Tx-Sync: Track spent WatchedOutputs and re-add if unconfirmed

lightning-transaction-sync/src/common.rs

@@ -1,4 +1,5 @@
 use lightning::chain::{Confirm, WatchedOutput};
+use lightning::chain::channelmonitor::ANTI_REORG_DELAY;
 use bitcoin::{Txid, BlockHash, Transaction, OutPoint};
 use bitcoin::block::Header;
 
@@ -13,6 +14,9 @@ pub(crate) struct SyncState {
 	// Outputs that were previously processed, but must not be forgotten yet as
 	// as we still need to monitor any spends on-chain.
 	pub watched_outputs: HashMap<OutPoint, WatchedOutput>,
+	// Outputs for which we previously saw a spend on-chain but kept around until the spends reach
+	// sufficient depth.
+	pub outputs_spends_pending_threshold_conf: Vec<(Txid, u32, OutPoint, WatchedOutput)>,
 	// The tip hash observed during our last sync.
 	pub last_sync_hash: Option<BlockHash>,
 	// Indicates whether we need to resync, e.g., after encountering an error.
@@ -24,6 +28,7 @@ impl SyncState {
 		Self {
 			watched_transactions: HashSet::new(),
 			watched_outputs: HashMap::new(),
+			outputs_spends_pending_threshold_conf: Vec::new(),
 			last_sync_hash: None,
 			pending_sync: false,
 		}
@@ -38,6 +43,17 @@ impl SyncState {
 			}
 
 			self.watched_transactions.insert(txid);
+
+			// If a previously-confirmed output spend is unconfirmed, re-add the watched output to
+			// the tracking map.
+			self.outputs_spends_pending_threshold_conf.retain(|(conf_txid, _, prev_outpoint, output)| {
+				if txid == *conf_txid {
+					self.watched_outputs.insert(*prev_outpoint, output.clone());
+					false
+				} else {
+					true
+				}
+			})
 		}
 	}
 
@@ -57,10 +73,18 @@ impl SyncState {
 			self.watched_transactions.remove(&ctx.tx.txid());
 
 			for input in &ctx.tx.input {
-				self.watched_outputs.remove(&input.previous_output);
+				if let Some(output) = self.watched_outputs.remove(&input.previous_output) {
+					self.outputs_spends_pending_threshold_conf.push((ctx.tx.txid(), ctx.block_height, input.previous_output, output));
+				}
 			}
 		}
 	}
+
+	pub fn prune_output_spends(&mut self, cur_height: u32) {
+		self.outputs_spends_pending_threshold_conf.retain(|(_, conf_height, _, _)| {
+			cur_height < conf_height + ANTI_REORG_DELAY - 1
+		});
+	}
 }
 
 
@@ -104,6 +128,7 @@ impl FilterQueue {
 #[derive(Debug)]
 pub(crate) struct ConfirmedTx {
 	pub tx: Transaction,
+	pub txid: Txid,
 	pub block_header: Header,
 	pub block_height: u32,
 	pub pos: usize,

lightning-transaction-sync/src/electrum.rs

@@ -157,6 +157,9 @@ where
 					for c in &confirmables {
 						c.best_block_updated(&tip_header, tip_height);
 					}
+
+					// Prune any sufficiently confirmed output spends
+					sync_state.prune_output_spends(tip_height);
 				}
 
 				match self.get_confirmed_transactions(&sync_state) {
@@ -254,7 +257,7 @@ where
 
 		// First, check the confirmation status of registered transactions as well as the
 		// status of dependent transactions of registered outputs.
-		let mut confirmed_txs = Vec::new();
+		let mut confirmed_txs: Vec<ConfirmedTx> = Vec::new();
 		let mut watched_script_pubkeys = Vec::with_capacity(
 			sync_state.watched_transactions.len() + sync_state.watched_outputs.len());
 		let mut watched_txs = Vec::with_capacity(sync_state.watched_transactions.len());
@@ -302,6 +305,9 @@ where
 
 				for (i, script_history) in tx_results.iter().enumerate() {
 					let (txid, tx) = &watched_txs[i];
+					if confirmed_txs.iter().any(|ctx| ctx.txid == **txid) {
+						continue;
+					}
 					let mut filtered_history = script_history.iter().filter(|h| h.tx_hash == **txid);
 					if let Some(history) = filtered_history.next()
 					{
@@ -321,6 +327,10 @@ where
 						}
 
 						let txid = possible_output_spend.tx_hash;
+						if confirmed_txs.iter().any(|ctx| ctx.txid == txid) {
+							continue;
+						}
+
 						match self.client.transaction_get(&txid) {
 							Ok(tx) => {
 								let mut is_spend = false;
@@ -416,6 +426,7 @@ where
 						}
 						let confirmed_tx = ConfirmedTx {
 							tx: tx.clone(),
+							txid,
 							block_header, block_height: prob_conf_height,
 							pos,
 						};

lightning-transaction-sync/src/esplora.rs

@@ -153,7 +153,7 @@ where
 						}
 					}
 
-					match maybe_await!(self.sync_best_block_updated(&confirmables, &tip_hash)) {
+					match maybe_await!(self.sync_best_block_updated(&confirmables, &mut sync_state, &tip_hash)) {
 						Ok(()) => {}
 						Err(InternalError::Inconsistency) => {
 							// Immediately restart syncing when we encounter any inconsistencies.
@@ -238,7 +238,7 @@ where
 
