Expose new BumpChannelClose event for channels with anchor outputs

lightning/src/chain/chainmonitor.rs

@@ -707,6 +707,7 @@ impl<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref> even
 	      L::Target: Logger,
 	      P::Target: Persist<ChannelSigner>,
 {
+	#[cfg(not(anchors))]
 	/// Processes [`SpendableOutputs`] events produced from each [`ChannelMonitor`] upon maturity.
 	///
 	/// An [`EventHandler`] may safely call back to the provider, though this shouldn't be needed in
@@ -722,6 +723,29 @@ impl<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref> even
 			handler.handle_event(&event);
 		}
 	}
+	#[cfg(anchors)]
+	/// Processes [`SpendableOutputs`] events produced from each [`ChannelMonitor`] upon maturity.
+	///
+	/// For channels featuring anchor outputs, this method will also process [`BumpTransaction`]
+	/// events produced from each [`ChannelMonitor`] while there is a balance to claim onchain
+	/// within each channel. As the confirmation of a commitment transaction may be critical to the
+	/// safety of funds, this method must be invoked frequently, ideally once for every chain tip
+	/// update (block connected or disconnected).
+	///
+	/// An [`EventHandler`] may safely call back to the provider, though this shouldn't be needed in
+	/// order to handle these events.
+	///
+	/// [`SpendableOutputs`]: events::Event::SpendableOutputs
+	/// [`BumpTransaction`]: events::Event::BumpTransaction
+	fn process_pending_events<H: Deref>(&self, handler: H) where H::Target: EventHandler {
+		let mut pending_events = Vec::new();
+		for monitor_state in self.monitors.read().unwrap().values() {
+			pending_events.append(&mut monitor_state.monitor.get_and_clear_pending_events());
+		}
+		for event in pending_events.drain(..) {
+			handler.handle_event(&event);
+		}
+	}
 }
 
 #[cfg(test)]

lightning/src/chain/channelmonitor.rs

@@ -21,8 +21,7 @@
 //! ChannelMonitors to get out of the HSM and onto monitoring devices.
 
 use bitcoin::blockdata::block::BlockHeader;
-use bitcoin::blockdata::transaction::{TxOut,Transaction};
-use bitcoin::blockdata::transaction::OutPoint as BitcoinOutPoint;
+use bitcoin::blockdata::transaction::{OutPoint as BitcoinOutPoint, TxOut, Transaction};
 use bitcoin::blockdata::script::{Script, Builder};
 use bitcoin::blockdata::opcodes;
 
@@ -44,13 +43,17 @@ use chain::{BestBlock, WatchedOutput};
 use chain::chaininterface::{BroadcasterInterface, FeeEstimator, LowerBoundedFeeEstimator};
 use chain::transaction::{OutPoint, TransactionData};
 use chain::keysinterface::{SpendableOutputDescriptor, StaticPaymentOutputDescriptor, DelayedPaymentOutputDescriptor, Sign, KeysInterface};
+#[cfg(anchors)]
+use chain::onchaintx::ClaimEvent;
 use chain::onchaintx::OnchainTxHandler;
 use chain::package::{CounterpartyOfferedHTLCOutput, CounterpartyReceivedHTLCOutput, HolderFundingOutput, HolderHTLCOutput, PackageSolvingData, PackageTemplate, RevokedOutput, RevokedHTLCOutput};
 use chain::Filter;
 use util::logger::Logger;
 use util::ser::{Readable, ReadableArgs, MaybeReadable, Writer, Writeable, U48, OptionDeserWrapper};
 use util::byte_utils;
 use util::events::Event;
+#[cfg(anchors)]
+use util::events::{AnchorDescriptor, BumpTransactionEvent};
 
 use prelude::*;
 use core::{cmp, mem};
@@ -263,6 +266,20 @@ impl_writeable_tlv_based!(HolderSignedTx, {
 	(14, htlc_outputs, vec_type)
 });
 
