Remove unnecessary aquiring of the channel_state lock

Author: ViktorTigerstrom

lightning/src/ln/channelmanager.rs

@@ -1891,7 +1891,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 
 		for htlc_source in failed_htlcs.drain(..) {
 			let receiver = HTLCDestination::NextHopChannel { node_id: Some(*counterparty_node_id), channel_id: *channel_id };
-			self.fail_htlc_backwards_internal(self.channel_state.lock().unwrap(), htlc_source.0, &htlc_source.1, HTLCFailReason::Reason { failure_code: 0x4000 | 8, data: Vec::new() }, receiver);
+			self.fail_htlc_backwards_internal(htlc_source.0, &htlc_source.1, HTLCFailReason::Reason { failure_code: 0x4000 | 8, data: Vec::new() }, receiver);
 		}
 
 		let _ = handle_error!(self, result, *counterparty_node_id);
@@ -1949,7 +1949,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 		for htlc_source in failed_htlcs.drain(..) {
 			let (source, payment_hash, counterparty_node_id, channel_id) = htlc_source;
 			let receiver = HTLCDestination::NextHopChannel { node_id: Some(counterparty_node_id), channel_id: channel_id };
-			self.fail_htlc_backwards_internal(self.channel_state.lock().unwrap(), source, &payment_hash, HTLCFailReason::Reason { failure_code: 0x4000 | 8, data: Vec::new() }, receiver);
+			self.fail_htlc_backwards_internal(source, &payment_hash, HTLCFailReason::Reason { failure_code: 0x4000 | 8, data: Vec::new() }, receiver);
 		}
 		if let Some((funding_txo, monitor_update)) = monitor_update_option {
 			// There isn't anything we can do if we get an update failure - we're already
@@ -3493,7 +3493,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 		}
 
 		for (htlc_source, payment_hash, failure_reason, destination) in failed_forwards.drain(..) {
-			self.fail_htlc_backwards_internal(self.channel_state.lock().unwrap(), htlc_source, &payment_hash, failure_reason, destination);
+			self.fail_htlc_backwards_internal(htlc_source, &payment_hash, failure_reason, destination);
 		}
 		self.forward_htlcs(&mut phantom_receives);
 
@@ -3717,7 +3717,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 
 			for htlc_source in timed_out_mpp_htlcs.drain(..) {
 				let receiver = HTLCDestination::FailedPayment { payment_hash: htlc_source.1 };
-				self.fail_htlc_backwards_internal(self.channel_state.lock().unwrap(), HTLCSource::PreviousHopData(htlc_source.0.clone()), &htlc_source.1, HTLCFailReason::Reason { failure_code: 23, data: Vec::new() }, receiver );
+				self.fail_htlc_backwards_internal(HTLCSource::PreviousHopData(htlc_source.0.clone()), &htlc_source.1, HTLCFailReason::Reason { failure_code: 23, data: Vec::new() }, receiver );
 			}
 
 			for (err, counterparty_node_id) in handle_errors.drain(..) {
@@ -3751,7 +3751,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 				let mut htlc_msat_height_data = byte_utils::be64_to_array(htlc.value).to_vec();
 				htlc_msat_height_data.extend_from_slice(&byte_utils::be32_to_array(
 						self.best_block.read().unwrap().height()));
-				self.fail_htlc_backwards_internal(channel_state.take().unwrap(),
+				self.fail_htlc_backwards_internal(
 						HTLCSource::PreviousHopData(htlc.prev_hop), payment_hash,
 						HTLCFailReason::Reason { failure_code: 0x4000 | 15, data: htlc_msat_height_data },
 						HTLCDestination::FailedPayment { payment_hash: *payment_hash });
@@ -3823,10 +3823,8 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 							},
 							hash_map::Entry::Vacant(_) => (0x4000|10, Vec::new())
 						};
-					let channel_state = self.channel_state.lock().unwrap();
-
 					let receiver = HTLCDestination::NextHopChannel { node_id: Some(counterparty_node_id.clone()), channel_id };
-					self.fail_htlc_backwards_internal(channel_state, htlc_src, &payment_hash, HTLCFailReason::Reason { failure_code, data: onion_failure_data }, receiver)
+					self.fail_htlc_backwards_internal(htlc_src, &payment_hash, HTLCFailReason::Reason { failure_code, data: onion_failure_data }, receiver)
 				},
 				HTLCSource::OutboundRoute { session_priv, payment_id, path, payment_params, .. } => {
 					let mut session_priv_bytes = [0; 32];
@@ -3874,12 +3872,9 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 	}
 
