Check for timing-out HTLCs in remote unrevoked commitments
[rust-lightning] / src / ln / channelmanager.rs
index b5ee9b562aff2eff2a5b31b3feef8189c0fe3e63..0b7def9ad87bf8b02a9ae22565d9854de2617144 100644 (file)
@@ -39,7 +39,6 @@ use util::ser::{Readable, ReadableArgs, Writeable, Writer};
 use util::chacha20::ChaCha20;
 use util::logger::Logger;
 use util::errors::APIError;
-use util::errors;
 
 use std::{cmp, mem};
 use std::collections::{HashMap, hash_map, HashSet};
@@ -209,13 +208,16 @@ impl MsgHandleErrInternal {
 /// probably increase this significantly.
 const MIN_HTLC_RELAY_HOLDING_CELL_MILLIS: u32 = 50;
 
-pub(super) struct HTLCForwardInfo {
-       prev_short_channel_id: u64,
-       prev_htlc_id: u64,
-       #[cfg(test)]
-       pub(super) forward_info: PendingForwardHTLCInfo,
-       #[cfg(not(test))]
-       forward_info: PendingForwardHTLCInfo,
+pub(super) enum HTLCForwardInfo {
+       AddHTLC {
+               prev_short_channel_id: u64,
+               prev_htlc_id: u64,
+               forward_info: PendingForwardHTLCInfo,
+       },
+       FailHTLC {
+               htlc_id: u64,
+               err_packet: msgs::OnionErrorPacket,
+       },
 }
 
 /// For events which result in both a RevokeAndACK and a CommitmentUpdate, by default they should
@@ -1162,13 +1164,23 @@ impl ChannelManager {
                                                Some(chan_id) => chan_id.clone(),
                                                None => {
                                                        failed_forwards.reserve(pending_forwards.len());
-                                                       for HTLCForwardInfo { prev_short_channel_id, prev_htlc_id, forward_info } in pending_forwards.drain(..) {
-                                                               let htlc_source = HTLCSource::PreviousHopData(HTLCPreviousHopData {
-                                                                       short_channel_id: prev_short_channel_id,
-                                                                       htlc_id: prev_htlc_id,
-                                                                       incoming_packet_shared_secret: forward_info.incoming_shared_secret,
-                                                               });
-                                                               failed_forwards.push((htlc_source, forward_info.payment_hash, 0x4000 | 10, None));
+                                                       for forward_info in pending_forwards.drain(..) {
+                                                               match forward_info {
+                                                                       HTLCForwardInfo::AddHTLC { prev_short_channel_id, prev_htlc_id, forward_info } => {
+                                                                               let htlc_source = HTLCSource::PreviousHopData(HTLCPreviousHopData {
+                                                                                       short_channel_id: prev_short_channel_id,
+                                                                                       htlc_id: prev_htlc_id,
+                                                                                       incoming_packet_shared_secret: forward_info.incoming_shared_secret,
+                                                                               });
+                                                                               failed_forwards.push((htlc_source, forward_info.payment_hash, 0x4000 | 10, None));
+                                                                       },
+                                                                       HTLCForwardInfo::FailHTLC { .. } => {
+                                                                               // Channel went away before we could fail it. This implies
+                                                                               // the channel is now on chain and our counterparty is
+                                                                               // trying to broadcast the HTLC-Timeout, but that's their
+                                                                               // problem, not ours.