+#[cfg(anchors)]
+impl HolderSignedTx {
+	fn non_dust_htlcs(&self) -> Vec<HTLCOutputInCommitment> {
+		self.htlc_outputs.iter().filter_map(|(htlc, _, _)| {
+			if let Some(_) = htlc.transaction_output_index {
+				Some(htlc.clone())
+			} else {
+				None
+			}
+		})
+		.collect()
+	}
+}
+
 /// We use this to track static counterparty commitment transaction data and to generate any
 /// justice or 2nd-stage preimage/timeout transactions.
 #[derive(PartialEq, Eq)]
@@ -1221,7 +1238,7 @@ impl<Signer: Sign> ChannelMonitor<Signer> {
 		B::Target: BroadcasterInterface,
 		L::Target: Logger,
 	{
-		self.inner.lock().unwrap().broadcast_latest_holder_commitment_txn(broadcaster, logger)
+		self.inner.lock().unwrap().broadcast_latest_holder_commitment_txn(broadcaster, logger);
 	}
 
 	/// Updates a ChannelMonitor on the basis of some new information provided by the Channel
@@ -2222,6 +2239,7 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
 			panic!("Attempted to apply ChannelMonitorUpdates out of order, check the update_id before passing an update to update_monitor!");
 		}
 		let mut ret = Ok(());
+		let bounded_fee_estimator = LowerBoundedFeeEstimator::new(&*fee_estimator);
 		for update in updates.updates.iter() {
 			match update {
 				ChannelMonitorUpdateStep::LatestHolderCommitmentTXInfo { commitment_tx, htlc_outputs } => {
@@ -2239,7 +2257,6 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
 				},
 				ChannelMonitorUpdateStep::PaymentPreimage { payment_preimage } => {
 					log_trace!(logger, "Updating ChannelMonitor with payment preimage");
-					let bounded_fee_estimator = LowerBoundedFeeEstimator::new(&*fee_estimator);
 					self.provide_payment_preimage(&PaymentHash(Sha256::hash(&payment_preimage.0[..]).into_inner()), &payment_preimage, broadcaster, &bounded_fee_estimator, logger)
 				},
 				ChannelMonitorUpdateStep::CommitmentSecret { idx, secret } => {
@@ -2255,6 +2272,25 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
 					self.lockdown_from_offchain = true;
 					if *should_broadcast {
 						self.broadcast_latest_holder_commitment_txn(broadcaster, logger);
+						// If the channel supports anchor outputs, we'll need to emit an external
+						// event to be consumed such that a child transaction is broadcast with a
+						// high enough feerate for the parent commitment transaction to confirm.
+						if self.onchain_tx_handler.opt_anchors() {
+							let funding_output = HolderFundingOutput::build(
+								self.funding_redeemscript.clone(), self.channel_value_satoshis,
+								self.onchain_tx_handler.opt_anchors(),
+							);
+							let best_block_height = self.best_block.height();
+							let commitment_package = PackageTemplate::build_package(
+								self.funding_info.0.txid.clone(), self.funding_info.0.index as u32,
+								PackageSolvingData::HolderFundingOutput(funding_output),
+								best_block_height, false, best_block_height,
+							);
+							self.onchain_tx_handler.update_claims_view(
+								&[], vec![commitment_package], best_block_height, best_block_height,
+								broadcaster, &bounded_fee_estimator, logger,
+							);
+						}
 					} else if !self.holder_tx_signed {
 						log_error!(logger, "WARNING: You have a potentially-unsafe holder commitment transaction available to broadcast");
 						log_error!(logger, "    in channel monitor for channel {}!", log_bytes!(self.funding_info.0.to_channel_id()));
@@ -2309,6 +2345,34 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
 	pub fn get_and_clear_pending_events(&mut self) -> Vec<Event> {
 		let mut ret = Vec::new();
 		mem::swap(&mut ret, &mut self.pending_events);
+		#[cfg(anchors)]
+		for claim_event in self.onchain_tx_handler.get_and_clear_pending_claim_events().drain(..) {
+			match claim_event {
+				ClaimEvent::BumpCommitment {
+					package_target_feerate_sat_per_1000_weight, commitment_tx, anchor_output_idx,
+				} => {
+					let commitment_txid = commitment_tx.txid();
+					debug_assert_eq!(self.current_holder_commitment_tx.txid, commitment_txid);
+					let pending_htlcs = self.current_holder_commitment_tx.non_dust_htlcs();
+					let commitment_tx_fee_satoshis = self.channel_value_satoshis -
+						commitment_tx.output.iter().fold(0u64, |sum, output| sum + output.value);
+					ret.push(Event::BumpTransaction(BumpTransactionEvent::ChannelClose {
+						package_target_feerate_sat_per_1000_weight,
+						commitment_tx,
+						commitment_tx_fee_satoshis,
+						anchor_descriptor: AnchorDescriptor {
+							channel_keys_id: self.channel_keys_id,
+							channel_value_satoshis: self.channel_value_satoshis,
+							outpoint: BitcoinOutPoint {
+								txid: commitment_txid,
+								vout: anchor_output_idx,
+							},
+						},
+						pending_htlcs,
+					}));
+				},
+			}
+		}
 		ret
 	}
 
