Decode update_add_htlc onions before forwarding HTLCs
authorWilmer Paulino <wilmer@wilmerpaulino.com>
Sat, 9 Mar 2024 08:53:48 +0000 (00:53 -0800)
committerWilmer Paulino <wilmer@wilmerpaulino.com>
Wed, 27 Mar 2024 21:28:05 +0000 (14:28 -0700)
This commit completes all of the groundwork necessary to decode incoming
`update_add_htlc` onions once they're fully committed to by both sides.
HTLCs are tracked in batches per-channel on the channel they were
received on. While this path is unreachable for now, until
`InboundHTLCResolution::Resolved` is replaced with
`InboundHTLCResolution::Pending`, it will allow us to obtain
`HTLCHandlingFailed` events for _any_ failed HTLC that comes across a
channel.

lightning/src/ln/channelmanager.rs

index c76ba5d3afc040e8ccf9f62435576da18920c1ab..28513ebbc9ec921abc4bc539a98ff1d288fe0386 100644 (file)
@@ -4304,6 +4304,145 @@ where
                Ok(())
        }
 
+       fn process_pending_update_add_htlcs(&self) {
+               let mut decode_update_add_htlcs = new_hash_map();
+               mem::swap(&mut decode_update_add_htlcs, &mut self.decode_update_add_htlcs.lock().unwrap());
+
+               let get_failed_htlc_destination = |outgoing_scid_opt: Option<u64>, payment_hash: PaymentHash| {
+                       if let Some(outgoing_scid) = outgoing_scid_opt {
+                               match self.short_to_chan_info.read().unwrap().get(&outgoing_scid) {
+                                       Some((outgoing_counterparty_node_id, outgoing_channel_id)) =>
+                                               HTLCDestination::NextHopChannel {
+                                                       node_id: Some(*outgoing_counterparty_node_id),
+                                                       channel_id: *outgoing_channel_id,
+                                               },
+                                       None => HTLCDestination::UnknownNextHop {
+                                               requested_forward_scid: outgoing_scid,
+                                       },
+                               }
+                       } else {
+                               HTLCDestination::FailedPayment { payment_hash }
+                       }
+               };
+
+               'outer_loop: for (incoming_scid, update_add_htlcs) in decode_update_add_htlcs {
+                       let incoming_channel_details_opt = self.do_funded_channel_callback(incoming_scid, |chan: &mut Channel<SP>| {
+                               let counterparty_node_id = chan.context.get_counterparty_node_id();
+                               let channel_id = chan.context.channel_id();
+                               let funding_txo = chan.context.get_funding_txo().unwrap();
+                               let user_channel_id = chan.context.get_user_id();
+                               let accept_underpaying_htlcs = chan.context.config().accept_underpaying_htlcs;
+                               (counterparty_node_id, channel_id, funding_txo, user_channel_id, accept_underpaying_htlcs)
+                       });
+                       let (
+                               incoming_counterparty_node_id, incoming_channel_id, incoming_funding_txo,
+                               incoming_user_channel_id, incoming_accept_underpaying_htlcs
+                        ) = if let Some(incoming_channel_details) = incoming_channel_details_opt {
+                               incoming_channel_details
+                       } else {
+                               // The incoming channel no longer exists, HTLCs should be resolved onchain instead.
+                               continue;
+                       };
+
+                       let mut htlc_forwards = Vec::new();
+                       let mut htlc_fails = Vec::new();
+                       for update_add_htlc in &update_add_htlcs {
+                               let (next_hop, shared_secret, next_packet_details_opt) = match decode_incoming_update_add_htlc_onion(
+                                       &update_add_htlc, &self.node_signer, &self.logger, &self.secp_ctx
+                               ) {
+                                       Ok(decoded_onion) => decoded_onion,
+                                       Err(htlc_fail) => {
+                                               htlc_fails.push((htlc_fail, HTLCDestination::InvalidOnion));
+                                               continue;
+                                       },
+                               };
+
+                               let is_intro_node_blinded_forward = next_hop.is_intro_node_blinded_forward();
+                               let outgoing_scid_opt = next_packet_details_opt.as_ref().map(|d| d.outgoing_scid);
+
+                               // Process the HTLC on the incoming channel.
+                               match self.do_funded_channel_callback(incoming_scid, |chan: &mut Channel<SP>| {
+                                       let logger = WithChannelContext::from(&self.logger, &chan.context);
+                                       chan.can_accept_incoming_htlc(
+                                               update_add_htlc, &self.fee_estimator, &logger,
+                                       )
+                               }) {
+                                       Some(Ok(_)) => {},
+                                       Some(Err((err, code))) => {
+                                               let outgoing_chan_update_opt = if let Some(outgoing_scid) = outgoing_scid_opt.as_ref() {
+                                                       self.do_funded_channel_callback(*outgoing_scid, |chan: &mut Channel<SP>| {
+                                                               self.get_channel_update_for_onion(*outgoing_scid, chan).ok()
+                                                       }).flatten()
