9111774206

package channeldb

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

        "github.com/lightningnetwork/lnd/kvdb"
        "github.com/lightningnetwork/lnd/lnwire"
)

// ErrCorruptedFwdPkg signals that the on-disk structure of the forwarding
// package has potentially been mangled.
var ErrCorruptedFwdPkg = errors.New("fwding package db has been corrupted")

// FwdState is an enum used to describe the lifecycle of a FwdPkg.
type FwdState byte

const (
        // FwdStateLockedIn is the starting state for all forwarding packages.
        // Packages in this state have not yet committed to the exact set of
        // Adds to forward to the switch.
        FwdStateLockedIn FwdState = iota

        // FwdStateProcessed marks the state in which all Adds have been
        // locally processed and the forwarding decision to the switch has been
        // persisted.
        FwdStateProcessed

        // FwdStateCompleted signals that all Adds have been acked, and that all
        // settles and fails have been delivered to their sources. Packages in
        // this state can be removed permanently.
        FwdStateCompleted
)

var (
        // fwdPackagesKey is the root-level bucket that all forwarding packages
        // are written. This bucket is further subdivided based on the short
        // channel ID of each channel.
        //
        // Bucket hierarchy:
        //
        // fwdPackagesKey(root-bucket)
        //             |
        //             |-- <shortChannelID>
        //             |       |
        //             |       |-- <height>
        //             |       |       |-- ackFilterKey: <encoded bytes of PkgFilter>
        //             |       |       |-- settleFailFilterKey: <encoded bytes of PkgFilter>
        //             |       |       |-- fwdFilterKey: <encoded bytes of PkgFilter>
        //             |       |       |
        //             |       |       |-- addBucketKey
        //             |       |       |        |-- <index of LogUpdate>: <encoded bytes of LogUpdate>
        //             |       |       |        |-- <index of LogUpdate>: <encoded bytes of LogUpdate>
        //             |       |       |        ...
        //             |       |       |
        //             |       |       |-- failSettleBucketKey
        //             |       |                |-- <index of LogUpdate>: <encoded bytes of LogUpdate>
        //             |       |                |-- <index of LogUpdate>: <encoded bytes of LogUpdate>
        //             |       |                ...
        //             |       |
        //             |       |-- <height>
        //             |       |       |
        //             |       ...     ...
        //             |
        //             |
        //             |-- <shortChannelID>
        //             |       |
        //        |       ...
        //         ...
        //
        fwdPackagesKey = []byte("fwd-packages")

        // addBucketKey is the bucket to which all Add log updates are written.
        addBucketKey = []byte("add-updates")

        // failSettleBucketKey is the bucket to which all Settle/Fail log
        // updates are written.
        failSettleBucketKey = []byte("fail-settle-updates")

        // fwdFilterKey is a key used to write the set of Adds that passed
        // validation and are to be forwarded to the switch.
        // NOTE: The presence of this key within a forwarding package indicates
        // that the package has reached FwdStateProcessed.
        fwdFilterKey = []byte("fwd-filter-key")

        // ackFilterKey is a key used to access the PkgFilter indicating which
        // Adds have received a Settle/Fail. This response may come from a
        // number of sources, including: exitHop settle/fails, switch failures,
        // chain arbiter interjections, as well as settle/fails from the
        // next hop in the route.
        ackFilterKey = []byte("ack-filter-key")

        // settleFailFilterKey is a key used to access the PkgFilter indicating
        // which Settles/Fails in have been received and processed by the link
        // that originally received the Add.
        settleFailFilterKey = []byte("settle-fail-filter-key")
)

// PkgFilter is used to compactly represent a particular subset of the Adds in a
// forwarding package. Each filter is represented as a simple, statically-sized
// bitvector, where the elements are intended to be the indices of the Adds as
// they are written in the FwdPkg.
type PkgFilter struct {
        count  uint16
        filter []byte
}

// NewPkgFilter initializes an empty PkgFilter supporting `count` elements.
func NewPkgFilter(count uint16) *PkgFilter {
        // We add 7 to ensure that the integer division yields properly rounded
        // values.
        filterLen := (count + 7) / 8

        return &PkgFilter{
                count:  count,
                filter: make([]byte, filterLen),
        }
}

// Count returns the number of elements represented by this PkgFilter.
func (f *PkgFilter) Count() uint16 {
        return f.count
}

