spliced, as it has already a splice pending",
@@ -11054,8 +11090,6 @@ where
 			});
 		}
 
-		// TODO(splicing): check for quiescence
-
 		let our_funding_contribution = contribution.value();
 		if our_funding_contribution == SignedAmount::ZERO {
 			return Err(APIError::APIMisuseError {
@@ -11150,8 +11184,50 @@ where
 			}
 		}
 
-		let prev_funding_input = self.funding.to_splice_funding_input();
+		let original_funding_txo = self.funding.get_funding_txo().ok_or_else(|| {
+			debug_assert!(false);
+			APIError::APIMisuseError { err: "Channel isn't yet fully funded".to_owned() }
+		})?;
+
 		let (our_funding_inputs, our_funding_outputs, change_script) = contribution.into_tx_parts();
+
+		let action = QuiescentAction::Splice(SpliceInstructions {
+			adjusted_funding_contribution,
+			our_funding_inputs,
+			our_funding_outputs,
+			change_script,
+			funding_feerate_per_kw,
+			locktime,
+			original_funding_txo,
+		});
+		self.propose_quiescence(logger, action)
+			.map_err(|e| APIError::APIMisuseError { err: e.to_owned() })
+	}
+
+	#[cfg(splicing)]
+	fn send_splice_init(
+		&mut self, instructions: SpliceInstructions,
+	) -> Result<msgs::SpliceInit, String> {
+		let SpliceInstructions {
+			adjusted_funding_contribution,
+			our_funding_inputs,
+			our_funding_outputs,
+			change_script,
+			funding_feerate_per_kw,
+			locktime,
+			original_funding_txo,
+		} = instructions;
+
+		// Check if a splice has been initiated already.
+		// Note: only a single outstanding splice is supported (per spec)
+		if self.pending_splice.is_some() {
+			return Err(format!(
+				"Channel {} cannot be spliced, as it has already a splice pending",
+				self.context.channel_id(),
+			));
+		}
+
+		let prev_funding_input = self.funding.to_splice_funding_input();
 		let funding_negotiation_context = FundingNegotiationContext {
 			is_initiator: true,
 			our_funding_contribution: adjusted_funding_contribution,
@@ -11307,6 +11383,10 @@ where
 		ES::Target: EntropySource,
 		L::Target: Logger,
 	{
+		if !self.context.channel_state.is_quiescent() {
+			return Err(ChannelError::WarnAndDisconnect("Quiescence needed to splice".to_owned()));
+		}
+
 		let our_funding_contribution = SignedAmount::from_sat(our_funding_contribution_satoshis);
 		let splice_funding = self.validate_splice_init(msg, our_funding_contribution)?;
 
@@ -11346,6 +11426,11 @@ where
 			})?;
 		debug_assert!(interactive_tx_constructor.take_initiator_first_message().is_none());
 
+		// TODO(splicing): if quiescent_action is set, integrate what the user wants to do into the
+		// counterparty-initiated splice. For always-on nodes this probably isn't a useful
+		// optimization, but for often-offline nodes it may be, as we may connect and immediately
+		// go into splicing from both sides.
+
 		let funding_pubkey = splice_funding.get_holder_pubkeys().funding_pubkey;
 
 		self.pending_splice = Some(PendingSplice {
@@ -12094,23 +12179,21 @@ where
 		);
 	}
 
-	#[cfg(any(test, fuzzing))]
+	#[cfg(any(splicing, test, fuzzing))]
 	#[rustfmt::skip]
 	pub fn propose_quiescence<L: Deref>(
 		&mut self, logger: &L, action: QuiescentAction,
-	) -> Result<Option<msgs::Stfu>, ChannelError>
+	) -> Result<Option<msgs::Stfu>, &'static str>
 	where
 		L::Target: Logger,
 	{
 		log_debug!(logger, "Attempting to initiate quiescence");
 
 		if !self.context.is_usable() {
-			return Err(ChannelError::Ignore(
-				"Channel is not in a usable state to propose quiescence".to_owned()
-			));
+			return Err("Channel is not in a usable state to propose quiescence");
 		}
 		if self.quiescent_action.is_some() {
-			return Err(ChannelError::Ignore("Channel is already quiescing".to_owned()));
+			return Err("Channel already has a pending quiescent action and cannot start another");
 		}
 
