Split HTLC tracking into separate Inbound/Outbound types
[rust-lightning] / src / ln / channel.rs
index d9633ea836284277c8c54fd6b7ab34dcea25850c..0477f68a3a75d858f9534f2d4c404113ed9adc96 100644 (file)
@@ -87,24 +87,49 @@ impl ChannelKeys {
 }
 
 #[derive(PartialEq)]
-enum HTLCState {
+enum InboundHTLCState {
        /// Added by remote, to be included in next local commitment tx.
-       /// Implies HTLCOutput::outbound: false
        RemoteAnnounced,
        /// Included in a received commitment_signed message (implying we've revoke_and_ack'ed it), but
        /// the remote side hasn't yet revoked their previous state, which we need them to do before we
        /// accept this HTLC. Implies AwaitingRemoteRevoke.
        /// We also have not yet included this HTLC in a commitment_signed message, and are waiting on
        /// a remote revoke_and_ack on a previous state before we can do so.
-       /// Implies HTLCOutput::outbound: false
        AwaitingRemoteRevokeToAnnounce,
        /// Included in a received commitment_signed message (implying we've revoke_and_ack'ed it), but
        /// the remote side hasn't yet revoked their previous state, which we need them to do before we
        /// accept this HTLC. Implies AwaitingRemoteRevoke.
        /// We have included this HTLC in our latest commitment_signed and are now just waiting on a
        /// revoke_and_ack.
-       /// Implies HTLCOutput::outbound: true
        AwaitingAnnouncedRemoteRevoke,
+       Committed,
+       /// Removed by us and a new commitment_signed was sent (if we were AwaitingRemoteRevoke when we
+       /// created it we would have put it in the holding cell instead). When they next revoke_and_ack
+       /// we'll drop it.
+       /// Note that we have to keep an eye on the HTLC until we've received a broadcastable
+       /// commitment transaction without it as otherwise we'll have to force-close the channel to
+       /// claim it before the timeout (obviously doesn't apply to revoked HTLCs that we can't claim
+       /// anyway). That said, ChannelMonitor does this for us (see
+       /// ChannelMonitor::would_broadcast_at_height) so we actually remove the HTLC from our own
+       /// local state before then, once we're sure that the next commitment_signed and
+       /// ChannelMonitor::provide_latest_local_commitment_tx_info will not include this HTLC.
+       LocalRemoved,
+}
+
+struct InboundHTLCOutput {
+       htlc_id: u64,
+       amount_msat: u64,
+       cltv_expiry: u32,
+       payment_hash: [u8; 32],
+       state: InboundHTLCState,
+       /// If we're in LocalRemoved, set to true if we fulfilled the HTLC, and can claim money
+       local_removed_fulfilled: bool,
+       /// state pre-Committed implies pending_forward_state, otherwise it must be None
+       pending_forward_state: Option<PendingHTLCStatus>,
+}
+
+#[derive(PartialEq)]
+enum OutboundHTLCState {
        /// Added by us and included in a commitment_signed (if we were AwaitingRemoteRevoke when we
        /// created it we would have put it in the holding cell instead). When they next revoke_and_ack
        /// we will promote to Committed (note that they may not accept it until the next time we
@@ -115,63 +140,42 @@ enum HTLCState {
        ///    allowed to remove it, the "can only be removed once committed on both sides" requirement
        ///    doesn't matter to us and its up to them to enforce it, worst-case they jump ahead but
        ///    we'll never get out of sync).
-       /// Implies HTLCOutput::outbound: true
        LocalAnnounced,
        Committed,
        /// Remote removed this (outbound) HTLC. We're waiting on their commitment_signed to finalize
        /// the change (though they'll need to revoke before we fail the payment).
-       /// Implies HTLCOutput::outbound: true
        RemoteRemoved,
        /// Remote removed this and sent a commitment_signed (implying we've revoke_and_ack'ed it), but
        /// the remote side hasn't yet revoked their previous state, which we need them to do before we
        /// can do any backwards failing. Implies AwaitingRemoteRevoke.
        /// We also have not yet removed this HTLC in a commitment_signed message, and are waiting on a
        /// remote revoke_and_ack on a previous state before we can do so.
-       /// Implies HTLCOutput::outbound: true
        AwaitingRemoteRevokeToRemove,
        /// Remote removed this and sent a commitment_signed (implying we've revoke_and_ack'ed it), but
        /// the remote side hasn't yet revoked their previous state, which we need them to do before we
        /// can do any backwards failing. Implies AwaitingRemoteRevoke.
        /// We have removed this HTLC in our latest commitment_signed and are now just waiting on a
        /// revoke_and_ack to drop completely.
-       /// Implies HTLCOutput::outbound: true
        AwaitingRemovedRemoteRevoke,
-       /// Removed by us and a new commitment_signed was sent (if we were AwaitingRemoteRevoke when we
-       /// created it we would have put it in the holding cell instead). When they next revoke_and_ack
-       /// we'll drop it.
-       /// Note that we have to keep an eye on the HTLC until we've received a broadcastable
-       /// commitment transaction without it as otherwise we'll have to force-close the channel to
-       /// claim it before the timeout (obviously doesn't apply to revoked HTLCs that we can't claim
-       /// anyway). That said, ChannelMonitor does this for us (see
-       /// ChannelMonitor::would_broadcast_at_height) so we actually remove the HTLC from our own
-       /// local state before then, once we're sure that the next commitment_signed and
-       /// ChannelMonitor::provide_latest_local_commitment_tx_info will not include this HTLC.
-       /// Implies HTLCOutput::outbound: false
-       LocalRemoved,
 }
 
