Claim HTLCs with preimage from currently confirmed commitment

We should always claim HTLCs from the currently confirmed commitment,
rather than always claiming from the latest or previous counterparty
commitment if we've seen either confirm onchain at a prior point.

Author: wpaulino

lightning/src/chain/channelmonitor.rs

@@ -2503,6 +2503,18 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitorImpl<Signer> {
 	{
 		self.payment_preimages.insert(payment_hash.clone(), payment_preimage.clone());
 
+		let confirmed_spend_txid = self.funding_spend_confirmed.or_else(|| {
+			self.onchain_events_awaiting_threshold_conf.iter().find_map(|event| match event.event {
+				OnchainEvent::FundingSpendConfirmation { .. } => Some(event.txid),
+				_ => None,
+			})
+		});
+		let confirmed_spend_txid = if let Some(txid) = confirmed_spend_txid {
+			txid
+		} else {
+			return;
+		};
+
 		// If the channel is force closed, try to claim the output from this preimage.
 		// First check if a counterparty commitment transaction has been broadcasted:
 		macro_rules! claim_htlcs {
@@ -2512,14 +2524,24 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitorImpl<Signer> {
 			}
 		}
 		if let Some(txid) = self.current_counterparty_commitment_txid {
-			if let Some(commitment_number) = self.counterparty_commitment_txn_on_chain.get(&txid) {
-				claim_htlcs!(*commitment_number, txid);
+			if txid == confirmed_spend_txid {
+				if let Some(commitment_number) = self.counterparty_commitment_txn_on_chain.get(&txid) {
+					claim_htlcs!(*commitment_number, txid);
+				} else {
+					debug_assert!(false);
+					log_error!(logger, "Detected counterparty commitment tx on-chain without tracking commitment number");
+				}
 				return;
 			}
 		}
 		if let Some(txid) = self.prev_counterparty_commitment_txid {
-			if let Some(commitment_number) = self.counterparty_commitment_txn_on_chain.get(&txid) {
-				claim_htlcs!(*commitment_number, txid);
+			if txid == confirmed_spend_txid {
+				if let Some(commitment_number) = self.counterparty_commitment_txn_on_chain.get(&txid) {
+					claim_htlcs!(*commitment_number, txid);
+				} else {
+					debug_assert!(false);
+					log_error!(logger, "Detected counterparty commitment tx on-chain without tracking commitment number");
+				}
 				return;
 			}
 		}
@@ -2530,13 +2552,22 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitorImpl<Signer> {
 		// *we* sign a holder commitment transaction, not when e.g. a watchtower broadcasts one of our
 		// holder commitment transactions.
 		if self.broadcasted_holder_revokable_script.is_some() {
-			// Assume that the broadcasted commitment transaction confirmed in the current best
-			// block. Even if not, its a reasonable metric for the bump criteria on the HTLC
-			// transactions.
-			let (claim_reqs, _) = self.get_broadcasted_holder_claims(&self.current_holder_commitment_tx, self.best_block.height());
-			self.onchain_tx_handler.update_claims_view_from_requests(claim_reqs, self.best_block.height(), self.best_block.height(), broadcaster, fee_estimator, logger);
-			if let Some(ref tx) = self.prev_holder_signed_commitment_tx {
-				let (claim_reqs, _) = self.get_broadcasted_holder_claims(&tx, self.best_block.height());
+			let holder_commitment_tx = if self.current_holder_commitment_tx.txid == confirmed_spend_txid {
+				Some(&self.current_holder_commitment_tx)
+			} else if let Some(prev_holder_commitment_tx) = &self.prev_holder_signed_commitment_tx {
+				if prev_holder_commitment_tx.txid == confirmed_spend_txid {
+					Some(prev_holder_commitment_tx)
+				} else {
+					None
+				}
+			} else {
+				None
+			};
+			if let Some(holder_commitment_tx) = holder_commitment_tx {
+				// Assume that the broadcasted commitment transaction confirmed in the current best
+				// block. Even if not, its a reasonable metric for the bump criteria on the HTLC
+				// transactions.
+				let (claim_reqs, _) = self.get_broadcasted_holder_claims(&holder_commitment_tx, self.best_block.height());
 				self.onchain_tx_handler.update_claims_view_from_requests(claim_reqs, self.best_block.height(), self.best_block.height(), broadcaster, fee_estimator, logger);
 			}
 		}