lnd.xprv/routing/payment_lifecycle.go

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package routing
import (
"fmt"
"sync"
"time"
"github.com/davecgh/go-spew/spew"
sphinx "github.com/lightningnetwork/lightning-onion"
"github.com/lightningnetwork/lnd/channeldb"
"github.com/lightningnetwork/lnd/htlcswitch"
"github.com/lightningnetwork/lnd/lntypes"
"github.com/lightningnetwork/lnd/lnwire"
"github.com/lightningnetwork/lnd/routing/route"
)
// paymentLifecycle holds all information about the current state of a payment
// needed to resume if from any point.
type paymentLifecycle struct {
router *ChannelRouter
totalAmount lnwire.MilliSatoshi
feeLimit lnwire.MilliSatoshi
paymentHash lntypes.Hash
paySession PaymentSession
timeoutChan <-chan time.Time
currentHeight int32
}
// payemntState holds a number of key insights learned from a given MPPayment
// that we use to determine what to do on each payment loop iteration.
type paymentState struct {
numShardsInFlight int
remainingAmt lnwire.MilliSatoshi
remainingFees lnwire.MilliSatoshi
terminate bool
}
// paymentState uses the passed payment to find the latest information we need
// to act on every iteration of the payment loop.
func (p *paymentLifecycle) paymentState(payment *channeldb.MPPayment) (
*paymentState, error) {
// Fetch the total amount and fees that has already been sent in
// settled and still in-flight shards.
sentAmt, fees := payment.SentAmt()
// Sanity check we haven't sent a value larger than the payment amount.
if sentAmt > p.totalAmount {
return nil, fmt.Errorf("amount sent %v exceeds "+
"total amount %v", sentAmt, p.totalAmount)
}
// We'll subtract the used fee from our fee budget, but allow the fees
// of the already sent shards to exceed our budget (can happen after
// restarts).
feeBudget := p.feeLimit
if fees <= feeBudget {
feeBudget -= fees
} else {
feeBudget = 0
}
// Get any terminal info for this payment.
settle, failure := payment.TerminalInfo()
// If either an HTLC settled, or the payment has a payment level
// failure recorded, it means we should terminate the moment all shards
// have returned with a result.
terminate := settle != nil || failure != nil
activeShards := payment.InFlightHTLCs()
return &paymentState{
numShardsInFlight: len(activeShards),
remainingAmt: p.totalAmount - sentAmt,
remainingFees: feeBudget,
terminate: terminate,
}, nil
}
// resumePayment resumes the paymentLifecycle from the current state.
func (p *paymentLifecycle) resumePayment() ([32]byte, *route.Route, error) {
shardHandler := &shardHandler{
router: p.router,
paymentHash: p.paymentHash,
shardErrors: make(chan error),
quit: make(chan struct{}),
}
// When the payment lifecycle loop exits, we make sure to signal any
// sub goroutine of the shardHandler to exit, then wait for them to
// return.
defer shardHandler.stop()
// If we had any existing attempts outstanding, we'll start by spinning
// up goroutines that'll collect their results and deliver them to the
// lifecycle loop below.
payment, err := p.router.cfg.Control.FetchPayment(
p.paymentHash,
)
if err != nil {
return [32]byte{}, nil, err
}
for _, a := range payment.InFlightHTLCs() {
a := a
log.Debugf("Resuming payment shard %v for hash %v",
a.AttemptID, p.paymentHash)
shardHandler.collectResultAsync(&a.HTLCAttemptInfo)
}
// We'll continue until either our payment succeeds, or we encounter a
// critical error during path finding.
for {
// Start by quickly checking if there are any outcomes already
// available to handle before we reevaluate our state.
if err := shardHandler.checkShards(); err != nil {
return [32]byte{}, nil, err
}
// We start every iteration by fetching the lastest state of
// the payment from the ControlTower. This ensures that we will
// act on the latest available information, whether we are
// resuming an existing payment or just sent a new attempt.
payment, err := p.router.cfg.Control.FetchPayment(
p.paymentHash,
)
if err != nil {
return [32]byte{}, nil, err
}
// Using this latest state of the payment, calculate
// information about our active shards and terminal conditions.