-struct HTLCOutput { //TODO: Refactor into Outbound/InboundHTLCOutput (will save memory and fewer panics)
-       outbound: bool, // ie to an HTLC-Timeout transaction
+struct OutboundHTLCOutput {
        htlc_id: u64,
        amount_msat: u64,
        cltv_expiry: u32,
        payment_hash: [u8; 32],
-       state: HTLCState,
-       /// If we're in a Remote* removed state, set if they failed, otherwise None
+       state: OutboundHTLCState,
+       /// If we're in a removed state, set if they failed, otherwise None
        fail_reason: Option<HTLCFailReason>,
-       /// If we're in LocalRemoved*, set to true if we fulfilled the HTLC, and can claim money
-       local_removed_fulfilled: bool,
-       /// state pre-committed Remote* implies pending_forward_state, otherwise it must be None
-       pending_forward_state: Option<PendingHTLCStatus>,
 }
 
-impl HTLCOutput {
-       fn get_in_commitment(&self, offered: bool) -> HTLCOutputInCommitment {
+macro_rules! get_htlc_in_commitment {
+       ($htlc: expr, $offered: expr) => {
                HTLCOutputInCommitment {
-                       offered: offered,
-                       amount_msat: self.amount_msat,
-                       cltv_expiry: self.cltv_expiry,
-                       payment_hash: self.payment_hash,
+                       offered: $offered,
+                       amount_msat: $htlc.amount_msat,
+                       cltv_expiry: $htlc.cltv_expiry,
+                       payment_hash: $htlc.payment_hash,
                        transaction_output_index: 0
                }
        }
@@ -262,7 +266,8 @@ pub struct Channel {
        cur_local_commitment_transaction_number: u64,
        cur_remote_commitment_transaction_number: u64,
        value_to_self_msat: u64, // Excluding all pending_htlcs, excluding fees
-       pending_htlcs: Vec<HTLCOutput>,
+       pending_inbound_htlcs: Vec<InboundHTLCOutput>,
+       pending_outbound_htlcs: Vec<OutboundHTLCOutput>,
        holding_cell_htlc_updates: Vec<HTLCUpdateAwaitingACK>,
        next_local_htlc_id: u64,
        next_remote_htlc_id: u64,
@@ -421,7 +426,8 @@ impl Channel {
                        cur_local_commitment_transaction_number: (1 << 48) - 1,
                        cur_remote_commitment_transaction_number: (1 << 48) - 1,
                        value_to_self_msat: channel_value_satoshis * 1000 - push_msat,
-                       pending_htlcs: Vec::new(),
+                       pending_inbound_htlcs: Vec::new(),
+                       pending_outbound_htlcs: Vec::new(),
                        holding_cell_htlc_updates: Vec::new(),
                        next_local_htlc_id: 0,
                        next_remote_htlc_id: 0,
@@ -578,7 +584,8 @@ impl Channel {
                        cur_local_commitment_transaction_number: (1 << 48) - 1,
                        cur_remote_commitment_transaction_number: (1 << 48) - 1,
                        value_to_self_msat: msg.push_msat,
-                       pending_htlcs: Vec::new(),
+                       pending_inbound_htlcs: Vec::new(),
+                       pending_outbound_htlcs: Vec::new(),
                        holding_cell_htlc_updates: Vec::new(),
                        next_local_htlc_id: 0,
                        next_remote_htlc_id: 0,
@@ -686,66 +693,83 @@ impl Channel {
                        ins
                };
 
-               let mut txouts: Vec<(TxOut, Option<HTLCOutputInCommitment>)> = Vec::with_capacity(self.pending_htlcs.len() + 2);
+               let mut txouts: Vec<(TxOut, Option<HTLCOutputInCommitment>)> = Vec::with_capacity(self.pending_inbound_htlcs.len() + self.pending_outbound_htlcs.len() + 2);
 
                let dust_limit_satoshis = if local { self.our_dust_limit_satoshis } else { self.their_dust_limit_satoshis };
                let mut remote_htlc_total_msat = 0;
                let mut local_htlc_total_msat = 0;
                let mut value_to_self_msat_offset = 0;
 