 	#[maybe_async]
 	fn sync_best_block_updated(
-		&self, confirmables: &Vec<&(dyn Confirm + Sync + Send)>, tip_hash: &BlockHash,
+		&self, confirmables: &Vec<&(dyn Confirm + Sync + Send)>, sync_state: &mut SyncState, tip_hash: &BlockHash,
 	) -> Result<(), InternalError> {
 
 		// Inform the interface of the new block.
@@ -249,6 +249,9 @@ where
 				for c in confirmables {
 					c.best_block_updated(&tip_header, tip_height);
 				}
+
+				// Prune any sufficiently confirmed output spends
+				sync_state.prune_output_spends(tip_height);
 			}
 		} else {
 			return Err(InternalError::Inconsistency);
@@ -264,10 +267,13 @@ where
 		// First, check the confirmation status of registered transactions as well as the
 		// status of dependent transactions of registered outputs.
 
-		let mut confirmed_txs = Vec::new();
+		let mut confirmed_txs: Vec<ConfirmedTx> = Vec::new();
 
 		for txid in &sync_state.watched_transactions {
-			if let Some(confirmed_tx) = maybe_await!(self.get_confirmed_tx(&txid, None, None))? {
+			if confirmed_txs.iter().any(|ctx| ctx.txid == *txid) {
+				continue;
+			}
+			if let Some(confirmed_tx) = maybe_await!(self.get_confirmed_tx(*txid, None, None))? {
 				confirmed_txs.push(confirmed_tx);
 			}
 		}
@@ -278,9 +284,19 @@ where
 			{
 				if let Some(spending_txid) = output_status.txid {
 					if let Some(spending_tx_status) = output_status.status {
+						if confirmed_txs.iter().any(|ctx| ctx.txid == spending_txid) {
+							if spending_tx_status.confirmed {
+								// Skip inserting duplicate ConfirmedTx entry
+								continue;
+							} else {
+								log_trace!(self.logger, "Inconsistency: Detected previously-confirmed Tx {} as unconfirmed", spending_txid);
+								return Err(InternalError::Inconsistency);
+							}
+						}
+
 						if let Some(confirmed_tx) = maybe_await!(self
 							.get_confirmed_tx(
-								&spending_txid,
+								spending_txid,
 								spending_tx_status.block_hash,
 								spending_tx_status.block_height,
 							))?
@@ -303,7 +319,7 @@ where
 
 	#[maybe_async]
 	fn get_confirmed_tx(
-		&self, txid: &Txid, expected_block_hash: Option<BlockHash>, known_block_height: Option<u32>,
+		&self, txid: Txid, expected_block_hash: Option<BlockHash>, known_block_height: Option<u32>,
 	) -> Result<Option<ConfirmedTx>, InternalError> {
 		if let Some(merkle_block) = maybe_await!(self.client.get_merkle_block(&txid))? {
 			let block_header = merkle_block.header;
@@ -318,22 +334,27 @@ where
 			let mut matches = Vec::new();
 			let mut indexes = Vec::new();
 			let _ = merkle_block.txn.extract_matches(&mut matches, &mut indexes);
-			if indexes.len() != 1 || matches.len() != 1 || matches[0] != *txid {
+			if indexes.len() != 1 || matches.len() != 1 || matches[0] != txid {
 				log_error!(self.logger, "Retrieved Merkle block for txid {} doesn't match expectations. This should not happen. Please verify server integrity.", txid);
 				return Err(InternalError::Failed);
 			}
 
 			// unwrap() safety: len() > 0 is checked above
 			let pos = *indexes.first().unwrap() as usize;
 			if let Some(tx) = maybe_await!(self.client.get_tx(&txid))? {
+				if tx.txid() != txid {
+					log_error!(self.logger, "Retrieved transaction for txid {} doesn't match expectations. This should not happen. Please verify server integrity.", txid);
+					return Err(InternalError::Failed);
+				}
+
 				if let Some(block_height) = known_block_height {
 					// We can take a shortcut here if a previous call already gave us the height.
-					return Ok(Some(ConfirmedTx { tx, block_header, pos, block_height }));
+					return Ok(Some(ConfirmedTx { tx, txid, block_header, pos, block_height }));
 				}
 
 				let block_status = maybe_await!(self.client.get_block_status(&block_hash))?;
 				if let Some(block_height) = block_status.height {
-					return Ok(Some(ConfirmedTx { tx, block_header, pos, block_height }));
+					return Ok(Some(ConfirmedTx { tx, txid, block_header, pos, block_height }));
 				} else {
 					// If any previously-confirmed block suddenly is no longer confirmed, we found
 					// an inconsistency and should start over.