From bfb9b46fb2fc6aae1c04f32c71bb8dff2bd1a05c Mon Sep 17 00:00:00 2001
From: Matt Corallo <git@bluematt.me>
Date: Fri, 7 Sep 2018 11:56:41 -0400
Subject: [PATCH] Refactor/dont re-enter block_conencted on duplicate watch
 calls

Previously we'd hit an infinite loop if a block_connected call
always resulted in the same ChainWatchInterface registrations.
While we're at it, we also split ChainWatchUtil in two to make
things a bit more flexible for users, though not sure if that
actually matters, and make the matching more aggressive in testing,
even if we pick the more performant option at runtime.
---
 src/chain/chaininterface.rs | 137 ++++++++++++++++++++++++++++--------
 1 file changed, 107 insertions(+), 30 deletions(-)

diff --git a/src/chain/chaininterface.rs b/src/chain/chaininterface.rs
index 3a0b2d73..5ff720c3 100644
--- a/src/chain/chaininterface.rs
+++ b/src/chain/chaininterface.rs
@@ -5,9 +5,12 @@ use bitcoin::blockdata::constants::genesis_block;
 use bitcoin::util::hash::Sha256dHash;
 use bitcoin::network::constants::Network;
 use bitcoin::network::serialize::BitcoinHash;
+
 use util::logger::Logger;
+
 use std::sync::{Mutex,Weak,MutexGuard,Arc};
 use std::sync::atomic::{AtomicUsize, Ordering};
+use std::collections::HashSet;
 
 /// Used to give chain error details upstream
 pub enum ChainError {
@@ -57,6 +60,8 @@ pub trait ChainListener: Sync + Send {
 	/// Note that if a new transaction/outpoint is watched during a block_connected call, the block
 	/// *must* be re-scanned with the new transaction/outpoints and block_connected should be
 	/// called again with the same header and (at least) the new transactions.
+	/// Note that if non-new transaction/outpoints may be registered during a call, a second call
+	/// *must not* happen.
 	/// This also means those counting confirmations using block_connected callbacks should watch
 	/// for duplicate headers and not count them towards confirmations!
 	fn block_connected(&self, header: &BlockHeader, height: u32, txn_matched: &[&Transaction], indexes_of_txn_matched: &[u32]);
@@ -85,11 +90,98 @@ pub trait FeeEstimator: Sync + Send {
 	fn get_est_sat_per_1000_weight(&self, confirmation_target: ConfirmationTarget) -> u64;
 }
 
+/// Utility for tracking registered txn/outpoints and checking for matches
+pub struct ChainWatchedUtil {
+	watch_all: bool,
+
+	// We are more conservative in matching during testing to ensure everything matches *exactly*,
+	// even though during normal runtime we take more optimized match approaches...
+	#[cfg(test)]
+	watched_txn: HashSet<(Sha256dHash, Script)>,
+	#[cfg(not(test))]
+	watched_txn: HashSet<Script>,
+
+	watched_outpoints: HashSet<(Sha256dHash, u32)>,
+}
+
+impl ChainWatchedUtil {
+	/// Constructs an empty (watches nothing) ChainWatchedUtil
+	pub fn new() -> Self {
+		Self {
+			watch_all: false,
+			watched_txn: HashSet::new(),
+			watched_outpoints: HashSet::new(),
+		}
+	}
+
+	/// Registers a tx for monitoring, returning true if it was a new tx and false if we'd already
+	/// been watching for it.
+	pub fn register_tx(&mut self, txid: &Sha256dHash, script_pub_key: &Script) -> bool {
+		if self.watch_all { return false; }
+		#[cfg(test)]
+		{
+			self.watched_txn.insert((txid.clone(), script_pub_key.clone()))
+		}
+		#[cfg(not(test))]
+		{
+			let _tx_unused = txid; // Its used in cfg(test), though
+			self.watched_txn.insert(script_pub_key.clone())
+		}
+	}
+
+	/// Registers an outpoint for monitoring, returning true if it was a new outpoint and false if
+	/// we'd already been watching for it
+	pub fn register_outpoint(&mut self, outpoint: (Sha256dHash, u32), _script_pub_key: &Script) -> bool {
+		if self.watch_all { return false; }
+		self.watched_outpoints.insert(outpoint)
+	}
+
+	/// Sets us to match all transactions, returning true if this is a new setting anf false if
+	/// we'd already been set to match everything.
+	pub fn watch_all(&mut self) -> bool {
+		if self.watch_all { return false; }
+		self.watch_all = true;
+		true
+	}
+
+	/// Checks if a given transaction matches the current filter.
+	pub fn does_match_tx(&self, tx: &Transaction) -> bool {
+		if self.watch_all {
+			return true;
+		}
+		for out in tx.output.iter() {
+			#[cfg(test)]
+			for &(ref txid, ref script) in self.watched_txn.iter() {
+				if *script == out.script_pubkey {
+					if tx.txid() == *txid {
+						return true;
+					}
+				}
+			}
+			#[cfg(not(test))]
+			for script in self.watched_txn.iter() {
+				if *script == out.script_pubkey {
+					return true;
+				}
+			}
+		}
+		for input in tx.input.iter() {
+			for outpoint in self.watched_outpoints.iter() {
+				let &(outpoint_hash, outpoint_index) = outpoint;
+				if outpoint_hash == input.previous_output.txid && outpoint_index == input.previous_output.vout {
+					return true;
+				}
+			}
+		}
+		false
+	}
+}
+
 /// Utility to capture some common parts of ChainWatchInterface implementors.
 /// Keeping a local copy of this in a ChainWatchInterface implementor is likely useful.
 pub struct ChainWatchInterfaceUtil {
 	network: Network,
-	watched: Mutex<(Vec<Script>, Vec<(Sha256dHash, u32)>, bool)>, //TODO: Something clever to optimize this
+	watched: Mutex<ChainWatchedUtil>,
 	listeners: Mutex<Vec<Weak<ChainListener>>>,
 	reentered: AtomicUsize,
 	logger: Arc<Logger>,
@@ -97,22 +189,25 @@ pub struct ChainWatchInterfaceUtil {
 