// Set marks the `i`-th element as included by this filter.
// NOTE: It is assumed that i is always less than count.
func (f *PkgFilter) Set(i uint16) {
        byt := i / 8
        bit := i % 8

        // Set the i-th bit in the filter.
        // TODO(conner): ignore if > count to prevent panic?
        f.filter[byt] |= byte(1 << (7 - bit))
}

// Contains queries the filter for membership of index `i`.
// NOTE: It is assumed that i is always less than count.
func (f *PkgFilter) Contains(i uint16) bool {
        byt := i / 8
        bit := i % 8

        // Read the i-th bit in the filter.
        // TODO(conner): ignore if > count to prevent panic?
        return f.filter[byt]&(1<<(7-bit)) != 0
}

// Equal checks two PkgFilters for equality.
func (f *PkgFilter) Equal(f2 *PkgFilter) bool {
        if f == f2 {
                return true
        }
        if f.count != f2.count {
                return false
        }

        return bytes.Equal(f.filter, f2.filter)
}

// IsFull returns true if every element in the filter has been Set, and false
// otherwise.
func (f *PkgFilter) IsFull() bool {
        // Batch validate bytes that are fully used.
        for i := uint16(0); i < f.count/8; i++ {
                if f.filter[i] != 0xFF {
                        return false
                }
        }

        // If the count is not a multiple of 8, check that the filter contains
        // all remaining bits.
        rem := f.count % 8
        for idx := f.count - rem; idx < f.count; idx++ {
                if !f.Contains(idx) {
                        return false
                }
        }

        return true
}

// Size returns number of bytes produced when the PkgFilter is serialized.
func (f *PkgFilter) Size() uint16 {
        // 2 bytes for uint16 `count`, then round up number of bytes required to
        // represent `count` bits.
        return 2 + (f.count+7)/8
}

// Encode writes the filter to the provided io.Writer.
func (f *PkgFilter) Encode(w io.Writer) error {
        if err := binary.Write(w, binary.BigEndian, f.count); err != nil {
                return err
        }

        _, err := w.Write(f.filter)

        return err
}

// Decode reads the filter from the provided io.Reader.
func (f *PkgFilter) Decode(r io.Reader) error {
        if err := binary.Read(r, binary.BigEndian, &f.count); err != nil {
                return err
        }

        f.filter = make([]byte, f.Size()-2)
        _, err := io.ReadFull(r, f.filter)

        return err
}

// FwdPkg records all adds, settles, and fails that were locked in as a result
// of the remote peer sending us a revocation. Each package is identified by
// the short chanid and remote commitment height corresponding to the revocation
// that locked in the HTLCs. For everything except a locally initiated payment,
// settles and fails in a forwarding package must have a corresponding Add in
// another package, and can be removed individually once the source link has
// received the fail/settle.
//
// Adds cannot be removed, as we need to present the same batch of Adds to
// properly handle replay protection. Instead, we use a PkgFilter to mark that
// we have finished processing a particular Add. A FwdPkg should only be deleted
// after the AckFilter is full and all settles and fails have been persistently
// removed.
type FwdPkg struct {
        // Source identifies the channel that wrote this forwarding package.
        Source lnwire.ShortChannelID

        // Height is the height of the remote commitment chain that locked in
        // this forwarding package.
        Height uint64

        // State signals the persistent condition of the package and directs how
        // to reprocess the package in the event of failures.
        State FwdState

        // Adds contains all add messages which need to be processed and
        // forwarded to the switch. Adds does not change over the life of a
        // forwarding package.
        Adds []LogUpdate

        // FwdFilter is a filter containing the indices of all Adds that were
        // forwarded to the switch.
        FwdFilter *PkgFilter

        // AckFilter is a filter containing the indices of all Adds for which
        // the source has received a settle or fail and is reflected in the next
        // commitment txn. A package should not be removed until IsFull()
        // returns true.
        AckFilter *PkgFilter

        // SettleFails contains all settle and fail messages that should be
        // forwarded to the switch.
        SettleFails []LogUpdate

        // SettleFailFilter is a filter containing the indices of all Settle or
        // Fails originating in this package that have been received and locked
        // into the incoming link's commitment state.
        SettleFailFilter *PkgFilter
}