+                                                                       }
+                                                               }
                                                        }
                                                        continue;
                                                }
@@ -1176,36 +1188,74 @@ impl ChannelManager {
                                        let forward_chan = &mut channel_state.by_id.get_mut(&forward_chan_id).unwrap();
 
                                        let mut add_htlc_msgs = Vec::new();
-                                       for HTLCForwardInfo { prev_short_channel_id, prev_htlc_id, forward_info } in pending_forwards.drain(..) {
-                                               let htlc_source = HTLCSource::PreviousHopData(HTLCPreviousHopData {
-                                                       short_channel_id: prev_short_channel_id,
-                                                       htlc_id: prev_htlc_id,
-                                                       incoming_packet_shared_secret: forward_info.incoming_shared_secret,
-                                               });
-                                               match forward_chan.send_htlc(forward_info.amt_to_forward, forward_info.payment_hash, forward_info.outgoing_cltv_value, htlc_source.clone(), forward_info.onion_packet.unwrap()) {
-                                                       Err(_e) => {
-                                                               let chan_update = self.get_channel_update(forward_chan).unwrap();
-                                                               failed_forwards.push((htlc_source, forward_info.payment_hash, 0x1000 | 7, Some(chan_update)));
-                                                               continue;
+                                       let mut fail_htlc_msgs = Vec::new();
+                                       for forward_info in pending_forwards.drain(..) {
+                                               match forward_info {
+                                                       HTLCForwardInfo::AddHTLC { prev_short_channel_id, prev_htlc_id, forward_info } => {
+                                                               log_trace!(self, "Adding HTLC from short id {} with payment_hash {} to channel with short id {} after delay", log_bytes!(forward_info.payment_hash.0), prev_short_channel_id, short_chan_id);
+                                                               let htlc_source = HTLCSource::PreviousHopData(HTLCPreviousHopData {
+                                                                       short_channel_id: prev_short_channel_id,
+                                                                       htlc_id: prev_htlc_id,
+                                                                       incoming_packet_shared_secret: forward_info.incoming_shared_secret,
+                                                               });
+                                                               match forward_chan.send_htlc(forward_info.amt_to_forward, forward_info.payment_hash, forward_info.outgoing_cltv_value, htlc_source.clone(), forward_info.onion_packet.unwrap()) {
+                                                                       Err(e) => {
+                                                                               if let ChannelError::Ignore(msg) = e {
+                                                                                       log_trace!(self, "Failed to forward HTLC with payment_hash {}: {}", log_bytes!(forward_info.payment_hash.0), msg);
+                                                                               } else {
+                                                                                       panic!("Stated return value requirements in send_htlc() were not met");
+                                                                               }
+                                                                               let chan_update = self.get_channel_update(forward_chan).unwrap();
+                                                                               failed_forwards.push((htlc_source, forward_info.payment_hash, 0x1000 | 7, Some(chan_update)));
+                                                                               continue;
+                                                                       },
+                                                                       Ok(update_add) => {
+                                                                               match update_add {
+                                                                                       Some(msg) => { add_htlc_msgs.push(msg); },
+                                                                                       None => {
+                                                                                               // Nothing to do here...we're waiting on a remote
+                                                                                               // revoke_and_ack before we can add anymore HTLCs. The Channel
+                                                                                               // will automatically handle building the update_add_htlc and
+                                                                                               // commitment_signed messages when we can.
+                                                                                               // TODO: Do some kind of timer to set the channel as !is_live()
+                                                                                               // as we don't really want others relying on us relaying through
+                                                                                               // this channel currently :/.
+                                                                                       }
+                                                                               }
+                                                                       }
+                                                               }
                                                        },
-                                                       Ok(update_add) => {
-                                                               match update_add {
-                                                                       Some(msg) => { add_htlc_msgs.push(msg); },
-                                                                       None => {
+                                                       HTLCForwardInfo::FailHTLC { htlc_id, err_packet } => {
+                                                               log_trace!(self, "Failing HTLC back to channel with short id {} after delay", short_chan_id);
+                                                               match forward_chan.get_update_fail_htlc(htlc_id, err_packet) {
+                                                                       Err(e) => {
+                                                                               if let ChannelError::Ignore(msg) = e {
+                                                                                       log_trace!(self, "Failed to fail backwards to short_id {}: {}", short_chan_id, msg);
+                                                                               } else {
+                                                                                       panic!("Stated return value requirements in get_update_fail_htlc() were not met");
+                                                                               }
+                                                                               // fail-backs are best-effort, we probably already have one
+                                                                               // pending, and if not that's OK, if not, the channel is on
+                                                                               // the chain and sending the HTLC-Timeout is their problem.
