Deduplicate PendingHTLCsForwardable events when queueing

Author: valentinewallace

lightning/src/ln/channelmanager.rs

@@ -3737,16 +3737,19 @@ where
 		// being fully configured. See the docs for `ChannelManagerReadArgs` for more.
 		match source {
 			HTLCSource::OutboundRoute { ref path, ref session_priv, ref payment_id, ref payment_params, .. } => {
-				self.pending_outbound_payments.fail_htlc(source, payment_hash, onion_error, path, session_priv, payment_id, payment_params, self.probing_cookie_secret, &self.secp_ctx, &self.pending_events, &self.logger);
+				if self.pending_outbound_payments.fail_htlc(source, payment_hash, onion_error, path,
+					session_priv, payment_id, payment_params, self.probing_cookie_secret, &self.secp_ctx,
+					&self.pending_events, &self.logger)
+				{ self.push_pending_forwards_ev(); }
 			},
 			HTLCSource::PreviousHopData(HTLCPreviousHopData { ref short_channel_id, ref htlc_id, ref incoming_packet_shared_secret, ref phantom_shared_secret, ref outpoint }) => {
 				log_trace!(self.logger, "Failing HTLC with payment_hash {} backwards from us with {:?}", log_bytes!(payment_hash.0), onion_error);
 				let err_packet = onion_error.get_encrypted_failure_packet(incoming_packet_shared_secret, phantom_shared_secret);
 
-				let mut forward_event = None;
+				let mut push_forward_ev = false;
 				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));
+					push_forward_ev = true;
 				}
 				match forward_htlcs.entry(*short_channel_id) {
 					hash_map::Entry::Occupied(mut entry) => {
@@ -3757,12 +3760,8 @@ where
 					}
 				}
 				mem::drop(forward_htlcs);
+				if push_forward_ev { self.push_pending_forwards_ev(); }
 				let mut pending_events = self.pending_events.lock().unwrap();
-				if let Some(time) = forward_event {
-					pending_events.push(events::Event::PendingHTLCsForwardable {
-						time_forwardable: time
-					});
-				}
 				pending_events.push(events::Event::HTLCHandlingFailed {
 					prev_channel_id: outpoint.to_channel_id(),
 					failed_next_destination: destination,
@@ -4839,7 +4838,7 @@ where
 	#[inline]
 	fn forward_htlcs(&self, per_source_pending_forwards: &mut [(u64, OutPoint, u128, Vec<(PendingHTLCInfo, u64)>)]) {
 		for &mut (prev_short_channel_id, prev_funding_outpoint, prev_user_channel_id, ref mut pending_forwards) in per_source_pending_forwards {
-			let mut forward_event = None;
+			let mut push_forward_event = false;
 			let mut new_intercept_events = Vec::new();
 			let mut failed_intercept_forwards = Vec::new();
 			if !pending_forwards.is_empty() {
@@ -4897,7 +4896,7 @@ where
 								// We don't want to generate a PendingHTLCsForwardable event if only intercepted
 								// payments are being processed.
 								if forward_htlcs_empty {
-									forward_event = Some(Duration::from_millis(MIN_HTLC_RELAY_HOLDING_CELL_MILLIS));
+									push_forward_event = true;
 								}
 								entry.insert(vec!(HTLCForwardInfo::AddHTLC(PendingAddHTLCInfo {
 									prev_short_channel_id, prev_funding_outpoint, prev_htlc_id, prev_user_channel_id, forward_info })));
@@ -4915,16 +4914,21 @@ where
 				let mut events = self.pending_events.lock().unwrap();
 				events.append(&mut new_intercept_events);
 			}
+			if push_forward_event { self.push_pending_forwards_ev() }
+		}
+	}
 
-			match forward_event {
-				Some(time) => {
-					let mut pending_events = self.pending_events.lock().unwrap();
-					pending_events.push(events::Event::PendingHTLCsForwardable {
-						time_forwardable: time
-					});
-				}
-				None => {},
-			}
+	// We only want to push a PendingHTLCsForwardable event if no others are queued.
+	fn push_pending_forwards_ev(&self) {
+		let mut pending_events = self.pending_events.lock().unwrap();
+		let forward_ev_exists = pending_events.iter()
+			.find(|ev| if let events::Event::PendingHTLCsForwardable { .. } = ev { true } else { false })
+			.is_some();
+		if !forward_ev_exists {
+			pending_events.push(events::Event::PendingHTLCsForwardable {
+				time_forwardable:
+					Duration::from_millis(MIN_HTLC_RELAY_HOLDING_CELL_MILLIS),
+			});
 		}
 	}
 

