lnd.xprv/htlcswitch/switch.go
Olaoluwa Osuntokun f028eaa152
Merge pull request #1698 from cfromknecht/switch-fwdpkg-cleanup
[htlcswitch] fwdpkg cleanup
2018-08-21 18:56:15 -07:00

2147 lines
66 KiB
Go

package htlcswitch
import (
"bytes"
"crypto/sha256"
"errors"
"fmt"
"sync"
"sync/atomic"
"time"
"github.com/btcsuite/btcd/btcec"
"github.com/coreos/bbolt"
"github.com/davecgh/go-spew/spew"
"github.com/btcsuite/btcd/wire"
"github.com/btcsuite/btcutil"
"github.com/lightningnetwork/lnd/chainntnfs"
"github.com/lightningnetwork/lnd/channeldb"
"github.com/lightningnetwork/lnd/contractcourt"
"github.com/lightningnetwork/lnd/lnrpc"
"github.com/lightningnetwork/lnd/lnwallet"
"github.com/lightningnetwork/lnd/lnwire"
"github.com/lightningnetwork/lnd/ticker"
)
const (
// DefaultFwdEventInterval is the duration between attempts to flush
// pending forwarding events to disk.
DefaultFwdEventInterval = 15 * time.Second
// DefaultLogInterval is the duration between attempts to log statistics
// about forwarding events.
DefaultLogInterval = 10 * time.Second
)
var (
// ErrChannelLinkNotFound is used when channel link hasn't been found.
ErrChannelLinkNotFound = errors.New("channel link not found")
// ErrDuplicateAdd signals that the ADD htlc was already forwarded
// through the switch and is locked into another commitment txn.
ErrDuplicateAdd = errors.New("duplicate add HTLC detected")
// ErrIncompleteForward is used when an htlc was already forwarded
// through the switch, but did not get locked into another commitment
// txn.
ErrIncompleteForward = errors.New("incomplete forward detected")
// ErrSwitchExiting signaled when the switch has received a shutdown
// request.
ErrSwitchExiting = errors.New("htlcswitch shutting down")
// zeroPreimage is the empty preimage which is returned when we have
// some errors.
zeroPreimage [sha256.Size]byte
)
// pendingPayment represents the payment which made by user and waits for
// updates to be received whether the payment has been rejected or proceed
// successfully.
type pendingPayment struct {
paymentHash lnwallet.PaymentHash
amount lnwire.MilliSatoshi
preimage chan [sha256.Size]byte
response chan *htlcPacket
err chan error
// deobfuscator is a serializable entity which is used if we received
// an error, it deobfuscates the onion failure blob, and extracts the
// exact error from it.
deobfuscator ErrorDecrypter
}
// plexPacket encapsulates switch packet and adds error channel to receive
// error from request handler.
type plexPacket struct {
pkt *htlcPacket
err chan error
}
// ChannelCloseType is an enum which signals the type of channel closure the
// peer should execute.
type ChannelCloseType uint8
const (
// CloseRegular indicates a regular cooperative channel closure
// should be attempted.
CloseRegular ChannelCloseType = iota
// CloseBreach indicates that a channel breach has been detected, and
// the link should immediately be marked as unavailable.
CloseBreach
)
// ChanClose represents a request which close a particular channel specified by
// its id.
type ChanClose struct {
// CloseType is a variable which signals the type of channel closure the
// peer should execute.
CloseType ChannelCloseType
// ChanPoint represent the id of the channel which should be closed.
ChanPoint *wire.OutPoint
// TargetFeePerKw is the ideal fee that was specified by the caller.
// This value is only utilized if the closure type is CloseRegular.
// This will be the starting offered fee when the fee negotiation
// process for the cooperative closure transaction kicks off.
TargetFeePerKw lnwallet.SatPerKWeight
// Updates is used by request creator to receive the notifications about
// execution of the close channel request.
Updates chan *lnrpc.CloseStatusUpdate
// Err is used by request creator to receive request execution error.
Err chan error
}
// Config defines the configuration for the service. ALL elements within the
// configuration MUST be non-nil for the service to carry out its duties.
type Config struct {
// SelfKey is the key of the backing Lightning node. This key is used
// to properly craft failure messages, such that the Layer 3 router can
// properly route around link./vertex failures.
SelfKey *btcec.PublicKey
// FwdingLog is an interface that will be used by the switch to log
// forwarding events. A forwarding event happens each time a payment
// circuit is successfully completed. So when we forward an HTLC, and a
// settle is eventually received.
FwdingLog ForwardingLog
// LocalChannelClose kicks-off the workflow to execute a cooperative or
// forced unilateral closure of the channel initiated by a local
// subsystem.
LocalChannelClose func(pubKey []byte, request *ChanClose)
// DB is the channeldb instance that will be used to back the switch's
// persistent circuit map.
DB *channeldb.DB
// SwitchPackager provides access to the forwarding packages of all
// active channels. This gives the switch the ability to read arbitrary
// forwarding packages, and ack settles and fails contained within them.
SwitchPackager channeldb.FwdOperator
// ExtractErrorEncrypter is an interface allowing switch to reextract
// error encrypters stored in the circuit map on restarts, since they
// are not stored directly within the database.
ExtractErrorEncrypter ErrorEncrypterExtracter
// FetchLastChannelUpdate retrieves the latest routing policy for a
// target channel. This channel will typically be the outgoing channel
// specified when we receive an incoming HTLC. This will be used to
// provide payment senders our latest policy when sending encrypted
// error messages.
FetchLastChannelUpdate func(lnwire.ShortChannelID) (*lnwire.ChannelUpdate, error)
// Notifier is an instance of a chain notifier that we'll use to signal
// the switch when a new block has arrived.
Notifier chainntnfs.ChainNotifier
// FwdEventTicker is a signal that instructs the htlcswitch to flush any
// pending forwarding events.
FwdEventTicker ticker.Ticker
// LogEventTicker is a signal instructing the htlcswitch to log
// aggregate stats about it's forwarding during the last interval.
LogEventTicker ticker.Ticker
}
// Switch is the central messaging bus for all incoming/outgoing HTLCs.
// Connected peers with active channels are treated as named interfaces which
// refer to active channels as links. A link is the switch's message
// communication point with the goroutine that manages an active channel. New
// links are registered each time a channel is created, and unregistered once
// the channel is closed. The switch manages the hand-off process for multi-hop
// HTLCs, forwarding HTLCs initiated from within the daemon, and finally
// notifies users local-systems concerning their outstanding payment requests.
type Switch struct {
started int32 // To be used atomically.
shutdown int32 // To be used atomically.
// bestHeight is the best known height of the main chain. The links will
// be used this information to govern decisions based on HTLC timeouts.
// This will be retrieved by the registered links atomically.
bestHeight uint32
wg sync.WaitGroup
quit chan struct{}
// cfg is a copy of the configuration struct that the htlc switch
// service was initialized with.
cfg *Config
// pendingPayments stores payments initiated by the user that are not yet
// settled. The map is used to later look up the payments and notify the
// user of the result when they are complete. Each payment is given a unique
// integer ID when it is created.
pendingPayments map[uint64]*pendingPayment
pendingMutex sync.RWMutex
paymentSequencer Sequencer
// circuits is storage for payment circuits which are used to
// forward the settle/fail htlc updates back to the add htlc initiator.
circuits CircuitMap
// mailOrchestrator manages the lifecycle of mailboxes used throughout
// the switch, and facilitates delayed delivery of packets to links that
// later come online.
mailOrchestrator *mailOrchestrator
// indexMtx is a read/write mutex that protects the set of indexes
// below.
indexMtx sync.RWMutex
// pendingLinkIndex holds links that have not had their final, live
// short_chan_id assigned. These links can be transitioned into the
// primary linkIndex by using UpdateShortChanID to load their live id.
pendingLinkIndex map[lnwire.ChannelID]ChannelLink
// links is a map of channel id and channel link which manages
// this channel.
linkIndex map[lnwire.ChannelID]ChannelLink
// forwardingIndex is an index which is consulted by the switch when it
// needs to locate the next hop to forward an incoming/outgoing HTLC
// update to/from.