+                                                                               continue;
+                                                                       },
+                                                                       Ok(Some(msg)) => { fail_htlc_msgs.push(msg); },
+                                                                       Ok(None) => {
                                                                                // Nothing to do here...we're waiting on a remote
-                                                                               // revoke_and_ack before we can add anymore HTLCs. The Channel
-                                                                               // will automatically handle building the update_add_htlc and
-                                                                               // commitment_signed messages when we can.
-                                                                               // TODO: Do some kind of timer to set the channel as !is_live()
-                                                                               // as we don't really want others relying on us relaying through
-                                                                               // this channel currently :/.
+                                                                               // revoke_and_ack before we can update the commitment
+                                                                               // transaction. The Channel will automatically handle
+                                                                               // building the update_fail_htlc and commitment_signed
+                                                                               // messages when we can.
+                                                                               // We don't need any kind of timer here as they should fail
+                                                                               // the channel onto the chain if they can't get our
+                                                                               // update_fail_htlc in time, its not our problem.
                                                                        }
                                                                }
-                                                       }
+                                                       },
                                                }
                                        }
 
-                                       if !add_htlc_msgs.is_empty() {
+                                       if !add_htlc_msgs.is_empty() || !fail_htlc_msgs.is_empty() {
                                                let (commitment_msg, monitor) = match forward_chan.send_commitment() {
                                                        Ok(res) => res,
                                                        Err(e) => {
@@ -1224,7 +1274,7 @@ impl ChannelManager {
                                                        updates: msgs::CommitmentUpdate {
                                                                update_add_htlcs: add_htlc_msgs,
                                                                update_fulfill_htlcs: Vec::new(),
-                                                               update_fail_htlcs: Vec::new(),
+                                                               update_fail_htlcs: fail_htlc_msgs,
                                                                update_fail_malformed_htlcs: Vec::new(),
                                                                update_fee: None,
                                                                commitment_signed: commitment_msg,
@@ -1232,20 +1282,27 @@ impl ChannelManager {
                                                });
                                        }
                                } else {
-                                       for HTLCForwardInfo { prev_short_channel_id, prev_htlc_id, forward_info } in pending_forwards.drain(..) {
-                                               let prev_hop_data = HTLCPreviousHopData {
-                                                       short_channel_id: prev_short_channel_id,
-                                                       htlc_id: prev_htlc_id,
-                                                       incoming_packet_shared_secret: forward_info.incoming_shared_secret,
-                                               };
-                                               match channel_state.claimable_htlcs.entry(forward_info.payment_hash) {
-                                                       hash_map::Entry::Occupied(mut entry) => entry.get_mut().push(prev_hop_data),
-                                                       hash_map::Entry::Vacant(entry) => { entry.insert(vec![prev_hop_data]); },
-                                               };
-                                               new_events.push(events::Event::PaymentReceived {
-                                                       payment_hash: forward_info.payment_hash,
-                                                       amt: forward_info.amt_to_forward,
-                                               });
+                                       for forward_info in pending_forwards.drain(..) {
+                                               match forward_info {
+                                                       HTLCForwardInfo::AddHTLC { prev_short_channel_id, prev_htlc_id, forward_info } => {
+                                                               let prev_hop_data = HTLCPreviousHopData {
+                                                                       short_channel_id: prev_short_channel_id,
+                                                                       htlc_id: prev_htlc_id,
+                                                                       incoming_packet_shared_secret: forward_info.incoming_shared_secret,
+                                                               };
+                                                               match channel_state.claimable_htlcs.entry(forward_info.payment_hash) {
+                                                                       hash_map::Entry::Occupied(mut entry) => entry.get_mut().push(prev_hop_data),
+                                                                       hash_map::Entry::Vacant(entry) => { entry.insert(vec![prev_hop_data]); },
+                                                               };
+                                                               new_events.push(events::Event::PaymentReceived {
+                                                                       payment_hash: forward_info.payment_hash,
+                                                                       amt: forward_info.amt_to_forward,
+                                                               });
+                                                       },
+                                                       HTLCForwardInfo::FailHTLC { .. } => {
+                                                               panic!("Got pending fail of our own HTLC");
+                                                       }
+                                               }
                                        }
                                }
                        }
@@ -1290,6 +1347,10 @@ impl ChannelManager {
        /// drop it). In other words, no assumptions are made that entries in claimable_htlcs point to
        /// still-available channels.