 /// Register listener
 impl ChainWatchInterface for ChainWatchInterfaceUtil {
-	fn install_watch_tx(&self, _txid: &Sha256dHash, script_pub_key: &Script) {
+	fn install_watch_tx(&self, txid: &Sha256dHash, script_pub_key: &Script) {
 		let mut watched = self.watched.lock().unwrap();
-		watched.0.push(script_pub_key.clone());
-		self.reentered.fetch_add(1, Ordering::Relaxed);
+		if watched.register_tx(txid, script_pub_key) {
+			self.reentered.fetch_add(1, Ordering::Relaxed);
+		}
 	}
 
-	fn install_watch_outpoint(&self, outpoint: (Sha256dHash, u32), _out_script: &Script) {
+	fn install_watch_outpoint(&self, outpoint: (Sha256dHash, u32), out_script: &Script) {
 		let mut watched = self.watched.lock().unwrap();
-		watched.1.push(outpoint);
-		self.reentered.fetch_add(1, Ordering::Relaxed);
+		if watched.register_outpoint(outpoint, out_script) {
+			self.reentered.fetch_add(1, Ordering::Relaxed);
+		}
 	}
 
 	fn watch_all_txn(&self) {
 		let mut watched = self.watched.lock().unwrap();
-		watched.2 = true;
-		self.reentered.fetch_add(1, Ordering::Relaxed);
+		if watched.watch_all() {
+			self.reentered.fetch_add(1, Ordering::Relaxed);
+		}
 	}
 
 	fn register_listener(&self, listener: Weak<ChainListener>) {
@@ -132,7 +227,7 @@ impl ChainWatchInterfaceUtil {
 	pub fn new(network: Network, logger: Arc<Logger>) -> ChainWatchInterfaceUtil {
 		ChainWatchInterfaceUtil {
 			network: network,
-			watched: Mutex::new((Vec::new(), Vec::new(), false)),
+			watched: Mutex::new(ChainWatchedUtil::new()),
 			listeners: Mutex::new(Vec::new()),
 			reentered: AtomicUsize::new(1),
 			logger: logger,
@@ -195,25 +290,7 @@ impl ChainWatchInterfaceUtil {
 		self.does_match_tx_unguarded (tx, &watched)
 	}
 
-	fn does_match_tx_unguarded(&self, tx: &Transaction, watched: &MutexGuard<(Vec<Script>, Vec<(Sha256dHash, u32)>, bool)>) -> bool {
-		if watched.2 {
-			return true;
-		}
-		for out in tx.output.iter() {
-			for script in watched.0.iter() {
-				if script[..] == out.script_pubkey[..] {
-					return true;
-				}
-			}
-		}
-		for input in tx.input.iter() {
-			for outpoint in watched.1.iter() {
-				let &(outpoint_hash, outpoint_index) = outpoint;
-				if outpoint_hash == input.previous_output.txid && outpoint_index == input.previous_output.vout {
-					return true;
-				}
-			}
-		}
-		false
+	fn does_match_tx_unguarded(&self, tx: &Transaction, watched: &MutexGuard<ChainWatchedUtil>) -> bool {
+		watched.does_match_tx(tx)
 	}
 }
-- 
2.30.2