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chanbackup: always combine new backup data w/ on-disk state

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In this commit, we fix a bug that could possibly cause a user's on disk
back up file to be wiped out, if they ever started _another_ lnd node
with different channel state. To remedy this, before we swap out the
channel state with what's on disk, we'll first read out the contents of
the on-disk SCB file and _combine_ that with what we have in memory.

Fixes #4377
This commit is contained in:
Olaoluwa Osuntokun 2020-06-15 17:38:12 -07:00
parent 87880c0d56
commit fc65c9b2cc
No known key found for this signature in database
GPG Key ID: BC13F65E2DC84465
2 changed files with 109 additions and 23 deletions
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66
chanbackup/pubsub.go
View File

@ -18,12 +18,14 @@ type Swapper interface {
// UpdateAndSwap attempts to atomically update the main multi back up
// file location with the new fully packed multi-channel backup.
UpdateAndSwap(newBackup PackedMulti) error
// ExtractMulti attempts to obtain and decode the current SCB instance
// stored by the Swapper instance.
ExtractMulti(keychain keychain.KeyRing) (*Multi, error)
}
// ChannelWithAddrs bundles an open channel along with all the addresses for
// the channel peer.
//
// TODO(roasbeef): use channel shell instead?
type ChannelWithAddrs struct {
*channeldb.OpenChannel
@ -75,8 +77,6 @@ type ChannelNotifier interface {
// update the file state on disk with the new set of open channels. This can
// be used to implement a system that always keeps the multi-chan backup file
// on disk in a consistent state for safety purposes.
//
// TODO(roasbeef): better name lol
type SubSwapper struct {
started sync.Once
stopped sync.Once
@ -155,12 +155,50 @@ func (s *SubSwapper) Stop() error {
}
// updateBackupFile updates the backup file in place given the current state of
// the SubSwapper.
func (s *SubSwapper) updateBackupFile() error {
// the SubSwapper. We accept the set of channels that were closed between this
// update and the last to make sure we leave them out of our backup set union.
func (s *SubSwapper) updateBackupFile(closedChans ...wire.OutPoint) error {
// Before we pack the new set of SCBs, we'll first decode what we
// already have on-disk, to make sure we can decode it (proper seed)
// and that we're able to combine it with our new data.
diskMulti, err := s.Swapper.ExtractMulti(s.keyRing)
if err != nil {
return fmt.Errorf("unable to extract on disk encrypted "+
"SCB: %v", err)
}
// Now that we have channels stored on-disk, we'll create a new set of
// the combined old and new channels to make sure we retain what's
// already on-disk.
//
// NOTE: The ordering of this operations means that our in-memory
// structure will replace what we read from disk.
combinedBackup := make(map[wire.OutPoint]Single)
if diskMulti != nil {
for _, diskChannel := range diskMulti.StaticBackups {
chanPoint := diskChannel.FundingOutpoint
combinedBackup[chanPoint] = diskChannel
}
}
for _, memChannel := range s.backupState {
chanPoint := memChannel.FundingOutpoint
if _, ok := combinedBackup[chanPoint]; ok {
log.Warnf("Replacing disk backup for ChannelPoint(%v) "+
"w/ newer version", chanPoint)
}
combinedBackup[chanPoint] = memChannel
}
// Remove the set of closed channels from the final set of backups.
for _, closedChan := range closedChans {
delete(combinedBackup, closedChan)
}
// With our updated channel state obtained, we'll create a new multi
// from our series of singles.
var newMulti Multi
for _, backup := range s.backupState {
for _, backup := range combinedBackup {
newMulti.StaticBackups = append(
newMulti.StaticBackups, backup,
)
@ -169,13 +207,14 @@ func (s *SubSwapper) updateBackupFile() error {
// Now that our multi has been assembled, we'll attempt to pack
// (encrypt+encode) the new channel state to our target reader.
var b bytes.Buffer
err := newMulti.PackToWriter(&b, s.keyRing)
err = newMulti.PackToWriter(&b, s.keyRing)
if err != nil {
return fmt.Errorf("unable to pack multi backup: %v", err)
}
// Finally, we'll swap out the old backup for this new one in a single
// atomic step.
// atomic step, combining the file already on-disk with this set of new
// channels.
err = s.Swapper.UpdateAndSwap(PackedMulti(b.Bytes()))
if err != nil {
return fmt.Errorf("unable to update multi backup: %v", err)
@ -198,6 +237,8 @@ func (s *SubSwapper) backupUpdater() {
// Before we enter our main loop, we'll update the on-disk state with
// the latest Single state, as nodes may have new advertised addresses.
//
// TODO(roasbeef): do in Start() so we don't start with an invalid SCB?
if err := s.updateBackupFile(); err != nil {
log.Errorf("Unable to refresh backup file: %v", err)
}
@ -223,6 +264,9 @@ func (s *SubSwapper) backupUpdater() {
// For all closed channels, we'll remove the prior
// backup state.
closedChans := make(
[]wire.OutPoint, 0, len(chanUpdate.ClosedChans),
)
for i, closedChan := range chanUpdate.ClosedChans {
log.Debugf("Removing channel %v from backup "+
"state", newLogClosure(func() string {
@ -230,6 +274,8 @@ func (s *SubSwapper) backupUpdater() {
}))
delete(s.backupState, closedChan)
closedChans = append(closedChans, closedChan)
}
newStateSize := len(s.backupState)
@ -240,7 +286,7 @@ func (s *SubSwapper) backupUpdater() {
// With out new state constructed, we'll, atomically
// update the on-disk backup state.
if err := s.updateBackupFile(); err != nil {
if err := s.updateBackupFile(closedChans...); err != nil {
log.Errorf("unable to update backup file: %v",
err)
}

