From 96b0faf124c069181ae1440664200c2f766b7a18 Mon Sep 17 00:00:00 2001
From: Matt Corallo <git@bluematt.me>
Date: Tue, 20 Apr 2021 21:35:11 +0000
Subject: [PATCH] Log info about HTLC failures when we fail them back

---
 lightning/src/ln/channel.rs        | 6 ++++--
 lightning/src/ln/channelmanager.rs | 2 +-
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/lightning/src/ln/channel.rs b/lightning/src/ln/channel.rs
index 8db346a9e..639ac8449 100644
--- a/lightning/src/ln/channel.rs
+++ b/lightning/src/ln/channel.rs
@@ -1332,7 +1332,7 @@ impl<Signer: Sign> Channel<Signer> {
 	///
 	/// Note that it is still possible to hit these assertions in case we find a preimage on-chain
 	/// but then have a reorg which settles on an HTLC-failure on chain.
-	pub fn get_update_fail_htlc(&mut self, htlc_id_arg: u64, err_packet: msgs::OnionErrorPacket) -> Result<Option<msgs::UpdateFailHTLC>, ChannelError> {
+	pub fn get_update_fail_htlc<L: Deref>(&mut self, htlc_id_arg: u64, err_packet: msgs::OnionErrorPacket, logger: &L) -> Result<Option<msgs::UpdateFailHTLC>, ChannelError> where L::Target: Logger {
 		if (self.channel_state & (ChannelState::ChannelFunded as u32)) != (ChannelState::ChannelFunded as u32) {
 			panic!("Was asked to fail an HTLC when channel was not in an operational state");
 		}
@@ -1382,6 +1382,7 @@ impl<Signer: Sign> Channel<Signer> {
 					_ => {}
 				}
 			}
+			log_trace!(logger, "Placing failure for HTLC ID {} in holding cell", htlc_id_arg);
 			self.holding_cell_htlc_updates.push(HTLCUpdateAwaitingACK::FailHTLC {
 				htlc_id: htlc_id_arg,
 				err_packet,
@@ -1389,6 +1390,7 @@ impl<Signer: Sign> Channel<Signer> {
 			return Ok(None);
 		}
 
+		log_trace!(logger, "Failing HTLC ID {} back with a update_fail_htlc message", htlc_id_arg);
 		{
 			let htlc = &mut self.pending_inbound_htlcs[pending_idx];
 			htlc.state = InboundHTLCState::LocalRemoved(InboundHTLCRemovalReason::FailRelay(err_packet.clone()));
@@ -2382,7 +2384,7 @@ impl<Signer: Sign> Channel<Signer> {
 						}
 					},
 					&HTLCUpdateAwaitingACK::FailHTLC { htlc_id, ref err_packet } => {
-						match self.get_update_fail_htlc(htlc_id, err_packet.clone()) {
+						match self.get_update_fail_htlc(htlc_id, err_packet.clone(), logger) {
 							Ok(update_fail_msg_option) => update_fail_htlcs.push(update_fail_msg_option.unwrap()),
 							Err(e) => {
 								if let ChannelError::Ignore(_) = e {}
diff --git a/lightning/src/ln/channelmanager.rs b/lightning/src/ln/channelmanager.rs
index 9445f518c..9f9820c1d 100644
--- a/lightning/src/ln/channelmanager.rs
+++ b/lightning/src/ln/channelmanager.rs
@@ -2069,7 +2069,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 								},
 								HTLCForwardInfo::FailHTLC { htlc_id, err_packet } => {
 									log_trace!(self.logger, "Failing HTLC back to channel with short id {} after delay", short_chan_id);
-									match chan.get_mut().get_update_fail_htlc(htlc_id, err_packet) {
+									match chan.get_mut().get_update_fail_htlc(htlc_id, err_packet, &self.logger) {
 										Err(e) => {
 											if let ChannelError::Ignore(msg) = e {
 												log_trace!(self.logger, "Failed to fail backwards to short_id {}: {}", short_chan_id, msg);
-- 
2.39.5