13566028875

Committed 27 Feb 2025 12:09PM UTC coverage: 49.396% (-9.4%) from 58.748%

Build # 13566028875

Build Type

Pull #9555

github

Committed by

ellemouton

Commit Message

graph/db: populate the graph cache in Start instead of during construction

In this commit, we move the graph cache population logic out of the
ChannelGraph constructor and into its Start method instead.

Pull Request Pull Request #9555: graph: extract cache from CRUD [6]

Run Details

34 of 54 new or added lines in 4 files covered. (62.96%)

27464 existing lines in 436 files now uncovered.

101095 of 204664 relevant lines covered (49.4%)

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Source File
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71.62

/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 / 13566028875

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