//
// TODO(roasbeef): eventually add a NetworkHop mapping before the
// ChannelLink
forwardingIndex map[lnwire.ShortChannelID]ChannelLink
// interfaceIndex maps the compressed public key of a peer to all the
// channels that the switch maintains with that peer.
interfaceIndex map[[33]byte]map[lnwire.ChannelID]ChannelLink
// htlcPlex is the channel which all connected links use to coordinate
// the setup/teardown of Sphinx (onion routing) payment circuits.
// Active links forward any add/settle messages over this channel each
// state transition, sending new adds/settles which are fully locked
// in.
htlcPlex chan *plexPacket
// chanCloseRequests is used to transfer the channel close request to
// the channel close handler.
chanCloseRequests chan *ChanClose
// resolutionMsgs is the channel that all external contract resolution
// messages will be sent over.
resolutionMsgs chan *resolutionMsg
// linkControl is a channel used to propagate add/remove/get htlc
// switch handler commands.
linkControl chan interface{}
// pendingFwdingEvents is the set of forwarding events which have been
// collected during the current interval, but hasn't yet been written
// to the forwarding log.
fwdEventMtx sync.Mutex
pendingFwdingEvents []channeldb.ForwardingEvent
// blockEpochStream is an active block epoch event stream backed by an
// active ChainNotifier instance. This will be used to retrieve the
// lastest height of the chain.
blockEpochStream *chainntnfs.BlockEpochEvent
}
// New creates the new instance of htlc switch.
func New(cfg Config, currentHeight uint32) (*Switch, error) {
circuitMap, err := NewCircuitMap(&CircuitMapConfig{
DB: cfg.DB,
ExtractErrorEncrypter: cfg.ExtractErrorEncrypter,
})
if err != nil {
return nil, err
}
sequencer, err := NewPersistentSequencer(cfg.DB)
if err != nil {
return nil, err
}
return &Switch{
bestHeight: currentHeight,
cfg: &cfg,
circuits: circuitMap,
paymentSequencer: sequencer,
linkIndex: make(map[lnwire.ChannelID]ChannelLink),
mailOrchestrator: newMailOrchestrator(),
forwardingIndex: make(map[lnwire.ShortChannelID]ChannelLink),
interfaceIndex: make(map[[33]byte]map[lnwire.ChannelID]ChannelLink),
pendingLinkIndex: make(map[lnwire.ChannelID]ChannelLink),
pendingPayments: make(map[uint64]*pendingPayment),
htlcPlex: make(chan *plexPacket),
chanCloseRequests: make(chan *ChanClose),
resolutionMsgs: make(chan *resolutionMsg),
quit: make(chan struct{}),
}, nil
}
// resolutionMsg is a struct that wraps an existing ResolutionMsg with a done
// channel. We'll use this channel to synchronize delivery of the message with
// the caller.
type resolutionMsg struct {
contractcourt.ResolutionMsg
doneChan chan struct{}
}
// ProcessContractResolution is called by active contract resolvers once a
// contract they are watching over has been fully resolved. The message carries
// an external signal that *would* have been sent if the outgoing channel
// didn't need to go to the chain in order to fulfill a contract. We'll process
// this message just as if it came from an active outgoing channel.
func (s *Switch) ProcessContractResolution(msg contractcourt.ResolutionMsg) error {
done := make(chan struct{})
select {
case s.resolutionMsgs <- &resolutionMsg{
ResolutionMsg: msg,
doneChan: done,
}:
case <-s.quit:
return ErrSwitchExiting
}
select {
case <-done:
case <-s.quit:
return ErrSwitchExiting
}
return nil
}
// SendHTLC is used by other subsystems which aren't belong to htlc switch
// package in order to send the htlc update.
func (s *Switch) SendHTLC(firstHop lnwire.ShortChannelID,
htlc *lnwire.UpdateAddHTLC,
deobfuscator ErrorDecrypter) ([sha256.Size]byte, error) {
// Create payment and add to the map of payment in order later to be
// able to retrieve it and return response to the user.
payment := &pendingPayment{
err: make(chan error, 1),
response: make(chan *htlcPacket, 1),
preimage: make(chan [sha256.Size]byte, 1),
paymentHash: htlc.PaymentHash,
amount: htlc.Amount,
deobfuscator: deobfuscator,
}
paymentID, err := s.paymentSequencer.NextID()
if err != nil {
return zeroPreimage, err
}
s.pendingMutex.Lock()
s.pendingPayments[paymentID] = payment
s.pendingMutex.Unlock()
// Generate and send new update packet, if error will be received on
// this stage it means that packet haven't left boundaries of our
// system and something wrong happened.
packet := &htlcPacket{
incomingChanID: sourceHop,
incomingHTLCID: paymentID,
outgoingChanID: firstHop,
htlc: htlc,
}
if err := s.forward(packet); err != nil {
s.removePendingPayment(paymentID)
return zeroPreimage, err
}
// Returns channels so that other subsystem might wait/skip the
// waiting of handling of payment.
var preimage [sha256.Size]byte
var response *htlcPacket
select {
case e := <-payment.err:
err = e
case <-s.quit:
return zeroPreimage, ErrSwitchExiting
}
select {
case pkt := <-payment.response:
response = pkt
case <-s.quit:
return zeroPreimage, ErrSwitchExiting
}
select {
case p := <-payment.preimage:
preimage = p
case <-s.quit:
return zeroPreimage, ErrSwitchExiting
}
// Remove circuit since we are about to complete an add/fail of this
// HTLC.
if teardownErr := s.teardownCircuit(response); teardownErr != nil {
log.Warnf("unable to teardown circuit %s: %v",
response.inKey(), teardownErr)
return preimage, err
}
// Finally, if this response is contained in a forwarding package, ack
// the settle/fail so that we don't continue to retransmit the HTLC
// internally.
if response.destRef != nil {
if ackErr := s.ackSettleFail(*response.destRef); ackErr != nil {
log.Warnf("unable to ack settle/fail reference: %s: %v",
*response.destRef, ackErr)
}
}
return preimage, err
}
// UpdateForwardingPolicies sends a message to the switch to update the
// forwarding policies for the set of target channels. If the set of targeted
// channels is nil, then the forwarding policies for all active channels with
// be updated.
//
// NOTE: This function is synchronous and will block until either the
// forwarding policies for all links have been updated, or the switch shuts
// down.
func (s *Switch) UpdateForwardingPolicies(newPolicy ForwardingPolicy,
targetChans ...wire.OutPoint) error {
log.Debugf("Updating link policies: %v", newLogClosure(func() string {
return spew.Sdump(newPolicy)
}))
var linksToUpdate []ChannelLink
s.indexMtx.RLock()
// If no channels have been targeted, then we'll collect all inks to
// update their policies.
if len(targetChans) == 0 {
for _, link := range s.linkIndex {
linksToUpdate = append(linksToUpdate, link)
}
} else {
// Otherwise, we'll only attempt to update the forwarding
// policies for the set of targeted links.
for _, targetLink := range targetChans {
cid := lnwire.NewChanIDFromOutPoint(&targetLink)
// If we can't locate a link by its converted channel
// ID, then we'll return an error back to the caller.
link, ok := s.linkIndex[cid]
if !ok {
s.indexMtx.RUnlock()
return fmt.Errorf("unable to find "+
"ChannelPoint(%v) to update link "+
"policy", targetLink)
}
linksToUpdate = append(linksToUpdate, link)
}
}
s.indexMtx.RUnlock()
// With all the links we need to update collected, we can release the
// mutex then update each link directly.
for _, link := range linksToUpdate {
link.UpdateForwardingPolicy(newPolicy)
}
return nil
}
// forward is used in order to find next channel link and apply htlc update.
// Also this function is used by channel links itself in order to forward the
// update after it has been included in the channel.
func (s *Switch) forward(packet *htlcPacket) error {
switch htlc := packet.htlc.(type) {
case *lnwire.UpdateAddHTLC:
circuit := newPaymentCircuit(&htlc.PaymentHash, packet)
actions, err := s.circuits.CommitCircuits(circuit)
if err != nil {
log.Errorf("unable to commit circuit in switch: %v", err)
return err
}
// Drop duplicate packet if it has already been seen.
switch {
case len(actions.Drops) == 1:
return ErrDuplicateAdd
case len(actions.Fails) == 1:
if packet.incomingChanID == sourceHop {
return err
}
var failure lnwire.FailureMessage
update, err := s.cfg.FetchLastChannelUpdate(
packet.incomingChanID,
)
if err != nil {
failure = &lnwire.FailTemporaryNodeFailure{}
} else {
failure = lnwire.NewTemporaryChannelFailure(update)
}
addErr := ErrIncompleteForward
return s.failAddPacket(packet, failure, addErr)
}
packet.circuit = circuit
}
return s.route(packet)
}
// ForwardPackets adds a list of packets to the switch for processing. Fails
// and settles are added on a first past, simultaneously constructing circuits
// for any adds. After persisting the circuits, another pass of the adds is
// given to forward them through the router. The sending link's quit channel is
// used to prevent deadlocks when the switch stops a link in the midst of
// forwarding.