state, err := p.paymentState(payment)
if err != nil {
return [32]byte{}, nil, err
}
log.Debugf("Payment %v in state terminate=%v, "+
"active_shards=%v, rem_value=%v, fee_limit=%v",
p.paymentHash, state.terminate, state.numShardsInFlight,
state.remainingAmt, state.remainingFees)
switch {
// We have a terminal condition and no active shards, we are
// ready to exit.
case state.terminate && state.numShardsInFlight == 0:
// Find the first successful shard and return
// the preimage and route.
for _, a := range payment.HTLCs {
if a.Settle != nil {
return a.Settle.Preimage, &a.Route, nil
}
}
// Payment failed.
return [32]byte{}, nil, *payment.FailureReason
// If we either reached a terminal error condition (but had
// active shards still) or there is no remaining value to send,
// we'll wait for a shard outcome.
case state.terminate || state.remainingAmt == 0:
// We still have outstanding shards, so wait for a new
// outcome to be available before re-evaluating our
// state.
if err := shardHandler.waitForShard(); err != nil {
return [32]byte{}, nil, err
}
continue
}
// Before we attempt any new shard, we'll check to see if
// either we've gone past the payment attempt timeout, or the
// router is exiting. In either case, we'll stop this payment
// attempt short. If a timeout is not applicable, timeoutChan
// will be nil.
select {
case <-p.timeoutChan:
log.Warnf("payment attempt not completed before " +
"timeout")
// By marking the payment failed with the control
// tower, no further shards will be launched and we'll
// return with an error the moment all active shards
// have finished.
saveErr := p.router.cfg.Control.Fail(
p.paymentHash, channeldb.FailureReasonTimeout,
)
if saveErr != nil {
return [32]byte{}, nil, saveErr
}
continue
case <-p.router.quit:
return [32]byte{}, nil, ErrRouterShuttingDown
// Fall through if we haven't hit our time limit.
default:
}
// Create a new payment attempt from the given payment session.
rt, err := p.paySession.RequestRoute(
state.remainingAmt, state.remainingFees,
uint32(state.numShardsInFlight), uint32(p.currentHeight),
)
if err != nil {
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log.Warnf("Failed to find route for payment %v: %v",
p.paymentHash, err)
routeErr, ok := err.(noRouteError)
if !ok {
return [32]byte{}, nil, err
}
// There is no route to try, and we have no active
// shards. This means that there is no way for us to
// send the payment, so mark it failed with no route.
if state.numShardsInFlight == 0 {
failureCode := routeErr.FailureReason()
log.Debugf("Marking payment %v permanently "+
"failed with no route: %v",
p.paymentHash, failureCode)
saveErr := p.router.cfg.Control.Fail(
p.paymentHash, failureCode,
)
if saveErr != nil {
return [32]byte{}, nil, saveErr
}
continue
}
// We still have active shards, we'll wait for an
// outcome to be available before retrying.
if err := shardHandler.waitForShard(); err != nil {
return [32]byte{}, nil, err
}
continue
}
// We found a route to try, launch a new shard.
attempt, outcome, err := shardHandler.launchShard(rt)
if err != nil {
return [32]byte{}, nil, err
}
// If we encountered a non-critical error when launching the
// shard, handle it.
if outcome.err != nil {
log.Warnf("Failed to launch shard %v for "+
"payment %v: %v", attempt.AttemptID,
p.paymentHash, outcome.err)
// We must inspect the error to know whether it was
// critical or not, to decide whether we should
// continue trying.
err := shardHandler.handleSendError(
attempt, outcome.err,
)
if err != nil {
return [32]byte{}, nil, err
}
// Error was handled successfully, continue to make a
// new attempt.
continue
}
// Now that the shard was successfully sent, launch a go
// routine that will handle its result when its back.
shardHandler.collectResultAsync(attempt)
}
}
// shardHandler holds what is necessary to send and collect the result of
// shards.
type shardHandler struct {
paymentHash lntypes.Hash
router *ChannelRouter
// shardErrors is a channel where errors collected by calling
// collectResultAsync will be delivered. These results are meant to be
// inspected by calling waitForShard or checkShards, and the channel
// doesn't need to be initiated if the caller is using the sync
// collectResult directly.
shardErrors chan error
// quit is closed to signal the sub goroutines of the payment lifecycle
// to stop.
quit chan struct{}
wg sync.WaitGroup
}
// stop signals any active shard goroutine to exit and waits for them to exit.
func (p *shardHandler) stop() {
close(p.quit)
p.wg.Wait()
}
// waitForShard blocks until any of the outstanding shards return.