-               for ref htlc in self.pending_htlcs.iter() {
-                       let include = match htlc.state {
-                               HTLCState::RemoteAnnounced => !generated_by_local,
-                               HTLCState::AwaitingRemoteRevokeToAnnounce => !generated_by_local,
-                               HTLCState::AwaitingAnnouncedRemoteRevoke => true,
-                               HTLCState::LocalAnnounced => generated_by_local,
-                               HTLCState::Committed => true,
-                               HTLCState::RemoteRemoved => generated_by_local,
-                               HTLCState::AwaitingRemoteRevokeToRemove => generated_by_local,
-                               HTLCState::AwaitingRemovedRemoteRevoke => false,
-                               HTLCState::LocalRemoved => !generated_by_local,
-                       };
-
-                       if include {
-                               if htlc.outbound == local { // "offered HTLC output"
-                                       if htlc.amount_msat / 1000 >= dust_limit_satoshis + (self.feerate_per_kw * HTLC_TIMEOUT_TX_WEIGHT / 1000) {
-                                               let htlc_in_tx = htlc.get_in_commitment(true);
+               macro_rules! add_htlc_output {
+                       ($htlc: expr, $outbound: expr) => {
+                               if $outbound == local { // "offered HTLC output"
+                                       if $htlc.amount_msat / 1000 >= dust_limit_satoshis + (self.feerate_per_kw * HTLC_TIMEOUT_TX_WEIGHT / 1000) {
+                                               let htlc_in_tx = get_htlc_in_commitment!($htlc, true);
                                                txouts.push((TxOut {
                                                        script_pubkey: chan_utils::get_htlc_redeemscript(&htlc_in_tx, &keys).to_v0_p2wsh(),
-                                                       value: htlc.amount_msat / 1000
+                                                       value: $htlc.amount_msat / 1000
                                                }, Some(htlc_in_tx)));
                                        }
                                } else {
-                                       if htlc.amount_msat / 1000 >= dust_limit_satoshis + (self.feerate_per_kw * HTLC_SUCCESS_TX_WEIGHT / 1000) {
-                                               let htlc_in_tx = htlc.get_in_commitment(false);
+                                       if $htlc.amount_msat / 1000 >= dust_limit_satoshis + (self.feerate_per_kw * HTLC_SUCCESS_TX_WEIGHT / 1000) {
+                                               let htlc_in_tx = get_htlc_in_commitment!($htlc, false);
                                                txouts.push((TxOut { // "received HTLC output"
                                                        script_pubkey: chan_utils::get_htlc_redeemscript(&htlc_in_tx, &keys).to_v0_p2wsh(),
-                                                       value: htlc.amount_msat / 1000
+                                                       value: $htlc.amount_msat / 1000
                                                }, Some(htlc_in_tx)));
                                        }
-                               };
-                               if htlc.outbound {
-                                       local_htlc_total_msat += htlc.amount_msat;
-                               } else {
-                                       remote_htlc_total_msat += htlc.amount_msat;
                                }
+                       }
+               }
+
+               for ref htlc in self.pending_inbound_htlcs.iter() {
+                       let include = match htlc.state {
+                               InboundHTLCState::RemoteAnnounced => !generated_by_local,
+                               InboundHTLCState::AwaitingRemoteRevokeToAnnounce => !generated_by_local,
+                               InboundHTLCState::AwaitingAnnouncedRemoteRevoke => true,
+                               InboundHTLCState::Committed => true,
+                               InboundHTLCState::LocalRemoved => !generated_by_local,
+                       };
+
+                       if include {
+                               add_htlc_output!(htlc, false);
+                               remote_htlc_total_msat += htlc.amount_msat;
+                       } else {
+                               match htlc.state {
+                                       InboundHTLCState::LocalRemoved => {
+                                               if generated_by_local && htlc.local_removed_fulfilled {
+                                                       value_to_self_msat_offset += htlc.amount_msat as i64;
+                                               }
+                                       },
+                                       _ => {},
+                               }
+                       }
+               }
+
+               for ref htlc in self.pending_outbound_htlcs.iter() {
+                       let include = match htlc.state {
+                               OutboundHTLCState::LocalAnnounced => generated_by_local,
+                               OutboundHTLCState::Committed => true,
+                               OutboundHTLCState::RemoteRemoved => generated_by_local,
+                               OutboundHTLCState::AwaitingRemoteRevokeToRemove => generated_by_local,
+                               OutboundHTLCState::AwaitingRemovedRemoteRevoke => false,
+                       };
+
+                       if include {
+                               add_htlc_output!(htlc, true);
+                               local_htlc_total_msat += htlc.amount_msat;
                        } else {
                                match htlc.state {
-                                       HTLCState::AwaitingRemoteRevokeToRemove|HTLCState::AwaitingRemovedRemoteRevoke => {
+                                       OutboundHTLCState::AwaitingRemoteRevokeToRemove|OutboundHTLCState::AwaitingRemovedRemoteRevoke => {
                                                if htlc.fail_reason.is_none() {
                                                        value_to_self_msat_offset -= htlc.amount_msat as i64;
                                                }
                                        },
-                                       HTLCState::RemoteRemoved => {
+                                       OutboundHTLCState::RemoteRemoved => {
                                                if !generated_by_local && htlc.fail_reason.is_none() {
                                                        value_to_self_msat_offset -= htlc.amount_msat as i64;
                                                }
                                        },
-                                       HTLCState::LocalRemoved => {
-                                               if generated_by_local && htlc.local_removed_fulfilled {
-                                                       value_to_self_msat_offset += htlc.amount_msat as i64;
-                                               }
-                                       },
                                        _ => {},
                                }
                        }
@@ -820,7 +844,8 @@ impl Channel {
                        ins
                };
 