 	/// Fails an HTLC backwards to the sender of it to us.
-	/// Note that while we take a channel_state lock as input, we do *not* assume consistency here.
-	/// There are several callsites that do stupid things like loop over a list of payment_hashes
-	/// to fail and take the channel_state lock for each iteration (as we take ownership and may
-	/// drop it). In other words, no assumptions are made that entries in claimable_htlcs point to
-	/// still-available channels.
-	fn fail_htlc_backwards_internal(&self, mut channel_state_lock: MutexGuard<ChannelHolder<Signer>>, source: HTLCSource, payment_hash: &PaymentHash, onion_error: HTLCFailReason, destination: HTLCDestination) {
+	/// Note that while this function pushes events as well as FailHTLC's to fail htlcs for
+	/// designated channels, no assumptions are made that the channels are still available.
+	fn fail_htlc_backwards_internal(&self, source: HTLCSource, payment_hash: &PaymentHash, onion_error: HTLCFailReason,destination: HTLCDestination) {
 		//TODO: There is a timing attack here where if a node fails an HTLC back to us they can
 		//identify whether we sent it or not based on the (I presume) very different runtime
 		//between the branches here. We should make this async and move it into the forward HTLCs
@@ -3918,7 +3913,6 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 					log_trace!(self.logger, "Received duplicative fail for HTLC with payment_hash {}", log_bytes!(payment_hash.0));
 					return;
 				}
-				mem::drop(channel_state_lock);
 				let mut retry = if let Some(payment_params_data) = payment_params {
 					let path_last_hop = path.last().expect("Outbound payments must have had a valid path");
 					Some(RouteParameters {
@@ -4042,7 +4036,6 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 					}
 				}
 				mem::drop(forward_htlcs);
-				mem::drop(channel_state_lock);
 				let mut pending_events = self.pending_events.lock().unwrap();
 				if let Some(time) = forward_event {
 					pending_events.push(events::Event::PendingHTLCsForwardable {
@@ -4142,7 +4135,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 					let mut htlc_msat_height_data = byte_utils::be64_to_array(htlc.value).to_vec();
 					htlc_msat_height_data.extend_from_slice(&byte_utils::be32_to_array(
 							self.best_block.read().unwrap().height()));
-					self.fail_htlc_backwards_internal(channel_state.take().unwrap(),
+					self.fail_htlc_backwards_internal(
 									 HTLCSource::PreviousHopData(htlc.prev_hop), &payment_hash,
 									 HTLCFailReason::Reason { failure_code: 0x4000|15, data: htlc_msat_height_data },
 									 HTLCDestination::FailedPayment { payment_hash } );
@@ -4426,7 +4419,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 		self.finalize_claims(finalized_claims);
 		for failure in pending_failures.drain(..) {
 			let receiver = HTLCDestination::NextHopChannel { node_id: Some(counterparty_node_id), channel_id: funding_txo.to_channel_id() };
-			self.fail_htlc_backwards_internal(self.channel_state.lock().unwrap(), failure.0, &failure.1, failure.2, receiver);
+			self.fail_htlc_backwards_internal(failure.0, &failure.1, failure.2, receiver);
 		}
 	}
 
