13586005509

Committed 28 Feb 2025 10:14AM UTC coverage: 68.629% (+9.9%) from 58.77%

Build # 13586005509

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Pull #9521

github

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web-flow

Commit Message

Merge 37d3a70a5 into 8532955b3

Pull Request Pull Request #9521: unit: remove GOACC, use Go 1.20 native coverage functionality

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89.04

/routing/result_interpretation.go

package routing

import (
        "bytes"
        "fmt"
        "io"

        "github.com/lightningnetwork/lnd/channeldb"
        "github.com/lightningnetwork/lnd/fn/v2"
        "github.com/lightningnetwork/lnd/lnwire"
        "github.com/lightningnetwork/lnd/routing/route"
        "github.com/lightningnetwork/lnd/tlv"
)

// Instantiate variables to allow taking a reference from the failure reason.
var (
        reasonError            = channeldb.FailureReasonError
        reasonIncorrectDetails = channeldb.FailureReasonPaymentDetails
)

// pairResult contains the result of the interpretation of a payment attempt for
// a specific node pair.
type pairResult struct {
        // amt is the amount that was forwarded for this pair. Can be set to
        // zero for failures that are amount independent.
        amt lnwire.MilliSatoshi

        // success indicates whether the payment attempt was successful through
        // this pair.
        success bool
}

// failPairResult creates a new result struct for a failure.
func failPairResult(minPenalizeAmt lnwire.MilliSatoshi) pairResult {
        return pairResult{
                amt: minPenalizeAmt,
        }
}

// newSuccessPairResult creates a new result struct for a success.
func successPairResult(successAmt lnwire.MilliSatoshi) pairResult {
        return pairResult{
                success: true,
                amt:     successAmt,
        }
}

// String returns the human-readable representation of a pair result.
func (p pairResult) String() string {
        var resultType string
        if p.success {
                resultType = "success"
        } else {
                resultType = "failed"
        }

        return fmt.Sprintf("%v (amt=%v)", resultType, p.amt)
}

// interpretedResult contains the result of the interpretation of a payment
// attempt.
type interpretedResult struct {
        // nodeFailure points to a node pubkey if all channels of that node are
        // responsible for the result.
        nodeFailure *route.Vertex

        // pairResults contains a map of node pairs for which we have a result.
        pairResults map[DirectedNodePair]pairResult

        // finalFailureReason is set to a non-nil value if it makes no more
        // sense to start another payment attempt. It will contain the reason
        // why.
        finalFailureReason *channeldb.FailureReason

        // policyFailure is set to a node pair if there is a policy failure on
        // that connection. This is used to control the second chance logic for
        // policy failures.
        policyFailure *DirectedNodePair
}

// interpretResult interprets a payment outcome and returns an object that
// contains information required to update mission control.
func interpretResult(rt *mcRoute,
        failure fn.Option[paymentFailure]) *interpretedResult {

        i := &interpretedResult{
                pairResults: make(map[DirectedNodePair]pairResult),
        }

        return fn.ElimOption(failure, func() *interpretedResult {
                i.processSuccess(rt)

                return i
        }, func(info paymentFailure) *interpretedResult {
                i.processFail(rt, info)

                return i
        })
}

// processSuccess processes a successful payment attempt.
func (i *interpretedResult) processSuccess(route *mcRoute) {
        // For successes, all nodes must have acted in the right way.
        // Therefore we mark all of them with a success result. However we need
        // to handle the blinded route part separately because for intermediate
        // blinded nodes the amount field is set to zero so we use the receiver
        // amount.
        introIdx, isBlinded := introductionPointIndex(route)
        if isBlinded {
                // Report success for all the pairs until the introduction
                // point.
                i.successPairRange(route, 0, introIdx-1)

                // Handle the blinded route part.
                //
                // NOTE: The introIdx index here does describe the node after
                // the introduction point.
                i.markBlindedRouteSuccess(route, introIdx)

                return
        }

        // Mark nodes as successful in the non-blinded case of the payment.
        i.successPairRange(route, 0, len(route.hops.Val)-1)
}