-               assert!(self.pending_htlcs.is_empty());
+               assert!(self.pending_inbound_htlcs.is_empty());
+               assert!(self.pending_outbound_htlcs.is_empty());
                let mut txouts: Vec<(TxOut, ())> = Vec::new();
 
                let mut total_fee_satoshis = proposed_total_fee_satoshis;
@@ -1010,9 +1035,9 @@ impl Channel {
                sha.result(&mut payment_hash_calc);
 
                let mut pending_idx = std::usize::MAX;
-               for (idx, htlc) in self.pending_htlcs.iter().enumerate() {
-                       if !htlc.outbound && htlc.payment_hash == payment_hash_calc &&
-                                       htlc.state != HTLCState::LocalRemoved {
+               for (idx, htlc) in self.pending_inbound_htlcs.iter().enumerate() {
+                       if htlc.payment_hash == payment_hash_calc &&
+                                       htlc.state != InboundHTLCState::LocalRemoved {
                                if let Some(PendingHTLCStatus::Fail(_)) = htlc.pending_forward_state {
                                } else {
                                        if pending_idx != std::usize::MAX {
@@ -1055,11 +1080,11 @@ impl Channel {
                }
 
                let htlc_id = {
-                       let htlc = &mut self.pending_htlcs[pending_idx];
-                       if htlc.state == HTLCState::Committed {
-                               htlc.state = HTLCState::LocalRemoved;
+                       let htlc = &mut self.pending_inbound_htlcs[pending_idx];
+                       if htlc.state == InboundHTLCState::Committed {
+                               htlc.state = InboundHTLCState::LocalRemoved;
                                htlc.local_removed_fulfilled = true;
-                       } else if htlc.state == HTLCState::RemoteAnnounced || htlc.state == HTLCState::AwaitingRemoteRevokeToAnnounce || htlc.state == HTLCState::AwaitingAnnouncedRemoteRevoke {
+                       } else if htlc.state == InboundHTLCState::RemoteAnnounced || htlc.state == InboundHTLCState::AwaitingRemoteRevokeToAnnounce || htlc.state == InboundHTLCState::AwaitingAnnouncedRemoteRevoke {
                                // Theoretically we can hit this if we get the preimage on an HTLC prior to us
                                // having forwarded it to anyone. This implies that the sender is busted as someone
                                // else knows the preimage, but handling this case and implementing the logic to
@@ -1068,7 +1093,7 @@ impl Channel {
                                // channel_monitor and pretend we didn't just see the preimage.
                                return Ok((None, Some(self.channel_monitor.clone())));
                        } else {
-                               // LocalRemoved/LocalRemovedAwaitingCOmmitment handled in the search loop
+                               // LocalRemoved handled in the search loop
                                panic!("Have an inbound HTLC when not awaiting remote revoke that had a garbage state");
                        }
                        htlc.htlc_id
@@ -1124,11 +1149,11 @@ impl Channel {
 
                let mut htlc_id = 0;
                let mut htlc_amount_msat = 0;
-               for htlc in self.pending_htlcs.iter_mut() {
-                       if !htlc.outbound && htlc.payment_hash == *payment_hash_arg {
-                               if htlc.state == HTLCState::Committed {
-                                       htlc.state = HTLCState::LocalRemoved;
-                               } else if htlc.state == HTLCState::RemoteAnnounced {
+               for htlc in self.pending_inbound_htlcs.iter_mut() {
+                       if htlc.payment_hash == *payment_hash_arg {
+                               if htlc.state == InboundHTLCState::Committed {
+                                       htlc.state = InboundHTLCState::LocalRemoved;
+                               } else if htlc.state == InboundHTLCState::RemoteAnnounced {
                                        if let Some(PendingHTLCStatus::Forward(_)) = htlc.pending_forward_state {
                                                panic!("Somehow forwarded HTLC prior to remote revocation!");
                                        } else {
@@ -1137,7 +1162,7 @@ impl Channel {
                                                // we'll fail this one as soon as remote commits to it.
                                                continue;
                                        }
-                               } else if htlc.state == HTLCState::LocalRemoved {
+                               } else if htlc.state == InboundHTLCState::LocalRemoved {
                                        return Err(HandleError{err: "Unable to find a pending HTLC which matched the given payment preimage", action: None});
                                } else {
                                        panic!("Have an inbound HTLC when not awaiting remote revoke that had a garbage state");
@@ -1361,30 +1386,34 @@ impl Channel {
        /// totals, though there is little reason to outside of further avoiding any race condition
        /// issues.
        fn get_pending_htlc_stats(&self, for_remote_update_check: bool) -> (u32, u32, u64, u64) {
+               //TODO: Can probably split this into inbound/outbound
                let mut inbound_htlc_count: u32 = 0;
                let mut outbound_htlc_count: u32 = 0;
                let mut htlc_outbound_value_msat = 0;
                let mut htlc_inbound_value_msat = 0;
-               for ref htlc in self.pending_htlcs.iter() {
+               for ref htlc in self.pending_inbound_htlcs.iter() {
                        match htlc.state {
-                               HTLCState::RemoteAnnounced => {},
-                               HTLCState::AwaitingRemoteRevokeToAnnounce => {},
-                               HTLCState::AwaitingAnnouncedRemoteRevoke => {},
-                               HTLCState::LocalAnnounced => { if for_remote_update_check { continue; } },
-                               HTLCState::Committed => {},
-                               HTLCState::RemoteRemoved => { if for_remote_update_check { continue; } },
-                               HTLCState::AwaitingRemoteRevokeToRemove => { if for_remote_update_check { continue; } },
-                               HTLCState::AwaitingRemovedRemoteRevoke => { if for_remote_update_check { continue; } },
-                               HTLCState::LocalRemoved => {},
+                               InboundHTLCState::RemoteAnnounced => {},
+                               InboundHTLCState::AwaitingRemoteRevokeToAnnounce => {},
+                               InboundHTLCState::AwaitingAnnouncedRemoteRevoke => {},
+                               InboundHTLCState::Committed => {},
+                               InboundHTLCState::LocalRemoved => {},
                        }
-                       if !htlc.outbound {
-                               inbound_htlc_count += 1;
-                               htlc_inbound_value_msat += htlc.amount_msat;
-                       } else {
-                               outbound_htlc_count += 1;
-                               htlc_outbound_value_msat += htlc.amount_msat;
+                       inbound_htlc_count += 1;
+                       htlc_inbound_value_msat += htlc.amount_msat;
+               }
+               for ref htlc in self.pending_outbound_htlcs.iter() {
+                       match htlc.state {
+                               OutboundHTLCState::LocalAnnounced => { if for_remote_update_check { continue; } },
+                               OutboundHTLCState::Committed => {},
+                               OutboundHTLCState::RemoteRemoved => { if for_remote_update_check { continue; } },
+                               OutboundHTLCState::AwaitingRemoteRevokeToRemove => { if for_remote_update_check { continue; } },
+                               OutboundHTLCState::AwaitingRemovedRemoteRevoke => { if for_remote_update_check { continue; } },
                        }
+                       outbound_htlc_count += 1;
+                       htlc_outbound_value_msat += htlc.amount_msat;
                }
+
                (inbound_htlc_count, outbound_htlc_count, htlc_outbound_value_msat, htlc_inbound_value_msat)
        }
 