66
chanbackup/pubsub_test.go
View File

@ -2,12 +2,10 @@ package chanbackup
import (
"fmt"
"reflect"
"testing"
"time"
"github.com/btcsuite/btcd/wire"
"github.com/davecgh/go-spew/spew"
"github.com/lightningnetwork/lnd/keychain"
)
@ -15,11 +13,17 @@ type mockSwapper struct {
fail bool
swaps chan PackedMulti
swapState *Multi
keyChain keychain.KeyRing
}
func newMockSwapper() *mockSwapper {
func newMockSwapper(keychain keychain.KeyRing) *mockSwapper {
return &mockSwapper{
swaps: make(chan PackedMulti),
swaps: make(chan PackedMulti),
keyChain: keychain,
swapState: &Multi{},
}
}
@ -28,11 +32,22 @@ func (m *mockSwapper) UpdateAndSwap(newBackup PackedMulti) error {
return fmt.Errorf("fail")
}
swapState, err := newBackup.Unpack(m.keyChain)
if err != nil {
return fmt.Errorf("unable to decode on disk swaps: %v", err)
}
m.swapState = swapState
m.swaps <- newBackup
return nil
}
func (m *mockSwapper) ExtractMulti(keychain keychain.KeyRing) (*Multi, error) {
return m.swapState, nil
}
type mockChannelNotifier struct {
fail bool
@ -87,7 +102,7 @@ func assertExpectedBackupSwap(t *testing.T, swapper *mockSwapper,
case newPackedMulti := <-swapper.swaps:
// If we unpack the new multi, then we should find all the old
// channels, and also the new channel included and any deleted
// channel omitted..
// channel omitted.
newMulti, err := newPackedMulti.Unpack(keyRing)
if err != nil {
t.Fatalf("unable to unpack multi: %v", err)
@ -111,12 +126,19 @@ func assertExpectedBackupSwap(t *testing.T, swapper *mockSwapper,
}
}
// The internal state of the sub-swapper should also be one
// larger.
if !reflect.DeepEqual(expectedChanSet, subSwapper.backupState) {
t.Fatalf("backup set doesn't match: expected %v got %v",
spew.Sdump(expectedChanSet),
spew.Sdump(subSwapper.backupState))
// The same applies for our in-memory state, but it's also
// possible for there to be items in the on-disk state that we
// don't know of explicit.
newChans := make(map[wire.OutPoint]Single)
for _, newChan := range newMulti.StaticBackups {
newChans[newChan.FundingOutpoint] = newChan
}
for _, backup := range subSwapper.backupState {
_, ok := newChans[backup.FundingOutpoint]
if !ok {
t.Fatalf("didn't find backup in original set: %v",
backup.FundingOutpoint)
}
}
case <-time.After(time.Second * 5):
@ -133,7 +155,7 @@ func TestSubSwapperIdempotentStartStop(t *testing.T) {
var chanNotifier mockChannelNotifier
swapper := newMockSwapper()
swapper := newMockSwapper(keyRing)
subSwapper, err := NewSubSwapper(nil, &chanNotifier, keyRing, swapper)
if err != nil {
t.Fatalf("unable to init subSwapper: %v", err)
@ -162,7 +184,7 @@ func TestSubSwapperUpdater(t *testing.T) {
keyRing := &mockKeyRing{}
chanNotifier := newMockChannelNotifier()
swapper := newMockSwapper()
swapper := newMockSwapper(keyRing)
// First, we'll start out by creating a channels set for the initial
// set of channels known to the sub-swapper.
@ -181,6 +203,24 @@ func TestSubSwapperUpdater(t *testing.T) {
initialChanSet = append(initialChanSet, single)
}
// We'll also generate two additional channels which will already be
// present on disk. However, these will at first only be known by the
// on disk backup (the backup set).
const numDiskChans = 2
for i := 0; i < numDiskChans; i++ {
channel, err := genRandomOpenChannelShell()
if err != nil {
t.Fatalf("unable to make test chan: %v", err)
}
single := NewSingle(channel, nil)
backupSet[channel.FundingOutpoint] = single
swapper.swapState.StaticBackups = append(
swapper.swapState.StaticBackups, single,
)
}
// With our channel set created, we'll make a fresh sub swapper
// instance to begin our test.
subSwapper, err := NewSubSwapper(