func (p *shardHandler) waitForShard() error {
select {
case err := <-p.shardErrors:
return err
case <-p.quit:
return fmt.Errorf("shard handler quitting")
case <-p.router.quit:
return ErrRouterShuttingDown
}
}
// checkShards is a non-blocking method that check if any shards has finished
// their execution.
func (p *shardHandler) checkShards() error {
for {
select {
case err := <-p.shardErrors:
if err != nil {
return err
}
case <-p.quit:
return fmt.Errorf("shard handler quitting")
case <-p.router.quit:
return ErrRouterShuttingDown
default:
return nil
}
}
}
// launchOutcome is a type returned from launchShard that indicates whether the
// shard was successfully send onto the network.
type launchOutcome struct {
// err is non-nil if a non-critical error was encountered when trying
// to send the shard, and we successfully updated the control tower to
// reflect this error. This can be errors like not enough local
// balance for the given route etc.
err error
// attempt is the attempt structure as recorded in the database.
attempt *channeldb.HTLCAttempt
}
// launchShard creates and sends an HTLC attempt along the given route,
// registering it with the control tower before sending it. It returns the
// HTLCAttemptInfo that was created for the shard, along with a launchOutcome.
// The launchOutcome is used to indicate whether the attempt was successfully
// sent. If the launchOutcome wraps a non-nil error, it means that the attempt
// was not sent onto the network, so no result will be available in the future
// for it.
func (p *shardHandler) launchShard(rt *route.Route) (*channeldb.HTLCAttemptInfo,
*launchOutcome, error) {
// Using the route received from the payment session, create a new
// shard to send.
firstHop, htlcAdd, attempt, err := p.createNewPaymentAttempt(
rt,
)
if err != nil {
return nil, nil, err
}
// Before sending this HTLC to the switch, we checkpoint the fresh
// paymentID and route to the DB. This lets us know on startup the ID
// of the payment that we attempted to send, such that we can query the
// Switch for its whereabouts. The route is needed to handle the result
// when it eventually comes back.
err = p.router.cfg.Control.RegisterAttempt(p.paymentHash, attempt)
if err != nil {
return nil, nil, err
}
// Now that the attempt is created and checkpointed to the DB, we send
// it.
sendErr := p.sendPaymentAttempt(attempt, firstHop, htlcAdd)
if sendErr != nil {
// TODO(joostjager): Distinguish unexpected internal errors
// from real send errors.
htlcAttempt, err := p.failAttempt(attempt, sendErr)
if err != nil {
return nil, nil, err
}
// Return a launchOutcome indicating the shard failed.
return attempt, &launchOutcome{
attempt: htlcAttempt,
err: sendErr,
}, nil
}
return attempt, &launchOutcome{}, nil
}
// shardResult holds the resulting outcome of a shard sent.
type shardResult struct {
// attempt is the attempt structure as recorded in the database.
attempt *channeldb.HTLCAttempt
// err indicates that the shard failed.
err error
}
// collectResultAsync launches a goroutine that will wait for the result of the
// given HTLC attempt to be available then handle its result. Note that it will
// fail the payment with the control tower if a terminal error is encountered.
func (p *shardHandler) collectResultAsync(attempt *channeldb.HTLCAttemptInfo) {
p.wg.Add(1)
go func() {
defer p.wg.Done()
// Block until the result is available.
result, err := p.collectResult(attempt)
if err != nil {
if err != ErrRouterShuttingDown &&
err != htlcswitch.ErrSwitchExiting {
log.Errorf("Error collecting result for "+
"shard %v for payment %v: %v",
attempt.AttemptID, p.paymentHash, err)
}
select {
case p.shardErrors <- err:
case <-p.router.quit:
case <-p.quit:
}
return
}
// If a non-critical error was encountered handle it and mark
// the payment failed if the failure was terminal.
if result.err != nil {
err := p.handleSendError(attempt, result.err)
if err != nil {
select {
case p.shardErrors <- err:
case <-p.router.quit:
case <-p.quit:
}
return
}
}
select {
case p.shardErrors <- nil:
case <-p.router.quit:
case <-p.quit:
}
}()
}
// collectResult waits for the result for the given attempt to be available
// from the Switch, then records the attempt outcome with the control tower. A
// shardResult is returned, indicating the final outcome of this HTLC attempt.
func (p *shardHandler) collectResult(attempt *channeldb.HTLCAttemptInfo) (
*shardResult, error) {
// Regenerate the circuit for this attempt.
