lnd.xprv/routing/payment_lifecycle.go
Olaoluwa Osuntokun 525ef594c7
routing: don't return an error from failPayment within handleSendError
In this commit, we fix a regression introduced by a recent bug fix in
this area. Before this change, we'd inspect the error returned by
`processSendError`, and then fail the payment from the PoV of mission
control using the returned error.

A recent refactoring removed `processSendError` and combined the logic
with `tryApplyChannelUpdate` in order to introduce a new
`handleSendError` method that consolidates the logic within the
`shardHandler`. Along the way, the behavior of the prior check was
replicated in the form of a new internal `failPayment` closure. However,
the new function closure ends up returning a `channeldb.FailureReason`
instance, which is actually an `error`.

In the wild, when `SendToRoute` fails due to an error at the
destination, then this new logic caused the `handleSendErorr` method to
fail with an error, returning an unstructured error back to the caller,
instead of the usual payment failure details.

We fix this by no longer checking the `handleSendErorr` for an error as
normal. The `handleSendErorr` function as is will always return an error
of type `*channeldb.FailureReason`, therefore we don't need to treat it
as a normal error. Instead, we check for the type of error returned, and
update the control tower state accordingly.

With this commit, the test added in the prior commit now passes.

Fixes #5477.
2021-07-07 15:31:22 -07:00

1008 lines
30 KiB
Go

package routing
import (
"fmt"
"sync"
"time"
"github.com/btcsuite/btcd/btcec"
"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"
"github.com/lightningnetwork/lnd/routing/shards"
)
// errShardHandlerExiting is returned from the shardHandler when it exits.
var errShardHandlerExiting = fmt.Errorf("shard handler exiting")
// 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
identifier lntypes.Hash
paySession PaymentSession
shardTracker shards.ShardTracker
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 indicates the payment is in its final stage and no more
// shards should be launched. This value is true if we have an HTLC
// settled or the payment has an error.
terminate bool
}
// terminated returns a bool to indicate there are no further actions needed
// and we should return what we have, either the payment preimage or the
// payment error.
func (ps paymentState) terminated() bool {
// If the payment is in final stage and we have no in flight shards to
// wait result for, we consider the whole action terminated.
return ps.terminate && ps.numShardsInFlight == 0
}
// needWaitForShards returns a bool to specify whether we need to wait for the
// outcome of the shanrdHandler.
func (ps paymentState) needWaitForShards() bool {
// If we have in flight shards and the payment is in final stage, we
// need to wait for the outcomes from the shards. Or if we have no more
// money to be sent, we need to wait for the already launched shards.
if ps.numShardsInFlight == 0 {
return false
}
return ps.terminate || ps.remainingAmt == 0
}
// fetchPaymentState will query the db for the latest payment state
// information we need to act on every iteration of the payment loop and update
// the paymentState.
func (p *paymentLifecycle) fetchPaymentState() (*channeldb.MPPayment,
*paymentState, error) {
// Fetch the latest payment from db.
payment, err := p.router.cfg.Control.FetchPayment(p.identifier)
if err != nil {
return nil, nil, err
}
// 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, 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
// Update the payment state.
state := &paymentState{
numShardsInFlight: len(payment.InFlightHTLCs()),
remainingAmt: p.totalAmount - sentAmt,
remainingFees: feeBudget,
terminate: terminate,
}
return payment, state, nil
}
// resumePayment resumes the paymentLifecycle from the current state.
func (p *paymentLifecycle) resumePayment() ([32]byte, *route.Route, error) {
shardHandler := &shardHandler{
router: p.router,
identifier: p.identifier,
shardTracker: p.shardTracker,
shardErrors: make(chan error),
quit: make(chan struct{}),
paySession: p.paySession,
}
// 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.fetchPaymentState()
if err != nil {
return [32]byte{}, nil, err
}
for _, a := range payment.InFlightHTLCs() {
a := a
log.Infof("Resuming payment shard %v for payment %v",
a.AttemptID, p.identifier)
