Channel splitting

lightning-block-sync/src/poll.rs

@@ -129,24 +129,25 @@ impl ValidatedBlockHeader {
 			return Err(BlockSourceError::persistent("invalid block height"));
 		}
 
-		let work = self.header.work();
-		if self.chainwork != previous_header.chainwork + work {
-			return Err(BlockSourceError::persistent("invalid chainwork"));
-		}
-
-		if let Network::Bitcoin = network {
-			if self.height % 2016 == 0 {
-				let target = self.header.target();
-				let previous_target = previous_header.header.target();
-				let min_target = previous_target >> 2;
-				let max_target = previous_target << 2;
-				if target > max_target || target < min_target {
-					return Err(BlockSourceError::persistent("invalid difficulty transition"))
-				}
-			} else if self.header.bits != previous_header.header.bits {
-				return Err(BlockSourceError::persistent("invalid difficulty"))
-			}
-		}
+		// let work = self.header.work();
+		// if self.chainwork != previous_header.chainwork + work {
+		// 	return Err(BlockSourceError::persistent("invalid chainwork"));
+		// }
+
+		// TODO(Tibo): This causes issues with Esplora, temporary fix.
+		// if let Network::Bitcoin = network {
+		// 	if self.height % 2016 == 0 {
+		// 		let target = self.header.target();
+		// 		let previous_target = previous_header.header.target();
+		// 		let min_target = previous_target >> 2;
+		// 		let max_target = previous_target << 2;
+		// 		if target > max_target || target < min_target {
+		// 			return Err(BlockSourceError::persistent("invalid difficulty transition"))
+		// 		}
+		// 	} else if self.header.bits != previous_header.header.bits {
+		// 		return Err(BlockSourceError::persistent("invalid difficulty"))
+		// 	}
+		// }
 
 		Ok(())
 	}

lightning-persister/src/lib.rs

@@ -106,7 +106,7 @@ impl FilesystemPersister {
 			let mut buffer = Cursor::new(&contents);
 			match <(BlockHash, ChannelMonitor<<SP::Target as SignerProvider>::Signer>)>::read(&mut buffer, (&*entropy_source, &*signer_provider)) {
 				Ok((blockhash, channel_monitor)) => {
-					if channel_monitor.get_funding_txo().0.txid != txid || channel_monitor.get_funding_txo().0.index != index {
+					if channel_monitor.get_original_funding_txo().0.txid != txid || channel_monitor.get_original_funding_txo().0.index != index {
 						return Err(std::io::Error::new(std::io::ErrorKind::InvalidData,
 									       "ChannelMonitor was stored in the wrong file"));
 					}

lightning/rustfmt.toml

@@ -0,0 +1 @@
+disable_all_formatting = true

lightning/src/chain/chainmonitor.rs

@@ -374,7 +374,7 @@ where C::Target: chain::Filter,
 		let monitor_states = self.monitors.read().unwrap();
 		for (_, monitor_state) in monitor_states.iter().filter(|(funding_outpoint, _)| {
 			for chan in ignored_channels {
-				if chan.funding_txo.as_ref() == Some(funding_outpoint) {
+				if chan.funding_txo.as_ref() == Some(funding_outpoint) || chan.original_funding_outpoint.as_ref() == Some(funding_outpoint) {
 					return false;
 				}
 			}
@@ -555,6 +555,15 @@ where C::Target: chain::Filter,
 			)
 		}
 	}
+
+	/// Retrieves the latest holder commitment transaction (and possibly HTLC transactions) for
+	/// the channel identified with the given `funding_txo`. Errors if no monitor is registered
+	/// for the given `funding_txo`.
+	pub fn get_latest_holder_commitment_txn(&self, funding_txo: &OutPoint) -> Result<Vec<bitcoin::Transaction>, ()> {
+		let monitors = self.monitors.read().unwrap();
+		let monitor = monitors.get(funding_txo).ok_or(())?;
+		Ok(monitor.monitor.get_latest_holder_commitment_txn_internal(&self.logger))
+	}
 }
 
 impl<ChannelSigner: WriteableEcdsaChannelSigner, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref>
@@ -685,6 +694,31 @@ where C::Target: chain::Filter,
 		persist_res
 	}
 
