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 a9565af9e06baf013a33384561e1bf1c12fc827a..b4c0a90cb3964e3cf99ae3d857ad5d4d4e04346b 100644 (file)
--- 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));
                                                }
                                        },