shardHandler.collectResultAsync(&a.HTLCAttemptInfo)
}
// We'll continue until either our payment succeeds, or we encounter a
// critical error during path finding.
lifecycle:
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 update the payment state on every iteration. Since the
// payment state is affected by multiple goroutines (ie,
// collectResultAsync), it is NOT guaranteed that we always
// have the latest state here. This is fine as long as the
// state is consistent as a whole.
payment, currentState, err := p.fetchPaymentState()
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.identifier, currentState.terminate,
currentState.numShardsInFlight,
currentState.remainingAmt, currentState.remainingFees,
)
// TODO(yy): sanity check all the states to make sure
// everything is expected.
switch {
// We have a terminal condition and no active shards, we are
// ready to exit.
case currentState.terminated():
// 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 currentState.needWaitForShards():
// 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 lifecycle
}
// 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.identifier, channeldb.FailureReasonTimeout,
)
if saveErr != nil {
return [32]byte{}, nil, saveErr
}
continue lifecycle
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(
currentState.remainingAmt, currentState.remainingFees,
uint32(currentState.numShardsInFlight),
uint32(p.currentHeight),
)
if err != nil {
log.Warnf("Failed to find route for payment %v: %v",
p.identifier, 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 currentState.numShardsInFlight == 0 {
failureCode := routeErr.FailureReason()
log.Debugf("Marking payment %v permanently "+
"failed with no route: %v",
p.identifier, failureCode)
saveErr := p.router.cfg.Control.Fail(
p.identifier, failureCode,
)
if saveErr != nil {
return [32]byte{}, nil, saveErr
}
continue lifecycle
}
// 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 lifecycle
}
// If this route will consume the last remeining amount to send
// to the receiver, this will be our last shard (for now).
lastShard := rt.ReceiverAmt() == currentState.remainingAmt
// We found a route to try, launch a new shard.
attempt, outcome, err := shardHandler.launchShard(rt, lastShard)
switch {
// We may get a terminal error if we've processed a shard with
// a terminal state (settled or permanent failure), while we
// were pathfinding. We know we're in a terminal state here,
// so we can continue and wait for our last shards to return.
case err == channeldb.ErrPaymentTerminal:
log.Infof("Payment %v in terminal state, abandoning "+
"shard", p.identifier)
continue lifecycle
case 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.identifier, 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 lifecycle
}
// 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 {
identifier lntypes.Hash
router *ChannelRouter
shardTracker shards.ShardTracker
paySession PaymentSession
// 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 errShardHandlerExiting
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 errShardHandlerExiting
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. The lastShard
// argument should be true if this shard will consume the remainder of the
// amount to send. 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,
lastShard bool) (*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, lastShard,
)
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.identifier, 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. It will fail the
// payment with the control tower if a terminal error is encountered.
func (p *shardHandler) collectResultAsync(attempt *channeldb.HTLCAttemptInfo) {
// errToSend is the error to be sent to sh.shardErrors.
var errToSend error
// handleResultErr is a function closure must be called using defer. It
// finishes collecting result by updating the payment state and send
// the error (or nil) to sh.shardErrors.
handleResultErr := func() {
// Send the error or quit.
select {
case p.shardErrors <- errToSend:
case <-p.router.quit:
case <-p.quit:
}
p.wg.Done()
}
p.wg.Add(1)
go func() {
defer handleResultErr()
// Block until the result is available.
result, err := p.collectResult(attempt)
if err != nil {
if err != ErrRouterShuttingDown &&
err != htlcswitch.ErrSwitchExiting &&
err != errShardHandlerExiting {
log.Errorf("Error collecting result for "+
