From: Matt Corallo <git@bluematt.me>
Date: Thu, 19 Mar 2020 01:10:22 +0000 (-0400)
Subject: Remove bogus mon_update_id += 1 fulfilling already-fulfilled HTLCs
X-Git-Tag: v0.0.12~98^2~4
X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=commitdiff_plain;h=32d62ada96faab954bbcee4fc5d9ec58d2eff482;p=rust-lightning

Remove bogus mon_update_id += 1 fulfilling already-fulfilled HTLCs

If we call get_update_fulfill_htlc (in this case via
ChannelManager::claim_funds_internal ->
Channel::get_update_fulfill_htlc_and_commit) and it finds that we
already have a holding-cell pending HTLC claim, it will return no
monitor update but leave latest_monitor_update_id incremented.

If we later go and add a new monitor update we'll panic as the
updates appear to have been applied out-of-order.
---

diff --git a/lightning/src/ln/channel.rs b/lightning/src/ln/channel.rs
index a9565af9e..b4c0a90cb 100644
--- a/lightning/src/ln/channel.rs
+++ b/lightning/src/ln/channel.rs
@@ -1200,6 +1200,8 @@ impl<ChanSigner: ChannelKeys> Channel<ChanSigner> {
 				match pending_update {
 					&HTLCUpdateAwaitingACK::ClaimHTLC { htlc_id, .. } => {
 						if htlc_id_arg == htlc_id {
+							// Make sure we don't leave latest_monitor_update_id incremented here:
+							self.latest_monitor_update_id -= 1;
 							return Ok((None, None));
 						}
 					},