        fn fail_htlc_backwards_internal(&self, mut channel_state_lock: MutexGuard<ChannelHolder>, source: HTLCSource, payment_hash: &PaymentHash, onion_error: HTLCFailReason) {
+               //TODO: There is a timing attack here where if a node fails an HTLC back to us they can
+               //identify whether we sent it or not based on the (I presume) very different runtime
+               //between the branches here. We should make this async and move it into the forward HTLCs
+               //timer handling.
                match source {
                        HTLCSource::OutboundRoute { ref route, .. } => {
                                log_trace!(self, "Failing outbound payment HTLC with payment_hash {}", log_bytes!(payment_hash.0));
@@ -1297,9 +1358,9 @@ impl ChannelManager {
                                match &onion_error {
                                        &HTLCFailReason::ErrorPacket { ref err } => {
 #[cfg(test)]
-                                               let (channel_update, payment_retryable, onion_error_code) = self.process_onion_failure(&source, err.data.clone());
+                                               let (channel_update, payment_retryable, onion_error_code) = onion_utils::process_onion_failure(&self.secp_ctx, &self.logger, &source, err.data.clone());
 #[cfg(not(test))]
-                                               let (channel_update, payment_retryable, _) = self.process_onion_failure(&source, err.data.clone());
+                                               let (channel_update, payment_retryable, _) = onion_utils::process_onion_failure(&self.secp_ctx, &self.logger, &source, err.data.clone());
                                                // TODO: If we decided to blame ourselves (or one of our channels) in
                                                // process_onion_failure we should close that channel as it implies our
                                                // next-hop is needlessly blaming us!
@@ -1354,36 +1415,25 @@ impl ChannelManager {
                                        }
                                };
 
-                               let channel_state = channel_state_lock.borrow_parts();
-
-                               let chan_id = match channel_state.short_to_id.get(&short_channel_id) {
-                                       Some(chan_id) => chan_id.clone(),
-                                       None => return
-                               };
-
-                               let chan = channel_state.by_id.get_mut(&chan_id).unwrap();
-                               match chan.get_update_fail_htlc_and_commit(htlc_id, err_packet) {
-                                       Ok(Some((msg, commitment_msg, chan_monitor))) => {
-                                               if let Err(_e) = self.monitor.add_update_monitor(chan_monitor.get_funding_txo().unwrap(), chan_monitor) {
-                                                       unimplemented!();
-                                               }
-                                               channel_state.pending_msg_events.push(events::MessageSendEvent::UpdateHTLCs {
-                                                       node_id: chan.get_their_node_id(),
-                                                       updates: msgs::CommitmentUpdate {
-                                                               update_add_htlcs: Vec::new(),
-                                                               update_fulfill_htlcs: Vec::new(),
-                                                               update_fail_htlcs: vec![msg],
-                                                               update_fail_malformed_htlcs: Vec::new(),
-                                                               update_fee: None,
-                                                               commitment_signed: commitment_msg,
-                                                       },
-                                               });
-                                       },
-                                       Ok(None) => {},
-                                       Err(_e) => {
-                                               //TODO: Do something with e?