@@ -2521,13 +2585,13 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
 							CounterpartyOfferedHTLCOutput::build(*per_commitment_point,
 								self.counterparty_commitment_params.counterparty_delayed_payment_base_key,
 								self.counterparty_commitment_params.counterparty_htlc_base_key,
-								preimage.unwrap(), htlc.clone()))
+								preimage.unwrap(), htlc.clone(), self.onchain_tx_handler.opt_anchors()))
 					} else {
 						PackageSolvingData::CounterpartyReceivedHTLCOutput(
 							CounterpartyReceivedHTLCOutput::build(*per_commitment_point,
 								self.counterparty_commitment_params.counterparty_delayed_payment_base_key,
 								self.counterparty_commitment_params.counterparty_htlc_base_key,
-								htlc.clone()))
+								htlc.clone(), self.onchain_tx_handler.opt_anchors()))
 					};
 					let aggregation = if !htlc.offered { false } else { true };
 					let counterparty_package = PackageTemplate::build_package(commitment_txid, transaction_output_index, counterparty_htlc_outp, htlc.cltv_expiry,aggregation, 0);
@@ -2884,21 +2948,26 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
 
 		let should_broadcast = self.should_broadcast_holder_commitment_txn(logger);
 		if should_broadcast {
-			let funding_outp = HolderFundingOutput::build(self.funding_redeemscript.clone());
+			let funding_outp = HolderFundingOutput::build(self.funding_redeemscript.clone(), self.channel_value_satoshis, self.onchain_tx_handler.opt_anchors());
 			let commitment_package = PackageTemplate::build_package(self.funding_info.0.txid.clone(), self.funding_info.0.index as u32, PackageSolvingData::HolderFundingOutput(funding_outp), self.best_block.height(), false, self.best_block.height());
 			claimable_outpoints.push(commitment_package);
 			self.pending_monitor_events.push(MonitorEvent::CommitmentTxConfirmed(self.funding_info.0));
 			let commitment_tx = self.onchain_tx_handler.get_fully_signed_holder_tx(&self.funding_redeemscript);
 			self.holder_tx_signed = true;
-			// Because we're broadcasting a commitment transaction, we should construct the package
-			// assuming it gets confirmed in the next block. Sadly, we have code which considers
-			// "not yet confirmed" things as discardable, so we cannot do that here.
-			let (mut new_outpoints, _) = self.get_broadcasted_holder_claims(&self.current_holder_commitment_tx, self.best_block.height());
-			let new_outputs = self.get_broadcasted_holder_watch_outputs(&self.current_holder_commitment_tx, &commitment_tx);
-			if !new_outputs.is_empty() {
-				watch_outputs.push((self.current_holder_commitment_tx.txid.clone(), new_outputs));
+			// We can't broadcast our HTLC transactions while the commitment transaction is
+			// unconfirmed. We'll delay doing so until we detect the confirmed commitment in
+			// `transactions_confirmed`.
+			if !self.onchain_tx_handler.opt_anchors() {
+				// Because we're broadcasting a commitment transaction, we should construct the package
+				// assuming it gets confirmed in the next block. Sadly, we have code which considers
+				// "not yet confirmed" things as discardable, so we cannot do that here.
+				let (mut new_outpoints, _) = self.get_broadcasted_holder_claims(&self.current_holder_commitment_tx, self.best_block.height());
+				let new_outputs = self.get_broadcasted_holder_watch_outputs(&self.current_holder_commitment_tx, &commitment_tx);
+				if !new_outputs.is_empty() {
+					watch_outputs.push((self.current_holder_commitment_tx.txid.clone(), new_outputs));
+				}
+				claimable_outpoints.append(&mut new_outpoints);
 			}
-			claimable_outpoints.append(&mut new_outpoints);
 		}
 