// NewFwdPkg initializes a new forwarding package in FwdStateLockedIn. This
// should be used to create a package at the time we receive a revocation.
func NewFwdPkg(source lnwire.ShortChannelID, height uint64,
        addUpdates, settleFailUpdates []LogUpdate) *FwdPkg {

        nAddUpdates := uint16(len(addUpdates))
        nSettleFailUpdates := uint16(len(settleFailUpdates))

        return &FwdPkg{
                Source:           source,
                Height:           height,
                State:            FwdStateLockedIn,
                Adds:             addUpdates,
                FwdFilter:        NewPkgFilter(nAddUpdates),
                AckFilter:        NewPkgFilter(nAddUpdates),
                SettleFails:      settleFailUpdates,
                SettleFailFilter: NewPkgFilter(nSettleFailUpdates),
        }
}

// ID returns an unique identifier for this package, used to ensure that sphinx
// replay processing of this batch is idempotent.
func (f *FwdPkg) ID() []byte {
        var id = make([]byte, 16)
        byteOrder.PutUint64(id[:8], f.Source.ToUint64())
        byteOrder.PutUint64(id[8:], f.Height)
        return id
}

// String returns a human-readable description of the forwarding package.
func (f *FwdPkg) String() string {
        return fmt.Sprintf("%T(src=%v, height=%v, nadds=%v, nfailsettles=%v)",
                f, f.Source, f.Height, len(f.Adds), len(f.SettleFails))
}

// AddRef is used to identify a particular Add in a FwdPkg. The short channel ID
// is assumed to be that of the packager.
type AddRef struct {
        // Height is the remote commitment height that locked in the Add.
        Height uint64

        // Index is the index of the Add within the fwd pkg's Adds.
        //
        // NOTE: This index is static over the lifetime of a forwarding package.
        Index uint16
}

// Encode serializes the AddRef to the given io.Writer.
func (a *AddRef) Encode(w io.Writer) error {
        if err := binary.Write(w, binary.BigEndian, a.Height); err != nil {
                return err
        }

        return binary.Write(w, binary.BigEndian, a.Index)
}

// Decode deserializes the AddRef from the given io.Reader.
func (a *AddRef) Decode(r io.Reader) error {
        if err := binary.Read(r, binary.BigEndian, &a.Height); err != nil {
                return err
        }

        return binary.Read(r, binary.BigEndian, &a.Index)
}

// SettleFailRef is used to locate a Settle/Fail in another channel's FwdPkg. A
// channel does not remove its own Settle/Fail htlcs, so the source is provided
// to locate a db bucket belonging to another channel.
type SettleFailRef struct {
        // Source identifies the outgoing link that locked in the settle or
        // fail. This is then used by the *incoming* link to find the settle
        // fail in another link's forwarding packages.
        Source lnwire.ShortChannelID

        // Height is the remote commitment height that locked in this
        // Settle/Fail.
        Height uint64

        // Index is the index of the Add with the fwd pkg's SettleFails.
        //
        // NOTE: This index is static over the lifetime of a forwarding package.
        Index uint16
}

// SettleFailAcker is a generic interface providing the ability to acknowledge
// settle/fail HTLCs stored in forwarding packages.
type SettleFailAcker interface {
        // AckSettleFails atomically updates the settle-fail filters in *other*
        // channels' forwarding packages.
        AckSettleFails(tx kvdb.RwTx, settleFailRefs ...SettleFailRef) error
}

// GlobalFwdPkgReader is an interface used to retrieve the forwarding packages
// of any active channel.
type GlobalFwdPkgReader interface {
        // LoadChannelFwdPkgs loads all known forwarding packages for the given
        // channel.
        LoadChannelFwdPkgs(tx kvdb.RTx,
                source lnwire.ShortChannelID) ([]*FwdPkg, error)
}

// FwdOperator defines the interfaces for managing forwarding packages that are
// external to a particular channel. This interface is used by the switch to
// read forwarding packages from arbitrary channels, and acknowledge settles and
// fails for locally-sourced payments.
type FwdOperator interface {
        // GlobalFwdPkgReader provides read access to all known forwarding
        // packages
        GlobalFwdPkgReader

        // SettleFailAcker grants the ability to acknowledge settles or fails
        // residing in arbitrary forwarding packages.
        SettleFailAcker
}