 		self.quiescent_action = Some(action);
@@ -12131,7 +12214,7 @@ where
 
 	// Assumes we are either awaiting quiescence or our counterparty has requested quiescence.
 	#[rustfmt::skip]
-	pub fn send_stfu<L: Deref>(&mut self, logger: &L) -> Result<msgs::Stfu, ChannelError>
+	pub fn send_stfu<L: Deref>(&mut self, logger: &L) -> Result<msgs::Stfu, &'static str>
 	where
 		L::Target: Logger,
 	{
@@ -12145,9 +12228,7 @@ where
 		if self.context.is_waiting_on_peer_pending_channel_update()
 			|| self.context.is_monitor_or_signer_pending_channel_update()
 		{
-			return Err(ChannelError::Ignore(
-				"We cannot send `stfu` while state machine is pending".to_owned()
-			));
+			return Err("We cannot send `stfu` while state machine is pending")
 		}
 
 		let initiator = if self.context.channel_state.is_remote_stfu_sent() {
@@ -12173,7 +12254,7 @@ where
 	#[rustfmt::skip]
 	pub fn stfu<L: Deref>(
 		&mut self, msg: &msgs::Stfu, logger: &L
-	) -> Result<Option<msgs::Stfu>, ChannelError> where L::Target: Logger {
+	) -> Result<Option<StfuResponse>, ChannelError> where L::Target: Logger {
 		if self.context.channel_state.is_quiescent() {
 			return Err(ChannelError::Warn("Channel is already quiescent".to_owned()));
 		}
@@ -12204,7 +12285,10 @@ where
 			self.context.channel_state.set_remote_stfu_sent();
 
 			log_debug!(logger, "Received counterparty stfu proposing quiescence");
-			return self.send_stfu(logger).map(|stfu| Some(stfu));
+			return self
+				.send_stfu(logger)
+				.map(|stfu| Some(StfuResponse::Stfu(stfu)))
+				.map_err(|e| ChannelError::Ignore(e.to_owned()));
 		}
 
 		// We already sent `stfu` and are now processing theirs. It may be in response to ours, or
@@ -12245,6 +12329,13 @@ where
 						"Internal Error: Didn't have anything to do after reaching quiescence".to_owned()
 					));
 				},
+				Some(QuiescentAction::Splice(_instructions)) => {
+					#[cfg(splicing)]
+					return self.send_splice_init(_instructions)
+						.map(|splice_init| Some(StfuResponse::SpliceInit(splice_init)))
+						.map_err(|e| ChannelError::WarnAndDisconnect(e.to_owned()));
+				},
+				#[cfg(any(test, fuzzing))]
 				Some(QuiescentAction::DoNothing) => {
 					// In quiescence test we want to just hang out here, letting the test manually
 					// leave quiescence.
@@ -12277,7 +12368,10 @@ where
 			|| (self.context.channel_state.is_remote_stfu_sent()
 				&& !self.context.channel_state.is_local_stfu_sent())
 		{
-			return self.send_stfu(logger).map(|stfu| Some(stfu));
+			return self
+				.send_stfu(logger)
+				.map(|stfu| Some(stfu))
+				.map_err(|e| ChannelError::Ignore(e.to_owned()));
 		}
 
 		// We're either:
@@ -16478,8 +16572,8 @@ mod tests {
 				2000,
 			);
 			assert_eq!(
-				format!("{:?}", res.err().unwrap()),
-				"Warn: Total input amount 100000 is lower than needed for contribution 220000, considering fees of 1746. Need more inputs.",
+				res.err().unwrap(),
+				"Total input amount 100000 is lower than needed for contribution 220000, considering fees of 1746. Need more inputs.",
 			);
 		}
 
@@ -16514,8 +16608,8 @@ mod tests {
 				2200,
 			);
 			assert_eq!(
-				format!("{:?}", res.err().unwrap()),
-				"Warn: Total input amount 300000 is lower than needed for contribution 298032, considering fees of 2522. Need more inputs.",
+				res.err().unwrap(),
+				"Total input amount 300000 is lower than needed for contribution 298032, considering fees of 2522. Need more inputs.",
 			);
 		}