Ensure all HTLCs for a claimed payment are claimed on startup

[rust-lightning] / lightning / src / ln / channel.rs

diff --git a/lightning/src/ln/channel.rs b/lightning/src/ln/channel.rs
index 43032c51a3c09cdc67988e96050835fd7a17d9d7..1d204d18a17ed620b24a228d66856175137ceb5a 100644 (file)
--- a/lightning/src/ln/channel.rs
+++ b/lightning/src/ln/channel.rs
@@ -1703,6 +1703,28 @@ impl<Signer: Sign> Channel<Signer> {
                make_funding_redeemscript(&self.get_holder_pubkeys().funding_pubkey, self.counterparty_funding_pubkey())
        }
 
+       /// Claims an HTLC while we're disconnected from a peer, dropping the ChannelMonitorUpdate
+       /// entirely.
+       ///
+       /// The ChannelMonitor for this channel MUST be updated out-of-band with the preimage provided
+       /// (i.e. without calling [`crate::chain::Watch::update_channel`]).
+       ///
+       /// The HTLC claim will end up in the holding cell (because the caller must ensure the peer is
+       /// disconnected).
+       pub fn claim_htlc_while_disconnected_dropping_mon_update<L: Deref>
+               (&mut self, htlc_id_arg: u64, payment_preimage_arg: PaymentPreimage, logger: &L)
+       where L::Target: Logger {
+               // Assert that we'll add the HTLC claim to the holding cell in `get_update_fulfill_htlc`
+               // (see equivalent if condition there).
+               assert!(self.channel_state & (ChannelState::AwaitingRemoteRevoke as u32 | ChannelState::PeerDisconnected as u32 | ChannelState::MonitorUpdateFailed as u32) != 0);
+               let mon_update_id = self.latest_monitor_update_id; // Forget the ChannelMonitor update
+               let fulfill_resp = self.get_update_fulfill_htlc(htlc_id_arg, payment_preimage_arg, logger);
+               self.latest_monitor_update_id = mon_update_id;
+               if let UpdateFulfillFetch::NewClaim { msg, .. } = fulfill_resp {
+                       assert!(msg.is_none()); // The HTLC must have ended up in the holding cell.
+               }
+       }
+
        fn get_update_fulfill_htlc<L: Deref>(&mut self, htlc_id_arg: u64, payment_preimage_arg: PaymentPreimage, logger: &L) -> UpdateFulfillFetch where L::Target: Logger {
                // Either ChannelFunded got set (which means it won't be unset) or there is no way any
                // caller thought we could have something claimed (cause we wouldn't have accepted in an
@@ -1765,6 +1787,10 @@ impl<Signer: Sign> Channel<Signer> {
                };
 
                if (self.channel_state & (ChannelState::AwaitingRemoteRevoke as u32 | ChannelState::PeerDisconnected as u32 | ChannelState::MonitorUpdateFailed as u32)) != 0 {
+                       // Note that this condition is the same as the assertion in
+                       // `claim_htlc_while_disconnected_dropping_mon_update` and must match exactly -
+                       // `claim_htlc_while_disconnected_dropping_mon_update` would not work correctly if we
+                       // do not not get into this branch.
                        for pending_update in self.holding_cell_htlc_updates.iter() {
                                match pending_update {
                                        &HTLCUpdateAwaitingACK::ClaimHTLC { htlc_id, .. } => {