lnd.xprv/htlcswitch/link.go

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package htlcswitch
import (
"bytes"
"fmt"
"sync"
"sync/atomic"
"time"
"io"
"github.com/lightningnetwork/lnd/lnwallet"
"github.com/lightningnetwork/lnd/lnwire"
"github.com/roasbeef/btcd/btcec"
"github.com/roasbeef/btcd/chaincfg/chainhash"
"github.com/roasbeef/btcd/wire"
"github.com/roasbeef/btcutil"
)
// 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 btcutil.Amount
// 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.
//
// TODO(roasbeef): need to be in mSAT
BaseFee btcutil.Amount
// 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 btcutil.Amount
// 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 btcutil.Amount) btcutil.Amount {
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.
Switch *Switch
// DecodeOnion function responsible for decoding htlc Sphinx onion
// blob, and creating hop iterator which will give us next destination
// of htlc.
DecodeOnion func(r io.Reader, meta []byte) (HopIterator, 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
// 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
}
// 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
// cancelReasons stores the reason why a particular HTLC was cancelled.
// The index of the HTLC within the log is mapped to the cancellation
// reason. This value is used to thread the proper error through to the
// htlcSwitch, or subsystem that initiated the HTLC.
//
// TODO(andrew.shvv) remove after payment descriptor start store
// htlc cancel reasons.
cancelReasons map[uint64]lnwire.OpaqueReason
// clearedOnionBlobs tracks the remote log index of the incoming
// htlc's, mapped to the htlc onion blob which encapsulates the next
// hop. HTLC's are added to this map once the HTLC has been cleared,
// meaning the commitment state reflects the update encoded within this
// HTLC.
//
// TODO(andrew.shvv) remove after payment descriptor start store
// htlc onion blobs.
clearedOnionBlobs map[uint64][lnwire.OnionPacketSize]byte
// 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
// 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
// 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) ChannelLink {
return &channelLink{
cfg: cfg,
channel: channel,
clearedOnionBlobs: make(map[uint64][lnwire.OnionPacketSize]byte),
upstream: make(chan lnwire.Message),
downstream: make(chan *htlcPacket),
linkControl: make(chan interface{}),
cancelReasons: make(map[uint64]lnwire.OpaqueReason),
logCommitTimer: time.NewTimer(300 * time.Millisecond),
overflowQueue: newWaitingQueue(),
quit: make(chan struct{}),
}
}
// 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) {
log.Warnf("channel link(%v): already started", l)
return nil
}
log.Infof("ChannelLink(%v) is starting", l)
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)
close(l.quit)
l.wg.Wait()
}
// 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 l.wg.Done()
log.Infof("HTLC manager for ChannelPoint(%v) started, "+
"bandwidth=%v", l.channel.ChannelPoint(), l.getBandwidth())
// A new session for this active channel has just started, therefore we
// need to send our initial revocation window to the remote peer.
for i := 0; i < lnwallet.InitialRevocationWindow; i++ {
rev, err := l.channel.ExtendRevocationWindow()
if err != nil {
log.Errorf("unable to expand revocation window: %v", err)
continue
}
l.cfg.Peer.SendMessage(rev)
}
// 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 {
// 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())
if err := l.cfg.Peer.WipeChannel(l.channel); err != nil {
log.Errorf("unable to wipe channel %v", err)
}
// TODO(roasbeef): need to send HTLC outputs to nursery
l.cfg.SettledContracts <- l.channel.ChannelPoint()
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 {
log.Errorf("unable to update commitment: %v",
err)
l.cfg.Peer.Disconnect()
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 {
log.Errorf("unable to update "+
"commitment: %v", err)
l.cfg.Peer.Disconnect()
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.pending:
msg := packet.htlc.(*lnwire.UpdateAddHTLC)
log.Tracef("Reprocessing downstream add update "+
"with payment hash(%x)",
msg.PaymentHash[:])
l.handleDownStreamPkt(packet)
// 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: %v",
htlc.PaymentHash[:],
l.batchCounter)
l.overflowQueue.consume(pkt)
continue
}
l.handleDownStreamPkt(pkt)
// 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)
case cmd := <-l.linkControl:
switch req := cmd.(type) {
case *getBandwidthCmd:
req.resp <- l.getBandwidth()
case *policyUpdate:
l.cfg.FwrdingPolicy = req.policy
if req.done != nil {
close(req.done)
}
}
case <-l.quit:
break out
}
}
log.Infof("ChannelLink(%v) has exited", l)
}
// 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.
func (l *channelLink) handleDownStreamPkt(pkt *htlcPacket) {
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 == 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.consume(pkt)
return
} else if err != nil {
failPacket := newFailPacket(
l.ShortChanID(),
&lnwire.UpdateFailHTLC{
Reason: []byte{byte(0)},
},
htlc.PaymentHash,
htlc.Amount,
)
// The HTLC was unable to be added to the state
// machine, as a result, we'll signal the switch to
// cancel the pending payment.
