12320026784

Committed 13 Dec 2024 05:14PM UTC coverage: 57.562% (-1.1%) from 58.636%

Build # 12320026784

Build Type

Pull #9315

github

Committed by

web-flow

Commit Message

Merge pull request #9277 from yyforyongyu/yy-blockbeat-end

Beat [4/4]: implement `Consumer` in `chainWatcher`

Pull Request Pull Request #9315: Implement `blockbeat`

Run Details

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71.91

/contractcourt/htlc_incoming_contest_resolver.go

package contractcourt

import (
        "bytes"
        "encoding/binary"
        "errors"
        "fmt"
        "io"

        "github.com/btcsuite/btcd/btcutil"
        "github.com/btcsuite/btcd/txscript"
        "github.com/lightningnetwork/lnd/channeldb"
        "github.com/lightningnetwork/lnd/fn/v2"
        "github.com/lightningnetwork/lnd/graph/db/models"
        "github.com/lightningnetwork/lnd/htlcswitch/hop"
        "github.com/lightningnetwork/lnd/invoices"
        "github.com/lightningnetwork/lnd/lntypes"
        "github.com/lightningnetwork/lnd/lnwallet"
        "github.com/lightningnetwork/lnd/lnwire"
        "github.com/lightningnetwork/lnd/queue"
)

// htlcIncomingContestResolver is a ContractResolver that's able to resolve an
// incoming HTLC that is still contested. An HTLC is still contested, if at the
// time of commitment broadcast, we don't know of the preimage for it yet, and
// it hasn't expired. In this case, we can resolve the HTLC if we learn of the
// preimage, otherwise the remote party will sweep it after it expires.
//
// TODO(roasbeef): just embed the other resolver?
type htlcIncomingContestResolver struct {
        // htlcExpiry is the absolute expiry of this incoming HTLC. We use this
        // value to determine if we can exit early as if the HTLC times out,
        // before we learn of the preimage then we can't claim it on chain
        // successfully.
        htlcExpiry uint32

        // htlcSuccessResolver is the inner resolver that may be utilized if we
        // learn of the preimage.
        *htlcSuccessResolver
}

// newIncomingContestResolver instantiates a new incoming htlc contest resolver.
func newIncomingContestResolver(
        res lnwallet.IncomingHtlcResolution, broadcastHeight uint32,
        htlc channeldb.HTLC, resCfg ResolverConfig) *htlcIncomingContestResolver {

        success := newSuccessResolver(
                res, broadcastHeight, htlc, resCfg,
        )

        return &htlcIncomingContestResolver{
                htlcExpiry:          htlc.RefundTimeout,
                htlcSuccessResolver: success,
        }
}

func (h *htlcIncomingContestResolver) processFinalHtlcFail() error {
        // Mark the htlc as final failed.
        err := h.ChainArbitratorConfig.PutFinalHtlcOutcome(
                h.ChannelArbitratorConfig.ShortChanID, h.htlc.HtlcIndex, false,
        )
        if err != nil {
                return err
        }

        // Send notification.
        h.ChainArbitratorConfig.HtlcNotifier.NotifyFinalHtlcEvent(
                models.CircuitKey{
                        ChanID: h.ShortChanID,
                        HtlcID: h.htlc.HtlcIndex,
                },
                channeldb.FinalHtlcInfo{
                        Settled:  false,
                        Offchain: false,
                },
        )

        return nil
}

// Launch will call the inner resolver's launch method if the preimage can be
// found, otherwise it's a no-op.
func (h *htlcIncomingContestResolver) Launch() error {
        // NOTE: we don't mark this resolver as launched as the inner resolver
        // will set it when it's launched.
        if h.isLaunched() {
                h.log.Tracef("already launched")
                return nil
        }

        h.log.Debugf("launching contest resolver...")