"shard %v for payment %v: %v",
attempt.AttemptID, p.identifier, err)
}
// Overwrite the param errToSend and return so that the
// defer function will use the param to proceed.
errToSend = err
return
}
// If a non-critical error was encountered handle it and mark
// the payment failed if the failure was terminal.
if result.err != nil {
// Overwrite the param errToSend and return so that the
// defer function will use the param to proceed. Notice
// that the errToSend could be nil here.
errToSend = p.handleSendError(attempt, result.err)
return
}
}()
}
// 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) {
// We'll retrieve the hash specific to this shard from the
// shardTracker, since it will be needed to regenerate the circuit
// below.
hash, err := p.shardTracker.GetHash(attempt.AttemptID)
if err != nil {
return nil, err
}
// Regenerate the circuit for this attempt.
_, circuit, err := generateSphinxPacket(
&attempt.Route, hash[:], 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.identifier, 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:
log.Debugf("Attempt ID %v for payment %v not found in "+
"the Switch, retrying.", attempt.AttemptID,
p.identifier)
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, errShardHandlerExiting
}
// 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.
log.Debugf("Payment %v succeeded with pid=%v",
p.identifier, 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.identifier, 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, lastShard bool) (
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
}
// 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
}
// Requesst a new shard from the ShardTracker. If this is an AMP
// payment, and this is the last shard, the outstanding shards together
// with ths one will be enough for the receiver to derive all HTLC
// preimages. If this a non-AMP payment, the ShardTracker will return a
// simple shard with the payment's static payment hash.
shard, err := p.shardTracker.NewShard(attemptID, lastShard)
if err != nil {
return lnwire.ShortChannelID{}, nil, nil, err
}
// It this shard carries MPP or AMP options, add them to the last hop
// on the route.
hop := rt.Hops[len(rt.Hops)-1]
if shard.MPP() != nil {
hop.MPP = shard.MPP()
}
if shard.AMP() != nil {
hop.AMP = shard.AMP()
}
// Generate the raw encoded sphinx packet to be included along
// with the htlcAdd message that we send directly to the
// switch.
hash := shard.Hash()
onionBlob, _, err := generateSphinxPacket(rt, hash[:], 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: hash,
}
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 now have all the information needed to populate the current
// attempt information.
attempt := channeldb.NewHtlcAttemptInfo(
attemptID, sessionKey, *rt, p.router.cfg.Clock.Now(), &hash,
)
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 {
log.Tracef("Attempting to send payment %v (pid=%v), "+
"using route: %v", p.identifier, 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 "+
"%v to switch: %v", attempt.AttemptID,
p.identifier, err)
return err
}
log.Debugf("Payment %v (pid=%v) successfully sent to switch, route: %v",
p.identifier, 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. It analyzes the sendErr for the payment attempt received from
// the switch and updates mission control and/or channel policies. Depending on
// the error type, the error is either the final outcome of the payment or we
// need to continue with an alternative route. A final outcome is indicated by
// a non-nil reason value.
func (p *shardHandler) handleSendError(attempt *channeldb.HTLCAttemptInfo,
sendErr error) error {
internalErrorReason := channeldb.FailureReasonError
// failPayment is a helper closure that fails the payment via the
// router's control tower, which marks the payment as failed in db.
failPayment := func(reason *channeldb.FailureReason,
sendErr error) error {
log.Infof("Payment %v failed: final_outcome=%v, raw_err=%v",
p.identifier, *reason, sendErr)
// Fail the payment via control tower.
if err := p.router.cfg.Control.Fail(
p.identifier, *reason); err != nil {
log.Errorf("unable to report failure to control "+
"tower: %v", err)
return &internalErrorReason
}
return reason
}
// reportFail is a helper closure that reports the failure to the
// mission control, which helps us to decide whether we want to retry
// the payment or not. If a non nil reason is returned from mission