go l.cfg.Switch.forward(failPacket)
log.Errorf("unable to handle downstream add HTLC: %v",
err)
return
}
log.Tracef("Received downstream htlc: payment_hash=%x, "+
"local_log_index=%v, batch_size=%v",
htlc.PaymentHash[:], index, l.batchCounter+1)
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.
pre := htlc.PaymentPreimage
logIndex, err := l.channel.SettleHTLC(pre)
if err != nil {
// TODO(roasbeef): broadcast on-chain
log.Errorf("settle for incoming HTLC "+
"rejected: %v", err)
l.cfg.Peer.Disconnect()
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 = logIndex
// 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.
logIndex, err := l.channel.FailHTLC(pkt.payHash)
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 = logIndex
// 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 {
log.Errorf("unable to update "+
"commitment: %v", err)
l.cfg.Peer.Disconnect()
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.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 {
// TODO(roasbeef): fail channel
log.Errorf("unable to handle upstream add HTLC: %v",
err)
l.cfg.Peer.Disconnect()
return
}
log.Tracef("Receive upstream htlc with payment hash(%x), "+
"assigning index: %v", msg.PaymentHash[:], index)
// TODO(roasbeef): perform sanity checks on per-hop payload
// * time-lock is sane, fee, chain, etc
// Store the onion blob which encapsulate the htlc route and
// use in on stage of HTLC inclusion to retrieve the next hop
// and propagate the HTLC along the remaining route.
l.clearedOnionBlobs[index] = msg.OnionBlob
case *lnwire.UpdateFufillHTLC:
pre := msg.PaymentPreimage
idx := msg.ID
if err := l.channel.ReceiveHTLCSettle(pre, idx); err != nil {
// TODO(roasbeef): broadcast on-chain
log.Errorf("unable to handle upstream settle "+
"HTLC: %v", err)
l.cfg.Peer.Disconnect()
return
}
// TODO(roasbeef): add preimage to DB in order to swipe
// repeated r-values
case *lnwire.UpdateFailHTLC:
idx := msg.ID
if err := l.channel.ReceiveFailHTLC(idx); err != nil {
log.Errorf("unable to handle upstream fail HTLC: "+
"%v", err)
l.cfg.Peer.Disconnect()
return
}
l.cancelReasons[idx] = msg.Reason
case *lnwire.CommitSig:
// We just received a new update to our local commitment chain,
// validate this new commitment, closing the link if invalid.
//
// TODO(roasbeef): redundant re-serialization
sig := msg.CommitSig.Serialize()
if err := l.channel.ReceiveNewCommitment(sig); err != nil {
log.Errorf("unable to accept new commitment: %v", err)
l.cfg.Peer.Disconnect()
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 l.
if err := l.updateCommitTx(); err != nil {
log.Errorf("unable to update commitment: %v", err)
l.cfg.Peer.Disconnect()
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 {
log.Errorf("unable to accept revocation: %v", err)
l.cfg.Peer.Disconnect()
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() {
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)
}
}
}()
}
}
// 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 {
sigTheirs, 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
}
parsedSig, err := btcec.ParseSignature(sigTheirs, btcec.S256())
if err != nil {
return fmt.Errorf("unable to parse sig: %v", err)
}
commitSig := &lnwire.CommitSig{
ChanID: l.ChanID(),
CommitSig: parsedSig,
}
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 btcutil.Amount
}
// Bandwidth returns the amount which current link might pass through channel
// link. Execution through control channel gives as confidence that bandwidth
// will not be changed during function execution.
//
// NOTE: Part of the ChannelLink interface.
func (l *channelLink) Bandwidth() btcutil.Amount {
command := &getBandwidthCmd{
resp: make(chan btcutil.Amount, 1),
}
select {
case l.linkControl <- command:
return <-command.resp
case <-l.quit:
return 0
}
}
// getBandwidth returns the amount which current link might pass through
// channel link.
//
// NOTE: Should be used inside main goroutine only, otherwise the result might
// not be accurate.
func (l *channelLink) getBandwidth() btcutil.Amount {
return l.channel.LocalAvailableBalance() - l.overflowQueue.pendingAmount()
}
// 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: 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, btcutil.Amount, btcutil.Amount) {
snapshot := l.channel.StateSnapshot()
return snapshot.NumUpdates,
btcutil.Amount(snapshot.TotalSatoshisSent),
btcutil.Amount(snapshot.TotalSatoshisReceived)
}
// 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) {
select {
case l.downstream <- packet:
case <-l.quit:
}
}
// 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) {
select {
case l.upstream <- message:
case <-l.quit:
}
}
// 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 htlc's,
// cancelling them, or forwarding new HTLC's 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:
settleUpdate := &lnwire.UpdateFufillHTLC{
PaymentPreimage: pd.RPreimage,
}
settlePacket := newSettlePacket(l.ShortChanID(),
settleUpdate, pd.RHash, pd.Amount)
// 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.release()
// A failure 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.