 		// Find which on-chain events have reached their confirmation threshold.

lightning/src/chain/keysinterface.rs

@@ -36,6 +36,7 @@ use util::crypto::{hkdf_extract_expand_twice, sign};
 use util::ser::{Writeable, Writer, Readable, ReadableArgs};
 
 use chain::transaction::OutPoint;
+use ln::channel::ANCHOR_OUTPUT_VALUE_SATOSHI;
 use ln::{chan_utils, PaymentPreimage};
 use ln::chan_utils::{HTLCOutputInCommitment, make_funding_redeemscript, ChannelPublicKeys, HolderCommitmentTransaction, ChannelTransactionParameters, CommitmentTransaction, ClosingTransaction};
 use ln::msgs::UnsignedChannelAnnouncement;
@@ -348,6 +349,12 @@ pub trait BaseSign {
 	/// chosen to forgo their output as dust.
 	fn sign_closing_transaction(&self, closing_tx: &ClosingTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()>;
 
+	/// Computes the signature for a commitment transaction's anchor output used as an
+	/// input within `anchor_tx`, which spends the commitment transaction, at index `input`.
+	fn sign_holder_anchor_input(
+		&self, anchor_tx: &mut Transaction, input: usize, secp_ctx: &Secp256k1<secp256k1::All>,
+	) -> Result<Signature, ()>;
+
 	/// Signs a channel announcement message with our funding key and our node secret key (aka
 	/// node_id or network_key), proving it comes from one of the channel participants.
 	///
@@ -645,6 +652,7 @@ impl InMemorySigner {
 		witness.push(witness_script.clone().into_bytes());
 		Ok(witness)
 	}
+
 }
 
 impl BaseSign for InMemorySigner {
@@ -762,6 +770,16 @@ impl BaseSign for InMemorySigner {
 		Ok(closing_tx.trust().sign(&self.funding_key, &channel_funding_redeemscript, self.channel_value_satoshis, secp_ctx))
 	}
 
+	fn sign_holder_anchor_input(
+		&self, anchor_tx: &mut Transaction, input: usize, secp_ctx: &Secp256k1<secp256k1::All>,
+	) -> Result<Signature, ()> {
+		let witness_script = chan_utils::get_anchor_redeemscript(&self.holder_channel_pubkeys.funding_pubkey);
+		let sighash = sighash::SighashCache::new(&*anchor_tx).segwit_signature_hash(
+			input, &witness_script, ANCHOR_OUTPUT_VALUE_SATOSHI, EcdsaSighashType::All,
+		).unwrap();
+		Ok(sign(secp_ctx, &hash_to_message!(&sighash[..]), &self.funding_key))
+	}
+
 	fn sign_channel_announcement(&self, msg: &UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<secp256k1::All>)
 	-> Result<(Signature, Signature), ()> {
 		let msghash = hash_to_message!(&Sha256dHash::hash(&msg.encode()[..])[..]);