//
// NOTE: This method guarantees that the returned err chan will eventually be
// closed. The receiver should read on the channel until receiving such a
// signal.
func (s *Switch) ForwardPackets(linkQuit chan struct{},
packets ...*htlcPacket) chan error {
var (
// fwdChan is a buffered channel used to receive err msgs from
// the htlcPlex when forwarding this batch.
fwdChan = make(chan error, len(packets))
// errChan is a buffered channel returned to the caller, that is
// proxied by the fwdChan. This method guarantees that errChan
// will be closed eventually to alert the receiver that it can
// stop reading from the channel.
errChan = make(chan error, len(packets))
// numSent keeps a running count of how many packets are
// forwarded to the switch, which determines how many responses
// we will wait for on the fwdChan..
numSent int
)
// No packets, nothing to do.
if len(packets) == 0 {
close(errChan)
return errChan
}
// Setup a barrier to prevent the background tasks from processing
// responses until this function returns to the user.
var wg sync.WaitGroup
wg.Add(1)
defer wg.Done()
// Before spawning the following goroutine to proxy our error responses,
// check to see if we have already been issued a shutdown request. If
// so, we exit early to avoid incrementing the switch's waitgroup while
// it is already in the process of shutting down.
select {
case <-linkQuit:
close(errChan)
return errChan
case <-s.quit:
close(errChan)
return errChan
default:
// Spawn a goroutine the proxy the errs back to the returned err
// chan. This is done to ensure the err chan returned to the
// caller closed properly, alerting the receiver of completion
// or shutdown.
s.wg.Add(1)
go s.proxyFwdErrs(&numSent, &wg, fwdChan, errChan)
}
// Make a first pass over the packets, forwarding any settles or fails.
// As adds are found, we create a circuit and append it to our set of
// circuits to be written to disk.
var circuits []*PaymentCircuit
var addBatch []*htlcPacket
for _, packet := range packets {
switch htlc := packet.htlc.(type) {
case *lnwire.UpdateAddHTLC:
circuit := newPaymentCircuit(&htlc.PaymentHash, packet)
packet.circuit = circuit
circuits = append(circuits, circuit)
addBatch = append(addBatch, packet)
default:
err := s.routeAsync(packet, fwdChan, linkQuit)
if err != nil {
return errChan
}
numSent++
}
}
// If this batch did not contain any circuits to commit, we can return
// early.
if len(circuits) == 0 {
return errChan
}
// Write any circuits that we found to disk.
actions, err := s.circuits.CommitCircuits(circuits...)
if err != nil {
log.Errorf("unable to commit circuits in switch: %v", err)
}
// Split the htlc packets by comparing an in-order seek to the head of
// the added, dropped, or failed circuits.
//
// NOTE: This assumes each list is guaranteed to be a subsequence of the
// circuits, and that the union of the sets results in the original set
// of circuits.
var addedPackets, failedPackets []*htlcPacket
for _, packet := range addBatch {
switch {
case len(actions.Adds) > 0 && packet.circuit == actions.Adds[0]:
addedPackets = append(addedPackets, packet)
actions.Adds = actions.Adds[1:]
case len(actions.Drops) > 0 && packet.circuit == actions.Drops[0]:
actions.Drops = actions.Drops[1:]
case len(actions.Fails) > 0 && packet.circuit == actions.Fails[0]:
failedPackets = append(failedPackets, packet)
actions.Fails = actions.Fails[1:]
}
}
// Now, forward any packets for circuits that were successfully added to
// the switch's circuit map.
for _, packet := range addedPackets {
err := s.routeAsync(packet, fwdChan, linkQuit)
if err != nil {
return errChan
}
numSent++
}
// Lastly, for any packets that failed, this implies that they were
// left in a half added state, which can happen when recovering from
// failures.
if len(failedPackets) > 0 {
var failure lnwire.FailureMessage
update, err := s.cfg.FetchLastChannelUpdate(
failedPackets[0].incomingChanID,
)
if err != nil {
failure = &lnwire.FailTemporaryNodeFailure{}
} else {
failure = lnwire.NewTemporaryChannelFailure(update)
}
for _, packet := range failedPackets {
addErr := errors.New("failing packet after " +
"detecting incomplete forward")
// We don't handle the error here since this method
// always returns an error.
s.failAddPacket(packet, failure, addErr)
}
}
return errChan
}
// proxyFwdErrs transmits any errors received on `fwdChan` back to `errChan`,
// and guarantees that the `errChan` will be closed after 1) all errors have
// been sent, or 2) the switch has received a shutdown. The `errChan` should be
// buffered with at least the value of `num` after the barrier has been
// released.
//
// NOTE: The receiver of `errChan` should read until the channel closed, since
// this proxying guarantees that the close will happen.
func (s *Switch) proxyFwdErrs(num *int, wg *sync.WaitGroup,
fwdChan, errChan chan error) {
defer s.wg.Done()
defer close(errChan)
// Wait here until the outer function has finished persisting
// and routing the packets. This guarantees we don't read from num until
// the value is accurate.
wg.Wait()
numSent := *num
for i := 0; i < numSent; i++ {
select {
case err := <-fwdChan:
errChan <- err
case <-s.quit:
log.Errorf("unable to forward htlc packet " +
"htlc switch was stopped")
return
}
}
}
// route sends a single htlcPacket through the switch and synchronously awaits a
// response.
func (s *Switch) route(packet *htlcPacket) error {
command := &plexPacket{
pkt: packet,
err: make(chan error, 1),
}
select {
case s.htlcPlex <- command:
case <-s.quit:
return ErrSwitchExiting
}
select {
case err := <-command.err:
return err
case <-s.quit:
return ErrSwitchExiting
}
}
// routeAsync sends a packet through the htlc switch, using the provided err
// chan to propagate errors back to the caller. The link's quit channel is
// provided so that the send can be canceled if either the link or the switch
// receive a shutdown requuest. This method does not wait for a response from
// the htlcForwarder before returning.
func (s *Switch) routeAsync(packet *htlcPacket, errChan chan error,
linkQuit chan struct{}) error {
command := &plexPacket{
pkt: packet,
err: errChan,
}
select {
case s.htlcPlex <- command:
return nil
case <-linkQuit:
return ErrLinkShuttingDown
case <-s.quit:
return errors.New("Htlc Switch was stopped")
}
}
// handleLocalDispatch is used at the start/end of the htlc update life cycle.
// At the start (1) it is used to send the htlc to the channel link without
// creation of circuit. At the end (2) it is used to notify the user about the
// result of his payment is it was successful or not.