opaqueReason := l.cancelReasons[pd.ParentIndex]
failUpdate := &lnwire.UpdateFailHTLC{
Reason: opaqueReason,
ChanID: l.ChanID(),
}
failPacket := newFailPacket(l.ShortChanID(), failUpdate,
pd.RHash, pd.Amount)
// 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.release()
// An incoming HTLC add has been full-locked in. As a result we
// can no examine the forwarding details of the HTLC, and the
// HTLC itself ti 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.
onionBlob := l.clearedOnionBlobs[pd.Index]
delete(l.clearedOnionBlobs, pd.Index)
onionReader := bytes.NewReader(onionBlob[:])
// Before adding the new htlc to the state machine,
// parse the onion object in order to obtain the
// routing information with DecodeOnion 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.
chanIterator, err := l.cfg.DecodeOnion(onionReader,
pd.RHash[:])
if err != nil {
// If we're unable to parse the Sphinx packet,
// then we'll cancel the htlc.
log.Errorf("unable to get the next hop: %v", err)
reason := []byte{byte(lnwire.SphinxParseError)}
l.sendHTLCError(pd.RHash, reason)
needUpdate = true
continue
}
fwdInfo := chanIterator.ForwardingInstructions()
switch fwdInfo.NextHop {
case exitHop:
// 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 to locate:"+
" %v", err)
reason := []byte{byte(lnwire.UnknownPaymentHash)}
l.sendHTLCError(pd.RHash, reason)
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. Additionally, we'll ensure that
// our time-lock value has been computed
// correctly.
if 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)
reason := []byte{byte(lnwire.IncorrectValue)}
l.sendHTLCError(pd.RHash, reason)
needUpdate = true
continue
}
if fwdInfo.OutgoingCTLV != l.cfg.FwrdingPolicy.TimeLockDelta {
log.Errorf("Onion payload of incoming "+
"htlc(%x) has incorrect time-lock: "+
"expected %v, got %v",
l.cfg.FwrdingPolicy.TimeLockDelta,
fwdInfo.OutgoingCTLV)
reason := []byte{byte(lnwire.UpstreamTimeout)}
l.sendHTLCError(pd.RHash, reason)
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)
reason := []byte{byte(lnwire.IncorrectValue)}
l.sendHTLCError(pd.RHash, reason)
needUpdate = true
continue
}
preimage := invoice.Terms.PaymentPreimage
logIndex, err := l.channel.SettleHTLC(preimage)
if err != nil {
log.Errorf("unable to settle htlc: %v", err)
l.cfg.Peer.Disconnect()
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 {
log.Errorf("unable to settle invoice: %v", err)
l.cfg.Peer.Disconnect()
return nil
}
// HTLC was successfully settled locally send
// notification about it remote peer.
l.cfg.Peer.SendMessage(&lnwire.UpdateFufillHTLC{
ChanID: l.ChanID(),
ID: logIndex,
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:
// As our first 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)
reason := []byte{byte(lnwire.IncorrectValue)}
l.sendHTLCError(pd.RHash, reason)
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,
pd.Amount,
)
// 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[:],
btcutil.Amount(pd.Amount-fwdInfo.AmountToForward),
btcutil.Amount(expectedFee))
// TODO(andrew.shvv): send proper back error
reason := []byte{byte(lnwire.IncorrectValue)}
l.sendHTLCError(pd.RHash, reason)
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.
timeDelta := l.cfg.FwrdingPolicy.TimeLockDelta
if pd.Timeout-timeDelta != fwdInfo.OutgoingCTLV {
// TODO(andrew.shvv): send proper back error
log.Errorf("Incoming htlc(%x) has "+
"incorrect time-lock value: expected "+
"%v blocks, got %v blocks",
pd.Timeout-timeDelta, fwdInfo.OutgoingCTLV)
// TODO(andrew.shvv): send proper back error
reason := []byte{byte(lnwire.UpstreamTimeout)}
l.sendHTLCError(pd.RHash, reason)
needUpdate = true
continue
}
// 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)
reason := []byte{byte(lnwire.UnknownError)}
l.sendHTLCError(pd.RHash, reason)
needUpdate = true
continue
}
updatePacket := newAddPacket(l.ShortChanID(),
fwdInfo.NextHop, addMsg)
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 {
log.Errorf("unable to update commitment: %v", err)
l.cfg.Peer.Disconnect()
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(rHash [32]byte,
reason lnwire.OpaqueReason) {
index, err := l.channel.FailHTLC(rHash)
if err != nil {
log.Errorf("unable cancel htlc: %v", err)
return
}
l.cfg.Peer.SendMessage(&lnwire.UpdateFailHTLC{
ChanID: l.ChanID(),
ID: index,
Reason: reason,
})
}