-                                               return;
+                               let mut forward_event = None;
+                               if channel_state_lock.forward_htlcs.is_empty() {
+                                       forward_event = Some(Instant::now() + Duration::from_millis(((rng::rand_f32() * 4.0 + 1.0) * MIN_HTLC_RELAY_HOLDING_CELL_MILLIS as f32) as u64));
+                                       channel_state_lock.next_forward = forward_event.unwrap();
+                               }
+                               match channel_state_lock.forward_htlcs.entry(short_channel_id) {
+                                       hash_map::Entry::Occupied(mut entry) => {
+                                               entry.get_mut().push(HTLCForwardInfo::FailHTLC { htlc_id, err_packet });
                                        },
+                                       hash_map::Entry::Vacant(entry) => {
+                                               entry.insert(vec!(HTLCForwardInfo::FailHTLC { htlc_id, err_packet }));
+                                       }
+                               }
+                               mem::drop(channel_state_lock);
+                               if let Some(time) = forward_event {
+                                       let mut pending_events = self.pending_events.lock().unwrap();
+                                       pending_events.push(events::Event::PendingHTLCsForwardable {
+                                               time_forwardable: time
+                                       });
                                }
                        },
                }
@@ -1865,155 +1915,6 @@ impl ChannelManager {
                Ok(())
        }
 
-       // Process failure we got back from upstream on a payment we sent. Returns update and a boolean
-       // indicating that the payment itself failed
-       fn process_onion_failure(&self, htlc_source: &HTLCSource, mut packet_decrypted: Vec<u8>) -> (Option<msgs::HTLCFailChannelUpdate>, bool, Option<u16>) {
-               if let &HTLCSource::OutboundRoute { ref route, ref session_priv, ref first_hop_htlc_msat } = htlc_source {
-
-                       let mut res = None;
-                       let mut htlc_msat = *first_hop_htlc_msat;
-                       let mut error_code_ret = None;
-                       let mut next_route_hop_ix = 0;
-                       let mut is_from_final_node = false;
-
-                       // Handle packed channel/node updates for passing back for the route handler
-                       onion_utils::construct_onion_keys_callback(&self.secp_ctx, route, session_priv, |shared_secret, _, _, route_hop| {
-                               next_route_hop_ix += 1;
-                               if res.is_some() { return; }
-
-                               let amt_to_forward = htlc_msat - route_hop.fee_msat;
-                               htlc_msat = amt_to_forward;
-
-                               let ammag = onion_utils::gen_ammag_from_shared_secret(&shared_secret[..]);
-
-                               let mut decryption_tmp = Vec::with_capacity(packet_decrypted.len());
-                               decryption_tmp.resize(packet_decrypted.len(), 0);
-                               let mut chacha = ChaCha20::new(&ammag, &[0u8; 8]);
-                               chacha.process(&packet_decrypted, &mut decryption_tmp[..]);
-                               packet_decrypted = decryption_tmp;
-
-                               is_from_final_node = route.hops.last().unwrap().pubkey == route_hop.pubkey;
-
-                               if let Ok(err_packet) = msgs::DecodedOnionErrorPacket::read(&mut Cursor::new(&packet_decrypted)) {
-                                       let um = onion_utils::gen_um_from_shared_secret(&shared_secret[..]);
-                                       let mut hmac = HmacEngine::<Sha256>::new(&um);
-                                       hmac.input(&err_packet.encode()[32..]);
-
-                                       if fixed_time_eq(&Hmac::from_engine(hmac).into_inner(), &err_packet.hmac) {
-                                               if let Some(error_code_slice) = err_packet.failuremsg.get(0..2) {
-                                                       const PERM: u16 = 0x4000;
-                                                       const NODE: u16 = 0x2000;
-                                                       const UPDATE: u16 = 0x1000;
-
-                                                       let error_code = byte_utils::slice_to_be16(&error_code_slice);
-                                                       error_code_ret = Some(error_code);
-
-                                                       let (debug_field, debug_field_size) = errors::get_onion_debug_field(error_code);
-
-                                                       // indicate that payment parameter has failed and no need to
-                                                       // update Route object
-                                                       let payment_failed = (match error_code & 0xff {
-                                                               15|16|17|18|19 => true,
-                                                               _ => false,
-                                                       } && is_from_final_node) // PERM bit observed below even this error is from the intermediate nodes
-                                                       || error_code == 21; // Special case error 21 as the Route object is bogus, TODO: Maybe fail the node if the CLTV was reasonable?