        // Query the preimage and apply it if we already know it.
        applied, err := h.findAndapplyPreimage()
        if err != nil {
                return err
        }

        // No preimage found, leave it to be handled by the resolver.
        if !applied {
                return nil
        }

        h.log.Debugf("found preimage for htlc=%x,  transforming into success "+
                "resolver and launching it", h.htlc.RHash)

        // Once we've applied the preimage, we'll launch the inner resolver to
        // attempt to claim the HTLC.
        return h.htlcSuccessResolver.Launch()
}

// Resolve attempts to resolve this contract. As we don't yet know of the
// preimage for the contract, we'll wait for one of two things to happen:
//
//  1. We learn of the preimage! In this case, we can sweep the HTLC incoming
//     and ensure that if this was a multi-hop HTLC we are made whole. In this
//     case, an additional ContractResolver will be returned to finish the
//     job.
//
//  2. The HTLC expires. If this happens, then the contract is fully resolved
//     as we have no remaining actions left at our disposal.
//
// NOTE: Part of the ContractResolver interface.
func (h *htlcIncomingContestResolver) Resolve() (ContractResolver, error) {
        // If we're already full resolved, then we don't have anything further
        // to do.
        if h.IsResolved() {
                h.log.Errorf("already resolved")
                return nil, nil
        }

        // First try to parse the payload. If that fails, we can stop resolution
        // now.
        payload, nextHopOnionBlob, err := h.decodePayload()
        if err != nil {
                h.log.Debugf("cannot decode payload of htlc %v", h.HtlcPoint())

                // If we've locked in an htlc with an invalid payload on our
                // commitment tx, we don't need to resolve it. The other party
                // will time it out and get their funds back. This situation
                // can present itself when we crash before processRemoteAdds in
                // the link has ran.
                h.markResolved()

                if err := h.processFinalHtlcFail(); err != nil {
                        return nil, err
                }

                // We write a report to disk that indicates we could not decode
                // the htlc.
                resReport := h.report().resolverReport(
                        nil, channeldb.ResolverTypeIncomingHtlc,
                        channeldb.ResolverOutcomeAbandoned,
                )
                return nil, h.PutResolverReport(nil, resReport)
        }

        // Register for block epochs. After registration, the current height
        // will be sent on the channel immediately.
        blockEpochs, err := h.Notifier.RegisterBlockEpochNtfn(nil)
        if err != nil {
                return nil, err
        }
        defer blockEpochs.Cancel()

        var currentHeight int32
        select {
        case newBlock, ok := <-blockEpochs.Epochs:
                if !ok {
                        return nil, errResolverShuttingDown
                }
                currentHeight = newBlock.Height
        case <-h.quit:
                return nil, errResolverShuttingDown
        }

        log.Debugf("%T(%v): Resolving incoming HTLC(expiry=%v, height=%v)", h,
                h.htlcResolution.ClaimOutpoint, h.htlcExpiry, currentHeight)

        // We'll first check if this HTLC has been timed out, if so, we can
        // return now and mark ourselves as resolved. If we're past the point of
        // expiry of the HTLC, then at this point the sender can sweep it, so
        // we'll end our lifetime. Here we deliberately forego the chance that
        // the sender doesn't sweep and we already have or will learn the
        // preimage. Otherwise the resolver could potentially stay active
        // indefinitely and the channel will never close properly.
        if uint32(currentHeight) >= h.htlcExpiry {
                // TODO(roasbeef): should also somehow check if outgoing is
                // resolved or not
                //  * may need to hook into the circuit map
                //  * can't timeout before the outgoing has been

                log.Infof("%T(%v): HTLC has timed out (expiry=%v, height=%v), "+
                        "abandoning", h, h.htlcResolution.ClaimOutpoint,
                        h.htlcExpiry, currentHeight)
                h.markResolved()

                if err := h.processFinalHtlcFail(); err != nil {
                        return nil, err
                }

                // Finally, get our report and checkpoint our resolver with a
                // timeout outcome report.
                report := h.report().resolverReport(
                        nil, channeldb.ResolverTypeIncomingHtlc,
                        channeldb.ResolverOutcomeTimeout,
                )
                return nil, h.Checkpoint(h, report)
        }

        // Define a closure to process htlc resolutions either directly or
        // triggered by future notifications.
        processHtlcResolution := func(e invoices.HtlcResolution) (
                ContractResolver, error) {

                // Take action based on the type of resolution we have
                // received.
                switch resolution := e.(type) {
                // If the htlc resolution was a settle, apply the
                // preimage and return a success resolver.
                case *invoices.HtlcSettleResolution:
                        err := h.applyPreimage(resolution.Preimage)
                        if err != nil {
                                return nil, err
                        }

                        return h.htlcSuccessResolver, nil

                // If the htlc was failed, mark the htlc as
                // resolved.
                case *invoices.HtlcFailResolution:
                        log.Infof("%T(%v): Exit hop HTLC canceled "+
                                "(expiry=%v, height=%v), abandoning", h,
                                h.htlcResolution.ClaimOutpoint,
                                h.htlcExpiry, currentHeight)

                        h.markResolved()

                        if err := h.processFinalHtlcFail(); err != nil {
                                return nil, err
                        }

                        // Checkpoint our resolver with an abandoned outcome
                        // because we take no further action on this htlc.
                        report := h.report().resolverReport(
                                nil, channeldb.ResolverTypeIncomingHtlc,
                                channeldb.ResolverOutcomeAbandoned,
                        )
                        return nil, h.Checkpoint(h, report)

                // Error if the resolution type is unknown, we are only
                // expecting settles and fails.
                default:
                        return nil, fmt.Errorf("unknown resolution"+
                                " type: %v", e)
                }
        }

        var (
                hodlChan       <-chan interface{}
                witnessUpdates <-chan lntypes.Preimage
        )
        if payload.FwdInfo.NextHop == hop.Exit {
                // Create a buffered hodl chan to prevent deadlock.
                hodlQueue := queue.NewConcurrentQueue(10)
                hodlQueue.Start()

                hodlChan = hodlQueue.ChanOut()

                // Notify registry that we are potentially resolving as an exit
                // hop on-chain. If this HTLC indeed pays to an existing
                // invoice, the invoice registry will tell us what to do with
                // the HTLC. This is identical to HTLC resolution in the link.
                circuitKey := models.CircuitKey{
                        ChanID: h.ShortChanID,
                        HtlcID: h.htlc.HtlcIndex,
                }

                resolution, err := h.Registry.NotifyExitHopHtlc(
                        h.htlc.RHash, h.htlc.Amt, h.htlcExpiry, currentHeight,
                        circuitKey, hodlQueue.ChanIn(), nil, payload,
                )
                if err != nil {
                        return nil, err
                }

                h.log.Debugf("received resolution from registry: %v",
                        resolution)

                defer func() {
                        h.Registry.HodlUnsubscribeAll(hodlQueue.ChanIn())

                        hodlQueue.Stop()
                }()

                // Take action based on the resolution we received. If the htlc
                // was settled, or a htlc for a known invoice failed we can
                // resolve it directly. If the resolution is nil, the htlc was
                // neither accepted nor failed, so we cannot take action yet.
                switch res := resolution.(type) {
                case *invoices.HtlcFailResolution:
                        // In the case where the htlc failed, but the invoice
                        // was known to the registry, we can directly resolve
                        // the htlc.
                        if res.Outcome != invoices.ResultInvoiceNotFound {
                                return processHtlcResolution(resolution)
                        }

                // If we settled the htlc, we can resolve it.
                case *invoices.HtlcSettleResolution:
                        return processHtlcResolution(resolution)

                // If the resolution is nil, the htlc was neither settled nor
                // failed so we cannot take action at present.
                case nil:

                default:
                        return nil, fmt.Errorf("unknown htlc resolution type: %T",
                                resolution)
                }
        } else {
                // If the HTLC hasn't expired yet, then we may still be able to
                // claim it if we learn of the pre-image, so we'll subscribe to
                // the preimage database to see if it turns up, or the HTLC
                // times out.
                //
                // NOTE: This is done BEFORE opportunistically querying the db,
                // to ensure the preimage can't be delivered between querying
                // and registering for the preimage subscription.
                preimageSubscription, err := h.PreimageDB.SubscribeUpdates(
                        h.htlcSuccessResolver.ShortChanID, &h.htlc,
                        payload, nextHopOnionBlob,
                )
                if err != nil {
                        return nil, err
                }
                defer preimageSubscription.CancelSubscription()

                // With the epochs and preimage subscriptions initialized, we'll
                // query to see if we already know the preimage.
                preimage, ok := h.PreimageDB.LookupPreimage(h.htlc.RHash)
                if ok {
                        // If we do, then this means we can claim the HTLC!
                        // However, we don't know how to ourselves, so we'll
                        // return our inner resolver which has the knowledge to
                        // do so.
                        h.log.Debugf("Found preimage for htlc=%x", h.htlc.RHash)

                        if err := h.applyPreimage(preimage); err != nil {
                                return nil, err
                        }

                        return h.htlcSuccessResolver, nil
                }

                witnessUpdates = preimageSubscription.WitnessUpdates
        }

        for {
                select {
                case preimage := <-witnessUpdates:
                        // We received a new preimage, but we need to ignore
                        // all except the preimage we are waiting for.
                        if !preimage.Matches(h.htlc.RHash) {
                                continue
                        }

                        h.log.Debugf("Received preimage for htlc=%x",
                                h.htlc.RHash)

                        if err := h.applyPreimage(preimage); err != nil {
                                return nil, err
                        }

                        // We've learned of the preimage and this information
                        // has been added to our inner resolver. We return it so
                        // it can continue contract resolution.
                        return h.htlcSuccessResolver, nil

                case hodlItem := <-hodlChan:
                        htlcResolution := hodlItem.(invoices.HtlcResolution)
                        return processHtlcResolution(htlcResolution)

                case newBlock, ok := <-blockEpochs.Epochs:
                        if !ok {
                                return nil, errResolverShuttingDown
                        }

                        // If this new height expires the HTLC, then this means
                        // we never found out the preimage, so we can mark
                        // resolved and exit.
                        newHeight := uint32(newBlock.Height)
                        if newHeight >= h.htlcExpiry {
                                log.Infof("%T(%v): HTLC has timed out "+
                                        "(expiry=%v, height=%v), abandoning", h,
                                        h.htlcResolution.ClaimOutpoint,
                                        h.htlcExpiry, currentHeight)

                                h.markResolved()

                                if err := h.processFinalHtlcFail(); err != nil {
                                        return nil, err
                                }

                                report := h.report().resolverReport(
                                        nil,
                                        channeldb.ResolverTypeIncomingHtlc,
                                        channeldb.ResolverOutcomeTimeout,
                                )
                                return nil, h.Checkpoint(h, report)
                        }

                case <-h.quit:
                        return nil, errResolverShuttingDown
                }
        }
}

// applyPreimage is a helper function that will populate our internal resolver
// with the preimage we learn of. This should be called once the preimage is
// revealed so the inner resolver can properly complete its duties. The error
// return value indicates whether the preimage was properly applied.
func (h *htlcIncomingContestResolver) applyPreimage(
        preimage lntypes.Preimage) error {

        // Sanity check to see if this preimage matches our htlc. At this point
        // it should never happen that it does not match.
        if !preimage.Matches(h.htlc.RHash) {
                return errors.New("preimage does not match hash")
        }

        // We may already have the preimage since both the `Launch` and
        // `Resolve` methods will look for it.
        if h.htlcResolution.Preimage != lntypes.ZeroHash {
                h.log.Debugf("already applied preimage for htlc=%x",
                        h.htlc.RHash)

                return nil
        }

        // Update htlcResolution with the matching preimage.
        h.htlcResolution.Preimage = preimage

        log.Infof("%T(%v): applied preimage=%v", h,
                h.htlcResolution.ClaimOutpoint, preimage)

        isSecondLevel := h.htlcResolution.SignedSuccessTx != nil

        // If we didn't have to go to the second level to claim (this
        // is the remote commitment transaction), then we don't need to
        // modify our canned witness.
        if !isSecondLevel {
                return nil
        }

        isTaproot := txscript.IsPayToTaproot(
                h.htlcResolution.SignedSuccessTx.TxOut[0].PkScript,
        )

        // If this is our commitment transaction, then we'll need to
        // populate the witness for the second-level HTLC transaction.
        switch {
        // For taproot channels, the witness for sweeping with success
        // looks like:
        //   - <sender sig> <receiver sig> <preimage> <success_script>
        //     <control_block>
        //
        // So we'll insert it at the 3rd index of the witness.
        case isTaproot:
                //nolint:ll
                h.htlcResolution.SignedSuccessTx.TxIn[0].Witness[2] = preimage[:]

        // Within the witness for the success transaction, the
        // preimage is the 4th element as it looks like:
        //
        //  * <0> <sender sig> <recvr sig> <preimage> <witness script>
        //
        // We'll populate it within the witness, as since this
        // was a "contest" resolver, we didn't yet know of the
        // preimage.
        case !isTaproot:
                //nolint:ll
                h.htlcResolution.SignedSuccessTx.TxIn[0].Witness[3] = preimage[:]
        }

        return nil
}

// report returns a report on the resolution state of the contract.
func (h *htlcIncomingContestResolver) report() *ContractReport {
        // No locking needed as these values are read-only.

        finalAmt := h.htlc.Amt.ToSatoshis()
        if h.htlcResolution.SignedSuccessTx != nil {
                finalAmt = btcutil.Amount(
                        h.htlcResolution.SignedSuccessTx.TxOut[0].Value,
                )
        }

        return &ContractReport{
                Outpoint:       h.htlcResolution.ClaimOutpoint,
                Type:           ReportOutputIncomingHtlc,
                Amount:         finalAmt,
                MaturityHeight: h.htlcExpiry,
                LimboBalance:   finalAmt,
                Stage:          1,
        }
}

// Stop signals the resolver to cancel any current resolution processes, and
// suspend.
//
// NOTE: Part of the ContractResolver interface.
func (h *htlcIncomingContestResolver) Stop() {
        h.log.Debugf("stopping...")
        defer h.log.Debugf("stopped")
        close(h.quit)
}

// Encode writes an encoded version of the ContractResolver into the passed
// Writer.
//
// NOTE: Part of the ContractResolver interface.
func (h *htlcIncomingContestResolver) Encode(w io.Writer) error {
        // We'll first write out the one field unique to this resolver.
        if err := binary.Write(w, endian, h.htlcExpiry); err != nil {
                return err
        }

        // Then we'll write out our internal resolver.
        return h.htlcSuccessResolver.Encode(w)
}

// newIncomingContestResolverFromReader attempts to decode an encoded ContractResolver
// from the passed Reader instance, returning an active ContractResolver
// instance.
func newIncomingContestResolverFromReader(r io.Reader, resCfg ResolverConfig) (
        *htlcIncomingContestResolver, error) {

        h := &htlcIncomingContestResolver{}

        // We'll first read the one field unique to this resolver.
        if err := binary.Read(r, endian, &h.htlcExpiry); err != nil {
                return nil, err
        }

        // Then we'll decode our internal resolver.
        successResolver, err := newSuccessResolverFromReader(r, resCfg)
        if err != nil {
                return nil, err
        }
        h.htlcSuccessResolver = successResolver

        return h, nil
}

// Supplement adds additional information to the resolver that is required
// before Resolve() is called.
//
// NOTE: Part of the htlcContractResolver interface.
func (h *htlcIncomingContestResolver) Supplement(htlc channeldb.HTLC) {
        h.htlc = htlc
}

// SupplementDeadline does nothing for an incoming htlc resolver.
//
// NOTE: Part of the htlcContractResolver interface.
func (h *htlcIncomingContestResolver) SupplementDeadline(_ fn.Option[int32]) {
}

// decodePayload (re)decodes the hop payload of a received htlc.
func (h *htlcIncomingContestResolver) decodePayload() (*hop.Payload,
        []byte, error) {

        blindingInfo := hop.ReconstructBlindingInfo{
                IncomingAmt:    h.htlc.Amt,
                IncomingExpiry: h.htlc.RefundTimeout,
                BlindingKey:    h.htlc.BlindingPoint,
        }

        onionReader := bytes.NewReader(h.htlc.OnionBlob[:])
        iterator, err := h.OnionProcessor.ReconstructHopIterator(
                onionReader, h.htlc.RHash[:], blindingInfo,
        )
        if err != nil {
                return nil, nil, err
        }

        payload, _, err := iterator.HopPayload()
        if err != nil {
                return nil, nil, err
        }

        // Transform onion blob for the next hop.
        var onionBlob [lnwire.OnionPacketSize]byte
        buf := bytes.NewBuffer(onionBlob[0:0])
        err = iterator.EncodeNextHop(buf)
        if err != nil {
                return nil, nil, err
        }

        return payload, onionBlob[:], nil
}

// A compile time assertion to ensure htlcIncomingContestResolver meets the
// ContractResolver interface.
var _ htlcContractResolver = (*htlcIncomingContestResolver)(nil)

// findAndapplyPreimage performs a non-blocking read to find the preimage for
// the incoming HTLC. If found, it will be applied to the resolver. This method
// is used for the resolver to decide whether it wants to transform into a
// success resolver during launching.
//
// NOTE: Since we have two places to query the preimage, we need to check both
// the preimage db and the invoice db to look up the preimage.
func (h *htlcIncomingContestResolver) findAndapplyPreimage() (bool, error) {
        // Query to see if we already know the preimage.
        preimage, ok := h.PreimageDB.LookupPreimage(h.htlc.RHash)

        // If the preimage is known, we'll apply it.
        if ok {
                if err := h.applyPreimage(preimage); err != nil {
                        return false, err
                }

                // Successfully applied the preimage, we can now return.
                return true, nil
        }

        // First try to parse the payload.
        payload, _, err := h.decodePayload()
        if err != nil {
                h.log.Errorf("Cannot decode payload of htlc %v", h.HtlcPoint())

                // If we cannot decode the payload, we will return a nil error
                // and let it to be handled in `Resolve`.
                return false, nil
        }

        // Exit early if this is not the exit hop, which means we are not the
        // payment receiver and don't have preimage.
        if payload.FwdInfo.NextHop != hop.Exit {
                return false, nil
        }

        // Notify registry that we are potentially resolving as an exit hop
        // on-chain. If this HTLC indeed pays to an existing invoice, the
        // invoice registry will tell us what to do with the HTLC. This is
        // identical to HTLC resolution in the link.
        circuitKey := models.CircuitKey{
                ChanID: h.ShortChanID,
                HtlcID: h.htlc.HtlcIndex,
        }

        // Try get the resolution - if it doesn't give us a resolution
        // immediately, we'll assume we don't know it yet and let the `Resolve`
        // handle the waiting.
        //
        // NOTE: we use a nil subscriber here and a zero current height as we
        // are only interested in the settle resolution.
        //
        // TODO(yy): move this logic to link and let the preimage be accessed
        // via the preimage beacon.
        resolution, err := h.Registry.NotifyExitHopHtlc(
                h.htlc.RHash, h.htlc.Amt, h.htlcExpiry, 0,
                circuitKey, nil, nil, payload,
        )
        if err != nil {
                return false, err
        }

        res, ok := resolution.(*invoices.HtlcSettleResolution)

        // Exit early if it's not a settle resolution.
        if !ok {
                return false, nil
        }

        // Otherwise we have a settle resolution, apply the preimage.
        err = h.applyPreimage(res.Preimage)
        if err != nil {
                return false, err
        }

        return true, nil
}

lightningnetwork / lnd / 12320026784

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