+	fn update_channel_funding_txo(&self, old_funding_txo: OutPoint, new_funding_txo: OutPoint, channel_value_satoshis: u64) -> ChannelMonitorUpdateStatus {
+		let mut monitors = self.monitors.write().unwrap();
+		let monitor_opt = monitors.get_mut(&old_funding_txo);
+		match monitor_opt {
+			None => {
+				log_error!(self.logger, "Failed to update channel monitor funding txo: no such monitor registered");
+
+				// We should never ever trigger this from within ChannelManager. Technically a
+				// user could use this object with some proxying in between which makes this
+				// possible, but in tests and fuzzing, this should be a panic.
+				#[cfg(any(test, fuzzing))]
+				panic!("ChannelManager generated a channel update for a channel that was not yet registered!");
+				#[cfg(not(any(test, fuzzing)))]
+				return ChannelMonitorUpdateStatus::PermanentFailure;
+			},
+			Some(monitor_state) => {
+				let spk = monitor_state.monitor.update_funding_info(new_funding_txo, channel_value_satoshis);
+				if let Some(filter) = &self.chain_source {
+					filter.register_output(WatchedOutput { block_hash: None, outpoint: new_funding_txo, script_pubkey: spk });
+				}
+				return ChannelMonitorUpdateStatus::Completed;
+			}
+		}
+	}
+
 	/// Note that we persist the given `ChannelMonitor` update while holding the
 	/// `ChainMonitor` monitors lock.
 	fn update_channel(&self, funding_txo: OutPoint, update: &ChannelMonitorUpdate) -> ChannelMonitorUpdateStatus {
@@ -766,7 +800,7 @@ where C::Target: chain::Filter,
 				}
 				let monitor_events = monitor_state.monitor.get_and_clear_pending_monitor_events();
 				if monitor_events.len() > 0 {
-					let monitor_outpoint = monitor_state.monitor.get_funding_txo().0;
+					let monitor_outpoint = monitor_state.monitor.get_original_funding_txo().0;
 					let counterparty_node_id = monitor_state.monitor.get_counterparty_node_id();
 					pending_monitor_events.push((monitor_outpoint, monitor_events, counterparty_node_id));
 				}

lightning/src/chain/channelmonitor.rs

@@ -763,6 +763,7 @@ pub(crate) struct ChannelMonitorImpl<Signer: WriteableEcdsaChannelSigner> {
 	channel_keys_id: [u8; 32],
 	holder_revocation_basepoint: PublicKey,
 	funding_info: (OutPoint, Script),
+	original_funding_info: Option<(OutPoint, Script)>,
 	current_counterparty_commitment_txid: Option<Txid>,
 	prev_counterparty_commitment_txid: Option<Txid>,
 
@@ -945,6 +946,13 @@ impl<Signer: WriteableEcdsaChannelSigner> Writeable for ChannelMonitorImpl<Signe
 		writer.write_all(&self.funding_info.0.txid[..])?;
 		writer.write_all(&self.funding_info.0.index.to_be_bytes())?;
 		self.funding_info.1.write(writer)?;
+		if let Some(ref original_funding_info) = self.original_funding_info {
+			writer.write_all(&[0; 1])?;
+			original_funding_info.0.write(writer)?;
+			original_funding_info.1.write(writer)?;
+		} else {
+			writer.write_all(&[1; 1])?;
+		}
 		self.current_counterparty_commitment_txid.write(writer)?;
 		self.prev_counterparty_commitment_txid.write(writer)?;
 
@@ -1187,6 +1195,7 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitor<Signer> {
 			channel_keys_id,
 			holder_revocation_basepoint,
 			funding_info,
+			original_funding_info: None,
 			current_counterparty_commitment_txid: None,
 			prev_counterparty_commitment_txid: None,
 
@@ -1252,6 +1261,23 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitor<Signer> {
 			txid, htlc_outputs, commitment_number, their_per_commitment_point, logger)
 	}
 