_, circuit, err := generateSphinxPacket(
&attempt.Route, p.paymentHash[:],
attempt.SessionKey,
)
if err != nil {
return nil, err
}
// Using the created circuit, initialize the error decrypter so we can
// parse+decode any failures incurred by this payment within the
// switch.
errorDecryptor := &htlcswitch.SphinxErrorDecrypter{
OnionErrorDecrypter: sphinx.NewOnionErrorDecrypter(circuit),
}
// Now ask the switch to return the result of the payment when
// available.
resultChan, err := p.router.cfg.Payer.GetPaymentResult(
attempt.AttemptID, p.paymentHash, errorDecryptor,
)
switch {
// If this attempt ID is unknown to the Switch, it means it was never
// checkpointed and forwarded by the switch before a restart. In this
// case we can safely send a new payment attempt, and wait for its
// result to be available.
case err == htlcswitch.ErrPaymentIDNotFound:
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log.Debugf("Payment ID %v for hash %v not found in "+
"the Switch, retrying.", attempt.AttemptID,
p.paymentHash)
attempt, cErr := p.failAttempt(attempt, err)
if cErr != nil {
return nil, cErr
}
return &shardResult{
attempt: attempt,
err: err,
}, nil
// A critical, unexpected error was encountered.
case err != nil:
log.Errorf("Failed getting result for attemptID %d "+
"from switch: %v", attempt.AttemptID, err)
return nil, err
}
// The switch knows about this payment, we'll wait for a result to be
// available.
var (
result *htlcswitch.PaymentResult
ok bool
)
select {
case result, ok = <-resultChan:
if !ok {
return nil, htlcswitch.ErrSwitchExiting
}
case <-p.router.quit:
return nil, ErrRouterShuttingDown
case <-p.quit:
return nil, fmt.Errorf("shard handler exiting")
}
// In case of a payment failure, fail the attempt with the control
// tower and return.
if result.Error != nil {
attempt, err := p.failAttempt(attempt, result.Error)
if err != nil {
return nil, err
}
return &shardResult{
attempt: attempt,
err: result.Error,
}, nil
}
// We successfully got a payment result back from the switch.
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log.Debugf("Payment %v succeeded with pid=%v",
p.paymentHash, attempt.AttemptID)
// Report success to mission control.
err = p.router.cfg.MissionControl.ReportPaymentSuccess(
attempt.AttemptID, &attempt.Route,
)
if err != nil {
log.Errorf("Error reporting payment success to mc: %v",
err)
}
// In case of success we atomically store settle result to the DB move
// the shard to the settled state.
htlcAttempt, err := p.router.cfg.Control.SettleAttempt(
p.paymentHash, attempt.AttemptID,
&channeldb.HTLCSettleInfo{
Preimage: result.Preimage,
SettleTime: p.router.cfg.Clock.Now(),
},
)
if err != nil {
log.Errorf("Unable to succeed payment attempt: %v", err)
return nil, err
}
return &shardResult{
attempt: htlcAttempt,
}, nil
}
// createNewPaymentAttempt creates a new payment attempt from the given route.
func (p *shardHandler) createNewPaymentAttempt(rt *route.Route) (
lnwire.ShortChannelID, *lnwire.UpdateAddHTLC,
*channeldb.HTLCAttemptInfo, error) {
// Generate a new key to be used for this attempt.
sessionKey, err := generateNewSessionKey()
if err != nil {
return lnwire.ShortChannelID{}, nil, nil, err
}
// Generate the raw encoded sphinx packet to be included along
// with the htlcAdd message that we send directly to the
// switch.
onionBlob, _, err := generateSphinxPacket(
rt, p.paymentHash[:], sessionKey,
)
if err != nil {
return lnwire.ShortChannelID{}, nil, nil, err
}
// Craft an HTLC packet to send to the layer 2 switch. The
// metadata within this packet will be used to route the
// payment through the network, starting with the first-hop.
htlcAdd := &lnwire.UpdateAddHTLC{
Amount: rt.TotalAmount,
Expiry: rt.TotalTimeLock,
PaymentHash: p.paymentHash,
}
copy(htlcAdd.OnionBlob[:], onionBlob)
// Attempt to send this payment through the network to complete
// the payment. If this attempt fails, then we'll continue on
// to the next available route.
firstHop := lnwire.NewShortChanIDFromInt(
rt.Hops[0].ChannelID,
)
// We generate a new, unique payment ID that we will use for
// this HTLC.
attemptID, err := p.router.cfg.NextPaymentID()
if err != nil {
return lnwire.ShortChannelID{}, nil, nil, err
}
// We now have all the information needed to populate
// the current attempt information.
attempt := &channeldb.HTLCAttemptInfo{
AttemptID: attemptID,
AttemptTime: p.router.cfg.Clock.Now(),
SessionKey: sessionKey,
Route: *rt,
}
return firstHop, htlcAdd, attempt, nil
}
// sendPaymentAttempt attempts to send the current attempt to the switch.
func (p *shardHandler) sendPaymentAttempt(
attempt *channeldb.HTLCAttemptInfo, firstHop lnwire.ShortChannelID,
htlcAdd *lnwire.UpdateAddHTLC) error {
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log.Tracef("Attempting to send payment %v (pid=%v), "+
"using route: %v", p.paymentHash, attempt.AttemptID,
newLogClosure(func() string {
return spew.Sdump(attempt.Route)
}),
)
// Send it to the Switch. When this method returns we assume
// the Switch successfully has persisted the payment attempt,
// such that we can resume waiting for the result after a
// restart.
err := p.router.cfg.Payer.SendHTLC(
firstHop, attempt.AttemptID, htlcAdd,
)
if err != nil {
log.Errorf("Failed sending attempt %d for payment "+
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"%v to switch: %v", attempt.AttemptID,
p.paymentHash, err)
return err
}
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log.Debugf("Payment %v (pid=%v) successfully sent to switch, route: %v",
p.paymentHash, attempt.AttemptID, &attempt.Route)
return nil
}
// handleSendError inspects the given error from the Switch and determines
// whether we should make another payment attempt, or if it should be
// considered a terminal error. Terminal errors will be recorded with the
// control tower.
func (p *shardHandler) handleSendError(attempt *channeldb.HTLCAttemptInfo,
sendErr error) error {
reason := p.router.processSendError(
attempt.AttemptID, &attempt.Route, sendErr,
)
if reason == nil {
return nil
}
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log.Debugf("Payment %v failed: final_outcome=%v, raw_err=%v",
p.paymentHash, *reason, sendErr)
err := p.router.cfg.Control.Fail(p.paymentHash, *reason)
if err != nil {
return err
}
return nil
}
// failAttempt calls control tower to fail the current payment attempt.
func (p *shardHandler) failAttempt(attempt *channeldb.HTLCAttemptInfo,
sendError error) (*channeldb.HTLCAttempt, error) {
log.Warnf("Attempt %v for payment %v failed: %v", attempt.AttemptID,
p.paymentHash, sendError)
failInfo := marshallError(
sendError,
p.router.cfg.Clock.Now(),
)
return p.router.cfg.Control.FailAttempt(
p.paymentHash, attempt.AttemptID,
failInfo,
)
}
// marshallError marshall an error as received from the switch to a structure
// that is suitable for database storage.
func marshallError(sendError error, time time.Time) *channeldb.HTLCFailInfo {
response := &channeldb.HTLCFailInfo{
FailTime: time,
}
switch sendError {
case htlcswitch.ErrPaymentIDNotFound:
response.Reason = channeldb.HTLCFailInternal
return response
case htlcswitch.ErrUnreadableFailureMessage:
response.Reason = channeldb.HTLCFailUnreadable
return response
}
rtErr, ok := sendError.(htlcswitch.ClearTextError)
if !ok {
response.Reason = channeldb.HTLCFailInternal
return response
}
message := rtErr.WireMessage()
if message != nil {
response.Reason = channeldb.HTLCFailMessage
response.Message = message
} else {
response.Reason = channeldb.HTLCFailUnknown
}
// If the ClearTextError received is a ForwardingError, the error
// originated from a node along the route, not locally on our outgoing
// link. We set failureSourceIdx to the index of the node where the
// failure occurred. If the error is not a ForwardingError, the failure
// occurred at our node, so we leave the index as 0 to indicate that
// we failed locally.
fErr, ok := rtErr.(*htlcswitch.ForwardingError)
if ok {
response.FailureSourceIndex = uint32(fErr.FailureSourceIdx)
}
return response
}