// processFail processes a failed payment attempt.
func (i *interpretedResult) processFail(rt *mcRoute, failure paymentFailure) {
        if failure.info.IsNone() {
                i.processPaymentOutcomeUnknown(rt)
                return
        }

        var (
                idx     int
                failMsg lnwire.FailureMessage
        )

        failure.info.WhenSome(
                func(r tlv.RecordT[tlv.TlvType0, paymentFailureInfo]) {
                        idx = int(r.Val.sourceIdx.Val)
                        failMsg = r.Val.msg.Val.FailureMessage
                },
        )

        // If the payment was to a blinded route and we received an error from
        // after the introduction point, handle this error separately - there
        // has been a protocol violation from the introduction node. This
        // penalty applies regardless of the error code that is returned.
        introIdx, isBlinded := introductionPointIndex(rt)
        if isBlinded && introIdx < idx {
                i.processPaymentOutcomeBadIntro(rt, introIdx, idx)
                return
        }

        switch idx {
        // We are the source of the failure.
        case 0:
                i.processPaymentOutcomeSelf(rt, failMsg)

        // A failure from the final hop was received.
        case len(rt.hops.Val):
                i.processPaymentOutcomeFinal(rt, failMsg)

        // An intermediate hop failed. Interpret the outcome, update reputation
        // and try again.
        default:
                i.processPaymentOutcomeIntermediate(rt, idx, failMsg)
        }
}

// processPaymentOutcomeBadIntro handles the case where we have made payment
// to a blinded route, but received an error from a node after the introduction
// node. This indicates that the introduction node is not obeying the route
// blinding specification, as we expect all errors from the introduction node
// to be source from it.
func (i *interpretedResult) processPaymentOutcomeBadIntro(route *mcRoute,
        introIdx, errSourceIdx int) {

        // We fail the introduction node for not obeying the specification.
        i.failNode(route, introIdx)

        // Other preceding channels in the route forwarded correctly. Note
        // that we do not assign success to the incoming link to the
        // introduction node because it has not handled the error correctly.
        if introIdx > 1 {
                i.successPairRange(route, 0, introIdx-2)
        }

        // If the source of the failure was from the final node, we also set
        // a final failure reason because the recipient can't process the
        // payment (independent of the introduction failing to convert the
        // error, we can't complete the payment if the last hop fails).
        if errSourceIdx == len(route.hops.Val) {
                i.finalFailureReason = &reasonError
        }
}

// processPaymentOutcomeSelf handles failures sent by ourselves.
func (i *interpretedResult) processPaymentOutcomeSelf(rt *mcRoute,
        failure lnwire.FailureMessage) {

        switch failure.(type) {

        // We receive a malformed htlc failure from our peer. We trust ourselves
        // to send the correct htlc, so our peer must be at fault.
        case *lnwire.FailInvalidOnionVersion,
                *lnwire.FailInvalidOnionHmac,
                *lnwire.FailInvalidOnionKey:

                i.failNode(rt, 1)

                // If this was a payment to a direct peer, we can stop trying.
                if len(rt.hops.Val) == 1 {
                        i.finalFailureReason = &reasonError
                }

        // Any other failure originating from ourselves should be temporary and
        // caused by changing conditions between path finding and execution of
        // the payment. We just retry and trust that the information locally
        // available in the link has been updated.
        default:
                log.Warnf("Routing failure for local channel %v occurred",
                        rt.hops.Val[0].channelID)
        }
}

// processPaymentOutcomeFinal handles failures sent by the final hop.
func (i *interpretedResult) processPaymentOutcomeFinal(route *mcRoute,
        failure lnwire.FailureMessage) {

        n := len(route.hops.Val)

        failNode := func() {
                i.failNode(route, n)

                // Other channels in the route forwarded correctly.
                if n > 1 {
                        i.successPairRange(route, 0, n-2)
                }

                i.finalFailureReason = &reasonError
        }

        // If a failure from the final node is received, we will fail the
        // payment in almost all cases. Only when the penultimate node sends an
        // incorrect htlc, we want to retry via another route. Invalid onion
        // failures are not expected, because the final node wouldn't be able to
        // encrypt that failure.
        switch failure.(type) {

        // Expiry or amount of the HTLC doesn't match the onion, try another
        // route.
        case *lnwire.FailFinalIncorrectCltvExpiry,
                *lnwire.FailFinalIncorrectHtlcAmount:

                // We trust ourselves. If this is a direct payment, we penalize
                // the final node and fail the payment.
                if n == 1 {
                        i.failNode(route, n)
                        i.finalFailureReason = &reasonError

                        return
                }

                // Otherwise penalize the last pair of the route and retry.
                // Either the final node is at fault, or it gets sent a bad htlc
                // from its predecessor.
                i.failPair(route, n-1)

                // The other hops relayed correctly, so assign those pairs a
                // success result. At this point, n >= 2.
                i.successPairRange(route, 0, n-2)

        // We are using wrong payment hash or amount, fail the payment.
        case *lnwire.FailIncorrectPaymentAmount,
                *lnwire.FailIncorrectDetails:

                // Assign all pairs a success result, as the payment reached the
                // destination correctly.
                i.successPairRange(route, 0, n-1)

                i.finalFailureReason = &reasonIncorrectDetails

        // The HTLC that was extended to the final hop expires too soon. Fail
        // the payment, because we may be using the wrong final cltv delta.
        case *lnwire.FailFinalExpiryTooSoon:
                // TODO(roasbeef): can happen to to race condition, try again
                // with recent block height

                // TODO(joostjager): can also happen because a node delayed
                // deliberately. What to penalize?
                i.finalFailureReason = &reasonIncorrectDetails

        case *lnwire.FailMPPTimeout:
                // Assign all pairs a success result, as the payment reached the
                // destination correctly. Continue the payment process.
                i.successPairRange(route, 0, n-1)

        // We do not expect to receive an invalid blinding error from the final
        // node in the route. This could erroneously happen in the following
        // cases:
        // 1. Unblinded node: misuses the error code.
        // 2. A receiving introduction node: erroneously sends the error code,
        //    as the spec indicates that receiving introduction nodes should
        //    use regular errors.
        //
        // Note that we expect the case where this error is sent from a node
        // after the introduction node to be handled elsewhere as this is part
        // of a more general class of errors where the introduction node has
        // failed to convert errors for the blinded route.
        case *lnwire.FailInvalidBlinding:
                failNode()

        // All other errors are considered terminal if coming from the
        // final hop. They indicate that something is wrong at the
        // recipient, so we do apply a penalty.
        default:
                failNode()
        }
}

// processPaymentOutcomeIntermediate handles failures sent by an intermediate
// hop.
//
//nolint:funlen
func (i *interpretedResult) processPaymentOutcomeIntermediate(route *mcRoute,
        errorSourceIdx int, failure lnwire.FailureMessage) {

        reportOutgoing := func() {
                i.failPair(
                        route, errorSourceIdx,
                )
        }

        reportOutgoingBalance := func() {
                i.failPairBalance(
                        route, errorSourceIdx,
                )

                // All nodes up to the failing pair must have forwarded
                // successfully.
                i.successPairRange(route, 0, errorSourceIdx-1)
        }

        reportIncoming := func() {
                // We trust ourselves. If the error comes from the first hop, we
                // can penalize the whole node. In that case there is no
                // uncertainty as to which node to blame.
                if errorSourceIdx == 1 {
                        i.failNode(route, errorSourceIdx)
                        return
                }

                // Otherwise report the incoming pair.
                i.failPair(
                        route, errorSourceIdx-1,
                )

                // All nodes up to the failing pair must have forwarded
                // successfully.
                if errorSourceIdx > 1 {
                        i.successPairRange(route, 0, errorSourceIdx-2)
                }
        }

        reportNode := func() {
                // Fail only the node that reported the failure.
                i.failNode(route, errorSourceIdx)

                // Other preceding channels in the route forwarded correctly.
                if errorSourceIdx > 1 {
                        i.successPairRange(route, 0, errorSourceIdx-2)
                }
        }

        reportAll := func() {
                // We trust ourselves. If the error comes from the first hop, we
                // can penalize the whole node. In that case there is no
                // uncertainty as to which node to blame.
                if errorSourceIdx == 1 {
                        i.failNode(route, errorSourceIdx)
                        return
                }

                // Otherwise penalize all pairs up to the error source. This
                // includes our own outgoing connection.
                i.failPairRange(
                        route, 0, errorSourceIdx-1,
                )
        }

        switch failure.(type) {

        // If a node reports onion payload corruption or an invalid version,
        // that node may be responsible, but it could also be that it is just
        // relaying a malformed htlc failure from it successor. By reporting the
        // outgoing channel set, we will surely hit the responsible node. At
        // this point, it is not possible that the node's predecessor corrupted
        // the onion blob. If the predecessor would have corrupted the payload,
        // the error source wouldn't have been able to encrypt this failure
        // message for us.
        case *lnwire.FailInvalidOnionVersion,
                *lnwire.FailInvalidOnionHmac,
                *lnwire.FailInvalidOnionKey:

                reportOutgoing()

        // If InvalidOnionPayload is received, we penalize only the reporting
        // node. We know the preceding hop didn't corrupt the onion, since the
        // reporting node is able to send the failure. We assume that we
        // constructed a valid onion payload and that the failure is most likely
        // an unknown required type or a bug in their implementation.
        case *lnwire.InvalidOnionPayload:
                reportNode()

        // If the next hop in the route wasn't known or offline, we'll only
        // penalize the channel set which we attempted to route over. This is
        // conservative, and it can handle faulty channels between nodes
        // properly. Additionally, this guards against routing nodes returning
        // errors in order to attempt to black list another node.
        case *lnwire.FailUnknownNextPeer:
                reportOutgoing()

        // Some implementations use this error when the next hop is offline, so we
        // do the same as FailUnknownNextPeer and also process the channel update.
        case *lnwire.FailChannelDisabled:

                // Set the node pair for which a channel update may be out of
                // date. The second chance logic uses the policyFailure field.
                i.policyFailure = &DirectedNodePair{
                        From: route.hops.Val[errorSourceIdx-1].pubKeyBytes.Val,
                        To:   route.hops.Val[errorSourceIdx].pubKeyBytes.Val,
                }

                reportOutgoing()

                // All nodes up to the failing pair must have forwarded
                // successfully.
                i.successPairRange(route, 0, errorSourceIdx-1)

        // If we get a permanent channel, we'll prune the channel set in both
        // directions and continue with the rest of the routes.
        case *lnwire.FailPermanentChannelFailure:
                reportOutgoing()

        // When an HTLC parameter is incorrect, the node sending the error may
        // be doing something wrong. But it could also be that its predecessor
        // is intentionally modifying the htlc parameters that we instructed it
        // via the hop payload. Therefore we penalize the incoming node pair. A
        // third cause of this error may be that we have an out of date channel
        // update. This is handled by the second chance logic up in mission
        // control.
        case *lnwire.FailAmountBelowMinimum,
                *lnwire.FailFeeInsufficient,
                *lnwire.FailIncorrectCltvExpiry:

                // Set the node pair for which a channel update may be out of
                // date. The second chance logic uses the policyFailure field.
                i.policyFailure = &DirectedNodePair{
                        From: route.hops.Val[errorSourceIdx-1].pubKeyBytes.Val,
                        To:   route.hops.Val[errorSourceIdx].pubKeyBytes.Val,
                }

                // We report incoming channel. If a second pair is granted in
                // mission control, this report is ignored.
                reportIncoming()

        // If the outgoing channel doesn't have enough capacity, we penalize.
        // But we penalize only in a single direction and only for amounts
        // greater than the attempted amount.
        case *lnwire.FailTemporaryChannelFailure:
                reportOutgoingBalance()

        // If FailExpiryTooSoon is received, there must have been some delay
        // along the path. We can't know which node is causing the delay, so we
        // penalize all of them up to the error source.
        //
        // Alternatively it could also be that we ourselves have fallen behind
        // somehow. We ignore that case for now.
        case *lnwire.FailExpiryTooSoon:
                reportAll()

        // We only expect to get FailInvalidBlinding from an introduction node
        // in a blinded route. The introduction node in a blinded route is
        // always responsible for reporting errors for the blinded portion of
        // the route (to protect the privacy of the members of the route), so
        // we need to be careful not to unfairly "shoot the messenger".
        //
        // The introduction node has no incentive to falsely report errors to
        // sabotage the blinded route because:
        //   1. Its ability to route this payment is strictly tied to the
        //      blinded route.
        //   2. The pubkeys in the blinded route are ephemeral, so doing so
        //      will have no impact on the nodes beyond the individual payment.
        //
        // Here we handle a few cases where we could unexpectedly receive this
        // error:
        // 1. Outside of a blinded route: erring node is not spec compliant.
        // 2. Before the introduction point: erring node is not spec compliant.
        //
        // Note that we expect the case where this error is sent from a node
        // after the introduction node to be handled elsewhere as this is part
        // of a more general class of errors where the introduction node has
        // failed to convert errors for the blinded route.
        case *lnwire.FailInvalidBlinding:
                introIdx, isBlinded := introductionPointIndex(route)

                // Deal with cases where a node has incorrectly returned a
                // blinding error:
                // 1. A node before the introduction point returned it.
                // 2. A node in a non-blinded route returned it.
                if errorSourceIdx < introIdx || !isBlinded {
                        reportNode()
                        return
                }

                // Otherwise, the error was at the introduction node. All
                // nodes up until the introduction node forwarded correctly,
                // so we award them as successful.
                if introIdx >= 1 {
                        i.successPairRange(route, 0, introIdx-1)
                }

                // If the hop after the introduction node that sent us an
                // error is the final recipient, then we finally fail the
                // payment because the receiver has generated a blinded route
                // that they're unable to use. We have this special case so
                // that we don't penalize the introduction node, and there is
                // no point in retrying the payment while LND only supports
                // one blinded route per payment.
                //
                // Note that if LND is extended to support multiple blinded
                // routes, this will terminate the payment without re-trying
                // the other routes.
                if introIdx == len(route.hops.Val)-1 {
                        i.finalFailureReason = &reasonError
                } else {
                        // We penalize the final hop of the blinded route which
                        // is sufficient to not reuse this route again and is
                        // also more memory efficient because the other hops
                        // of the blinded path are ephemeral and will only be
                        // used in conjunction with the final hop. Moreover we
                        // don't want to punish the introduction node because
                        // the blinded failure does not necessarily mean that
                        // the introduction node was at fault.
                        //
                        // TODO(ziggie): Make sure we only keep mc data for
                        // blinded paths, in both the success and failure case,
                        // in memory during the time of the payment and remove
                        // it afterwards. Blinded paths and their blinded hop
                        // keys are always changing per blinded route so there
                        // is no point in persisting this data.
                        i.failBlindedRoute(route)
                }

        // In all other cases, we penalize the reporting node. These are all
        // failures that should not happen.
        default:
                i.failNode(route, errorSourceIdx)
        }
}

// introductionPointIndex returns the index of an introduction point in a
// route, using the same indexing in the route that we use for errorSourceIdx
// (i.e., that we consider our own node to be at index zero). A boolean is
// returned to indicate whether the route contains a blinded portion at all.
func introductionPointIndex(route *mcRoute) (int, bool) {
        for i, hop := range route.hops.Val {
                if hop.hasBlindingPoint.IsSome() {
                        return i + 1, true
                }
        }

        return 0, false
}

// processPaymentOutcomeUnknown processes a payment outcome for which no failure
// message or source is available.
func (i *interpretedResult) processPaymentOutcomeUnknown(route *mcRoute) {
        n := len(route.hops.Val)

        // If this is a direct payment, the destination must be at fault.
        if n == 1 {
                i.failNode(route, n)
                i.finalFailureReason = &reasonError
                return
        }

        // Otherwise penalize all channels in the route to make sure the
        // responsible node is at least hit too. We even penalize the connection
        // to our own peer, because that peer could also be responsible.
        i.failPairRange(route, 0, n-1)
}

// extractMCRoute extracts the fields required by MC from the Route struct to
// create the more minimal mcRoute struct.
func extractMCRoute(r *route.Route) *mcRoute {
        return &mcRoute{
                sourcePubKey: tlv.NewRecordT[tlv.TlvType0](r.SourcePubKey),
                totalAmount:  tlv.NewRecordT[tlv.TlvType1](r.TotalAmount),
                hops: tlv.NewRecordT[tlv.TlvType2](
                        extractMCHops(r.Hops),
                ),
        }
}

// extractMCHops extracts the Hop fields that MC actually uses from a slice of
// Hops.
func extractMCHops(hops []*route.Hop) mcHops {
        return fn.Map(hops, extractMCHop)
}

// extractMCHop extracts the Hop fields that MC actually uses from a Hop.
func extractMCHop(hop *route.Hop) *mcHop {
        h := mcHop{
                channelID: tlv.NewPrimitiveRecord[tlv.TlvType0](
                        hop.ChannelID,
                ),
                pubKeyBytes: tlv.NewRecordT[tlv.TlvType1](hop.PubKeyBytes),
                amtToFwd:    tlv.NewRecordT[tlv.TlvType2](hop.AmtToForward),
        }

        if hop.BlindingPoint != nil {
                h.hasBlindingPoint = tlv.SomeRecordT(
                        tlv.NewRecordT[tlv.TlvType3](lnwire.TrueBoolean{}),
                )
        }

        if hop.CustomRecords != nil {
                h.hasCustomRecords = tlv.SomeRecordT(
                        tlv.NewRecordT[tlv.TlvType4](lnwire.TrueBoolean{}),
                )
        }

        return &h
}

// mcRoute holds the bare minimum info about a payment attempt route that MC
// requires.
type mcRoute struct {
        sourcePubKey tlv.RecordT[tlv.TlvType0, route.Vertex]
        totalAmount  tlv.RecordT[tlv.TlvType1, lnwire.MilliSatoshi]
        hops         tlv.RecordT[tlv.TlvType2, mcHops]
}

// Record returns a TLV record that can be used to encode/decode an mcRoute
// to/from a TLV stream.
func (r *mcRoute) Record() tlv.Record {
        recordSize := func() uint64 {
                var (
                        b   bytes.Buffer
                        buf [8]byte
                )
                if err := encodeMCRoute(&b, r, &buf); err != nil {
                        panic(err)
                }

                return uint64(len(b.Bytes()))
        }

        return tlv.MakeDynamicRecord(
                0, r, recordSize, encodeMCRoute, decodeMCRoute,
        )
}

func encodeMCRoute(w io.Writer, val interface{}, _ *[8]byte) error {
        if v, ok := val.(*mcRoute); ok {
                return serializeRoute(w, v)
        }

        return tlv.NewTypeForEncodingErr(val, "routing.mcRoute")
}

func decodeMCRoute(r io.Reader, val interface{}, _ *[8]byte, l uint64) error {
        if v, ok := val.(*mcRoute); ok {
                route, err := deserializeRoute(io.LimitReader(r, int64(l)))
                if err != nil {
                        return err
                }

                *v = *route

                return nil
        }

        return tlv.NewTypeForDecodingErr(val, "routing.mcRoute", l, l)
}

// mcHops is a list of mcHop records.
type mcHops []*mcHop

// Record returns a TLV record that can be used to encode/decode a list of
// mcHop to/from a TLV stream.
func (h *mcHops) Record() tlv.Record {
        recordSize := func() uint64 {
                var (
                        b   bytes.Buffer
                        buf [8]byte
                )
                if err := encodeMCHops(&b, h, &buf); err != nil {
                        panic(err)
                }

                return uint64(len(b.Bytes()))
        }

        return tlv.MakeDynamicRecord(
                0, h, recordSize, encodeMCHops, decodeMCHops,
        )
}

func encodeMCHops(w io.Writer, val interface{}, buf *[8]byte) error {
        if v, ok := val.(*mcHops); ok {
                // Encode the number of hops as a var int.
                if err := tlv.WriteVarInt(w, uint64(len(*v)), buf); err != nil {
                        return err
                }

                // With that written out, we'll now encode the entries
                // themselves as a sub-TLV record, which includes its _own_
                // inner length prefix.
                for _, hop := range *v {
                        var hopBytes bytes.Buffer
                        if err := serializeHop(&hopBytes, hop); err != nil {
                                return err
                        }

                        // We encode the record with a varint length followed by
                        // the _raw_ TLV bytes.
                        tlvLen := uint64(len(hopBytes.Bytes()))
                        if err := tlv.WriteVarInt(w, tlvLen, buf); err != nil {
                                return err
                        }

                        if _, err := w.Write(hopBytes.Bytes()); err != nil {
                                return err
                        }
                }

                return nil
        }

        return tlv.NewTypeForEncodingErr(val, "routing.mcHops")
}

func decodeMCHops(r io.Reader, val interface{}, buf *[8]byte, l uint64) error {
        if v, ok := val.(*mcHops); ok {
                // First, we'll decode the varint that encodes how many hops
                // are encoded in the stream.
                numHops, err := tlv.ReadVarInt(r, buf)
                if err != nil {
                        return err
                }

                // Now that we know how many records we'll need to read, we can
                // iterate and read them all out in series.
                for i := uint64(0); i < numHops; i++ {
                        // Read out the varint that encodes the size of this
                        // inner TLV record.
                        hopSize, err := tlv.ReadVarInt(r, buf)
                        if err != nil {
                                return err
                        }

                        // Using this information, we'll create a new limited
                        // reader that'll return an EOF once the end has been
                        // reached so the stream stops consuming bytes.
                        innerTlvReader := &io.LimitedReader{
                                R: r,
                                N: int64(hopSize),
                        }

                        hop, err := deserializeHop(innerTlvReader)
                        if err != nil {
                                return err
                        }

                        *v = append(*v, hop)
                }

                return nil
        }

        return tlv.NewTypeForDecodingErr(val, "routing.mcHops", l, l)
}

// mcHop holds the bare minimum info about a payment attempt route hop that MC
// requires.
type mcHop struct {
        channelID        tlv.RecordT[tlv.TlvType0, uint64]
        pubKeyBytes      tlv.RecordT[tlv.TlvType1, route.Vertex]
        amtToFwd         tlv.RecordT[tlv.TlvType2, lnwire.MilliSatoshi]
        hasBlindingPoint tlv.OptionalRecordT[tlv.TlvType3, lnwire.TrueBoolean]
        hasCustomRecords tlv.OptionalRecordT[tlv.TlvType4, lnwire.TrueBoolean]
}

// failNode marks the node indicated by idx in the route as failed. It also
// marks the incoming and outgoing channels of the node as failed. This function
// intentionally panics when the self node is failed.
func (i *interpretedResult) failNode(rt *mcRoute, idx int) {
        // Mark the node as failing.
        i.nodeFailure = &rt.hops.Val[idx-1].pubKeyBytes.Val

        // Mark the incoming connection as failed for the node. We intent to
        // penalize as much as we can for a node level failure, including future
        // outgoing traffic for this connection. The pair as it is returned by
        // getPair is penalized in the original and the reversed direction. Note
        // that this will also affect the score of the failing node's peers.
        // This is necessary to prevent future routes from keep going into the
        // same node again.
        incomingChannelIdx := idx - 1
        inPair, _ := getPair(rt, incomingChannelIdx)
        i.pairResults[inPair] = failPairResult(0)
        i.pairResults[inPair.Reverse()] = failPairResult(0)

        // If not the ultimate node, mark the outgoing connection as failed for
        // the node.
        if idx < len(rt.hops.Val) {
                outgoingChannelIdx := idx
                outPair, _ := getPair(rt, outgoingChannelIdx)
                i.pairResults[outPair] = failPairResult(0)
                i.pairResults[outPair.Reverse()] = failPairResult(0)
        }
}

// failPairRange marks the node pairs from node fromIdx to node toIdx as failed
// in both direction.
func (i *interpretedResult) failPairRange(rt *mcRoute, fromIdx, toIdx int) {
        for idx := fromIdx; idx <= toIdx; idx++ {
                i.failPair(rt, idx)
        }
}

// failPair marks a pair as failed in both directions.
func (i *interpretedResult) failPair(rt *mcRoute, idx int) {
        pair, _ := getPair(rt, idx)

        // Report pair in both directions without a minimum penalization amount.
        i.pairResults[pair] = failPairResult(0)
        i.pairResults[pair.Reverse()] = failPairResult(0)
}

// failPairBalance marks a pair as failed with a minimum penalization amount.
func (i *interpretedResult) failPairBalance(rt *mcRoute, channelIdx int) {
        pair, amt := getPair(rt, channelIdx)

        i.pairResults[pair] = failPairResult(amt)
}

// successPairRange marks the node pairs from node fromIdx to node toIdx as
// succeeded.
func (i *interpretedResult) successPairRange(rt *mcRoute, fromIdx, toIdx int) {
        for idx := fromIdx; idx <= toIdx; idx++ {
                pair, amt := getPair(rt, idx)

                i.pairResults[pair] = successPairResult(amt)
        }
}

// failBlindedRoute marks a blinded route as failed for the specific amount to
// send by only punishing the last pair.
func (i *interpretedResult) failBlindedRoute(rt *mcRoute) {
        // We fail the last pair of the route, in order to fail the complete
        // blinded route. This is because the combination of ephemeral pubkeys
        // is unique to the route. We fail the last pair in order to not punish
        // the introduction node, since we don't want to disincentivize them
        // from providing that service.
        pair, _ := getPair(rt, len(rt.hops.Val)-1)

        // Since all the hops along a blinded path don't have any amount set, we
        // extract the minimal amount to punish from the value that is tried to
        // be sent to the receiver.
        amt := rt.hops.Val[len(rt.hops.Val)-1].amtToFwd.Val

        i.pairResults[pair] = failPairResult(amt)
}

// markBlindedRouteSuccess marks the hops of the blinded route AFTER the
// introduction node as successful.
//
// NOTE: The introIdx must be the index of the first hop of the blinded route
// AFTER the introduction node.
func (i *interpretedResult) markBlindedRouteSuccess(rt *mcRoute, introIdx int) {
        // For blinded hops we do not have the forwarding amount so we take the
        // minimal amount which went through the route by looking at the last
        // hop.
        successAmt := rt.hops.Val[len(rt.hops.Val)-1].amtToFwd.Val
        for idx := introIdx; idx < len(rt.hops.Val); idx++ {
                pair, _ := getPair(rt, idx)

                i.pairResults[pair] = successPairResult(successAmt)
        }
}

// getPair returns a node pair from the route and the amount passed between that
// pair.
func getPair(rt *mcRoute, channelIdx int) (DirectedNodePair,
        lnwire.MilliSatoshi) {

        nodeTo := rt.hops.Val[channelIdx].pubKeyBytes.Val
        var (
                nodeFrom route.Vertex
                amt      lnwire.MilliSatoshi
        )

        if channelIdx == 0 {
                nodeFrom = rt.sourcePubKey.Val
                amt = rt.totalAmount.Val
        } else {
                nodeFrom = rt.hops.Val[channelIdx-1].pubKeyBytes.Val
                amt = rt.hops.Val[channelIdx-1].amtToFwd.Val
        }

        pair := NewDirectedNodePair(nodeFrom, nodeTo)

        return pair, amt
}

lightningnetwork / lnd / 13586005509

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