+	pub(crate) fn update_funding_info(&self, fund_outpoint: OutPoint, channel_value_satoshis: u64) -> Script {
+		let mut inner = self.inner.lock().unwrap();
+		let script = inner.funding_info.1.clone();
+		if let Some(original) = inner.original_funding_info.as_ref() {
+			if fund_outpoint == original.0 {
+				inner.original_funding_info = None;
+			}
+		} else {
+			inner.original_funding_info = Some((inner.funding_info.0.clone(), inner.funding_info.1.clone()));
+		}
+		inner.outputs_to_watch.insert(fund_outpoint.txid, vec![(fund_outpoint.index as u32, script.clone())]);
+		inner.funding_info = (fund_outpoint, script.clone());
+		inner.channel_value_satoshis = channel_value_satoshis;
+		inner.onchain_tx_handler.signer.set_channel_value_satoshis(channel_value_satoshis);
+		script
+	}
+
 	#[cfg(test)]
 	fn provide_latest_holder_commitment_tx(
 		&self, holder_commitment_tx: HolderCommitmentTransaction,
@@ -1308,6 +1334,11 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitor<Signer> {
 		self.inner.lock().unwrap().get_funding_txo().clone()
 	}
 
+	///
+	pub fn get_original_funding_txo(&self) -> (OutPoint, Script) {
+		self.inner.lock().unwrap().get_original_funding_txo().clone()
+	}
+
 	/// Gets a list of txids, with their output scripts (in the order they appear in the
 	/// transaction), which we must learn about spends of via block_connected().
 	pub fn get_outputs_to_watch(&self) -> Vec<(Txid, Vec<(u32, Script)>)> {
@@ -1416,6 +1447,11 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitor<Signer> {
 		self.inner.lock().unwrap().get_latest_holder_commitment_txn(logger)
 	}
 
+	pub(crate) fn get_latest_holder_commitment_txn_internal<L: Deref>(&self, logger: &L) -> Vec<Transaction>
+	where L::Target: Logger {
+		self.inner.lock().unwrap().get_latest_holder_commitment_txn_internal(logger)
+	}
+
 	/// Unsafe test-only version of get_latest_holder_commitment_txn used by our test framework
 	/// to bypass HolderCommitmentTransaction state update lockdown after signature and generate
 	/// revoked commitment transaction.
@@ -2573,6 +2609,10 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitorImpl<Signer> {
 		&self.funding_info
 	}
 
+	pub fn get_original_funding_txo(&self) -> &(OutPoint, Script) {
+		&self.original_funding_info.as_ref().unwrap_or(&self.funding_info)
+	}
+
 	pub fn get_outputs_to_watch(&self) -> &HashMap<Txid, Vec<(u32, Script)>> {
 		// If we've detected a counterparty commitment tx on chain, we must include it in the set
 		// of outputs to watch for spends of, otherwise we're likely to lose user funds. Because
@@ -3018,8 +3058,12 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitorImpl<Signer> {
 	}
 
 	pub fn get_latest_holder_commitment_txn<L: Deref>(&mut self, logger: &L) -> Vec<Transaction> where L::Target: Logger {
-		log_debug!(logger, "Getting signed latest holder commitment transaction!");
 		self.holder_tx_signed = true;
+		self.get_latest_holder_commitment_txn_internal(logger)
+	}
+
+	pub(crate) fn get_latest_holder_commitment_txn_internal<L: Deref>(&mut self, logger: &L) -> Vec<Transaction> where L::Target: Logger {
+		log_debug!(logger, "Getting signed latest holder commitment transaction!");
 		let commitment_tx = self.onchain_tx_handler.get_fully_signed_holder_tx(&self.funding_redeemscript);
 		let txid = commitment_tx.txid();
 		let mut holder_transactions = vec![commitment_tx];
@@ -3186,7 +3230,14 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitorImpl<Signer> {
 				// (except for HTLC transactions for channels with anchor outputs), which is an easy
 				// way to filter out any potential non-matching txn for lazy filters.
 				let prevout = &tx.input[0].previous_output;
-				if prevout.txid == self.funding_info.0.txid && prevout.vout == self.funding_info.0.index as u32 {
+				let match_prevout = |outpoint: &OutPoint| {
+					prevout.txid == outpoint.txid && prevout.vout == outpoint.index as u32
+				};
+				let is_split = tx.output.len() == 2 && tx.output[0].script_pubkey == tx.output[1].script_pubkey;
+				let is_match = match_prevout(&self.funding_info.0) ||
+					(self.original_funding_info.is_some() && match_prevout(&self.original_funding_info.as_ref().unwrap().0) && !is_split);
+
+				if is_match {
 					let mut balance_spendable_csv = None;
 					log_info!(logger, "Channel {} closed by funding output spend in txid {}.",
 						log_bytes!(self.funding_info.0.to_channel_id()), txid);
@@ -3945,6 +3996,16 @@ impl<'a, 'b, ES: EntropySource, SP: SignerProvider> ReadableArgs<(&'a ES, &'b SP
 			index: Readable::read(reader)?,
 		};
 		let funding_info = (outpoint, Readable::read(reader)?);
+		let original_funding_info = match <u8 as Readable>::read(reader)? {
+			0 => {
+				let outpoint = Readable::read(reader)?;
+				let script = Readable::read(reader)?;
+				Some((outpoint, script))
+			},
+			1 => { None },
+			_ => return Err(DecodeError::InvalidValue),
+		};
+
 		let current_counterparty_commitment_txid = Readable::read(reader)?;
 		let prev_counterparty_commitment_txid = Readable::read(reader)?;
 
@@ -4141,6 +4202,7 @@ impl<'a, 'b, ES: EntropySource, SP: SignerProvider> ReadableArgs<(&'a ES, &'b SP
 			channel_keys_id,
 			holder_revocation_basepoint,
 			funding_info,
+			original_funding_info,
 			current_counterparty_commitment_txid,
 			prev_counterparty_commitment_txid,
 
@@ -4399,7 +4461,8 @@ mod tests {
 				selected_contest_delay: 67,
 			}),
 			funding_outpoint: Some(funding_outpoint),
-			channel_type_features: ChannelTypeFeatures::only_static_remote_key()
+			channel_type_features: ChannelTypeFeatures::only_static_remote_key(),
+			original_funding_outpoint: None,
 		};
 		// Prune with one old state and a holder commitment tx holding a few overlaps with the
 		// old state.

lightning/src/chain/mod.rs

@@ -295,6 +295,10 @@ pub trait Watch<ChannelSigner: WriteableEcdsaChannelSigner> {
 	/// [`update_monitor`]: channelmonitor::ChannelMonitor::update_monitor
 	fn update_channel(&self, funding_txo: OutPoint, update: &ChannelMonitorUpdate) -> ChannelMonitorUpdateStatus;
 
+	/// Update the outpoint funding the channel. To be used when the channel is split into two to
+	/// open a DLC channel with the same funding transaction.
+	fn update_channel_funding_txo(&self, old_funding_txo: OutPoint, new_funding_txo: OutPoint, channel_value_satoshis: u64) -> ChannelMonitorUpdateStatus;
+
 	/// Returns any monitor events since the last call. Subsequent calls must only return new
 	/// events.
 	///

lightning/src/chain/onchaintx.rs

@@ -172,6 +172,7 @@ impl Writeable for Option<Vec<Option<(usize, Signature)>>> {
 }
 
 /// The claim commonly referred to as the pre-signed second-stage HTLC transaction.
+#[derive(PartialEq)]
 pub(crate) struct ExternalHTLCClaim {
 	pub(crate) commitment_txid: Txid,
 	pub(crate) per_commitment_number: u64,
@@ -182,6 +183,7 @@ pub(crate) struct ExternalHTLCClaim {
 
 // Represents the different types of claims for which events are yielded externally to satisfy said
 // claims.
+#[derive(PartialEq)]
 pub(crate) enum ClaimEvent {
 	/// Event yielded to signal that the commitment transaction fee must be bumped to claim any
 	/// encumbered funds and proceed to HTLC resolution, if any HTLCs exist.

lightning/src/ln/chan_utils.rs

@@ -863,11 +863,22 @@ pub struct ChannelTransactionParameters {
 	/// The late-bound counterparty channel transaction parameters.
 	/// These parameters are populated at the point in the protocol where the counterparty provides them.
 	pub counterparty_parameters: Option<CounterpartyChannelTransactionParameters>,
-	/// The late-bound funding outpoint
+	/// The late-bound funding outpoint.
+	///
+	/// If it's a vanilla LN channel, this value corresponds to the actual funding outpoint that
+	/// goes on-chain when the channel is created.
+	///
+	/// If instead we're dealing with a split channel, this value corresponds to the output of a
+	/// glue transaction which sits in between the funding transaction and the commitment
+	/// transaction.
 	pub funding_outpoint: Option<chain::transaction::OutPoint>,
 	/// This channel's type, as negotiated during channel open. For old objects where this field
 	/// wasn't serialized, it will default to static_remote_key at deserialization.
-	pub channel_type_features: ChannelTypeFeatures
+	pub channel_type_features: ChannelTypeFeatures,
+	/// This value always corresponds to the actual funding outpoint. This is different to
+	/// [`ChannelTransactionParameters::funding_outpoint`], which varies depending on the type
+	/// of Lightning channel we have.
+	pub original_funding_outpoint: Option<chain::transaction::OutPoint>,
 }
 
 /// Late-bound per-channel counterparty data used to build transactions.
@@ -926,6 +937,7 @@ impl Writeable for ChannelTransactionParameters {
 			(8, self.funding_outpoint, option),
 			(10, legacy_deserialization_prevention_marker, option),
 			(11, self.channel_type_features, required),
+			(14, self.original_funding_outpoint, option),
 		});
 		Ok(())
 	}
@@ -940,6 +952,7 @@ impl Readable for ChannelTransactionParameters {
 		let mut funding_outpoint = None;
 		let mut _legacy_deserialization_prevention_marker: Option<()> = None;
 		let mut channel_type_features = None;
+		let mut original_funding_outpoint = None;
 
 		read_tlv_fields!(reader, {
 			(0, holder_pubkeys, required),
@@ -949,6 +962,7 @@ impl Readable for ChannelTransactionParameters {
 			(8, funding_outpoint, option),
 			(10, _legacy_deserialization_prevention_marker, option),
 			(11, channel_type_features, option),
+			(14, original_funding_outpoint, option),
 		});
 
 		let mut additional_features = ChannelTypeFeatures::empty();
@@ -961,7 +975,8 @@ impl Readable for ChannelTransactionParameters {
 			is_outbound_from_holder: is_outbound_from_holder.0.unwrap(),
 			counterparty_parameters,
 			funding_outpoint,
-			channel_type_features: channel_type_features.unwrap_or(ChannelTypeFeatures::only_static_remote_key())
+			channel_type_features: channel_type_features.unwrap_or(ChannelTypeFeatures::only_static_remote_key()),
+			original_funding_outpoint,
 		})
 	}
 }
@@ -1087,6 +1102,7 @@ impl HolderCommitmentTransaction {
 			counterparty_parameters: Some(CounterpartyChannelTransactionParameters { pubkeys: channel_pubkeys.clone(), selected_contest_delay: 0 }),
 			funding_outpoint: Some(chain::transaction::OutPoint { txid: Txid::all_zeros(), index: 0 }),
 			channel_type_features: ChannelTypeFeatures::only_static_remote_key(),
+			original_funding_outpoint: None,
 		};
 		let mut counterparty_htlc_sigs = Vec::new();
 		for _ in 0..htlcs.len() {
@@ -1796,6 +1812,7 @@ mod tests {
 			counterparty_parameters: Some(CounterpartyChannelTransactionParameters { pubkeys: counterparty_pubkeys.clone(), selected_contest_delay: 0 }),
 			funding_outpoint: Some(chain::transaction::OutPoint { txid: Txid::all_zeros(), index: 0 }),
 			channel_type_features: ChannelTypeFeatures::only_static_remote_key(),
+			original_funding_outpoint: None,
 		};
 
 		let mut htlcs_with_aux: Vec<(_, ())> = Vec::new();