+                                               } else {
+                                                       None
+                                               };
+                                               let htlc_fail = self.htlc_failure_from_update_add_err(
+                                                       &update_add_htlc, &incoming_counterparty_node_id, err, code,
+                                                       outgoing_chan_update_opt, is_intro_node_blinded_forward, &shared_secret,
+                                               );
+                                               let htlc_destination = get_failed_htlc_destination(outgoing_scid_opt, update_add_htlc.payment_hash);
+                                               htlc_fails.push((htlc_fail, htlc_destination));
+                                               continue;
+                                       },
+                                       // The incoming channel no longer exists, HTLCs should be resolved onchain instead.
+                                       None => continue 'outer_loop,
+                               }
+
+                               // Now process the HTLC on the outgoing channel if it's a forward.
+                               if let Some(next_packet_details) = next_packet_details_opt.as_ref() {
+                                       if let Err((err, code, chan_update_opt)) = self.can_forward_htlc(
+                                               &update_add_htlc, next_packet_details
+                                       ) {
+                                               let htlc_fail = self.htlc_failure_from_update_add_err(
+                                                       &update_add_htlc, &incoming_counterparty_node_id, err, code,
+                                                       chan_update_opt, is_intro_node_blinded_forward, &shared_secret,
+                                               );
+                                               let htlc_destination = get_failed_htlc_destination(outgoing_scid_opt, update_add_htlc.payment_hash);
+                                               htlc_fails.push((htlc_fail, htlc_destination));
+                                               continue;
+                                       }
+                               }
+
+                               match self.construct_pending_htlc_status(
+                                       &update_add_htlc, &incoming_counterparty_node_id, shared_secret, next_hop,
+                                       incoming_accept_underpaying_htlcs, next_packet_details_opt.map(|d| d.next_packet_pubkey),
+                               ) {
+                                       PendingHTLCStatus::Forward(htlc_forward) => {
+                                               htlc_forwards.push((htlc_forward, update_add_htlc.htlc_id));
+                                       },
+                                       PendingHTLCStatus::Fail(htlc_fail) => {
+                                               let htlc_destination = get_failed_htlc_destination(outgoing_scid_opt, update_add_htlc.payment_hash);
+                                               htlc_fails.push((htlc_fail, htlc_destination));
+                                       },
+                               }
+                       }
+
+                       // Process all of the forwards and failures for the channel in which the HTLCs were
+                       // proposed to as a batch.
+                       let pending_forwards = (incoming_scid, incoming_funding_txo, incoming_channel_id,
+                               incoming_user_channel_id, htlc_forwards.drain(..).collect());
+                       self.forward_htlcs_without_forward_event(&mut [pending_forwards]);
+                       for (htlc_fail, htlc_destination) in htlc_fails.drain(..) {
+                               let failure = match htlc_fail {
+                                       HTLCFailureMsg::Relay(fail_htlc) => HTLCForwardInfo::FailHTLC {
+                                               htlc_id: fail_htlc.htlc_id,
+                                               err_packet: fail_htlc.reason,
+                                       },
+                                       HTLCFailureMsg::Malformed(fail_malformed_htlc) => HTLCForwardInfo::FailMalformedHTLC {
+                                               htlc_id: fail_malformed_htlc.htlc_id,
+                                               sha256_of_onion: fail_malformed_htlc.sha256_of_onion,
+                                               failure_code: fail_malformed_htlc.failure_code,
+                                       },
+                               };
+                               self.forward_htlcs.lock().unwrap().entry(incoming_scid).or_insert(vec![]).push(failure);
+                               self.pending_events.lock().unwrap().push_back((events::Event::HTLCHandlingFailed {
+                                       prev_channel_id: incoming_channel_id,
+                                       failed_next_destination: htlc_destination,
+                               }, None));
+                       }
+               }
+       }
+
        /// Processes HTLCs which are pending waiting on random forward delay.
        ///
        /// Should only really ever be called in response to a PendingHTLCsForwardable event.
@@ -4311,6 +4450,8 @@ where
        pub fn process_pending_htlc_forwards(&self) {
                let _persistence_guard = PersistenceNotifierGuard::notify_on_drop(self);
 
+               self.process_pending_update_add_htlcs();
+
                let mut new_events = VecDeque::new();
                let mut failed_forwards = Vec::new();
                let mut phantom_receives: Vec<(u64, OutPoint, ChannelId, u128, Vec<(PendingHTLCInfo, u64)>)> = Vec::new();