lightning/src/ln/outbound_payment.rs

@@ -15,7 +15,7 @@ use bitcoin::secp256k1::{self, Secp256k1, SecretKey};
 
 use crate::chain::keysinterface::{EntropySource, NodeSigner, Recipient};
 use crate::ln::{PaymentHash, PaymentPreimage, PaymentSecret};
-use crate::ln::channelmanager::{ChannelDetails, HTLCSource, IDEMPOTENCY_TIMEOUT_TICKS, MIN_HTLC_RELAY_HOLDING_CELL_MILLIS, PaymentId};
+use crate::ln::channelmanager::{ChannelDetails, HTLCSource, IDEMPOTENCY_TIMEOUT_TICKS, PaymentId};
 use crate::ln::channelmanager::MIN_FINAL_CLTV_EXPIRY_DELTA as LDK_DEFAULT_MIN_FINAL_CLTV_EXPIRY_DELTA;
 use crate::ln::msgs::DecodeError;
 use crate::ln::onion_utils::HTLCFailReason;
@@ -30,7 +30,6 @@ use crate::util::time::tests::SinceEpoch;
 use core::cmp;
 use core::fmt::{self, Display, Formatter};
 use core::ops::Deref;
-use core::time::Duration;
 
 use crate::prelude::*;
 use crate::sync::Mutex;
@@ -1012,12 +1011,13 @@ impl OutboundPayments {
 		});
 	}
 
+	// Returns a bool indicating whether a PendingHTLCsForwardable event should be generated.
 	pub(super) fn fail_htlc<L: Deref>(
 		&self, source: &HTLCSource, payment_hash: &PaymentHash, onion_error: &HTLCFailReason,
 		path: &Vec<RouteHop>, session_priv: &SecretKey, payment_id: &PaymentId,
 		payment_params: &Option<PaymentParameters>, probing_cookie_secret: [u8; 32],
 		secp_ctx: &Secp256k1<secp256k1::All>, pending_events: &Mutex<Vec<events::Event>>, logger: &L
-	) where L::Target: Logger {
+	) -> bool where L::Target: Logger {
 		#[cfg(test)]
 		let (network_update, short_channel_id, payment_retryable, onion_error_code, onion_error_data) = onion_error.decode_onion_failure(secp_ctx, logger, &source);
 		#[cfg(not(test))]
@@ -1044,16 +1044,16 @@ impl OutboundPayments {
 
 		let mut all_paths_failed = false;
 		let mut full_failure_ev = None;
-		let mut pending_retry_ev = None;
+		let mut pending_retry_ev = false;
 		let mut retry = None;
 		let attempts_remaining = if let hash_map::Entry::Occupied(mut payment) = outbounds.entry(*payment_id) {
 			if !payment.get_mut().remove(&session_priv_bytes, Some(&path)) {
 				log_trace!(logger, "Received duplicative fail for HTLC with payment_hash {}", log_bytes!(payment_hash.0));
-				return
+				return false
 			}
 			if payment.get().is_fulfilled() {
 				log_trace!(logger, "Received failure of HTLC with payment_hash {} after payment completion", log_bytes!(payment_hash.0));
-				return
+				return false
 			}
 			let mut is_retryable_now = payment.get().is_auto_retryable_now();
 			if let Some(scid) = short_channel_id {
@@ -1105,7 +1105,7 @@ impl OutboundPayments {
 			is_retryable_now
 		} else {
 			log_trace!(logger, "Received duplicative fail for HTLC with payment_hash {}", log_bytes!(payment_hash.0));
-			return
+			return false
 		};
 		core::mem::drop(outbounds);
 		log_trace!(logger, "Failing outbound payment HTLC with payment_hash {}", log_bytes!(payment_hash.0));
@@ -1137,9 +1137,7 @@ impl OutboundPayments {
 				// payment will sit in our outbounds forever.
 				if attempts_remaining && !already_awaiting_retry {
 					debug_assert!(full_failure_ev.is_none());
-					pending_retry_ev = Some(events::Event::PendingHTLCsForwardable {
-						time_forwardable: Duration::from_millis(MIN_HTLC_RELAY_HOLDING_CELL_MILLIS),
-					});
+					pending_retry_ev = true;
 				}
 				events::Event::PaymentPathFailed {
 					payment_id: Some(*payment_id),
@@ -1160,7 +1158,7 @@ impl OutboundPayments {
 		let mut pending_events = pending_events.lock().unwrap();
 		pending_events.push(path_failure);
 		if let Some(ev) = full_failure_ev { pending_events.push(ev); }
-		if let Some(ev) = pending_retry_ev { pending_events.push(ev); }
+		pending_retry_ev
 	}
 
 	pub(super) fn abandon_payment(