@@ -1425,14 +1454,12 @@ impl Channel {
 
                // Now update local state:
                self.next_remote_htlc_id += 1;
-               self.pending_htlcs.push(HTLCOutput {
-                       outbound: false,
+               self.pending_inbound_htlcs.push(InboundHTLCOutput {
                        htlc_id: msg.htlc_id,
                        amount_msat: msg.amount_msat,
                        payment_hash: msg.payment_hash,
                        cltv_expiry: msg.cltv_expiry,
-                       state: HTLCState::RemoteAnnounced,
-                       fail_reason: None,
+                       state: InboundHTLCState::RemoteAnnounced,
                        local_removed_fulfilled: false,
                        pending_forward_state: Some(pending_forward_state),
                });
@@ -1443,8 +1470,8 @@ impl Channel {
        /// Removes an outbound HTLC which has been commitment_signed by the remote end
        #[inline]
        fn mark_outbound_htlc_removed(&mut self, htlc_id: u64, check_preimage: Option<[u8; 32]>, fail_reason: Option<HTLCFailReason>) -> Result<[u8; 32], HandleError> {
-               for htlc in self.pending_htlcs.iter_mut() {
-                       if htlc.outbound && htlc.htlc_id == htlc_id {
+               for htlc in self.pending_outbound_htlcs.iter_mut() {
+                       if htlc.htlc_id == htlc_id {
                                match check_preimage {
                                        None => {},
                                        Some(payment_hash) =>
@@ -1452,15 +1479,15 @@ impl Channel {
                                                        return Err(HandleError{err: "Remote tried to fulfill HTLC with an incorrect preimage", action: None});
                                                }
                                };
-                               if htlc.state == HTLCState::LocalAnnounced {
-                                       return Err(HandleError{err: "Remote tried to fulfill HTLC before it had been committed", action: None});
-                               } else if htlc.state == HTLCState::Committed {
-                                       htlc.state = HTLCState::RemoteRemoved;
-                                       htlc.fail_reason = fail_reason;
-                               } else if htlc.state == HTLCState::AwaitingRemoteRevokeToRemove || htlc.state == HTLCState::AwaitingRemovedRemoteRevoke || htlc.state == HTLCState::RemoteRemoved {
-                                       return Err(HandleError{err: "Remote tried to fulfill HTLC that they'd already fulfilled", action: None});
-                               } else {
-                                       panic!("Got a non-outbound state on an outbound HTLC");
+                               match htlc.state {
+                                       OutboundHTLCState::LocalAnnounced =>
+                                               return Err(HandleError{err: "Remote tried to fulfill HTLC before it had been committed", action: None}),
+                                       OutboundHTLCState::Committed => {
+                                               htlc.state = OutboundHTLCState::RemoteRemoved;
+                                               htlc.fail_reason = fail_reason;
+                                       },
+                                       OutboundHTLCState::AwaitingRemoteRevokeToRemove | OutboundHTLCState::AwaitingRemovedRemoteRevoke | OutboundHTLCState::RemoteRemoved =>
+                                               return Err(HandleError{err: "Remote tried to fulfill HTLC that they'd already fulfilled", action: None}),
                                }
                                return Ok(htlc.payment_hash.clone());
                        }
@@ -1543,12 +1570,15 @@ impl Channel {
                self.channel_monitor.provide_latest_local_commitment_tx_info(local_commitment_tx.0, local_keys, self.feerate_per_kw, htlcs_and_sigs);
 