-
-                                                       let mut fail_channel_update = None;
-
-                                                       if error_code & NODE == NODE {
-                                                               fail_channel_update = Some(msgs::HTLCFailChannelUpdate::NodeFailure { node_id: route_hop.pubkey, is_permanent: error_code & PERM == PERM });
-                                                       }
-                                                       else if error_code & PERM == PERM {
-                                                               fail_channel_update = if payment_failed {None} else {Some(msgs::HTLCFailChannelUpdate::ChannelClosed {
-                                                                       short_channel_id: route.hops[next_route_hop_ix - if next_route_hop_ix == route.hops.len() { 1 } else { 0 }].short_channel_id,
-                                                                       is_permanent: true,
-                                                               })};
-                                                       }
-                                                       else if error_code & UPDATE == UPDATE {
-                                                               if let Some(update_len_slice) = err_packet.failuremsg.get(debug_field_size+2..debug_field_size+4) {
-                                                                       let update_len = byte_utils::slice_to_be16(&update_len_slice) as usize;
-                                                                       if let Some(update_slice) = err_packet.failuremsg.get(debug_field_size + 4..debug_field_size + 4 + update_len) {
-                                                                               if let Ok(chan_update) = msgs::ChannelUpdate::read(&mut Cursor::new(&update_slice)) {
-                                                                                       // if channel_update should NOT have caused the failure:
-                                                                                       // MAY treat the channel_update as invalid.
-                                                                                       let is_chan_update_invalid = match error_code & 0xff {
-                                                                                               7 => false,
-                                                                                               11 => amt_to_forward > chan_update.contents.htlc_minimum_msat,
-                                                                                               12 => {
-                                                                                                       let new_fee = amt_to_forward.checked_mul(chan_update.contents.fee_proportional_millionths as u64).and_then(|prop_fee| { (prop_fee / 1000000).checked_add(chan_update.contents.fee_base_msat as u64) });
-                                                                                                       new_fee.is_some() && route_hop.fee_msat >= new_fee.unwrap()
-                                                                                               }
-                                                                                               13 => route_hop.cltv_expiry_delta as u16 >= chan_update.contents.cltv_expiry_delta,
-                                                                                               14 => false, // expiry_too_soon; always valid?
-                                                                                               20 => chan_update.contents.flags & 2 == 0,
-                                                                                               _ => false, // unknown error code; take channel_update as valid
-                                                                                       };
-                                                                                       fail_channel_update = if is_chan_update_invalid {
-                                                                                               // This probably indicates the node which forwarded
-                                                                                               // to the node in question corrupted something.
-                                                                                               Some(msgs::HTLCFailChannelUpdate::ChannelClosed {
-                                                                                                       short_channel_id: route_hop.short_channel_id,
-                                                                                                       is_permanent: true,
-                                                                                               })
-                                                                                       } else {
-                                                                                               Some(msgs::HTLCFailChannelUpdate::ChannelUpdateMessage {
-                                                                                                       msg: chan_update,
-                                                                                               })
-                                                                                       };
-                                                                               }
-                                                                       }
-                                                               }
-                                                               if fail_channel_update.is_none() {
-                                                                       // They provided an UPDATE which was obviously bogus, not worth
-                                                                       // trying to relay through them anymore.
-                                                                       fail_channel_update = Some(msgs::HTLCFailChannelUpdate::NodeFailure {
-                                                                               node_id: route_hop.pubkey,
-                                                                               is_permanent: true,
-                                                                       });
-                                                               }
-                                                       } else if !payment_failed {
-                                                               // We can't understand their error messages and they failed to
-                                                               // forward...they probably can't understand our forwards so its
-                                                               // really not worth trying any further.
-                                                               fail_channel_update = Some(msgs::HTLCFailChannelUpdate::NodeFailure {
-                                                                       node_id: route_hop.pubkey,
-                                                                       is_permanent: true,
-                                                               });
-                                                       }
-
-                                                       // TODO: Here (and a few other places) we assume that BADONION errors
-                                                       // are always "sourced" from the node previous to the one which failed
-                                                       // to decode the onion.