//
// Alice Bob Carol
// o --add----> o ---add----> o
// (1)
//
// (2)
// o <-settle-- o <--settle-- o
// Alice Bob Carol
//
func (s *Switch) handleLocalDispatch(pkt *htlcPacket) error {
// Pending payments use a special interpretation of the incomingChanID and
// incomingHTLCID fields on packet where the channel ID is blank and the
// HTLC ID is the payment ID. The switch basically views the users of the
// node as a special channel that also offers a sequence of HTLCs.
payment, err := s.findPayment(pkt.incomingHTLCID)
if err != nil {
return err
}
switch htlc := pkt.htlc.(type) {
// User have created the htlc update therefore we should find the
// appropriate channel link and send the payment over this link.
case *lnwire.UpdateAddHTLC:
s.indexMtx.RLock()
link, err := s.getLinkByShortID(pkt.outgoingChanID)
s.indexMtx.RUnlock()
if err != nil {
log.Errorf("Link %v not found", pkt.outgoingChanID)
return &ForwardingError{
ErrorSource: s.cfg.SelfKey,
FailureMessage: &lnwire.FailUnknownNextPeer{},
}
}
if !link.EligibleToForward() {
err := fmt.Errorf("Link %v is not available to forward",
pkt.outgoingChanID)
log.Error(err)
// The update does not need to be populated as the error
// will be returned back to the router.
htlcErr := lnwire.NewTemporaryChannelFailure(nil)
return &ForwardingError{
ErrorSource: s.cfg.SelfKey,
ExtraMsg: err.Error(),
FailureMessage: htlcErr,
}
}
if link.Bandwidth() < htlc.Amount {
err := fmt.Errorf("Link %v has insufficient capacity: "+
"need %v, has %v", pkt.outgoingChanID,
htlc.Amount, link.Bandwidth())
log.Error(err)
// The update does not need to be populated as the error
// will be returned back to the router.
htlcErr := lnwire.NewTemporaryChannelFailure(nil)
return &ForwardingError{
ErrorSource: s.cfg.SelfKey,
ExtraMsg: err.Error(),
FailureMessage: htlcErr,
}
}
return link.HandleSwitchPacket(pkt)
// We've just received a settle update which means we can finalize the
// user payment and return successful response.
case *lnwire.UpdateFulfillHTLC:
// Notify the user that his payment was successfully proceed.
payment.err <- nil
payment.response <- pkt
payment.preimage <- htlc.PaymentPreimage
s.removePendingPayment(pkt.incomingHTLCID)
// We've just received a fail update which means we can finalize the
// user payment and return fail response.
case *lnwire.UpdateFailHTLC:
payment.err <- s.parseFailedPayment(payment, pkt, htlc)
payment.response <- pkt
payment.preimage <- zeroPreimage
s.removePendingPayment(pkt.incomingHTLCID)
default:
return errors.New("wrong update type")
}
return nil
}
// parseFailedPayment determines the appropriate failure message to return to
// a user initiated payment. The three cases handled are:
// 1) A local failure, which should already plaintext.
// 2) A resolution from the chain arbitrator,
// 3) A failure from the remote party, which will need to be decrypted using the
// payment deobfuscator.
func (s *Switch) parseFailedPayment(payment *pendingPayment, pkt *htlcPacket,
htlc *lnwire.UpdateFailHTLC) *ForwardingError {
var failure *ForwardingError
switch {
// The payment never cleared the link, so we don't need to
// decrypt the error, simply decode it them report back to the
// user.
case pkt.localFailure:
var userErr string
r := bytes.NewReader(htlc.Reason)
failureMsg, err := lnwire.DecodeFailure(r, 0)
if err != nil {
userErr = fmt.Sprintf("unable to decode onion failure, "+
"htlc with hash(%x): %v", payment.paymentHash[:], err)
log.Error(userErr)
// As this didn't even clear the link, we don't need to
// apply an update here since it goes directly to the
// router.
failureMsg = lnwire.NewTemporaryChannelFailure(nil)
}
failure = &ForwardingError{
ErrorSource: s.cfg.SelfKey,
ExtraMsg: userErr,
FailureMessage: failureMsg,
}
// A payment had to be timed out on chain before it got past
// the first hop. In this case, we'll report a permanent
// channel failure as this means us, or the remote party had to
// go on chain.
case pkt.isResolution && htlc.Reason == nil:
userErr := fmt.Sprintf("payment was resolved " +
"on-chain, then cancelled back")
failure = &ForwardingError{
ErrorSource: s.cfg.SelfKey,
ExtraMsg: userErr,
FailureMessage: lnwire.FailPermanentChannelFailure{},
}
// A regular multi-hop payment error that we'll need to
// decrypt.
default:
var err error
// We'll attempt to fully decrypt the onion encrypted
// error. If we're unable to then we'll bail early.
failure, err = payment.deobfuscator.DecryptError(htlc.Reason)
if err != nil {
userErr := fmt.Sprintf("unable to de-obfuscate onion failure, "+
"htlc with hash(%x): %v", payment.paymentHash[:], err)
log.Error(userErr)
failure = &ForwardingError{
ErrorSource: s.cfg.SelfKey,
ExtraMsg: userErr,
FailureMessage: lnwire.NewTemporaryChannelFailure(nil),
}
}
}
return failure
}
// handlePacketForward is used in cases when we need forward the htlc update
// from one channel link to another and be able to propagate the settle/fail
// updates back. This behaviour is achieved by creation of payment circuits.
func (s *Switch) handlePacketForward(packet *htlcPacket) error {
switch htlc := packet.htlc.(type) {
// Channel link forwarded us a new htlc, therefore we initiate the
// payment circuit within our internal state so we can properly forward
// the ultimate settle message back latter.
case *lnwire.UpdateAddHTLC:
if packet.incomingChanID == sourceHop {
// A blank incomingChanID indicates that this is
// a pending user-initiated payment.
return s.handleLocalDispatch(packet)
}
s.indexMtx.RLock()
targetLink, err := s.getLinkByShortID(packet.outgoingChanID)
if err != nil {
s.indexMtx.RUnlock()
// If packet was forwarded from another channel link
// than we should notify this link that some error
// occurred.
failure := &lnwire.FailUnknownNextPeer{}
addErr := fmt.Errorf("unable to find link with "+
"destination %v", packet.outgoingChanID)
return s.failAddPacket(packet, failure, addErr)
}
interfaceLinks, _ := s.getLinks(targetLink.Peer().PubKey())
s.indexMtx.RUnlock()
// We'll keep track of any HTLC failures during the link
// selection process. This way we can return the error for
// precise link that the sender selected, while optimistically
// trying all links to utilize our available bandwidth.
linkErrs := make(map[lnwire.ShortChannelID]lnwire.FailureMessage)
// Try to find destination channel link with appropriate
// bandwidth.
var destination ChannelLink
for _, link := range interfaceLinks {
// We'll skip any links that aren't yet eligible for
// forwarding.
switch {
case !link.EligibleToForward():
continue
// If the link doesn't yet have a source chan ID, then
// we'll skip it as well.
case link.ShortChanID() == sourceHop:
continue
}
// Before we check the link's bandwidth, we'll ensure
// that the HTLC satisfies the current forwarding
// policy of this target link.
currentHeight := atomic.LoadUint32(&s.bestHeight)
err := link.HtlcSatifiesPolicy(
htlc.PaymentHash, packet.incomingAmount,
packet.amount, packet.incomingTimeout,
packet.outgoingTimeout, currentHeight,
)
if err != nil {
linkErrs[link.ShortChanID()] = err
continue
}
if link.Bandwidth() >= htlc.Amount {
destination = link
break
}
}
switch {
// If the channel link we're attempting to forward the update
// over has insufficient capacity, and didn't violate any
// forwarding policies, then we'll cancel the htlc as the
// payment cannot succeed.
case destination == nil && len(linkErrs) == 0:
// If packet was forwarded from another channel link
// than we should notify this link that some error
// occurred.
var failure lnwire.FailureMessage
update, err := s.cfg.FetchLastChannelUpdate(
packet.outgoingChanID,
)
if err != nil {
failure = &lnwire.FailTemporaryNodeFailure{}
} else {
failure = lnwire.NewTemporaryChannelFailure(update)
}
addErr := fmt.Errorf("unable to find appropriate "+
"channel link insufficient capacity, need "+
"%v", htlc.Amount)
return s.failAddPacket(packet, failure, addErr)
// If we had a forwarding failure due to the HTLC not
// satisfying the current policy, then we'll send back an
// error, but ensure we send back the error sourced at the
// *target* link.
case destination == nil && len(linkErrs) != 0:
// At this point, some or all of the links rejected the
// HTLC so we couldn't forward it. So we'll try to look
// up the error that came from the source.
linkErr, ok := linkErrs[packet.outgoingChanID]
if !ok {
// If we can't find the error of the source,
// then we'll return an unknown next peer,
// though this should never happen.
linkErr = &lnwire.FailUnknownNextPeer{}
log.Warnf("unable to find err source for "+
"outgoing_link=%v, errors=%v",
packet.outgoingChanID, newLogClosure(func() string {
return spew.Sdump(linkErrs)
}))
}
addErr := fmt.Errorf("incoming HTLC(%x) violated "+
"target outgoing link (id=%v) policy: %v",
htlc.PaymentHash[:], packet.outgoingChanID,
linkErr)
return s.failAddPacket(packet, linkErr, addErr)
}
// Send the packet to the destination channel link which
// manages the channel.
packet.outgoingChanID = destination.ShortChanID()
return destination.HandleSwitchPacket(packet)
case *lnwire.UpdateFailHTLC, *lnwire.UpdateFulfillHTLC:
// If the source of this packet has not been set, use the
// circuit map to lookup the origin.
circuit, err := s.closeCircuit(packet)
if err != nil {
return err
}
fail, isFail := htlc.(*lnwire.UpdateFailHTLC)
if isFail && !packet.hasSource {
switch {
case circuit.ErrorEncrypter == nil:
// No message to encrypt, locally sourced
// payment.
case packet.isResolution:
// If this is a resolution message, then we'll need to encrypt
// it as it's actually internally sourced.
var err error
// TODO(roasbeef): don't need to pass actually?
failure := &lnwire.FailPermanentChannelFailure{}
fail.Reason, err = circuit.ErrorEncrypter.EncryptFirstHop(
failure,
)
if err != nil {
err = fmt.Errorf("unable to obfuscate "+
"error: %v", err)
log.Error(err)
}
default:
// Otherwise, it's a forwarded error, so we'll perform a
// wrapper encryption as normal.
fail.Reason = circuit.ErrorEncrypter.IntermediateEncrypt(
fail.Reason,
)
}
} else if !isFail && circuit.Outgoing != nil {
// If this is an HTLC settle, and it wasn't from a
// locally initiated HTLC, then we'll log a forwarding
// event so we can flush it to disk later.
//
// TODO(roasbeef): only do this once link actually
// fully settles?
localHTLC := packet.incomingChanID == sourceHop
if !localHTLC {
s.fwdEventMtx.Lock()
s.pendingFwdingEvents = append(
s.pendingFwdingEvents,
channeldb.ForwardingEvent{
Timestamp: time.Now(),
IncomingChanID: circuit.Incoming.ChanID,
OutgoingChanID: circuit.Outgoing.ChanID,
AmtIn: circuit.IncomingAmount,
AmtOut: circuit.OutgoingAmount,
},
)
s.fwdEventMtx.Unlock()
}
}
// A blank IncomingChanID in a circuit indicates that it is a pending
// user-initiated payment.
if packet.incomingChanID == sourceHop {
return s.handleLocalDispatch(packet)
}
// Check to see that the source link is online before removing
// the circuit.
return s.mailOrchestrator.Deliver(packet.incomingChanID, packet)
default:
return errors.New("wrong update type")
}
}
// failAddPacket encrypts a fail packet back to an add packet's source.
// The ciphertext will be derived from the failure message proivded by context.
// This method returns the failErr if all other steps complete successfully.
func (s *Switch) failAddPacket(packet *htlcPacket,
failure lnwire.FailureMessage, failErr error) error {
// Encrypt the failure so that the sender will be able to read the error
// message. Since we failed this packet, we use EncryptFirstHop to
// obfuscate the failure for their eyes only.
reason, err := packet.obfuscator.EncryptFirstHop(failure)
if err != nil {
err := fmt.Errorf("unable to obfuscate "+
"error: %v", err)
log.Error(err)
return err
}
log.Error(failErr)
failPkt := &htlcPacket{
sourceRef: packet.sourceRef,
incomingChanID: packet.incomingChanID,
incomingHTLCID: packet.incomingHTLCID,
circuit: packet.circuit,
htlc: &lnwire.UpdateFailHTLC{
Reason: reason,
},
}
// Route a fail packet back to the source link.
err = s.mailOrchestrator.Deliver(failPkt.incomingChanID, failPkt)
if err != nil {
err = fmt.Errorf("source chanid=%v unable to "+
"handle switch packet: %v",
packet.incomingChanID, err)
log.Error(err)
return err
}
return failErr
}
// closeCircuit accepts a settle or fail htlc and the associated htlc packet and
// attempts to determine the source that forwarded this htlc. This method will
// set the incoming chan and htlc ID of the given packet if the source was
// found, and will properly [re]encrypt any failure messages.
func (s *Switch) closeCircuit(pkt *htlcPacket) (*PaymentCircuit, error) {
// If the packet has its source, that means it was failed locally by
// the outgoing link. We fail it here to make sure only one response
// makes it through the switch.
if pkt.hasSource {
circuit, err := s.circuits.FailCircuit(pkt.inKey())
switch err {
// Circuit successfully closed.
case nil:
return circuit, nil
// Circuit was previously closed, but has not been deleted.
// We'll just drop this response until the circuit has been
// fully removed.
case ErrCircuitClosing:
return nil, err
// Failed to close circuit because it does not exist. This is
// likely because the circuit was already successfully closed.
// Since this packet failed locally, there is no forwarding
// package entry to acknowledge.
case ErrUnknownCircuit:
return nil, err
// Unexpected error.
default:
return nil, err
}
}
// Otherwise, this is packet was received from the remote party. Use
// circuit map to find the incoming link to receive the settle/fail.
circuit, err := s.circuits.CloseCircuit(pkt.outKey())
switch err {
// Open circuit successfully closed.
case nil:
pkt.incomingChanID = circuit.Incoming.ChanID
pkt.incomingHTLCID = circuit.Incoming.HtlcID
pkt.circuit = circuit
pkt.sourceRef = &circuit.AddRef
pktType := "SETTLE"
if _, ok := pkt.htlc.(*lnwire.UpdateFailHTLC); ok {
pktType = "FAIL"
}
log.Debugf("Closed completed %s circuit for %x: "+
"(%s, %d) <-> (%s, %d)", pktType, pkt.circuit.PaymentHash,
pkt.incomingChanID, pkt.incomingHTLCID,
pkt.outgoingChanID, pkt.outgoingHTLCID)
return circuit, nil
// Circuit was previously closed, but has not been deleted. We'll just
// drop this response until the circuit has been removed.
case ErrCircuitClosing:
return nil, err
// Failed to close circuit because it does not exist. This is likely
// because the circuit was already successfully closed.
case ErrUnknownCircuit:
err := fmt.Errorf("Unable to find target channel "+
"for HTLC settle/fail: channel ID = %s, "+
"HTLC ID = %d", pkt.outgoingChanID,
pkt.outgoingHTLCID)
log.Error(err)
// TODO(conner): ack settle/fail
if pkt.destRef != nil {
if err := s.ackSettleFail(*pkt.destRef); err != nil {
return nil, err
}
}
return nil, err
// Unexpected error.
default:
return nil, err
}
}
// ackSettleFail is used by the switch to ACK any settle/fail entries in the
// forwarding package of the outgoing link for a payment circuit. We do this if
// we're the originator of the payment, so the link stops attempting to
// re-broadcast.
func (s *Switch) ackSettleFail(settleFailRef channeldb.SettleFailRef) error {
return s.cfg.DB.Batch(func(tx *bolt.Tx) error {
return s.cfg.SwitchPackager.AckSettleFails(tx, settleFailRef)
})
}
// teardownCircuit removes a pending or open circuit from the switch's circuit
// map and prints useful logging statements regarding the outcome.
func (s *Switch) teardownCircuit(pkt *htlcPacket) error {
var pktType string
switch htlc := pkt.htlc.(type) {
case *lnwire.UpdateFulfillHTLC:
pktType = "SETTLE"
case *lnwire.UpdateFailHTLC:
pktType = "FAIL"
default:
err := fmt.Errorf("cannot tear down packet of type: %T", htlc)
log.Errorf(err.Error())
return err
}
switch {
case pkt.circuit.HasKeystone():
log.Debugf("Tearing down open circuit with %s pkt, removing circuit=%v "+
"with keystone=%v", pktType, pkt.inKey(), pkt.outKey())
err := s.circuits.DeleteCircuits(pkt.inKey())
if err != nil {
log.Warnf("Failed to tear down open circuit (%s, %d) <-> (%s, %d) "+
"with payment_hash-%v using %s pkt",
pkt.incomingChanID, pkt.incomingHTLCID,
pkt.outgoingChanID, pkt.outgoingHTLCID,
pkt.circuit.PaymentHash, pktType)
return err
}
log.Debugf("Closed completed %s circuit for %x: "+
"(%s, %d) <-> (%s, %d)", pktType, pkt.circuit.PaymentHash,
pkt.incomingChanID, pkt.incomingHTLCID,
pkt.outgoingChanID, pkt.outgoingHTLCID)
default:
log.Debugf("Tearing down incomplete circuit with %s for inkey=%v",
pktType, pkt.inKey())
err := s.circuits.DeleteCircuits(pkt.inKey())
if err != nil {
log.Warnf("Failed to tear down pending %s circuit for %x: "+
"(%s, %d)", pktType, pkt.circuit.PaymentHash,
pkt.incomingChanID, pkt.incomingHTLCID)
return err
}
log.Debugf("Removed pending onion circuit for %x: "+
"(%s, %d)", pkt.circuit.PaymentHash,
pkt.incomingChanID, pkt.incomingHTLCID)
}
return nil
}
// CloseLink creates and sends the close channel command to the target link
// directing the specified closure type. If the closure type if CloseRegular,
// then the last parameter should be the ideal fee-per-kw that will be used as
// a starting point for close negotiation.
func (s *Switch) CloseLink(chanPoint *wire.OutPoint, closeType ChannelCloseType,
targetFeePerKw lnwallet.SatPerKWeight) (chan *lnrpc.CloseStatusUpdate,
chan error) {
// TODO(roasbeef) abstract out the close updates.
updateChan := make(chan *lnrpc.CloseStatusUpdate, 2)
errChan := make(chan error, 1)
command := &ChanClose{
CloseType: closeType,
ChanPoint: chanPoint,
Updates: updateChan,
TargetFeePerKw: targetFeePerKw,
Err: errChan,
}
select {
case s.chanCloseRequests <- command:
return updateChan, errChan
case <-s.quit:
errChan <- ErrSwitchExiting
close(updateChan)
return updateChan, errChan
}
}
// htlcForwarder is responsible for optimally forwarding (and possibly
// fragmenting) incoming/outgoing HTLCs amongst all active interfaces and their
// links. The duties of the forwarder are similar to that of a network switch,
// in that it facilitates multi-hop payments by acting as a central messaging
// bus. The switch communicates will active links to create, manage, and tear
// down active onion routed payments. Each active channel is modeled as
// networked device with metadata such as the available payment bandwidth, and
// total link capacity.
//
// NOTE: This MUST be run as a goroutine.
func (s *Switch) htlcForwarder() {
defer s.wg.Done()
defer func() {
s.blockEpochStream.Cancel()
// Remove all links once we've been signalled for shutdown.
var linksToStop []ChannelLink
s.indexMtx.Lock()
for _, link := range s.linkIndex {
activeLink := s.removeLink(link.ChanID())
if activeLink == nil {
log.Errorf("unable to remove ChannelLink(%v) "+
"on stop", link.ChanID())
continue
}
linksToStop = append(linksToStop, activeLink)
}
for _, link := range s.pendingLinkIndex {
pendingLink := s.removeLink(link.ChanID())
if pendingLink == nil {
log.Errorf("unable to remove ChannelLink(%v) "+
"on stop", link.ChanID())
continue
}
linksToStop = append(linksToStop, pendingLink)
}
s.indexMtx.Unlock()
// Now that all pending and live links have been removed from
// the forwarding indexes, stop each one before shutting down.
// We'll shut them down in parallel to make exiting as fast as
// possible.
var wg sync.WaitGroup
for _, link := range linksToStop {
wg.Add(1)
go func(l ChannelLink) {
defer wg.Done()
l.Stop()
}(link)
}
wg.Wait()
// Before we exit fully, we'll attempt to flush out any
// forwarding events that may still be lingering since the last
// batch flush.
if err := s.FlushForwardingEvents(); err != nil {
log.Errorf("unable to flush forwarding events: %v", err)
}
}()
// TODO(roasbeef): cleared vs settled distinction
var (
totalNumUpdates uint64
totalSatSent btcutil.Amount
totalSatRecv btcutil.Amount
)
s.cfg.LogEventTicker.Resume()
defer s.cfg.LogEventTicker.Stop()
// Every 15 seconds, we'll flush out the forwarding events that
// occurred during that period.
s.cfg.FwdEventTicker.Resume()
defer s.cfg.FwdEventTicker.Stop()
out:
for {
select {
case blockEpoch, ok := <-s.blockEpochStream.Epochs:
if !ok {
break out
}
atomic.StoreUint32(&s.bestHeight, uint32(blockEpoch.Height))
// A local close request has arrived, we'll forward this to the
// relevant link (if it exists) so the channel can be
// cooperatively closed (if possible).
case req := <-s.chanCloseRequests:
chanID := lnwire.NewChanIDFromOutPoint(req.ChanPoint)
s.indexMtx.RLock()
link, ok := s.linkIndex[chanID]
if !ok {
s.indexMtx.RUnlock()
req.Err <- fmt.Errorf("no peer for channel with "+
"chan_id=%x", chanID[:])
continue
}
s.indexMtx.RUnlock()
peerPub := link.Peer().PubKey()
log.Debugf("Requesting local channel close: peer=%v, "+
"chan_id=%x", link.Peer(), chanID[:])
go s.cfg.LocalChannelClose(peerPub[:], req)
case resolutionMsg := <-s.resolutionMsgs:
pkt := &htlcPacket{
outgoingChanID: resolutionMsg.SourceChan,
outgoingHTLCID: resolutionMsg.HtlcIndex,
isResolution: true,
}
// Resolution messages will either be cancelling
// backwards an existing HTLC, or settling a previously
// outgoing HTLC. Based on this, we'll map the message
// to the proper htlcPacket.
if resolutionMsg.Failure != nil {
pkt.htlc = &lnwire.UpdateFailHTLC{}
} else {
pkt.htlc = &lnwire.UpdateFulfillHTLC{
PaymentPreimage: *resolutionMsg.PreImage,
}
}
log.Infof("Received outside contract resolution, "+
"mapping to: %v", spew.Sdump(pkt))
// We don't check the error, as the only failure we can
// encounter is due to the circuit already being
// closed. This is fine, as processing this message is
// meant to be idempotent.
err := s.handlePacketForward(pkt)
if err != nil {
log.Errorf("Unable to forward resolution msg: %v", err)
}
// With the message processed, we'll now close out
close(resolutionMsg.doneChan)
// A new packet has arrived for forwarding, we'll interpret the
// packet concretely, then either forward it along, or
// interpret a return packet to a locally initialized one.
case cmd := <-s.htlcPlex:
cmd.err <- s.handlePacketForward(cmd.pkt)
// When this time ticks, then it indicates that we should
// collect all the forwarding events since the last internal,
// and write them out to our log.
case <-s.cfg.FwdEventTicker.Ticks():
s.wg.Add(1)
go func() {
defer s.wg.Done()
if err := s.FlushForwardingEvents(); err != nil {
log.Errorf("unable to flush "+
"forwarding events: %v", err)
}
}()
// The log ticker has fired, so we'll calculate some forwarding
// stats for the last 10 seconds to display within the logs to
// users.
case <-s.cfg.LogEventTicker.Ticks():
// First, we'll collate the current running tally of
// our forwarding stats.
prevSatSent := totalSatSent
prevSatRecv := totalSatRecv
prevNumUpdates := totalNumUpdates
var (
newNumUpdates uint64
newSatSent btcutil.Amount
newSatRecv btcutil.Amount
)
// Next, we'll run through all the registered links and
// compute their up-to-date forwarding stats.
s.indexMtx.RLock()
for _, link := range s.linkIndex {
// TODO(roasbeef): when links first registered
// stats printed.
updates, sent, recv := link.Stats()
newNumUpdates += updates
newSatSent += sent.ToSatoshis()
newSatRecv += recv.ToSatoshis()
}
s.indexMtx.RUnlock()
var (
diffNumUpdates uint64
diffSatSent btcutil.Amount
diffSatRecv btcutil.Amount
)
// If this is the first time we're computing these
// stats, then the diff is just the new value. We do
// this in order to avoid integer underflow issues.
if prevNumUpdates == 0 {
diffNumUpdates = newNumUpdates
diffSatSent = newSatSent
diffSatRecv = newSatRecv
} else {
diffNumUpdates = newNumUpdates - prevNumUpdates
diffSatSent = newSatSent - prevSatSent
diffSatRecv = newSatRecv - prevSatRecv
}
// If the diff of num updates is zero, then we haven't
// forwarded anything in the last 10 seconds, so we can
// skip this update.
if diffNumUpdates == 0 {
continue
}
// If the diff of num updates is negative, then some
// links may have been unregistered from the switch, so
// we'll update our stats to only include our registered
// links.
if int64(diffNumUpdates) < 0 {
totalNumUpdates = newNumUpdates
totalSatSent = newSatSent
totalSatRecv = newSatRecv
continue
}
// Otherwise, we'll log this diff, then accumulate the
// new stats into the running total.
log.Infof("Sent %d satoshis and received %d satoshis "+
"in the last 10 seconds (%f tx/sec)",
diffSatSent, diffSatRecv,
float64(diffNumUpdates)/10)
totalNumUpdates += diffNumUpdates
totalSatSent += diffSatSent
totalSatRecv += diffSatRecv
case <-s.quit:
return
}
}
}
// Start starts all helper goroutines required for the operation of the switch.
func (s *Switch) Start() error {
if !atomic.CompareAndSwapInt32(&s.started, 0, 1) {
log.Warn("Htlc Switch already started")
return errors.New("htlc switch already started")
}
log.Infof("Starting HTLC Switch")
blockEpochStream, err := s.cfg.Notifier.RegisterBlockEpochNtfn(nil)
if err != nil {
return err
}
s.blockEpochStream = blockEpochStream
s.wg.Add(1)
go s.htlcForwarder()
if err := s.reforwardResponses(); err != nil {
s.Stop()
log.Errorf("unable to reforward responses: %v", err)
return err
}
return nil
}
// reforwardResponses for every known, non-pending channel, loads all associated
// forwarding packages and reforwards any Settle or Fail HTLCs found. This is
// used to resurrect the switch's mailboxes after a restart.
func (s *Switch) reforwardResponses() error {
openChannels, err := s.cfg.DB.FetchAllOpenChannels()
if err != nil {
return err
}
for _, openChannel := range openChannels {
shortChanID := openChannel.ShortChanID()
// Locally-initiated payments never need reforwarding.
if shortChanID == sourceHop {
continue
}
// If the channel is pending, it should have no forwarding
// packages, and nothing to reforward.
if openChannel.IsPending {
continue
}
// Channels in open or waiting-close may still have responses in
// their forwarding packages. We will continue to reattempt
// forwarding on startup until the channel is fully-closed.
//
// Load this channel's forwarding packages, and deliver them to
// the switch.
fwdPkgs, err := s.loadChannelFwdPkgs(shortChanID)
if err != nil {
log.Errorf("unable to load forwarding "+
"packages for %v: %v", shortChanID, err)
return err
}
s.reforwardSettleFails(fwdPkgs)
}
return nil
}
// loadChannelFwdPkgs loads all forwarding packages owned by the `source` short
// channel identifier.
func (s *Switch) loadChannelFwdPkgs(source lnwire.ShortChannelID) ([]*channeldb.FwdPkg, error) {
var fwdPkgs []*channeldb.FwdPkg
if err := s.cfg.DB.Update(func(tx *bolt.Tx) error {
var err error
fwdPkgs, err = s.cfg.SwitchPackager.LoadChannelFwdPkgs(
tx, source,
)
return err
}); err != nil {
return nil, err
}
return fwdPkgs, nil
}
// reforwardSettleFails parses the Settle and Fail HTLCs from the list of
// forwarding packages, and reforwards those that have not been acknowledged.
// This is intended to occur on startup, in order to recover the switch's
// mailboxes, and to ensure that responses can be propagated in case the
// outgoing link never comes back online.
//
// NOTE: This should mimic the behavior processRemoteSettleFails.
func (s *Switch) reforwardSettleFails(fwdPkgs []*channeldb.FwdPkg) {
for _, fwdPkg := range fwdPkgs {
settleFails := lnwallet.PayDescsFromRemoteLogUpdates(
fwdPkg.Source, fwdPkg.Height, fwdPkg.SettleFails,
)
switchPackets := make([]*htlcPacket, 0, len(settleFails))
for i, pd := range settleFails {
// Skip any settles or fails that have already been
// acknowledged by the incoming link that originated the
// forwarded Add.
if fwdPkg.SettleFailFilter.Contains(uint16(i)) {
continue
}
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: fwdPkg.Source,
outgoingHTLCID: pd.ParentIndex,
destRef: pd.DestRef,
htlc: &lnwire.UpdateFulfillHTLC{
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.
switchPackets = append(switchPackets, settlePacket)
// 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: fwdPkg.Source,
outgoingHTLCID: pd.ParentIndex,
destRef: pd.DestRef,
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.
switchPackets = append(switchPackets, failPacket)
}
}
// Since this send isn't tied to a specific link, we pass a nil
// link quit channel, meaning the send will fail only if the
// switch receives a shutdown request.
errChan := s.ForwardPackets(nil, switchPackets...)
go handleBatchFwdErrs(errChan)
}
}
// handleBatchFwdErrs waits on the given errChan until it is closed, logging the
// errors returned from any unsuccessful forwarding attempts.
func handleBatchFwdErrs(errChan chan error) {
for {
err, ok := <-errChan
if !ok {
// Err chan has been drained or switch is shutting down.
// Either way, return.
return
}
if err == nil {
continue
}
log.Errorf("unhandled error while reforwarding htlc "+
"settle/fail over htlcswitch: %v", err)
}
}
// Stop gracefully stops all active helper goroutines, then waits until they've
// exited.
func (s *Switch) Stop() error {
if !atomic.CompareAndSwapInt32(&s.shutdown, 0, 1) {
log.Warn("Htlc Switch already stopped")
return errors.New("htlc switch already shutdown")
}
log.Infof("HTLC Switch shutting down")
close(s.quit)
s.wg.Wait()
// Wait until all active goroutines have finished exiting before
// stopping the mailboxes, otherwise the mailbox map could still be
// accessed and modified.
s.mailOrchestrator.Stop()
return nil
}
// AddLink is used to initiate the handling of the add link command. The
// request will be propagated and handled in the main goroutine.
func (s *Switch) AddLink(link ChannelLink) error {
s.indexMtx.Lock()
defer s.indexMtx.Unlock()
chanID := link.ChanID()
// First, ensure that this link is not already active in the switch.
_, err := s.getLink(chanID)
if err == nil {
return fmt.Errorf("unable to add ChannelLink(%v), already "+
"active", chanID)
}
// Get and attach the mailbox for this link, which buffers packets in
// case there packets that we tried to deliver while this link was
// offline.
mailbox := s.mailOrchestrator.GetOrCreateMailBox(chanID)
link.AttachMailBox(mailbox)
if err := link.Start(); err != nil {
s.removeLink(chanID)
return err
}
shortChanID := link.ShortChanID()
if shortChanID == sourceHop {
log.Infof("Adding pending link chan_id=%v, short_chan_id=%v",
chanID, shortChanID)
s.pendingLinkIndex[chanID] = link
} else {
log.Infof("Adding live link chan_id=%v, short_chan_id=%v",
chanID, shortChanID)
s.addLiveLink(link)
s.mailOrchestrator.BindLiveShortChanID(
mailbox, chanID, shortChanID,
)
}
return nil
}
// addLiveLink adds a link to all associated forwarding index, this makes it a
// candidate for forwarding HTLCs.
func (s *Switch) addLiveLink(link ChannelLink) {
// We'll add the link to the linkIndex which lets us quickly
// look up a channel when we need to close or register it, and
// the forwarding index which'll be used when forwarding HTLC's
// in the multi-hop setting.
s.linkIndex[link.ChanID()] = link
s.forwardingIndex[link.ShortChanID()] = link
// Next we'll add the link to the interface index so we can
// quickly look up all the channels for a particular node.
peerPub := link.Peer().PubKey()
if _, ok := s.interfaceIndex[peerPub]; !ok {
s.interfaceIndex[peerPub] = make(map[lnwire.ChannelID]ChannelLink)
}
s.interfaceIndex[peerPub][link.ChanID()] = link
}
// GetLink is used to initiate the handling of the get link command. The
// request will be propagated/handled to/in the main goroutine.
func (s *Switch) GetLink(chanID lnwire.ChannelID) (ChannelLink, error) {
s.indexMtx.RLock()
defer s.indexMtx.RUnlock()
return s.getLink(chanID)
}
// getLink returns the link stored in either the pending index or the live
// lindex.
func (s *Switch) getLink(chanID lnwire.ChannelID) (ChannelLink, error) {
link, ok := s.linkIndex[chanID]
if !ok {
link, ok = s.pendingLinkIndex[chanID]
if !ok {
return nil, ErrChannelLinkNotFound
}
}
return link, nil
}
// getLinkByShortID attempts to return the link which possesses the target
// short channel ID.
//
// NOTE: This MUST be called with the indexMtx held.
func (s *Switch) getLinkByShortID(chanID lnwire.ShortChannelID) (ChannelLink, error) {
link, ok := s.forwardingIndex[chanID]
if !ok {
return nil, ErrChannelLinkNotFound
}
return link, nil
}
// HasActiveLink returns true if the given channel ID has a link in the link
// index.
func (s *Switch) HasActiveLink(chanID lnwire.ChannelID) bool {
s.indexMtx.RLock()
defer s.indexMtx.RUnlock()
_, ok := s.linkIndex[chanID]
return ok
}
// RemoveLink purges the switch of any link associated with chanID. If a pending
// or active link is not found, this method does nothing. Otherwise, the method
// returns after the link has been completely shutdown.
func (s *Switch) RemoveLink(chanID lnwire.ChannelID) {
s.indexMtx.Lock()
link := s.removeLink(chanID)
s.indexMtx.Unlock()
if link != nil {
link.Stop()
}
}
// removeLink is used to remove and stop the channel link.
//
// NOTE: This MUST be called with the indexMtx held.
func (s *Switch) removeLink(chanID lnwire.ChannelID) ChannelLink {
log.Infof("Removing channel link with ChannelID(%v)", chanID)
link, err := s.getLink(chanID)
if err != nil {
return nil
}
// Remove the channel from live link indexes.
delete(s.pendingLinkIndex, link.ChanID())
delete(s.linkIndex, link.ChanID())
delete(s.forwardingIndex, link.ShortChanID())
// If the link has been added to the peer index, then we'll move to
// delete the entry within the index.
peerPub := link.Peer().PubKey()
if peerIndex, ok := s.interfaceIndex[peerPub]; ok {
delete(peerIndex, link.ChanID())
// If after deletion, there are no longer any links, then we'll
// remove the interface map all together.
if len(peerIndex) == 0 {
delete(s.interfaceIndex, peerPub)
}
}
return link
}
// UpdateShortChanID updates the short chan ID for an existing channel. This is
// required in the case of a re-org and re-confirmation or a channel, or in the
// case that a link was added to the switch before its short chan ID was known.
func (s *Switch) UpdateShortChanID(chanID lnwire.ChannelID) error {
s.indexMtx.Lock()
defer s.indexMtx.Unlock()
// Locate the target link in the pending link index. If no such link
// exists, then we will ignore the request.
link, ok := s.pendingLinkIndex[chanID]
if !ok {
return fmt.Errorf("link %v not found", chanID)
}
oldShortChanID := link.ShortChanID()
// Try to update the link's short channel ID, returning early if this
// update failed.
shortChanID, err := link.UpdateShortChanID()
if err != nil {
return err
}
// Reject any blank short channel ids.
if shortChanID == sourceHop {
return fmt.Errorf("refusing trivial short_chan_id for chan_id=%v"+
"live link", chanID)
}
log.Infof("Updated short_chan_id for ChannelLink(%v): old=%v, new=%v",
chanID, oldShortChanID, shortChanID)
// Since the link was in the pending state before, we will remove it
// from the pending link index and add it to the live link index so that
// it can be available in forwarding.
delete(s.pendingLinkIndex, chanID)
s.addLiveLink(link)
// Finally, alert the mail orchestrator to the change of short channel
// ID, and deliver any unclaimed packets to the link.
mailbox := s.mailOrchestrator.GetOrCreateMailBox(chanID)
s.mailOrchestrator.BindLiveShortChanID(
mailbox, chanID, shortChanID,
)
return nil
}
// GetLinksByInterface fetches all the links connected to a particular node
// identified by the serialized compressed form of its public key.
func (s *Switch) GetLinksByInterface(hop [33]byte) ([]ChannelLink, error) {
s.indexMtx.RLock()
defer s.indexMtx.RUnlock()
return s.getLinks(hop)
}
// getLinks is function which returns the channel links of the peer by hop
// destination id.
//
// NOTE: This MUST be called with the indexMtx held.
func (s *Switch) getLinks(destination [33]byte) ([]ChannelLink, error) {
links, ok := s.interfaceIndex[destination]
if !ok {
return nil, fmt.Errorf("unable to locate channel link by "+
"destination hop id %x", destination)
}
channelLinks := make([]ChannelLink, 0, len(links))
for _, link := range links {
channelLinks = append(channelLinks, link)
}
return channelLinks, nil
}
// removePendingPayment is the helper function which removes the pending user
// payment.
func (s *Switch) removePendingPayment(paymentID uint64) error {
s.pendingMutex.Lock()
defer s.pendingMutex.Unlock()
if _, ok := s.pendingPayments[paymentID]; !ok {
return fmt.Errorf("Cannot find pending payment with ID %d",
paymentID)
}
delete(s.pendingPayments, paymentID)
return nil
}
// findPayment is the helper function which find the payment.
func (s *Switch) findPayment(paymentID uint64) (*pendingPayment, error) {
s.pendingMutex.RLock()
defer s.pendingMutex.RUnlock()
payment, ok := s.pendingPayments[paymentID]
if !ok {
return nil, fmt.Errorf("Cannot find pending payment with ID %d",
paymentID)
}
return payment, nil
}
// CircuitModifier returns a reference to subset of the interfaces provided by
// the circuit map, to allow links to open and close circuits.
func (s *Switch) CircuitModifier() CircuitModifier {
return s.circuits
}
// numPendingPayments is helper function which returns the overall number of
// pending user payments.
func (s *Switch) numPendingPayments() int {
return len(s.pendingPayments)
}
// commitCircuits persistently adds a circuit to the switch's circuit map.
func (s *Switch) commitCircuits(circuits ...*PaymentCircuit) (
*CircuitFwdActions, error) {
return s.circuits.CommitCircuits(circuits...)
}
// openCircuits preemptively writes the keystones for Adds that are about to be
// added to a commitment txn.
func (s *Switch) openCircuits(keystones ...Keystone) error {
return s.circuits.OpenCircuits(keystones...)
}
// deleteCircuits persistently removes the circuit, and keystone if present,
// from the circuit map.
func (s *Switch) deleteCircuits(inKeys ...CircuitKey) error {
return s.circuits.DeleteCircuits(inKeys...)
}
// lookupCircuit queries the in memory representation of the circuit map to
// retrieve a particular circuit.
func (s *Switch) lookupCircuit(inKey CircuitKey) *PaymentCircuit {
return s.circuits.LookupCircuit(inKey)
}
// lookupOpenCircuit queries the in-memory representation of the circuit map for a
// circuit whose outgoing circuit key matches outKey.
func (s *Switch) lookupOpenCircuit(outKey CircuitKey) *PaymentCircuit {
return s.circuits.LookupOpenCircuit(outKey)
}
// FlushForwardingEvents flushes out the set of pending forwarding events to
// the persistent log. This will be used by the switch to periodically flush
// out the set of forwarding events to disk. External callers can also use this
// method to ensure all data is flushed to dis before querying the log.
func (s *Switch) FlushForwardingEvents() error {
// First, we'll obtain a copy of the current set of pending forwarding
// events.
s.fwdEventMtx.Lock()
// If we won't have any forwarding events, then we can exit early.
if len(s.pendingFwdingEvents) == 0 {
s.fwdEventMtx.Unlock()
return nil
}
events := make([]channeldb.ForwardingEvent, len(s.pendingFwdingEvents))
copy(events[:], s.pendingFwdingEvents[:])
// With the copy obtained, we can now clear out the header pointer of
// the current slice. This way, we can re-use the underlying storage
// allocated for the slice.
s.pendingFwdingEvents = s.pendingFwdingEvents[:0]
s.fwdEventMtx.Unlock()
// Finally, we'll write out the copied events to the persistent
// forwarding log.
return s.cfg.FwdingLog.AddForwardingEvents(events)
}
// BestHeight returns the best height known to the switch.
func (s *Switch) BestHeight() uint32 {
return atomic.LoadUint32(&s.bestHeight)
}