                let mut need_our_commitment = false;
-               for htlc in self.pending_htlcs.iter_mut() {
-                       if htlc.state == HTLCState::RemoteAnnounced {
-                               htlc.state = HTLCState::AwaitingRemoteRevokeToAnnounce;
+               for htlc in self.pending_inbound_htlcs.iter_mut() {
+                       if htlc.state == InboundHTLCState::RemoteAnnounced {
+                               htlc.state = InboundHTLCState::AwaitingRemoteRevokeToAnnounce;
                                need_our_commitment = true;
-                       } else if htlc.state == HTLCState::RemoteRemoved {
-                               htlc.state = HTLCState::AwaitingRemoteRevokeToRemove;
+                       }
+               }
+               for htlc in self.pending_outbound_htlcs.iter_mut() {
+                       if htlc.state == OutboundHTLCState::RemoteRemoved {
+                               htlc.state = OutboundHTLCState::AwaitingRemoteRevokeToRemove;
                                need_our_commitment = true;
                        }
                }
@@ -1673,13 +1703,16 @@ impl Channel {
                let mut require_commitment = false;
                let mut value_to_self_msat_diff: i64 = 0;
                // We really shouldnt have two passes here, but retain gives a non-mutable ref (Rust bug)
-               self.pending_htlcs.retain(|htlc| {
-                       if htlc.state == HTLCState::LocalRemoved {
+               self.pending_inbound_htlcs.retain(|htlc| {
+                       if htlc.state == InboundHTLCState::LocalRemoved {
                                if htlc.local_removed_fulfilled {
                                        value_to_self_msat_diff += htlc.amount_msat as i64;
                                }
                                false
-                       } else if htlc.state == HTLCState::AwaitingRemovedRemoteRevoke {
+                       } else { true }
+               });
+               self.pending_outbound_htlcs.retain(|htlc| {
+                       if htlc.state == OutboundHTLCState::AwaitingRemovedRemoteRevoke {
                                if let Some(reason) = htlc.fail_reason.clone() { // We really want take() here, but, again, non-mut ref :(
                                        revoked_htlcs.push((htlc.payment_hash, reason));
                                } else {
@@ -1689,16 +1722,14 @@ impl Channel {
                                false
                        } else { true }
                });
-               for htlc in self.pending_htlcs.iter_mut() {
-                       if htlc.state == HTLCState::LocalAnnounced {
-                               htlc.state = HTLCState::Committed;
-                       } else if htlc.state == HTLCState::AwaitingRemoteRevokeToAnnounce {
-                               htlc.state = HTLCState::AwaitingAnnouncedRemoteRevoke;
+               for htlc in self.pending_inbound_htlcs.iter_mut() {
+                       if htlc.state == InboundHTLCState::AwaitingRemoteRevokeToAnnounce {
+                               htlc.state = InboundHTLCState::AwaitingAnnouncedRemoteRevoke;
                                require_commitment = true;
-                       } else if htlc.state == HTLCState::AwaitingAnnouncedRemoteRevoke {
+                       } else if htlc.state == InboundHTLCState::AwaitingAnnouncedRemoteRevoke {
                                match htlc.pending_forward_state.take().unwrap() {
                                        PendingHTLCStatus::Fail(fail_msg) => {
-                                               htlc.state = HTLCState::LocalRemoved;
+                                               htlc.state = InboundHTLCState::LocalRemoved;
                                                require_commitment = true;
                                                match fail_msg {
                                                        HTLCFailureMsg::Relay(msg) => update_fail_htlcs.push(msg),
@@ -1707,11 +1738,16 @@ impl Channel {
                                        },
                                        PendingHTLCStatus::Forward(forward_info) => {
                                                to_forward_infos.push(forward_info);
-                                               htlc.state = HTLCState::Committed;
+                                               htlc.state = InboundHTLCState::Committed;
                                        }
                                }
-                       } else if htlc.state == HTLCState::AwaitingRemoteRevokeToRemove {
-                               htlc.state = HTLCState::AwaitingRemovedRemoteRevoke;
+                       }
+               }
+               for htlc in self.pending_outbound_htlcs.iter_mut() {
+                       if htlc.state == OutboundHTLCState::LocalAnnounced {
+                               htlc.state = OutboundHTLCState::Committed;
+                       } else if htlc.state == OutboundHTLCState::AwaitingRemoteRevokeToRemove {
+                               htlc.state = OutboundHTLCState::AwaitingRemovedRemoteRevoke;
                                require_commitment = true;
                        }
                }
@@ -1762,8 +1798,8 @@ impl Channel {
                        self.channel_update_count += 1;
                        return Ok((None, None, Vec::new()));
                }
-               for htlc in self.pending_htlcs.iter() {
-                       if htlc.state == HTLCState::RemoteAnnounced {
+               for htlc in self.pending_inbound_htlcs.iter() {
+                       if htlc.state == InboundHTLCState::RemoteAnnounced {
                                return Err(HandleError{err: "Got shutdown with remote pending HTLCs", action: None});
                        }
                }
@@ -1789,7 +1825,7 @@ impl Channel {
 
                let our_closing_script = self.get_closing_scriptpubkey();
 
-               let (proposed_feerate, proposed_fee, our_sig) = if self.channel_outbound && self.pending_htlcs.is_empty() {
+               let (proposed_feerate, proposed_fee, our_sig) = if self.channel_outbound && self.pending_inbound_htlcs.is_empty() && self.pending_outbound_htlcs.is_empty() {
                        let mut proposed_feerate = fee_estimator.get_est_sat_per_1000_weight(ConfirmationTarget::Background);
                        if self.feerate_per_kw > proposed_feerate {
                                proposed_feerate = self.feerate_per_kw;
@@ -1822,8 +1858,8 @@ impl Channel {
                                _ => true
                        }
                });
-               for htlc in self.pending_htlcs.iter() {
-                       if htlc.state == HTLCState::LocalAnnounced {
+               for htlc in self.pending_outbound_htlcs.iter() {
+                       if htlc.state == OutboundHTLCState::LocalAnnounced {
                                return Ok((None, None, dropped_outbound_htlcs));
                        }
                }
@@ -1839,7 +1875,7 @@ impl Channel {
 
                self.channel_state |= ChannelState::LocalShutdownSent as u32;
                self.channel_update_count += 1;
-               if self.pending_htlcs.is_empty() && self.channel_outbound {
+               if self.pending_inbound_htlcs.is_empty() && self.pending_outbound_htlcs.is_empty() && self.channel_outbound {
                        // There are no more HTLCs and we're the funder, this means we start the closing_signed
                        // dance with an initial fee proposal!
                        self.last_sent_closing_fee = Some((proposed_feerate.unwrap(), proposed_fee.unwrap()));
@@ -1857,7 +1893,7 @@ impl Channel {
                if self.channel_state & BOTH_SIDES_SHUTDOWN_MASK != BOTH_SIDES_SHUTDOWN_MASK {
                        return Err(HandleError{err: "Remote end sent us a closing_signed before both sides provided a shutdown", action: None});
                }
-               if !self.pending_htlcs.is_empty() {
+               if !self.pending_inbound_htlcs.is_empty() || !self.pending_outbound_htlcs.is_empty() {
                        return Err(HandleError{err: "Remote end sent us a closing_signed while there were still pending HTLCs", action: None});
                }
                if msg.fee_satoshis > 21000000 * 10000000 {
@@ -2362,16 +2398,13 @@ impl Channel {
                        return Ok(None);
                }
 
-               self.pending_htlcs.push(HTLCOutput {
-                       outbound: true,
+               self.pending_outbound_htlcs.push(OutboundHTLCOutput {
                        htlc_id: self.next_local_htlc_id,
                        amount_msat: amount_msat,
                        payment_hash: payment_hash.clone(),
                        cltv_expiry: cltv_expiry,
-                       state: HTLCState::LocalAnnounced,
+                       state: OutboundHTLCState::LocalAnnounced,
                        fail_reason: None,
-                       local_removed_fulfilled: false,
-                       pending_forward_state: None
                });
 
                let res = msgs::UpdateAddHTLC {
@@ -2399,8 +2432,8 @@ impl Channel {
                        panic!("Cannot create commitment tx until remote revokes their previous commitment");
                }
                let mut have_updates = false; // TODO initialize with "have we sent a fee update?"
-               for htlc in self.pending_htlcs.iter() {
-                       if htlc.state == HTLCState::LocalAnnounced {
+               for htlc in self.pending_outbound_htlcs.iter() {
+                       if htlc.state == OutboundHTLCState::LocalAnnounced {
                                have_updates = true;
                        }
                        if have_updates { break; }
@@ -2417,11 +2450,14 @@ impl Channel {
                // We can upgrade the status of some HTLCs that are waiting on a commitment, even if we
                // fail to generate this, we still are at least at a position where upgrading their status
                // is acceptable.
-               for htlc in self.pending_htlcs.iter_mut() {
-                       if htlc.state == HTLCState::AwaitingRemoteRevokeToAnnounce {
-                               htlc.state = HTLCState::AwaitingAnnouncedRemoteRevoke;
-                       } else if htlc.state == HTLCState::AwaitingRemoteRevokeToRemove {
-                               htlc.state = HTLCState::AwaitingRemovedRemoteRevoke;
+               for htlc in self.pending_inbound_htlcs.iter_mut() {
+                       if htlc.state == InboundHTLCState::AwaitingRemoteRevokeToAnnounce {
+                               htlc.state = InboundHTLCState::AwaitingAnnouncedRemoteRevoke;
+                       }
+               }
+               for htlc in self.pending_outbound_htlcs.iter_mut() {
+                       if htlc.state == OutboundHTLCState::AwaitingRemoteRevokeToRemove {
+                               htlc.state = OutboundHTLCState::AwaitingRemovedRemoteRevoke;
                        }
                }
 
@@ -2469,8 +2505,8 @@ impl Channel {
        /// Begins the shutdown process, getting a message for the remote peer and returning all
        /// holding cell HTLCs for payment failure.
        pub fn get_shutdown(&mut self) -> Result<(msgs::Shutdown, Vec<[u8; 32]>), HandleError> {
-               for htlc in self.pending_htlcs.iter() {
-                       if htlc.state == HTLCState::LocalAnnounced {
+               for htlc in self.pending_outbound_htlcs.iter() {
+                       if htlc.state == OutboundHTLCState::LocalAnnounced {
                                return Err(HandleError{err: "Cannot begin shutdown with pending HTLCs, call send_commitment first", action: None});
                        }
                }
@@ -2529,8 +2565,8 @@ impl Channel {
                        }
                }
 
-               for htlc in self.pending_htlcs.drain(..) {
-                       if htlc.state == HTLCState::LocalAnnounced {
+               for htlc in self.pending_outbound_htlcs.drain(..) {
+                       if htlc.state == OutboundHTLCState::LocalAnnounced {
                                dropped_outbound_htlcs.push(htlc.payment_hash);
                        }
                        //TODO: Do something with the remaining HTLCs
@@ -2554,7 +2590,7 @@ mod tests {
        use bitcoin::blockdata::script::Script;
        use bitcoin::blockdata::transaction::Transaction;
        use hex;
-       use ln::channel::{Channel,ChannelKeys,HTLCOutput,HTLCState,HTLCOutputInCommitment,TxCreationKeys};
+       use ln::channel::{Channel,ChannelKeys,InboundHTLCOutput,OutboundHTLCOutput,InboundHTLCState,OutboundHTLCState,HTLCOutputInCommitment,TxCreationKeys};
        use ln::channel::MAX_FUNDING_SATOSHIS;
        use ln::chan_utils;
        use chain::chaininterface::{FeeEstimator,ConfirmationTarget};
@@ -2693,15 +2729,13 @@ mod tests {
                                         "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");
                }
 
-               chan.pending_htlcs.push({
-                       let mut out = HTLCOutput{
+               chan.pending_inbound_htlcs.push({
+                       let mut out = InboundHTLCOutput{
                                htlc_id: 0,
-                               outbound: false,
                                amount_msat: 1000000,
                                cltv_expiry: 500,
                                payment_hash: [0; 32],
-                               state: HTLCState::Committed,
-                               fail_reason: None,
+                               state: InboundHTLCState::Committed,
                                local_removed_fulfilled: false,
                                pending_forward_state: None,
                        };
@@ -2710,15 +2744,13 @@ mod tests {
                        sha.result(&mut out.payment_hash);
                        out
                });
-               chan.pending_htlcs.push({
-                       let mut out = HTLCOutput{
+               chan.pending_inbound_htlcs.push({
+                       let mut out = InboundHTLCOutput{
                                htlc_id: 1,
-                               outbound: false,
                                amount_msat: 2000000,
                                cltv_expiry: 501,
                                payment_hash: [0; 32],
-                               state: HTLCState::Committed,
-                               fail_reason: None,
+                               state: InboundHTLCState::Committed,
                                local_removed_fulfilled: false,
                                pending_forward_state: None,
                        };
@@ -2727,49 +2759,41 @@ mod tests {
                        sha.result(&mut out.payment_hash);
                        out
                });
-               chan.pending_htlcs.push({
-                       let mut out = HTLCOutput{
+               chan.pending_outbound_htlcs.push({
+                       let mut out = OutboundHTLCOutput{
                                htlc_id: 2,
-                               outbound: true,
                                amount_msat: 2000000,
                                cltv_expiry: 502,
                                payment_hash: [0; 32],
-                               state: HTLCState::Committed,
+                               state: OutboundHTLCState::Committed,
                                fail_reason: None,
-                               local_removed_fulfilled: false,
-                               pending_forward_state: None,
                        };
                        let mut sha = Sha256::new();
                        sha.input(&hex::decode("0202020202020202020202020202020202020202020202020202020202020202").unwrap());
                        sha.result(&mut out.payment_hash);
                        out
                });
-               chan.pending_htlcs.push({
-                       let mut out = HTLCOutput{
+               chan.pending_outbound_htlcs.push({
+                       let mut out = OutboundHTLCOutput{
                                htlc_id: 3,
-                               outbound: true,
                                amount_msat: 3000000,
                                cltv_expiry: 503,
                                payment_hash: [0; 32],
-                               state: HTLCState::Committed,
+                               state: OutboundHTLCState::Committed,
                                fail_reason: None,
-                               local_removed_fulfilled: false,
-                               pending_forward_state: None,
                        };
                        let mut sha = Sha256::new();
                        sha.input(&hex::decode("0303030303030303030303030303030303030303030303030303030303030303").unwrap());
                        sha.result(&mut out.payment_hash);
                        out
                });
-               chan.pending_htlcs.push({
-                       let mut out = HTLCOutput{
+               chan.pending_inbound_htlcs.push({
+                       let mut out = InboundHTLCOutput{
                                htlc_id: 4,
-                               outbound: false,
                                amount_msat: 4000000,
                                cltv_expiry: 504,
                                payment_hash: [0; 32],
-                               state: HTLCState::Committed,
-                               fail_reason: None,
+                               state: InboundHTLCState::Committed,
                                local_removed_fulfilled: false,
                                pending_forward_state: None,
                        };