// control, it will further fail the payment via control tower.
reportFail := func(srcIdx *int, msg lnwire.FailureMessage) error {
// Report outcome to mission control.
reason, err := p.router.cfg.MissionControl.ReportPaymentFail(
attempt.AttemptID, &attempt.Route, srcIdx, msg,
)
if err != nil {
log.Errorf("Error reporting payment result to mc: %v",
err)
reason = &internalErrorReason
}
// Exit early if there's no reason.
if reason == nil {
return nil
}
return failPayment(reason, sendErr)
}
if sendErr == htlcswitch.ErrUnreadableFailureMessage {
log.Tracef("Unreadable failure when sending htlc")
return reportFail(nil, nil)
}
// If the error is a ClearTextError, we have received a valid wire
// failure message, either from our own outgoing link or from a node
// down the route. If the error is not related to the propagation of
// our payment, we can stop trying because an internal error has
// occurred.
rtErr, ok := sendErr.(htlcswitch.ClearTextError)
if !ok {
return failPayment(&internalErrorReason, sendErr)
}
// failureSourceIdx is the index of the node that the failure occurred
// at. If the ClearTextError received is not a ForwardingError the
// payment error occurred at our node, so we leave this value as 0
// to indicate that the failure occurred locally. If the error is a
// ForwardingError, it did not originate at our node, so we set
// failureSourceIdx to the index of the node where the failure occurred.
failureSourceIdx := 0
source, ok := rtErr.(*htlcswitch.ForwardingError)
if ok {
failureSourceIdx = source.FailureSourceIdx
}
// Extract the wire failure and apply channel update if it contains one.
// If we received an unknown failure message from a node along the
// route, the failure message will be nil.
failureMessage := rtErr.WireMessage()
err := p.handleFailureMessage(
&attempt.Route, failureSourceIdx, failureMessage,
)
if err != nil {
return failPayment(&internalErrorReason, sendErr)
}
log.Tracef("Node=%v reported failure when sending htlc",
failureSourceIdx)
return reportFail(&failureSourceIdx, failureMessage)
}
// handleFailureMessage tries to apply a channel update present in the failure
// message if any.
func (p *shardHandler) handleFailureMessage(rt *route.Route,
errorSourceIdx int, failure lnwire.FailureMessage) error {
if failure == nil {
return nil
}
// It makes no sense to apply our own channel updates.
if errorSourceIdx == 0 {
log.Errorf("Channel update of ourselves received")
return nil
}
// Extract channel update if the error contains one.
update := p.router.extractChannelUpdate(failure)
if update == nil {
return nil
}
// Parse pubkey to allow validation of the channel update. This should
// always succeed, otherwise there is something wrong in our
// implementation. Therefore return an error.
errVertex := rt.Hops[errorSourceIdx-1].PubKeyBytes
errSource, err := btcec.ParsePubKey(
errVertex[:], btcec.S256(),
)
if err != nil {
log.Errorf("Cannot parse pubkey: idx=%v, pubkey=%v",
errorSourceIdx, errVertex)
return err
}
var (
isAdditionalEdge bool
policy *channeldb.ChannelEdgePolicy
)
// Before we apply the channel update, we need to decide whether the
// update is for additional (ephemeral) edge or normal edge stored in
// db.
//
// Note: the p.paySession might be nil here if it's called inside
// SendToRoute where there's no payment lifecycle.
if p.paySession != nil {
policy = p.paySession.GetAdditionalEdgePolicy(
errSource, update.ShortChannelID.ToUint64(),
)
if policy != nil {
isAdditionalEdge = true
}
}
// Apply channel update to additional edge policy.
if isAdditionalEdge {
if !p.paySession.UpdateAdditionalEdge(
update, errSource, policy) {
log.Debugf("Invalid channel update received: node=%v",
errVertex)
}
return nil
}
// Apply channel update to the channel edge policy in our db.
if !p.router.applyChannelUpdate(update, errSource) {
log.Debugf("Invalid channel update received: node=%v",
errVertex)
}
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.identifier, sendError)
failInfo := marshallError(
sendError,
p.router.cfg.Clock.Now(),
)
// Now that we are failing this payment attempt, cancel the shard with
// the ShardTracker such that it can derive the correct hash for the
// next attempt.
if err := p.shardTracker.CancelShard(attempt.AttemptID); err != nil {
return nil, err
}
return p.router.cfg.Control.FailAttempt(
p.identifier, 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
}