// SwitchPackager is a concrete implementation of the FwdOperator interface.
// A SwitchPackager offers the ability to read any forwarding package, and ack
// arbitrary settle and fail HTLCs.
type SwitchPackager struct{}

// NewSwitchPackager instantiates a new SwitchPackager.
func NewSwitchPackager() *SwitchPackager {
        return &SwitchPackager{}
}

// AckSettleFails atomically updates the settle-fail filters in *other*
// channels' forwarding packages, to mark that the switch has received a settle
// or fail residing in the forwarding package of a link.
func (*SwitchPackager) AckSettleFails(tx kvdb.RwTx,
        settleFailRefs ...SettleFailRef) error {

        return ackSettleFails(tx, settleFailRefs)
}

// LoadChannelFwdPkgs loads all forwarding packages for a particular channel.
func (*SwitchPackager) LoadChannelFwdPkgs(tx kvdb.RTx,
        source lnwire.ShortChannelID) ([]*FwdPkg, error) {

        return loadChannelFwdPkgs(tx, source)
}

// FwdPackager supports all operations required to modify fwd packages, such as
// creation, updates, reading, and removal. The interfaces are broken down in
// this way to support future delegation of the subinterfaces.
type FwdPackager interface {
        // AddFwdPkg serializes and writes a FwdPkg for this channel at the
        // remote commitment height included in the forwarding package.
        AddFwdPkg(tx kvdb.RwTx, fwdPkg *FwdPkg) error

        // SetFwdFilter looks up the forwarding package at the remote `height`
        // and sets the `fwdFilter`, marking the Adds for which:
        // 1) We are not the exit node
        // 2) Passed all validation
        // 3) Should be forwarded to the switch immediately after a failure
        SetFwdFilter(tx kvdb.RwTx, height uint64, fwdFilter *PkgFilter) error

        // AckAddHtlcs atomically updates the add filters in this channel's
        // forwarding packages to mark the resolution of an Add that was
        // received from the remote party.
        AckAddHtlcs(tx kvdb.RwTx, addRefs ...AddRef) error

        // SettleFailAcker allows a link to acknowledge settle/fail HTLCs
        // belonging to other channels.
        SettleFailAcker

        // LoadFwdPkgs loads all known forwarding packages owned by this
        // channel.
        LoadFwdPkgs(tx kvdb.RTx) ([]*FwdPkg, error)

        // RemovePkg deletes a forwarding package owned by this channel at
        // the provided remote `height`.
        RemovePkg(tx kvdb.RwTx, height uint64) error

        // Wipe deletes all the forwarding packages owned by this channel.
        Wipe(tx kvdb.RwTx) error
}

// ChannelPackager is used by a channel to manage the lifecycle of its forwarding
// packages. The packager is tied to a particular source channel ID, allowing it
// to create and edit its own packages. Each packager also has the ability to
// remove fail/settle htlcs that correspond to an add contained in one of
// source's packages.
type ChannelPackager struct {
        source lnwire.ShortChannelID
}

// NewChannelPackager creates a new packager for a single channel.
func NewChannelPackager(source lnwire.ShortChannelID) *ChannelPackager {
        return &ChannelPackager{
                source: source,
        }
}

// AddFwdPkg writes a newly locked in forwarding package to disk.
func (*ChannelPackager) AddFwdPkg(tx kvdb.RwTx, fwdPkg *FwdPkg) error { // nolint: dupl
        fwdPkgBkt, err := tx.CreateTopLevelBucket(fwdPackagesKey)
        if err != nil {
                return err
        }

        source := makeLogKey(fwdPkg.Source.ToUint64())
        sourceBkt, err := fwdPkgBkt.CreateBucketIfNotExists(source[:])
        if err != nil {
                return err
        }

        heightKey := makeLogKey(fwdPkg.Height)
        heightBkt, err := sourceBkt.CreateBucketIfNotExists(heightKey[:])
        if err != nil {
                return err
        }

        // Write ADD updates we received at this commit height.
        addBkt, err := heightBkt.CreateBucketIfNotExists(addBucketKey)
        if err != nil {
                return err
        }

        // Write SETTLE/FAIL updates we received at this commit height.
        failSettleBkt, err := heightBkt.CreateBucketIfNotExists(failSettleBucketKey)
        if err != nil {
                return err
        }

        for i := range fwdPkg.Adds {
                err = putLogUpdate(addBkt, uint16(i), &fwdPkg.Adds[i])
                if err != nil {
                        return err
                }
        }

        // Persist the initialized pkg filter, which will be used to determine
        // when we can remove this forwarding package from disk.
        var ackFilterBuf bytes.Buffer
        if err := fwdPkg.AckFilter.Encode(&ackFilterBuf); err != nil {
                return err
        }

        if err := heightBkt.Put(ackFilterKey, ackFilterBuf.Bytes()); err != nil {
                return err
        }

        for i := range fwdPkg.SettleFails {
                err = putLogUpdate(failSettleBkt, uint16(i), &fwdPkg.SettleFails[i])
                if err != nil {
                        return err
                }
        }

        var settleFailFilterBuf bytes.Buffer
        err = fwdPkg.SettleFailFilter.Encode(&settleFailFilterBuf)
        if err != nil {
                return err
        }

        return heightBkt.Put(settleFailFilterKey, settleFailFilterBuf.Bytes())
}

// putLogUpdate writes an htlc to the provided `bkt`, using `index` as the key.
func putLogUpdate(bkt kvdb.RwBucket, idx uint16, htlc *LogUpdate) error {
        var b bytes.Buffer
        if err := serializeLogUpdate(&b, htlc); err != nil {
                return err
        }

        return bkt.Put(uint16Key(idx), b.Bytes())
}

// LoadFwdPkgs scans the forwarding log for any packages that haven't been
// processed, and returns their deserialized log updates in a map indexed by the
// remote commitment height at which the updates were locked in.
func (p *ChannelPackager) LoadFwdPkgs(tx kvdb.RTx) ([]*FwdPkg, error) {
        return loadChannelFwdPkgs(tx, p.source)
}

// loadChannelFwdPkgs loads all forwarding packages owned by `source`.
func loadChannelFwdPkgs(tx kvdb.RTx, source lnwire.ShortChannelID) ([]*FwdPkg, error) {
        fwdPkgBkt := tx.ReadBucket(fwdPackagesKey)
        if fwdPkgBkt == nil {
                return nil, nil
        }

        sourceKey := makeLogKey(source.ToUint64())
        sourceBkt := fwdPkgBkt.NestedReadBucket(sourceKey[:])
        if sourceBkt == nil {
                return nil, nil
        }

        var heights []uint64
        if err := sourceBkt.ForEach(func(k, _ []byte) error {
                if len(k) != 8 {
                        return ErrCorruptedFwdPkg
                }

                heights = append(heights, byteOrder.Uint64(k))

                return nil
        }); err != nil {
                return nil, err
        }

        // Load the forwarding package for each retrieved height.
        fwdPkgs := make([]*FwdPkg, 0, len(heights))
        for _, height := range heights {
                fwdPkg, err := loadFwdPkg(fwdPkgBkt, source, height)
                if err != nil {
                        return nil, err
                }

                fwdPkgs = append(fwdPkgs, fwdPkg)
        }

        return fwdPkgs, nil
}

// loadFwdPkg reads the packager's fwd pkg at a given height, and determines the
// appropriate FwdState.
func loadFwdPkg(fwdPkgBkt kvdb.RBucket, source lnwire.ShortChannelID,
        height uint64) (*FwdPkg, error) {

        sourceKey := makeLogKey(source.ToUint64())
        sourceBkt := fwdPkgBkt.NestedReadBucket(sourceKey[:])
        if sourceBkt == nil {
                return nil, ErrCorruptedFwdPkg
        }

        heightKey := makeLogKey(height)
        heightBkt := sourceBkt.NestedReadBucket(heightKey[:])
        if heightBkt == nil {
                return nil, ErrCorruptedFwdPkg
        }

        // Load ADDs from disk.
        addBkt := heightBkt.NestedReadBucket(addBucketKey)
        if addBkt == nil {
                return nil, ErrCorruptedFwdPkg
        }

        adds, err := loadHtlcs(addBkt)
        if err != nil {
                return nil, err
        }

        // Load ack filter from disk.
        ackFilterBytes := heightBkt.Get(ackFilterKey)
        if ackFilterBytes == nil {
                return nil, ErrCorruptedFwdPkg
        }
        ackFilterReader := bytes.NewReader(ackFilterBytes)

        ackFilter := &PkgFilter{}
        if err := ackFilter.Decode(ackFilterReader); err != nil {
                return nil, err
        }

        // Load SETTLE/FAILs from disk.
        failSettleBkt := heightBkt.NestedReadBucket(failSettleBucketKey)
        if failSettleBkt == nil {
                return nil, ErrCorruptedFwdPkg
        }

        failSettles, err := loadHtlcs(failSettleBkt)
        if err != nil {
                return nil, err
        }

        // Load settle fail filter from disk.
        settleFailFilterBytes := heightBkt.Get(settleFailFilterKey)
        if settleFailFilterBytes == nil {
                return nil, ErrCorruptedFwdPkg
        }
        settleFailFilterReader := bytes.NewReader(settleFailFilterBytes)

        settleFailFilter := &PkgFilter{}
        if err := settleFailFilter.Decode(settleFailFilterReader); err != nil {
                return nil, err
        }

        // Initialize the fwding package, which always starts in the
        // FwdStateLockedIn. We can determine what state the package was left in
        // by examining constraints on the information loaded from disk.
        fwdPkg := &FwdPkg{
                Source:           source,
                State:            FwdStateLockedIn,
                Height:           height,
                Adds:             adds,
                AckFilter:        ackFilter,
                SettleFails:      failSettles,
                SettleFailFilter: settleFailFilter,
        }

        // Check to see if we have written the set exported filter adds to
        // disk. If we haven't, processing of this package was never started, or
        // failed during the last attempt.
        fwdFilterBytes := heightBkt.Get(fwdFilterKey)
        if fwdFilterBytes == nil {
                nAdds := uint16(len(adds))
                fwdPkg.FwdFilter = NewPkgFilter(nAdds)
                return fwdPkg, nil
        }

        fwdFilterReader := bytes.NewReader(fwdFilterBytes)
        fwdPkg.FwdFilter = &PkgFilter{}
        if err := fwdPkg.FwdFilter.Decode(fwdFilterReader); err != nil {
                return nil, err
        }

        // Otherwise, a complete round of processing was completed, and we
        // advance the package to FwdStateProcessed.
        fwdPkg.State = FwdStateProcessed

        // If every add, settle, and fail has been fully acknowledged, we can
        // safely set the package's state to FwdStateCompleted, signalling that
        // it can be garbage collected.
        if fwdPkg.AckFilter.IsFull() && fwdPkg.SettleFailFilter.IsFull() {
                fwdPkg.State = FwdStateCompleted
        }

        return fwdPkg, nil
}

// loadHtlcs retrieves all serialized htlcs in a bucket, returning
// them in order of the indexes they were written under.
func loadHtlcs(bkt kvdb.RBucket) ([]LogUpdate, error) {
        var htlcs []LogUpdate
        if err := bkt.ForEach(func(_, v []byte) error {
                htlc, err := deserializeLogUpdate(bytes.NewReader(v))
                if err != nil {
                        return err
                }

                htlcs = append(htlcs, *htlc)

                return nil
        }); err != nil {
                return nil, err
        }

        return htlcs, nil
}

// SetFwdFilter writes the set of indexes corresponding to Adds at the
// `height` that are to be forwarded to the switch. Calling this method causes
// the forwarding package at `height` to be in FwdStateProcessed. We write this
// forwarding decision so that we always arrive at the same behavior for HTLCs
// leaving this channel. After a restart, we skip validation of these Adds,
// since they are assumed to have already been validated, and make the switch or
// outgoing link responsible for handling replays.
func (p *ChannelPackager) SetFwdFilter(tx kvdb.RwTx, height uint64,
        fwdFilter *PkgFilter) error {

        fwdPkgBkt := tx.ReadWriteBucket(fwdPackagesKey)
        if fwdPkgBkt == nil {
                return ErrCorruptedFwdPkg
        }

        source := makeLogKey(p.source.ToUint64())
        sourceBkt := fwdPkgBkt.NestedReadWriteBucket(source[:])
        if sourceBkt == nil {
                return ErrCorruptedFwdPkg
        }

        heightKey := makeLogKey(height)
        heightBkt := sourceBkt.NestedReadWriteBucket(heightKey[:])
        if heightBkt == nil {
                return ErrCorruptedFwdPkg
        }

        // If the fwd filter has already been written, we return early to avoid
        // modifying the persistent state.
        forwardedAddsBytes := heightBkt.Get(fwdFilterKey)
        if forwardedAddsBytes != nil {
                return nil
        }

        // Otherwise we serialize and write the provided fwd filter.
        var b bytes.Buffer
        if err := fwdFilter.Encode(&b); err != nil {
                return err
        }

        return heightBkt.Put(fwdFilterKey, b.Bytes())
}

// AckAddHtlcs accepts a list of references to add htlcs, and updates the
// AckAddFilter of those forwarding packages to indicate that a settle or fail
// has been received in response to the add.
func (p *ChannelPackager) AckAddHtlcs(tx kvdb.RwTx, addRefs ...AddRef) error {
        if len(addRefs) == 0 {
                return nil
        }

        fwdPkgBkt := tx.ReadWriteBucket(fwdPackagesKey)
        if fwdPkgBkt == nil {
                return ErrCorruptedFwdPkg
        }

        sourceKey := makeLogKey(p.source.ToUint64())
        sourceBkt := fwdPkgBkt.NestedReadWriteBucket(sourceKey[:])
        if sourceBkt == nil {
                return ErrCorruptedFwdPkg
        }

        // Organize the forward references such that we just get a single slice
        // of indexes for each unique height.
        heightDiffs := make(map[uint64][]uint16)
        for _, addRef := range addRefs {
                heightDiffs[addRef.Height] = append(
                        heightDiffs[addRef.Height],
                        addRef.Index,
                )
        }

        // Load each height bucket once and remove all acked htlcs at that
        // height.
        for height, indexes := range heightDiffs {
                err := ackAddHtlcsAtHeight(sourceBkt, height, indexes)
                if err != nil {
                        return err
                }
        }

        return nil
}

// ackAddHtlcsAtHeight updates the AddAckFilter of a single forwarding package
// with a list of indexes, writing the resulting filter back in its place.
func ackAddHtlcsAtHeight(sourceBkt kvdb.RwBucket, height uint64,
        indexes []uint16) error {

        heightKey := makeLogKey(height)
        heightBkt := sourceBkt.NestedReadWriteBucket(heightKey[:])
        if heightBkt == nil {
                // If the height bucket isn't found, this could be because the
                // forwarding package was already removed. We'll return nil to
                // signal that the operation is successful, as there is nothing
                // to ack.
                return nil
        }

        // Load ack filter from disk.
        ackFilterBytes := heightBkt.Get(ackFilterKey)
        if ackFilterBytes == nil {
                return ErrCorruptedFwdPkg
        }

        ackFilter := &PkgFilter{}
        ackFilterReader := bytes.NewReader(ackFilterBytes)
        if err := ackFilter.Decode(ackFilterReader); err != nil {
                return err
        }

        // Update the ack filter for this height.
        for _, index := range indexes {
                ackFilter.Set(index)
        }

        // Write the resulting filter to disk.
        var ackFilterBuf bytes.Buffer
        if err := ackFilter.Encode(&ackFilterBuf); err != nil {
                return err
        }

        return heightBkt.Put(ackFilterKey, ackFilterBuf.Bytes())
}

// AckSettleFails persistently acknowledges settles or fails from a remote forwarding
// package. This should only be called after the source of the Add has locked in
// the settle/fail, or it becomes otherwise safe to forgo retransmitting the
// settle/fail after a restart.
func (p *ChannelPackager) AckSettleFails(tx kvdb.RwTx, settleFailRefs ...SettleFailRef) error {
        return ackSettleFails(tx, settleFailRefs)
}

// ackSettleFails persistently acknowledges a batch of settle fail references.
func ackSettleFails(tx kvdb.RwTx, settleFailRefs []SettleFailRef) error {
        if len(settleFailRefs) == 0 {
                return nil
        }

        fwdPkgBkt := tx.ReadWriteBucket(fwdPackagesKey)
        if fwdPkgBkt == nil {
                return ErrCorruptedFwdPkg
        }

        // Organize the forward references such that we just get a single slice
        // of indexes for each unique destination-height pair.
        destHeightDiffs := make(map[lnwire.ShortChannelID]map[uint64][]uint16)
        for _, settleFailRef := range settleFailRefs {
                destHeights, ok := destHeightDiffs[settleFailRef.Source]
                if !ok {
                        destHeights = make(map[uint64][]uint16)
                        destHeightDiffs[settleFailRef.Source] = destHeights
                }

                destHeights[settleFailRef.Height] = append(
                        destHeights[settleFailRef.Height],
                        settleFailRef.Index,
                )
        }

        // With the references organized by destination and height, we now load
        // each remote bucket, and update the settle fail filter for any
        // settle/fail htlcs.
        for dest, destHeights := range destHeightDiffs {
                destKey := makeLogKey(dest.ToUint64())
                destBkt := fwdPkgBkt.NestedReadWriteBucket(destKey[:])
                if destBkt == nil {
                        // If the destination bucket is not found, this is
                        // likely the result of the destination channel being
                        // closed and having it's forwarding packages wiped. We
                        // won't treat this as an error, because the response
                        // will no longer be retransmitted internally.
                        continue
                }

                for height, indexes := range destHeights {
                        err := ackSettleFailsAtHeight(destBkt, height, indexes)
                        if err != nil {
                                return err
                        }
                }
        }

        return nil
}

// ackSettleFailsAtHeight given a destination bucket, acks the provided indexes
// at particular a height by updating the settle fail filter.
func ackSettleFailsAtHeight(destBkt kvdb.RwBucket, height uint64,
        indexes []uint16) error {

        heightKey := makeLogKey(height)
        heightBkt := destBkt.NestedReadWriteBucket(heightKey[:])
        if heightBkt == nil {
                // If the height bucket isn't found, this could be because the
                // forwarding package was already removed. We'll return nil to
                // signal that the operation is as there is nothing to ack.
                return nil
        }

        // Load ack filter from disk.
        settleFailFilterBytes := heightBkt.Get(settleFailFilterKey)
        if settleFailFilterBytes == nil {
                return ErrCorruptedFwdPkg
        }

        settleFailFilter := &PkgFilter{}
        settleFailFilterReader := bytes.NewReader(settleFailFilterBytes)
        if err := settleFailFilter.Decode(settleFailFilterReader); err != nil {
                return err
        }

        // Update the ack filter for this height.
        for _, index := range indexes {
                settleFailFilter.Set(index)
        }

        // Write the resulting filter to disk.
        var settleFailFilterBuf bytes.Buffer
        if err := settleFailFilter.Encode(&settleFailFilterBuf); err != nil {
                return err
        }

        return heightBkt.Put(settleFailFilterKey, settleFailFilterBuf.Bytes())
}

// RemovePkg deletes the forwarding package at the given height from the
// packager's source bucket.
func (p *ChannelPackager) RemovePkg(tx kvdb.RwTx, height uint64) error {
        fwdPkgBkt := tx.ReadWriteBucket(fwdPackagesKey)
        if fwdPkgBkt == nil {
                return nil
        }

        sourceBytes := makeLogKey(p.source.ToUint64())
        sourceBkt := fwdPkgBkt.NestedReadWriteBucket(sourceBytes[:])
        if sourceBkt == nil {
                return ErrCorruptedFwdPkg
        }

        heightKey := makeLogKey(height)

        return sourceBkt.DeleteNestedBucket(heightKey[:])
}

// Wipe deletes all the channel's forwarding packages, if any.
func (p *ChannelPackager) Wipe(tx kvdb.RwTx) error {
        // If the root bucket doesn't exist, there's no need to delete.
        fwdPkgBkt := tx.ReadWriteBucket(fwdPackagesKey)
        if fwdPkgBkt == nil {
                return nil
        }

        sourceBytes := makeLogKey(p.source.ToUint64())

        // If the nested bucket doesn't exist, there's no need to delete.
        if fwdPkgBkt.NestedReadWriteBucket(sourceBytes[:]) == nil {
                return nil
        }

        return fwdPkgBkt.DeleteNestedBucket(sourceBytes[:])
}

// uint16Key writes the provided 16-bit unsigned integer to a 2-byte slice.
func uint16Key(i uint16) []byte {
        key := make([]byte, 2)
        byteOrder.PutUint16(key, i)
        return key
}

// Compile-time constraint to ensure that ChannelPackager implements the public
// FwdPackager interface.
var _ FwdPackager = (*ChannelPackager)(nil)

// Compile-time constraint to ensure that SwitchPackager implements the public
// FwdOperator interface.
var _ FwdOperator = (*SwitchPackager)(nil)

lightningnetwork / lnd / 9111774206

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