-                                                       res = Some((fail_channel_update, !(error_code & PERM == PERM && is_from_final_node)));
-
-                                                       let (description, title) = errors::get_onion_error_description(error_code);
-                                                       if debug_field_size > 0 && err_packet.failuremsg.len() >= 4 + debug_field_size {
-                                                               log_warn!(self, "Onion Error[{}({:#x}) {}({})] {}", title, error_code, debug_field, log_bytes!(&err_packet.failuremsg[4..4+debug_field_size]), description);
-                                                       }
-                                                       else {
-                                                               log_warn!(self, "Onion Error[{}({:#x})] {}", title, error_code, description);
-                                                       }
-                                               } else {
-                                                       // Useless packet that we can't use but it passed HMAC, so it
-                                                       // definitely came from the peer in question
-                                                       res = Some((Some(msgs::HTLCFailChannelUpdate::NodeFailure {
-                                                               node_id: route_hop.pubkey,
-                                                               is_permanent: true,
-                                                       }), !is_from_final_node));
-                                               }
-                                       }
-                               }
-                       }).expect("Route that we sent via spontaneously grew invalid keys in the middle of it?");
-                       if let Some((channel_update, payment_retryable)) = res {
-                               (channel_update, payment_retryable, error_code_ret)
-                       } else {
-                               // only not set either packet unparseable or hmac does not match with any
-                               // payment not retryable only when garbage is from the final node
-                               (None, !is_from_final_node, None)
-                       }
-               } else { unreachable!(); }
-       }
-
        fn internal_update_fail_htlc(&self, their_node_id: &PublicKey, msg: &msgs::UpdateFailHTLC) -> Result<(), MsgHandleErrInternal> {
                let mut channel_lock = self.channel_state.lock().unwrap();
                let channel_state = channel_lock.borrow_parts();
@@ -2106,10 +2007,10 @@ impl ChannelManager {
                                for (forward_info, prev_htlc_id) in pending_forwards.drain(..) {
                                        match channel_state.forward_htlcs.entry(forward_info.short_channel_id) {
                                                hash_map::Entry::Occupied(mut entry) => {
-                                                       entry.get_mut().push(HTLCForwardInfo { prev_short_channel_id, prev_htlc_id, forward_info });
+                                                       entry.get_mut().push(HTLCForwardInfo::AddHTLC { prev_short_channel_id, prev_htlc_id, forward_info });
                                                },
                                                hash_map::Entry::Vacant(entry) => {
-                                                       entry.insert(vec!(HTLCForwardInfo { prev_short_channel_id, prev_htlc_id, forward_info }));
+                                                       entry.insert(vec!(HTLCForwardInfo::AddHTLC { prev_short_channel_id, prev_htlc_id, forward_info }));
                                                }
                                        }
                                }
@@ -2864,11 +2765,41 @@ impl<R: ::std::io::Read> Readable<R> for HTLCFailReason {
        }
 }
 
-impl_writeable!(HTLCForwardInfo, 0, {
-       prev_short_channel_id,
-       prev_htlc_id,
-       forward_info
-});
+impl Writeable for HTLCForwardInfo {
+       fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
+               match self {
+                       &HTLCForwardInfo::AddHTLC { ref prev_short_channel_id, ref prev_htlc_id, ref forward_info } => {
+                               0u8.write(writer)?;
+                               prev_short_channel_id.write(writer)?;
+                               prev_htlc_id.write(writer)?;
+                               forward_info.write(writer)?;
+                       },
+                       &HTLCForwardInfo::FailHTLC { ref htlc_id, ref err_packet } => {
+                               1u8.write(writer)?;
+                               htlc_id.write(writer)?;
+                               err_packet.write(writer)?;
+                       },
+               }
+               Ok(())
+       }
+}
+
+impl<R: ::std::io::Read> Readable<R> for HTLCForwardInfo {
+       fn read(reader: &mut R) -> Result<HTLCForwardInfo, DecodeError> {
+               match <u8 as Readable<R>>::read(reader)? {
+                       0 => Ok(HTLCForwardInfo::AddHTLC {
+                               prev_short_channel_id: Readable::read(reader)?,
+                               prev_htlc_id: Readable::read(reader)?,
+                               forward_info: Readable::read(reader)?,
+                       }),
+                       1 => Ok(HTLCForwardInfo::FailHTLC {
+                               htlc_id: Readable::read(reader)?,
+                               err_packet: Readable::read(reader)?,
+                       }),
+                       _ => Err(DecodeError::InvalidValue),
+               }
+       }
+}
 
 impl Writeable for ChannelManager {
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {