lnd.xprv/htlcswitch/link.go

1653 lines
53 KiB
Go

package htlcswitch
import (
"bytes"
"sync"
"sync/atomic"
"time"
"io"
"crypto/sha256"
"github.com/go-errors/errors"
"github.com/lightningnetwork/lnd/chainntnfs"
"github.com/lightningnetwork/lnd/lnwallet"
"github.com/lightningnetwork/lnd/lnwire"
"github.com/roasbeef/btcd/chaincfg/chainhash"
"github.com/roasbeef/btcd/wire"
"github.com/roasbeef/btcutil"
)
const (
// expiryGraceDelta is a grace period that the timeout of incoming
// HTLC's that pay directly to us (i.e we're the "exit node") must up
// hold. We'll reject any HTLC's who's timeout minus this value is less
// that or equal to the current block height. We require this in order
// to ensure that if the extending party goes to the chain, then we'll
// be able to claim the HTLC still.
//
// TODO(roasbeef): must be < default delta
expiryGraceDelta = 2
)
// ForwardingPolicy describes the set of constraints that a given ChannelLink
// is to adhere to when forwarding HTLC's. For each incoming HTLC, this set of
// constraints will be consulted in order to ensure that adequate fees are
// paid, and our time-lock parameters are respected. In the event that an
// incoming HTLC violates any of these constraints, it is to be _rejected_ with
// the error possibly carrying along a ChannelUpdate message that includes the
// latest policy.
type ForwardingPolicy struct {
// MinHTLC is the smallest HTLC that is to be forwarded.
MinHTLC lnwire.MilliSatoshi
// BaseFee is the base fee, expressed in milli-satoshi that must be
// paid for each incoming HTLC. This field, combined with FeeRate is
// used to compute the required fee for a given HTLC.
BaseFee lnwire.MilliSatoshi
// FeeRate is the fee rate, expressed in milli-satoshi that must be
// paid for each incoming HTLC. This field combined with BaseFee is
// used to compute the required fee for a given HTLC.
FeeRate lnwire.MilliSatoshi
// TimeLockDelta is the absolute time-lock value, expressed in blocks,
// that will be subtracted from an incoming HTLC's timelock value to
// create the time-lock value for the forwarded outgoing HTLC. The
// following constraint MUST hold for an HTLC to be forwarded:
//
// * incomingHtlc.timeLock - timeLockDelta = fwdInfo.OutgoingCTLV
//
// where fwdInfo is the forwarding information extracted from the
// per-hop payload of the incoming HTLC's onion packet.
TimeLockDelta uint32
// TODO(roasbeef): add fee module inside of switch
}
// ExpectedFee computes the expected fee for a given htlc amount. The value
// returned from this function is to be used as a sanity check when forwarding
// HTLC's to ensure that an incoming HTLC properly adheres to our propagated
// forwarding policy.
//
// TODO(roasbeef): also add in current available channel bandwidth, inverse
// func
func ExpectedFee(f ForwardingPolicy, htlcAmt lnwire.MilliSatoshi) lnwire.MilliSatoshi {
// TODO(roasbeef): write some basic table driven tests
return f.BaseFee + (htlcAmt*f.FeeRate)/1000000
}
// ChannelLinkConfig defines the configuration for the channel link. ALL
// elements within the configuration MUST be non-nil for channel link to carry
// out its duties.
type ChannelLinkConfig struct {
// FwrdingPolicy is the initial forwarding policy to be used when
// deciding whether to forwarding incoming HTLC's or not. This value
// can be updated with subsequent calls to UpdateForwardingPolicy
// targeted at a given ChannelLink concrete interface implementation.
FwrdingPolicy ForwardingPolicy
// Switch is a subsystem which is used to forward the incoming HTLC
// packets according to the encoded hop forwarding information
// contained in the forwarding blob within each HTLC.
//
// TODO(roasbeef): remove in favor of simple ForwardPacket closure func
Switch *Switch
// DecodeHopIterator function is responsible for decoding HTLC Sphinx
// onion blob, and creating hop iterator which will give us next
// destination of HTLC.
DecodeHopIterator func(r io.Reader, rHash []byte) (HopIterator, lnwire.FailCode)
// DecodeOnionObfuscator function is responsible for decoding HTLC
// Sphinx onion blob, and creating onion failure obfuscator.
DecodeOnionObfuscator func(r io.Reader) (ErrorEncrypter, lnwire.FailCode)
// GetLastChannelUpdate retrieves the latest routing policy for this
// particular channel. This will be used to provide payment senders our
// latest policy when sending encrypted error messages.
GetLastChannelUpdate func() (*lnwire.ChannelUpdate, error)
// Peer is a lightning network node with which we have the channel link
// opened.
Peer Peer
// Registry is a sub-system which responsible for managing the invoices
// in thread-safe manner.
Registry InvoiceDatabase
// FeeEstimator is an instance of a live fee estimator which will be
// used to dynamically regulate the current fee of the commitment
// transaction to ensure timely confirmation.
FeeEstimator lnwallet.FeeEstimator
// BlockEpochs is an active block epoch event stream backed by an
// active ChainNotifier instance. The ChannelLink will use new block
// notifications sent over this channel to decide when a _new_ HTLC is
// too close to expiry, and also when any active HTLC's have expired
// (or are close to expiry).
BlockEpochs *chainntnfs.BlockEpochEvent
// SettledContracts is used to notify that a channel has peacefully
// been closed. Once a channel has been closed the other subsystem no
// longer needs to watch for breach closes.
SettledContracts chan *wire.OutPoint
// DebugHTLC should be turned on if you want all HTLCs sent to a node
// with the debug htlc R-Hash are immediately settled in the next
// available state transition.
DebugHTLC bool
// HodlHTLC should be active if you want this node to refrain from
// settling all incoming HTLCs with the sender if it finds itself to be
// the exit node.
//
// NOTE: HodlHTLC should be active in conjunction with DebugHTLC.
HodlHTLC bool
// SyncStates is used to indicate that we need send the channel
// reestablishment message to the remote peer. It should be done if our
// clients have been restarted, or remote peer have been reconnected.
SyncStates bool
}
// channelLink is the service which drives a channel's commitment update
// state-machine. In the event that an htlc needs to be propagated to another
// link, the forward handler from config is used which sends htlc to the
// switch. Additionally, the link encapsulate logic of commitment protocol
// message ordering and updates.
type channelLink struct {
// The following fields are only meant to be used *atomically*
started int32
shutdown int32
// batchCounter is the number of updates which we received from remote
// side, but not include in commitment transaction yet and plus the
// current number of settles that have been sent, but not yet committed
// to the commitment.
//
// TODO(andrew.shvv) remove after we add additional
// BatchNumber() method in state machine.
batchCounter uint32
// bestHeight is the best known height of the main chain. The link will
// use this information to govern decisions based on HTLC timeouts.
bestHeight uint32
// channel is a lightning network channel to which we apply htlc
// updates.
channel *lnwallet.LightningChannel
// cfg is a structure which carries all dependable fields/handlers
// which may affect behaviour of the service.
cfg ChannelLinkConfig
// overflowQueue is used to store the htlc add updates which haven't
// been processed because of the commitment transaction overflow.
overflowQueue *packetQueue
// mailBox is the main interface between the outside world and the
// link. All incoming messages will be sent over this mailBox. Messages
// include new updates from our connected peer, and new packets to be
// forwarded sent by the switch.
mailBox *memoryMailBox
// upstream is a channel that new messages sent from the remote peer to
// the local peer will be sent across.
upstream chan lnwire.Message
// downstream is a channel in which new multi-hop HTLC's to be
// forwarded will be sent across. Messages from this channel are sent
// by the HTLC switch.
downstream chan *htlcPacket
// linkControl is a channel which is used to query the state of the
// link, or update various policies used which govern if an HTLC is to
// be forwarded and/or accepted.
linkControl chan interface{}
// logCommitTimer is a timer which is sent upon if we go an interval
// without receiving/sending a commitment update. It's role is to
// ensure both chains converge to identical state in a timely manner.
//
// TODO(roasbeef): timer should be >> then RTT
logCommitTimer *time.Timer
logCommitTick <-chan time.Time
wg sync.WaitGroup
quit chan struct{}
}
// NewChannelLink creates a new instance of a ChannelLink given a configuration
// and active channel that will be used to verify/apply updates to.
func NewChannelLink(cfg ChannelLinkConfig, channel *lnwallet.LightningChannel,
currentHeight uint32) ChannelLink {
link := &channelLink{
cfg: cfg,
channel: channel,
mailBox: newMemoryMailBox(),
linkControl: make(chan interface{}),
// TODO(roasbeef): just do reserve here?
logCommitTimer: time.NewTimer(300 * time.Millisecond),
overflowQueue: newPacketQueue(lnwallet.MaxHTLCNumber / 2),
bestHeight: currentHeight,
quit: make(chan struct{}),
}
link.upstream = link.mailBox.MessageOutBox()
link.downstream = link.mailBox.PacketOutBox()
return link
}
// A compile time check to ensure channelLink implements the ChannelLink
// interface.
var _ ChannelLink = (*channelLink)(nil)
// Start starts all helper goroutines required for the operation of the channel
// link.
//
// NOTE: Part of the ChannelLink interface.
func (l *channelLink) Start() error {
if !atomic.CompareAndSwapInt32(&l.started, 0, 1) {
err := errors.Errorf("channel link(%v): already started", l)
log.Warn(err)
return err
}
log.Infof("ChannelLink(%v) is starting", l)
l.mailBox.Start()
l.overflowQueue.Start()
l.wg.Add(1)
go l.htlcManager()
return nil
}
// Stop gracefully stops all active helper goroutines, then waits until they've
// exited.
//
// NOTE: Part of the ChannelLink interface.
func (l *channelLink) Stop() {
if !atomic.CompareAndSwapInt32(&l.shutdown, 0, 1) {
log.Warnf("channel link(%v): already stopped", l)
return
}
log.Infof("ChannelLink(%v) is stopping", l)
l.channel.Stop()
l.mailBox.Stop()
l.overflowQueue.Stop()
close(l.quit)
l.wg.Wait()
l.cfg.BlockEpochs.Cancel()
}
// EligibleToForward returns a bool indicating if the channel is able to
// actively accept requests to forward HTLC's. We're able to forward HTLC's if
// we know the remote party's next revocation point. Otherwise, we can't
// initiate new channel state.
func (l *channelLink) EligibleToForward() bool {
return l.channel.RemoteNextRevocation() != nil
}
// sampleNetworkFee samples the current fee rate on the network to get into the
// chain in a timely manner. The returned value is expressed in fee-per-kw, as
// this is the native rate used when computing the fee for commitment
// transactions, and the second-level HTLC transactions.
func (l *channelLink) sampleNetworkFee() (btcutil.Amount, error) {
// We'll first query for the sat/weight recommended to be confirmed
// within 3blocks.
feePerWeight, err := l.cfg.FeeEstimator.EstimateFeePerWeight(3)
if err != nil {
return 0, err
}
// Once we have this fee rate, we'll convert to sat-per-kw.
feePerKw := feePerWeight * 1000
log.Debugf("ChannelLink(%v): sampled fee rate for 3 block conf: %v "+
"sat/kw", l, int64(feePerKw))
return feePerKw, nil
}
// shouldAdjustCommitFee returns true if we should update our commitment fee to
// match that of the network fee. We'll only update our commitment fee if the
// network fee is +/- 10% to our network fee.
func shouldAdjustCommitFee(netFee, chanFee btcutil.Amount) bool {
switch {
// If the network fee is greater than the commitment fee, then we'll
// switch to it if it's at least 10% greater than the commit fee.
case netFee > chanFee && netFee >= (chanFee+(chanFee*10)/100):
return true
// If the network fee is less than our commitment fee, then we'll
// switch to it if it's at least 10% less than the commitment fee.
case netFee < chanFee && netFee <= (chanFee-(chanFee*10)/100):
return true
// Otherwise, we won't modify our fee.
default:
return false
}
}
// htlcManager is the primary goroutine which drives a channel's commitment
// update state-machine in response to messages received via several channels.
// This goroutine reads messages from the upstream (remote) peer, and also from
// downstream channel managed by the channel link. In the event that an htlc
// needs to be forwarded, then send-only forward handler is used which sends
// htlc packets to the switch. Additionally, the this goroutine handles acting
// upon all timeouts for any active HTLCs, manages the channel's revocation
// window, and also the htlc trickle queue+timer for this active channels.
//
// NOTE: This MUST be run as a goroutine.
func (l *channelLink) htlcManager() {
defer func() {
l.wg.Done()
log.Infof("ChannelLink(%v) has exited", l)
}()
log.Infof("HTLC manager for ChannelPoint(%v) started, "+
"bandwidth=%v", l.channel.ChannelPoint(), l.Bandwidth())
// TODO(roasbeef): need to call wipe chan whenever D/C?
// If this isn't the first time that this channel link has been
// created, then we'll need to check to see if we need to
// re-synchronize state with the remote peer.
if l.cfg.SyncStates {
log.Infof("Attempting to re-resynchronize ChannelPoint(%v)",
l.channel.ChannelPoint())
// First, we'll generate our ChanSync message to send to the
// other side. Based on this message, the remote party will
// decide if they need to retransmit any data or not.
localChanSyncMsg, err := l.channel.ChanSyncMsg()
if err != nil {
l.fail("unable to generate chan sync message for "+
"ChannelPoint(%v)", l.channel.ChannelPoint())
return
}
if err := l.cfg.Peer.SendMessage(localChanSyncMsg); err != nil {
l.fail("Unable to send chan sync message for "+
"ChannelPoint(%v)", l.channel.ChannelPoint())
return
}
// Next, we'll wait to receive the ChanSync message with a
// timeout period. The first message sent MUST be the ChanSync
// message, otherwise, we'll terminate the connection.
chanSyncDeadline := time.After(time.Second * 30)
select {
case msg := <-l.upstream:
remoteChanSyncMsg, ok := msg.(*lnwire.ChannelReestablish)
if !ok {
l.fail("first message sent to sync should be "+
"ChannelReestablish, instead "+
"received: %T", msg)
return
}
// If the remote party indicates that they think we
// haven't done any state updates yet, then we'll
// retransmit the funding locked message first. We do
// this, as at this point we can't be sure if they've
// really received the FundingLocked message.
if remoteChanSyncMsg.NextLocalCommitHeight == 1 &&
localChanSyncMsg.NextLocalCommitHeight == 1 &&
!l.channel.IsPending() {
log.Infof("ChannelPoint(%v): resending "+
"FundingLocked message to peer",
l.channel.ChannelPoint())
nextRevocation, err := l.channel.NextRevocationKey()
if err != nil {
l.fail("unable to create next "+
"revocation: %v", err)
return
}
fundingLockedMsg := lnwire.NewFundingLocked(
l.ChanID(), nextRevocation,
)
err = l.cfg.Peer.SendMessage(fundingLockedMsg)
if err != nil {
l.fail("unable to re-send "+
"FundingLocked: %v", err)
return
}
}
// In any case, we'll then process their ChanSync
// message.
l.handleUpstreamMsg(msg)
case <-l.quit:
return
case <-chanSyncDeadline:
l.fail("didn't receive ChannelReestablish before " +
"deadline")
return
}
}
// TODO(roasbeef): check to see if able to settle any currently pending
// HTLCs
// * also need signals when new invoices are added by the
// invoiceRegistry
batchTimer := time.NewTicker(50 * time.Millisecond)
defer batchTimer.Stop()
// TODO(roasbeef): fail chan in case of protocol violation
out:
for {
select {
// A new block has arrived, we'll check the network fee to see
// if we should adjust our commitment fee, and also update our
// track of the best current height.
case blockEpoch, ok := <-l.cfg.BlockEpochs.Epochs:
if !ok {
break out
}
l.bestHeight = uint32(blockEpoch.Height)
// If we're not the initiator of the channel, don't we
// don't control the fees, so we can ignore this.
if !l.channel.IsInitiator() {
continue
}
// If we are the initiator, then we'll sample the
// current fee rate to get into the chain within 3
// blocks.
feePerKw, err := l.sampleNetworkFee()
if err != nil {
log.Errorf("unable to sample network fee: %v", err)
continue
}
// We'll check to see if we should update the fee rate
// based on our current set fee rate.
commitFee := l.channel.CommitFeeRate()
if !shouldAdjustCommitFee(feePerKw, commitFee) {
continue
}
// If we do, then we'll send a new UpdateFee message to
// the remote party, to be locked in with a new update.
if err := l.updateChannelFee(feePerKw); err != nil {
log.Errorf("unable to update fee rate: %v", err)
continue
}
// The underlying channel has notified us of a unilateral close
// carried out by the remote peer. In the case of such an
// event, we'll wipe the channel state from the peer, and mark
// the contract as fully settled. Afterwards we can exit.
case <-l.channel.UnilateralCloseSignal:
log.Warnf("Remote peer has closed ChannelPoint(%v) on-chain",
l.channel.ChannelPoint())
// TODO(roasbeef): remove all together
go func() {
chanPoint := l.channel.ChannelPoint()
if err := l.cfg.Peer.WipeChannel(chanPoint); err != nil {
log.Errorf("unable to wipe channel %v", err)
}
// TODO(roasbeef): need to send HTLC outputs to nursery
// TODO(roasbeef): or let the arb sweep?
l.cfg.SettledContracts <- chanPoint
}()
break out
// A local sub-system has initiated a force close of the active
// channel. In this case we can exit immediately as no further
// updates should be processed for the channel.
case <-l.channel.ForceCloseSignal:
// TODO(roasbeef): path never taken now that server
// force closes's directly?
log.Warnf("ChannelPoint(%v) has been force "+
"closed, disconnecting from peer(%x)",
l.channel.ChannelPoint(), l.cfg.Peer.PubKey())
break out
case <-l.logCommitTick:
// If we haven't sent or received a new commitment
// update in some time, check to see if we have any
// pending updates we need to commit due to our
// commitment chains being desynchronized.
if l.channel.FullySynced() {
continue
}
if err := l.updateCommitTx(); err != nil {
l.fail("unable to update commitment: %v", err)
break out
}
case <-batchTimer.C:
// If the current batch is empty, then we have no work
// here.
if l.batchCounter == 0 {
continue
}
// Otherwise, attempt to extend the remote commitment
// chain including all the currently pending entries.
// If the send was unsuccessful, then abandon the
// update, waiting for the revocation window to open
// up.
if err := l.updateCommitTx(); err != nil {
l.fail("unable to update commitment: %v", err)
break out
}
// A packet that previously overflowed the commitment
// transaction is now eligible for processing once again. So
// we'll attempt to re-process the packet in order to allow it
// to continue propagating within the network.
case packet := <-l.overflowQueue.outgoingPkts:
msg := packet.htlc.(*lnwire.UpdateAddHTLC)
log.Tracef("Reprocessing downstream add update "+
"with payment hash(%x)", msg.PaymentHash[:])
l.handleDownStreamPkt(packet, true)
// A message from the switch was just received. This indicates
// that the link is an intermediate hop in a multi-hop HTLC
// circuit.
case pkt := <-l.downstream:
// If we have non empty processing queue then we'll add
// this to the overflow rather than processing it
// directly. Once an active HTLC is either settled or
// failed, then we'll free up a new slot.
htlc, ok := pkt.htlc.(*lnwire.UpdateAddHTLC)
if ok && l.overflowQueue.Length() != 0 {
log.Infof("Downstream htlc add update with "+
"payment hash(%x) have been added to "+
"reprocessing queue, batch_size=%v",
htlc.PaymentHash[:],
l.batchCounter)
l.overflowQueue.AddPkt(pkt)
continue
}
l.handleDownStreamPkt(pkt, false)
// A message from the connected peer was just received. This
// indicates that we have a new incoming HTLC, either directly
// for us, or part of a multi-hop HTLC circuit.
case msg := <-l.upstream:
l.handleUpstreamMsg(msg)
// TODO(roasbeef): make distinct goroutine to handle?
case cmd := <-l.linkControl:
switch req := cmd.(type) {
case *policyUpdate:
// In order to avoid overriding a valid policy
// with a "null" field in the new policy, we'll
// only update to the set sub policy if the new
// value isn't uninitialized.
if req.policy.MinHTLC != 0 {
l.cfg.FwrdingPolicy.MinHTLC = req.policy.MinHTLC
}
if req.policy.BaseFee != 0 {
l.cfg.FwrdingPolicy.BaseFee = req.policy.BaseFee
}
if req.policy.FeeRate != 0 {
l.cfg.FwrdingPolicy.FeeRate = req.policy.FeeRate
}
if req.policy.TimeLockDelta != 0 {
l.cfg.FwrdingPolicy.TimeLockDelta = req.policy.TimeLockDelta
}
if req.done != nil {
close(req.done)
}
}
case <-l.quit:
break out
}
}
}
// handleDownStreamPkt processes an HTLC packet sent from the downstream HTLC
// Switch. Possible messages sent by the switch include requests to forward new
// HTLCs, timeout previously cleared HTLCs, and finally to settle currently
// cleared HTLCs with the upstream peer.
//
// TODO(roasbeef): add sync ntfn to ensure switch always has consistent view?
func (l *channelLink) handleDownStreamPkt(pkt *htlcPacket, isReProcess bool) {
var isSettle bool
switch htlc := pkt.htlc.(type) {
case *lnwire.UpdateAddHTLC:
// A new payment has been initiated via the downstream channel,
// so we add the new HTLC to our local log, then update the
// commitment chains.
htlc.ChanID = l.ChanID()
index, err := l.channel.AddHTLC(htlc)
if err != nil {
switch err {
// The channels spare bandwidth is fully allocated, so
// we'll put this HTLC into the overflow queue.
case lnwallet.ErrMaxHTLCNumber:
log.Infof("Downstream htlc add update with "+
"payment hash(%x) have been added to "+
"reprocessing queue, batch: %v",
htlc.PaymentHash[:],
l.batchCounter)
l.overflowQueue.AddPkt(pkt)
return
// The HTLC was unable to be added to the state
// machine, as a result, we'll signal the switch to
// cancel the pending payment.
default:
log.Warnf("Unable to handle downstream add HTLC: %v", err)
var (
localFailure = false
reason lnwire.OpaqueReason
)
failure := lnwire.NewTemporaryChannelFailure(nil)
// Encrypt the error back to the source unless the payment was
// generated locally.
if pkt.obfuscator == nil {
var b bytes.Buffer
err := lnwire.EncodeFailure(&b, failure, 0)
if err != nil {
log.Errorf("unable to encode failure: %v", err)
return
}
reason = lnwire.OpaqueReason(b.Bytes())
localFailure = true
} else {
var err error
reason, err = pkt.obfuscator.EncryptFirstHop(failure)
if err != nil {
log.Errorf("unable to obfuscate error: %v", err)
return
}
}
failPkt := &htlcPacket{
incomingChanID: pkt.incomingChanID,
incomingHTLCID: pkt.incomingHTLCID,
amount: htlc.Amount,
isRouted: true,
localFailure: localFailure,
htlc: &lnwire.UpdateFailHTLC{
Reason: reason,
},
}
// TODO(roasbeef): need to identify if sent
// from switch so don't need to obfuscate
go l.cfg.Switch.forward(failPkt)
return
}
}
log.Tracef("Received downstream htlc: payment_hash=%x, "+
"local_log_index=%v, batch_size=%v",
htlc.PaymentHash[:], index, l.batchCounter+1)
// Create circuit (remember the path) in order to forward settle/fail
// packet back.
l.cfg.Switch.addCircuit(&PaymentCircuit{
PaymentHash: htlc.PaymentHash,
IncomingChanID: pkt.incomingChanID,
IncomingHTLCID: pkt.incomingHTLCID,
OutgoingChanID: l.ShortChanID(),
OutgoingHTLCID: index,
ErrorEncrypter: pkt.obfuscator,
})
htlc.ID = index
l.cfg.Peer.SendMessage(htlc)
case *lnwire.UpdateFufillHTLC:
// An HTLC we forward to the switch has just settled somewhere
// upstream. Therefore we settle the HTLC within the our local
// state machine.
err := l.channel.SettleHTLC(htlc.PaymentPreimage, pkt.incomingHTLCID)
if err != nil {
// TODO(roasbeef): broadcast on-chain
l.fail("unable to settle incoming HTLC: %v", err)
return
}
// With the HTLC settled, we'll need to populate the wire
// message to target the specific channel and HTLC to be
// cancelled.
htlc.ChanID = l.ChanID()
htlc.ID = pkt.incomingHTLCID
// Then we send the HTLC settle message to the connected peer
// so we can continue the propagation of the settle message.
l.cfg.Peer.SendMessage(htlc)
isSettle = true
case *lnwire.UpdateFailHTLC:
// An HTLC cancellation has been triggered somewhere upstream,
// we'll remove then HTLC from our local state machine.
err := l.channel.FailHTLC(pkt.incomingHTLCID, htlc.Reason)
if err != nil {
log.Errorf("unable to cancel HTLC: %v", err)
return
}
// With the HTLC removed, we'll need to populate the wire
// message to target the specific channel and HTLC to be
// cancelled. The "Reason" field will have already been set
// within the switch.
htlc.ChanID = l.ChanID()
htlc.ID = pkt.incomingHTLCID
// Finally, we send the HTLC message to the peer which
// initially created the HTLC.
l.cfg.Peer.SendMessage(htlc)
isSettle = true
}
l.batchCounter++
// If this newly added update exceeds the min batch size for adds, or
// this is a settle request, then initiate an update.
if l.batchCounter >= 10 || isSettle {
if err := l.updateCommitTx(); err != nil {
l.fail("unable to update commitment: %v", err)
return
}
}
}
// handleUpstreamMsg processes wire messages related to commitment state
// updates from the upstream peer. The upstream peer is the peer whom we have a
// direct channel with, updating our respective commitment chains.
func (l *channelLink) handleUpstreamMsg(msg lnwire.Message) {
switch msg := msg.(type) {
case *lnwire.ChannelReestablish:
log.Infof("Received re-establishment message from remote side "+
"for channel(%v)", l.channel.ChannelPoint())
// We've just received a ChnSync message from the remote party,
// so we'll process the message in order to determine if we
// need to re-transmit any messages to the remote party.
msgsToReSend, err := l.channel.ProcessChanSyncMsg(msg)
if err != nil {
// TODO(roasbeef): check concrete type of error, act
// accordingly
l.fail("unable to handle upstream reestablish "+
"message: %v", err)
return
}
if len(msgsToReSend) > 0 {
log.Infof("Sending %v updates to synchronize the "+
"state for ChannelPoint(%v)", len(msgsToReSend),
l.channel.ChannelPoint())
}
// If we have any messages to retransmit, we'll do so
// immediately so we return to a synchronized state as soon as
// possible.
for _, msg := range msgsToReSend {
l.cfg.Peer.SendMessage(msg)
}
return
case *lnwire.UpdateAddHTLC:
// We just received an add request from an upstream peer, so we
// add it to our state machine, then add the HTLC to our
// "settle" list in the event that we know the preimage.
index, err := l.channel.ReceiveHTLC(msg)
if err != nil {
l.fail("unable to handle upstream add HTLC: %v", err)
return
}
log.Tracef("Receive upstream htlc with payment hash(%x), "+
"assigning index: %v", msg.PaymentHash[:], index)
case *lnwire.UpdateFufillHTLC:
pre := msg.PaymentPreimage
idx := msg.ID
if err := l.channel.ReceiveHTLCSettle(pre, idx); err != nil {
// TODO(roasbeef): broadcast on-chain
l.fail("unable to handle upstream settle HTLC: %v", err)
return
}
// TODO(roasbeef): add preimage to DB in order to swipe
// repeated r-values
case *lnwire.UpdateFailMalformedHTLC:
// Convert the failure type encoded within the HTLC fail
// message to the proper generic lnwire error code.
var failure lnwire.FailureMessage
switch msg.FailureCode {
case lnwire.CodeInvalidOnionVersion:
failure = &lnwire.FailInvalidOnionVersion{
OnionSHA256: msg.ShaOnionBlob,
}
case lnwire.CodeInvalidOnionHmac:
failure = &lnwire.FailInvalidOnionHmac{
OnionSHA256: msg.ShaOnionBlob,
}
case lnwire.CodeInvalidOnionKey:
failure = &lnwire.FailInvalidOnionKey{
OnionSHA256: msg.ShaOnionBlob,
}
default:
log.Errorf("Unknown failure code: %v", msg.FailureCode)
failure = &lnwire.FailTemporaryChannelFailure{}
}
// With the error parsed, we'll convert the into it's opaque
// form.
var b bytes.Buffer
if err := lnwire.EncodeFailure(&b, failure, 0); err != nil {
log.Errorf("unable to encode malformed error: %v", err)
return
}
// If remote side have been unable to parse the onion blob we
// have sent to it, than we should transform the malformed HTLC
// message to the usual HTLC fail message.
err := l.channel.ReceiveFailHTLC(msg.ID, b.Bytes())
if err != nil {
l.fail("unable to handle upstream fail HTLC: %v", err)
return
}
case *lnwire.UpdateFailHTLC:
idx := msg.ID
err := l.channel.ReceiveFailHTLC(idx, msg.Reason[:])
if err != nil {
l.fail("unable to handle upstream fail HTLC: %v", err)
return
}
case *lnwire.CommitSig:
// We just received a new updates to our local commitment chain,
// validate this new commitment, closing the link if invalid.
err := l.channel.ReceiveNewCommitment(msg.CommitSig, msg.HtlcSigs)
if err != nil {
l.fail("unable to accept new commitment: %v", err)
return
}
// As we've just just accepted a new state, we'll now
// immediately send the remote peer a revocation for our prior
// state.
nextRevocation, err := l.channel.RevokeCurrentCommitment()
if err != nil {
log.Errorf("unable to revoke commitment: %v", err)
return
}
l.cfg.Peer.SendMessage(nextRevocation)
// As we've just received a commitment signature, we'll
// re-start the log commit timer to wake up the main processing
// loop to check if we need to send a commitment signature as
// we owe one.
//
// TODO(roasbeef): instead after revocation?
if !l.logCommitTimer.Stop() {
select {
case <-l.logCommitTimer.C:
default:
}
}
l.logCommitTimer.Reset(300 * time.Millisecond)
l.logCommitTick = l.logCommitTimer.C
// If both commitment chains are fully synced from our PoV,
// then we don't need to reply with a signature as both sides
// already have a commitment with the latest accepted l.
if l.channel.FullySynced() {
return
}
// Otherwise, the remote party initiated the state transition,
// so we'll reply with a signature to provide them with their
// version of the latest commitment.
if err := l.updateCommitTx(); err != nil {
l.fail("unable to update commitment: %v", err)
return
}
case *lnwire.RevokeAndAck:
// We've received a revocation from the remote chain, if valid,
// this moves the remote chain forward, and expands our
// revocation window.
htlcs, err := l.channel.ReceiveRevocation(msg)
if err != nil {
l.fail("unable to accept revocation: %v", err)
return
}
// After we treat HTLCs as included in both remote/local
// commitment transactions they might be safely propagated over
// htlc switch or settled if our node was last node in htlc
// path.
htlcsToForward := l.processLockedInHtlcs(htlcs)
go func() {
log.Debugf("ChannelPoint(%v) forwarding %v HTLC's",
l.channel.ChannelPoint(), len(htlcsToForward))
for _, packet := range htlcsToForward {
if err := l.cfg.Switch.forward(packet); err != nil {
log.Errorf("channel link(%v): "+
"unhandled error while forwarding "+
"htlc packet over htlc "+
"switch: %v", l, err)
}
}
}()
case *lnwire.UpdateFee:
// We received fee update from peer. If we are the initiator we
// will fail the channel, if not we will apply the update.
fee := btcutil.Amount(msg.FeePerKw)
if err := l.channel.ReceiveUpdateFee(fee); err != nil {
l.fail("error receiving fee update: %v", err)
return
}
}
}
// updateCommitTx signs, then sends an update to the remote peer adding a new
// commitment to their commitment chain which includes all the latest updates
// we've received+processed up to this point.
func (l *channelLink) updateCommitTx() error {
theirCommitSig, htlcSigs, err := l.channel.SignNextCommitment()
if err == lnwallet.ErrNoWindow {
log.Tracef("revocation window exhausted, unable to send %v",
l.batchCounter)
return nil
} else if err != nil {
return err
}
commitSig := &lnwire.CommitSig{
ChanID: l.ChanID(),
CommitSig: theirCommitSig,
HtlcSigs: htlcSigs,
}
l.cfg.Peer.SendMessage(commitSig)
// We've just initiated a state transition, attempt to stop the
// logCommitTimer. If the timer already ticked, then we'll consume the
// value, dropping
if l.logCommitTimer != nil && !l.logCommitTimer.Stop() {
select {
case <-l.logCommitTimer.C:
default:
}
}
l.logCommitTick = nil
// Finally, clear our the current batch, so we can accurately make
// further batch flushing decisions.
l.batchCounter = 0
return nil
}
// Peer returns the representation of remote peer with which we have the
// channel link opened.
//
// NOTE: Part of the ChannelLink interface.
func (l *channelLink) Peer() Peer {
return l.cfg.Peer
}
// ShortChanID returns the short channel ID for the channel link. The short
// channel ID encodes the exact location in the main chain that the original
// funding output can be found.
//
// NOTE: Part of the ChannelLink interface.
func (l *channelLink) ShortChanID() lnwire.ShortChannelID {
return l.channel.ShortChanID()
}
// ChanID returns the channel ID for the channel link. The channel ID is a more
// compact representation of a channel's full outpoint.
//
// NOTE: Part of the ChannelLink interface.
func (l *channelLink) ChanID() lnwire.ChannelID {
return lnwire.NewChanIDFromOutPoint(l.channel.ChannelPoint())
}
// getBandwidthCmd is a wrapper for get bandwidth handler.
type getBandwidthCmd struct {
resp chan lnwire.MilliSatoshi
}
// Bandwidth returns the total amount that can flow through the channel link at
// this given instance. The value returned is expressed in millisatoshi and can
// be used by callers when making forwarding decisions to determine if a link
// can accept an HTLC.
//
// NOTE: Part of the ChannelLink interface.
func (l *channelLink) Bandwidth() lnwire.MilliSatoshi {
// TODO(roasbeef): subtract reserve
channelBandwidth := l.channel.AvailableBalance()
overflowBandwidth := l.overflowQueue.TotalHtlcAmount()
return channelBandwidth - overflowBandwidth
}
// policyUpdate is a message sent to a channel link when an outside sub-system
// wishes to update the current forwarding policy.
type policyUpdate struct {
policy ForwardingPolicy
done chan struct{}
}
// UpdateForwardingPolicy updates the forwarding policy for the target
// ChannelLink. Once updated, the link will use the new forwarding policy to
// govern if it an incoming HTLC should be forwarded or not. Note that this
// processing of the new policy will ensure that uninitialized fields in the
// passed policy won't override already initialized fields in the current
// policy.
//
// NOTE: Part of the ChannelLink interface.
func (l *channelLink) UpdateForwardingPolicy(newPolicy ForwardingPolicy) {
cmd := &policyUpdate{
policy: newPolicy,
done: make(chan struct{}),
}
select {
case l.linkControl <- cmd:
case <-l.quit:
}
select {
case <-cmd.done:
case <-l.quit:
}
}
// Stats returns the statistics of channel link.
//
// NOTE: Part of the ChannelLink interface.
func (l *channelLink) Stats() (uint64, lnwire.MilliSatoshi, lnwire.MilliSatoshi) {
snapshot := l.channel.StateSnapshot()
return snapshot.ChannelCommitment.CommitHeight,
snapshot.TotalMSatSent,
snapshot.TotalMSatReceived
}
// String returns the string representation of channel link.
//
// NOTE: Part of the ChannelLink interface.
func (l *channelLink) String() string {
return l.channel.ChannelPoint().String()
}
// HandleSwitchPacket handles the switch packets. This packets which might be
// forwarded to us from another channel link in case the htlc update came from
// another peer or if the update was created by user
//
// NOTE: Part of the ChannelLink interface.
func (l *channelLink) HandleSwitchPacket(packet *htlcPacket) {
l.mailBox.AddPacket(packet)
}
// HandleChannelUpdate handles the htlc requests as settle/add/fail which sent
// to us from remote peer we have a channel with.
//
// NOTE: Part of the ChannelLink interface.
func (l *channelLink) HandleChannelUpdate(message lnwire.Message) {
l.mailBox.AddMessage(message)
}
// updateChannelFee updates the commitment fee-per-kw on this channel by
// committing to an update_fee message.
func (l *channelLink) updateChannelFee(feePerKw btcutil.Amount) error {
log.Infof("ChannelPoint(%v): updating commit fee to %v sat/kw", l,
feePerKw)
// We skip sending the UpdateFee message if the channel is not
// currently eligable to forward messages.
if !l.EligibleToForward() {
log.Debugf("ChannelPoint(%v): skipping fee update for " +
"inactive channel")
return nil
}
// First, we'll update the local fee on our commitment.
if err := l.channel.UpdateFee(feePerKw); err != nil {
return err
}
// We'll then attempt to send a new UpdateFee message, and also lock it
// in immediately by triggering a commitment update.
msg := lnwire.NewUpdateFee(l.ChanID(), uint32(feePerKw))
if err := l.cfg.Peer.SendMessage(msg); err != nil {
return err
}
return l.updateCommitTx()
}
// processLockedInHtlcs serially processes each of the log updates which have
// been "locked-in". An HTLC is considered locked-in once it has been fully
// committed to in both the remote and local commitment state. Once a channel
// updates is locked-in, then it can be acted upon, meaning: settling HTLCs,
// cancelling them, or forwarding new HTLCs to the next hop.
func (l *channelLink) processLockedInHtlcs(
paymentDescriptors []*lnwallet.PaymentDescriptor) []*htlcPacket {
var (
needUpdate bool
packetsToForward []*htlcPacket
)
for _, pd := range paymentDescriptors {
// TODO(roasbeef): rework log entries to a shared
// interface.
switch pd.EntryType {
// A settle for an HTLC we previously forwarded HTLC has been
// received. So we'll forward the HTLC to the switch which
// will handle propagating the settle to the prior hop.
case lnwallet.Settle:
settlePacket := &htlcPacket{
outgoingChanID: l.ShortChanID(),
outgoingHTLCID: pd.ParentIndex,
amount: pd.Amount,
htlc: &lnwire.UpdateFufillHTLC{
PaymentPreimage: pd.RPreimage,
},
}
// Add the packet to the batch to be forwarded, and
// notify the overflow queue that a spare spot has been
// freed up within the commitment state.
packetsToForward = append(packetsToForward, settlePacket)
l.overflowQueue.SignalFreeSlot()
// A failureCode message for a previously forwarded HTLC has been
// received. As a result a new slot will be freed up in our
// commitment state, so we'll forward this to the switch so the
// backwards undo can continue.
case lnwallet.Fail:
// Fetch the reason the HTLC was cancelled so we can
// continue to propagate it.
failPacket := &htlcPacket{
outgoingChanID: l.ShortChanID(),
outgoingHTLCID: pd.ParentIndex,
amount: pd.Amount,
htlc: &lnwire.UpdateFailHTLC{
Reason: lnwire.OpaqueReason(pd.FailReason),
},
}
// Add the packet to the batch to be forwarded, and
// notify the overflow queue that a spare spot has been
// freed up within the commitment state.
packetsToForward = append(packetsToForward, failPacket)
l.overflowQueue.SignalFreeSlot()
// An incoming HTLC add has been full-locked in. As a result we
// can now examine the forwarding details of the HTLC, and the
// HTLC itself to decide if: we should forward it, cancel it,
// or are able to settle it (and it adheres to our fee related
// constraints).
case lnwallet.Add:
// Fetch the onion blob that was included within this
// processed payment descriptor.
var onionBlob [lnwire.OnionPacketSize]byte
copy(onionBlob[:], pd.OnionBlob)
// Retrieve onion obfuscator from onion blob in order
// to produce initial obfuscation of the onion
// failureCode.
onionReader := bytes.NewReader(onionBlob[:])
obfuscator, failureCode := l.cfg.DecodeOnionObfuscator(
onionReader,
)
if failureCode != lnwire.CodeNone {
// If we're unable to process the onion blob
// than we should send the malformed htlc error
// to payment sender.
l.sendMalformedHTLCError(pd.HtlcIndex, failureCode,
onionBlob[:])
needUpdate = true
log.Errorf("unable to decode onion "+
"obfuscator: %v", failureCode)
continue
}
// Before adding the new htlc to the state machine,
// parse the onion object in order to obtain the
// routing information with DecodeHopIterator function
// which process the Sphinx packet.
//
// We include the payment hash of the htlc as it's
// authenticated within the Sphinx packet itself as
// associated data in order to thwart attempts a replay
// attacks. In the case of a replay, an attacker is
// *forced* to use the same payment hash twice, thereby
// losing their money entirely.
onionReader = bytes.NewReader(onionBlob[:])
chanIterator, failureCode := l.cfg.DecodeHopIterator(
onionReader, pd.RHash[:],
)
if failureCode != lnwire.CodeNone {
// If we're unable to process the onion blob
// than we should send the malformed htlc error
// to payment sender.
l.sendMalformedHTLCError(pd.HtlcIndex, failureCode,
onionBlob[:])
needUpdate = true
log.Errorf("unable to decode onion hop "+
"iterator: %v", failureCode)
continue
}
heightNow := l.bestHeight
fwdInfo := chanIterator.ForwardingInstructions()
switch fwdInfo.NextHop {
case exitHop:
// First, we'll check the expiry of the HTLC
// itself against, the current block height. If
// the timeout is too soon, then we'll reject
// the HTLC.
if pd.Timeout-expiryGraceDelta <= heightNow {
log.Errorf("htlc(%x) has an expiry "+
"that's too soon: expiry=%v, "+
"best_height=%v", pd.RHash[:],
pd.Timeout, heightNow)
failure := lnwire.FailFinalIncorrectCltvExpiry{}
l.sendHTLCError(pd.HtlcIndex, &failure, obfuscator)
needUpdate = true
continue
}
// We're the designated payment destination.
// Therefore we attempt to see if we have an
// invoice locally which'll allow us to settle
// this htlc.
invoiceHash := chainhash.Hash(pd.RHash)
invoice, err := l.cfg.Registry.LookupInvoice(invoiceHash)
if err != nil {
log.Errorf("unable to query invoice registry: "+
" %v", err)
failure := lnwire.FailUnknownPaymentHash{}
l.sendHTLCError(pd.HtlcIndex, failure, obfuscator)
needUpdate = true
continue
}
// If we're not currently in debug mode, and
// the extended htlc doesn't meet the value
// requested, then we'll fail the htlc.
// Otherwise, we settle this htlc within our
// local state update log, then send the update
// entry to the remote party.
if !l.cfg.DebugHTLC && pd.Amount < invoice.Terms.Value {
log.Errorf("rejecting htlc due to incorrect "+
"amount: expected %v, received %v",
invoice.Terms.Value, pd.Amount)
failure := lnwire.FailIncorrectPaymentAmount{}
l.sendHTLCError(pd.HtlcIndex, failure, obfuscator)
needUpdate = true
continue
}
// As we're the exit hop, we'll double check
// the hop-payload included in the HTLC to
// ensure that it was crafted correctly by the
// sender and matches the HTLC we were
// extended.
if !l.cfg.DebugHTLC &&
fwdInfo.AmountToForward != invoice.Terms.Value {
log.Errorf("Onion payload of incoming "+
"htlc(%x) has incorrect value: "+
"expected %v, got %v", pd.RHash,
invoice.Terms.Value,
fwdInfo.AmountToForward)
failure := lnwire.FailIncorrectPaymentAmount{}
l.sendHTLCError(pd.HtlcIndex, failure, obfuscator)
needUpdate = true
continue
}
// We'll also ensure that our time-lock value
// has been computed correctly.
//
// TODO(roasbeef): also accept global default?
expectedHeight := heightNow + l.cfg.FwrdingPolicy.TimeLockDelta
if !l.cfg.DebugHTLC {
switch {
case fwdInfo.OutgoingCTLV < expectedHeight:
log.Errorf("Onion payload of incoming "+
"htlc(%x) has incorrect time-lock: "+
"expected %v, got %v",
pd.RHash[:], expectedHeight,
fwdInfo.OutgoingCTLV)
failure := lnwire.NewFinalIncorrectCltvExpiry(
fwdInfo.OutgoingCTLV,
)
l.sendHTLCError(pd.HtlcIndex, failure, obfuscator)
needUpdate = true
continue
case pd.Timeout != fwdInfo.OutgoingCTLV:
log.Errorf("HTLC(%x) has incorrect "+
"time-lock: expected %v, got %v",
pd.RHash[:], pd.Timeout,
fwdInfo.OutgoingCTLV)
failure := lnwire.NewFinalIncorrectCltvExpiry(
fwdInfo.OutgoingCTLV,
)
l.sendHTLCError(pd.HtlcIndex, failure, obfuscator)
needUpdate = true
continue
}
}
if l.cfg.DebugHTLC && l.cfg.HodlHTLC {
log.Warnf("hodl HTLC mode enabled, " +
"will not attempt to settle " +
"HTLC with sender")
continue
}
preimage := invoice.Terms.PaymentPreimage
err = l.channel.SettleHTLC(preimage, pd.HtlcIndex)
if err != nil {
l.fail("unable to settle htlc: %v", err)
return nil
}
// Notify the invoiceRegistry of the invoices
// we just settled with this latest commitment
// update.
err = l.cfg.Registry.SettleInvoice(invoiceHash)
if err != nil {
l.fail("unable to settle invoice: %v", err)
return nil
}
// HTLC was successfully settled locally send
// notification about it remote peer.
l.cfg.Peer.SendMessage(&lnwire.UpdateFufillHTLC{
ChanID: l.ChanID(),
ID: pd.HtlcIndex,
PaymentPreimage: preimage,
})
needUpdate = true
// There are additional channels left within this
// route. So we'll verify that our forwarding
// constraints have been properly met by by this
// incoming HTLC.
default:
// We want to avoid forwarding an HTLC which
// will expire in the near future, so we'll
// reject an HTLC if its expiration time is too
// close to the current height.
timeDelta := l.cfg.FwrdingPolicy.TimeLockDelta
if pd.Timeout-timeDelta <= heightNow {
log.Errorf("htlc(%x) has an expiry "+
"that's too soon: outgoing_expiry=%v, "+
"best_height=%v", pd.RHash[:],
pd.Timeout-timeDelta, heightNow)
var failure lnwire.FailureMessage
update, err := l.cfg.GetLastChannelUpdate()
if err != nil {
failure = lnwire.NewTemporaryChannelFailure(nil)
} else {
failure = lnwire.NewExpiryTooSoon(*update)
}
l.sendHTLCError(pd.HtlcIndex, failure, obfuscator)
needUpdate = true
continue
}
// As our second sanity check, we'll ensure that
// the passed HTLC isn't too small. If so, then
// we'll cancel the HTLC directly.
if pd.Amount < l.cfg.FwrdingPolicy.MinHTLC {
log.Errorf("Incoming htlc(%x) is too "+
"small: min_htlc=%v, hltc_value=%v",
pd.RHash[:], l.cfg.FwrdingPolicy.MinHTLC,
pd.Amount)
// As part of the returned error, we'll
// send our latest routing policy so
// the sending node obtains the most up
// to date data.
var failure lnwire.FailureMessage
update, err := l.cfg.GetLastChannelUpdate()
if err != nil {
failure = lnwire.NewTemporaryChannelFailure(nil)
} else {
failure = lnwire.NewAmountBelowMinimum(
pd.Amount, *update)
}
l.sendHTLCError(pd.HtlcIndex, failure, obfuscator)
needUpdate = true
continue
}
// Next, using the amount of the incoming HTLC,
// we'll calculate the expected fee this
// incoming HTLC must carry in order to be
// accepted.
expectedFee := ExpectedFee(
l.cfg.FwrdingPolicy,
fwdInfo.AmountToForward,
)
// If the amount of the incoming HTLC, minus
// our expected fee isn't equal to the
// forwarding instructions, then either the
// values have been tampered with, or the send
// used incorrect/dated information to
// construct the forwarding information for
// this hop. In any case, we'll cancel this
// HTLC.
if pd.Amount-expectedFee < fwdInfo.AmountToForward {
log.Errorf("Incoming htlc(%x) has "+
"insufficient fee: expected "+
"%v, got %v", pd.RHash[:],
int64(expectedFee),
int64(pd.Amount-fwdInfo.AmountToForward))
// As part of the returned error, we'll
// send our latest routing policy so
// the sending node obtains the most up
// to date data.
var failure lnwire.FailureMessage
update, err := l.cfg.GetLastChannelUpdate()
if err != nil {
failure = lnwire.NewTemporaryChannelFailure(nil)
} else {
failure = lnwire.NewFeeInsufficient(pd.Amount,
*update)
}
l.sendHTLCError(pd.HtlcIndex, failure, obfuscator)
needUpdate = true
continue
}
// Finally, we'll ensure that the time-lock on
// the outgoing HTLC meets the following
// constraint: the incoming time-lock minus our
// time-lock delta should equal the outgoing
// time lock. Otherwise, whether the sender
// messed up, or an intermediate node tampered
// with the HTLC.
if pd.Timeout-timeDelta < fwdInfo.OutgoingCTLV {
log.Errorf("Incoming htlc(%x) has "+
"incorrect time-lock value: "+
"expected at least %v block delta, "+
"got %v block delta", pd.RHash[:],
timeDelta,
pd.Timeout-fwdInfo.OutgoingCTLV)
// Grab the latest routing policy so
// the sending node is up to date with
// our current policy.
update, err := l.cfg.GetLastChannelUpdate()
if err != nil {
l.fail("unable to create channel update "+
"while handling the error: %v", err)
return nil
}
failure := lnwire.NewIncorrectCltvExpiry(
pd.Timeout, *update)
l.sendHTLCError(pd.HtlcIndex, failure, obfuscator)
needUpdate = true
continue
}
// TODO(roasbeef): also add max timeout value
// With all our forwarding constraints met,
// we'll create the outgoing HTLC using the
// parameters as specified in the forwarding
// info.
addMsg := &lnwire.UpdateAddHTLC{
Expiry: fwdInfo.OutgoingCTLV,
Amount: fwdInfo.AmountToForward,
PaymentHash: pd.RHash,
}
// Finally, we'll encode the onion packet for
// the _next_ hop using the hop iterator
// decoded for the current hop.
buf := bytes.NewBuffer(addMsg.OnionBlob[0:0])
err := chanIterator.EncodeNextHop(buf)
if err != nil {
log.Errorf("unable to encode the "+
"remaining route %v", err)
failure := lnwire.NewTemporaryChannelFailure(nil)
l.sendHTLCError(pd.HtlcIndex, failure, obfuscator)
needUpdate = true
continue
}
updatePacket := &htlcPacket{
incomingChanID: l.ShortChanID(),
incomingHTLCID: pd.HtlcIndex,
outgoingChanID: fwdInfo.NextHop,
amount: addMsg.Amount,
htlc: addMsg,
obfuscator: obfuscator,
}
packetsToForward = append(packetsToForward, updatePacket)
}
}
}
if needUpdate {
// With all the settle/cancel updates added to the local and
// remote HTLC logs, initiate a state transition by updating
// the remote commitment chain.
if err := l.updateCommitTx(); err != nil {
l.fail("unable to update commitment: %v", err)
return nil
}
}
return packetsToForward
}
// sendHTLCError functions cancels HTLC and send cancel message back to the
// peer from which HTLC was received.
func (l *channelLink) sendHTLCError(htlcIndex uint64,
failure lnwire.FailureMessage, e ErrorEncrypter) {
reason, err := e.EncryptFirstHop(failure)
if err != nil {
log.Errorf("unable to obfuscate error: %v", err)
return
}
err = l.channel.FailHTLC(htlcIndex, reason)
if err != nil {
log.Errorf("unable cancel htlc: %v", err)
return
}
l.cfg.Peer.SendMessage(&lnwire.UpdateFailHTLC{
ChanID: l.ChanID(),
ID: htlcIndex,
Reason: reason,
})
}
// sendMalformedHTLCError helper function which sends the malformed HTLC update
// to the payment sender.
func (l *channelLink) sendMalformedHTLCError(htlcIndex uint64,
code lnwire.FailCode, onionBlob []byte) {
shaOnionBlob := sha256.Sum256(onionBlob)
err := l.channel.MalformedFailHTLC(htlcIndex, code, shaOnionBlob)
if err != nil {
log.Errorf("unable cancel htlc: %v", err)
return
}
l.cfg.Peer.SendMessage(&lnwire.UpdateFailMalformedHTLC{
ChanID: l.ChanID(),
ID: htlcIndex,
ShaOnionBlob: shaOnionBlob,
FailureCode: code,
})
}
// fail helper function which is used to encapsulate the action necessary for
// proper disconnect.
func (l *channelLink) fail(format string, a ...interface{}) {
reason := errors.Errorf(format, a...)
log.Error(reason)
l.cfg.Peer.Disconnect(reason)
}