@@ -4786,7 +4779,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 		};
 		for htlc_source in dropped_htlcs.drain(..) {
 			let receiver = HTLCDestination::NextHopChannel { node_id: Some(counterparty_node_id.clone()), channel_id: msg.channel_id };
-			self.fail_htlc_backwards_internal(self.channel_state.lock().unwrap(), htlc_source.0, &htlc_source.1, HTLCFailReason::Reason { failure_code: 0x4000 | 8, data: Vec::new() }, receiver);
+			self.fail_htlc_backwards_internal(htlc_source.0, &htlc_source.1, HTLCFailReason::Reason { failure_code: 0x4000 | 8, data: Vec::new() }, receiver);
 		}
 
 		let _ = handle_error!(self, result, *counterparty_node_id);
@@ -4988,7 +4981,6 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 		for &mut (prev_short_channel_id, prev_funding_outpoint, ref mut pending_forwards) in per_source_pending_forwards {
 			let mut forward_event = None;
 			if !pending_forwards.is_empty() {
-				let mut channel_state = self.channel_state.lock().unwrap();
 				let mut forward_htlcs = self.forward_htlcs.lock().unwrap();
 				if forward_htlcs.is_empty() {
 					forward_event = Some(Duration::from_millis(MIN_HTLC_RELAY_HOLDING_CELL_MILLIS))
@@ -5075,7 +5067,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 			{
 				for failure in pending_failures.drain(..) {
 					let receiver = HTLCDestination::NextHopChannel { node_id: Some(*counterparty_node_id), channel_id: channel_outpoint.to_channel_id() };
-					self.fail_htlc_backwards_internal(self.channel_state.lock().unwrap(), failure.0, &failure.1, failure.2, receiver);
+					self.fail_htlc_backwards_internal(failure.0, &failure.1, failure.2, receiver);
 				}
 				self.forward_htlcs(&mut [(short_channel_id, channel_outpoint, pending_forwards)]);
 				self.finalize_claims(finalized_claim_htlcs);
@@ -5232,7 +5224,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 						} else {
 							log_trace!(self.logger, "Failing HTLC with hash {} from our monitor", log_bytes!(htlc_update.payment_hash.0));
 							let receiver = HTLCDestination::NextHopChannel { node_id: counterparty_node_id, channel_id: funding_outpoint.to_channel_id() };
-							self.fail_htlc_backwards_internal(self.channel_state.lock().unwrap(), htlc_update.source, &htlc_update.payment_hash, HTLCFailReason::Reason { failure_code: 0x4000 | 8, data: Vec::new() }, receiver);
+							self.fail_htlc_backwards_internal(htlc_update.source, &htlc_update.payment_hash, HTLCFailReason::Reason { failure_code: 0x4000 | 8, data: Vec::new() }, receiver);
 						}
 					},
 					MonitorEvent::CommitmentTxConfirmed(funding_outpoint) |
@@ -5971,7 +5963,7 @@ where
 		self.handle_init_event_channel_failures(failed_channels);
 
 		for (source, payment_hash, reason, destination) in timed_out_htlcs.drain(..) {
-			self.fail_htlc_backwards_internal(self.channel_state.lock().unwrap(), source, &payment_hash, reason, destination);
+			self.fail_htlc_backwards_internal(source, &payment_hash, reason, destination);
 		}
 	}
 
@@ -7330,7 +7322,7 @@ impl<'a, Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
 		for htlc_source in failed_htlcs.drain(..) {
 			let (source, payment_hash, counterparty_node_id, channel_id) = htlc_source;
 			let receiver = HTLCDestination::NextHopChannel { node_id: Some(counterparty_node_id), channel_id };
-			channel_manager.fail_htlc_backwards_internal(channel_manager.channel_state.lock().unwrap(), source, &payment_hash, HTLCFailReason::Reason { failure_code: 0x4000 | 8, data: Vec::new() }, receiver);
+			channel_manager.fail_htlc_backwards_internal(source, &payment_hash, HTLCFailReason::Reason { failure_code: 0x4000 | 8, data: Vec::new() }, receiver);
 		}
 
 		//TODO: Broadcast channel update for closed channels, but only after we've made a