multi: implement new safe static channel backup and recovery scheme, RPCs, and cli commands

chainregistry.go

@@ -108,7 +108,7 @@ type chainControl struct {
 
 	signer input.Signer
 
-	keyRing keychain.KeyRing
+	keyRing keychain.SecretKeyRing
 
 	wc lnwallet.WalletController
 

chanbackup/backupfile.go

@@ -76,6 +76,8 @@ func (b *MultiFile) UpdateAndSwap(newBackup PackedMulti) error {
 		return ErrNoBackupFileExists
 	}
 
+	log.Infof("Updating backup file at %v", b.fileName)
+
 	// If the old back up file still exists, then we'll delete it before
 	// proceeding.
 	if _, err := os.Stat(b.tempFileName); err == nil {
@@ -94,17 +96,17 @@ func (b *MultiFile) UpdateAndSwap(newBackup PackedMulti) error {
 	var err error
 	b.tempFile, err = os.Create(b.tempFileName)
 	if err != nil {
-		return err
+		return fmt.Errorf("unable to create temp file: %v", err)
 	}
 
 	// With the file created, we'll write the new packed multi backup and
 	// remove the temporary file all together once this method exits.
 	_, err = b.tempFile.Write([]byte(newBackup))
 	if err != nil {
-		return err
+		return fmt.Errorf("unable to write backup to temp file: %v", err)
 	}
 	if err := b.tempFile.Sync(); err != nil {
-		return err
+		return fmt.Errorf("unable to sync temp file: %v", err)
 	}
 	defer os.Remove(b.tempFileName)
 

chanbackup/multi.go

@@ -19,6 +19,11 @@ const (
 	// backup. The serialized format for this version is simply: version ||
 	// numBackups || SCBs...
 	DefaultMultiVersion = 0
+
+	// NilMultiSizePacked is the size of a "nil" packed Multi (45 bytes).
+	// This consists of the 24 byte chacha nonce, the 16 byte MAC, one byte
+	// for the version, and 4 bytes to signal zero entries.
+	NilMultiSizePacked = 24 + 16 + 1 + 4
 )
 
 // Multi is a form of static channel backup that is amenable to being

chanbackup/pubsub.go

@@ -2,6 +2,7 @@ package chanbackup
 
 import (
 	"bytes"
+	"fmt"
 	"net"
 	"sync"
 	"sync/atomic"
@@ -47,9 +48,9 @@ type ChannelEvent struct {
 // ChannelSubscription represents an intent to be notified of any updates to
 // the primary channel state.
 type ChannelSubscription struct {
-	// ChanUpdates is a read-only channel that will be sent upon once the
-	// primary channel state is updated.
-	ChanUpdates <-chan ChannelEvent
+	// ChanUpdates is a channel that will be sent upon once the primary
+	// channel state is updated.
+	ChanUpdates chan ChannelEvent
 
 	// Cancel is a closure that allows the caller to cancel their
 	// subscription and free up any resources allocated.
@@ -160,6 +161,36 @@ func (s *SubSwapper) Stop() error {
 	return nil
 }
 
+// updateBackupFile updates the backup file in place given the current state of
+// the SubSwapper.
+func (s *SubSwapper) updateBackupFile() error {
+	// 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 {
+		newMulti.StaticBackups = append(
+			newMulti.StaticBackups, backup,
+		)
+	}
+
+	// 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)
+	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.
+	err = s.Swapper.UpdateAndSwap(PackedMulti(b.Bytes()))
+	if err != nil {
+		return fmt.Errorf("unable to update multi backup: %v", err)
+	}
+
+	return nil
+}
+
 // backupFileUpdater is the primary goroutine of the SubSwapper which is
 // responsible for listening for changes to the channel, and updating the
 // persistent multi backup state with a new packed multi of the latest channel
@@ -172,6 +203,12 @@ func (s *SubSwapper) backupUpdater() {
 
 	log.Debugf("SubSwapper's backupUpdater is active!")
 
+	// 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.
+	if err := s.updateBackupFile(); err != nil {
+		log.Errorf("Unable to refresh backup file: %v", err)
+	}
+
 	for {
 		select {
 		// The channel state has been modified! We'll evaluate all
@@ -183,7 +220,7 @@ func (s *SubSwapper) backupUpdater() {
 			// For all new open channels, we'll create a new SCB
 			// given the required information.
 			for _, newChan := range chanUpdate.NewChans {
-				log.Debugf("Adding chanenl %v to backup state",
+				log.Debugf("Adding channel %v to backup state",
 					newChan.FundingOutpoint)
 
 				s.backupState[newChan.FundingOutpoint] = NewSingle(
@@ -204,41 +241,20 @@ func (s *SubSwapper) backupUpdater() {
 
 			newStateSize := len(s.backupState)
 
-			// 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 {
-				newMulti.StaticBackups = append(
-					newMulti.StaticBackups, backup,
-				)
-			}
-
-			// 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)
-			if err != nil {
-				log.Errorf("unable to pack multi backup: %v",
-					err)
-				continue
-			}
-
 			log.Infof("Updating on-disk multi SCB backup: "+
 				"num_old_chans=%v, num_new_chans=%v",
 				oldStateSize, newStateSize)
 
-			// Finally, we'll swap out the old backup for this new
-			// one in a single atomic step.
-			err = s.Swapper.UpdateAndSwap(
-				PackedMulti(b.Bytes()),
-			)
-			if err != nil {
-				log.Errorf("unable to update multi "+
-					"backup: %v", err)
-				continue
+			// With out new state constructed, we'll, atomically
+			// update the on-disk backup state.
+			if err := s.updateBackupFile(); err != nil {
+				log.Errorf("unable to update backup file: %v",
+					err)
 			}
 
+		// TODO(roasbeef): refresh periodically on a time basis due to
+		// possible addr changes from node
+
 		// Exit at once if a quit signal is detected.
 		case <-s.quit:
 			return

chanbackup/pubsub_test.go

@@ -131,17 +131,23 @@ func TestSubSwapperIdempotentStartStop(t *testing.T) {
 
 	keyRing := &mockKeyRing{}
 
-	var (
-		swapper      mockSwapper
-		chanNotifier mockChannelNotifier
-	)
+	var chanNotifier mockChannelNotifier
 
-	subSwapper, err := NewSubSwapper(nil, &chanNotifier, keyRing, &swapper)
+	swapper := newMockSwapper()
+	subSwapper, err := NewSubSwapper(nil, &chanNotifier, keyRing, swapper)
 	if err != nil {
 		t.Fatalf("unable to init subSwapper: %v", err)
 	}
 
-	subSwapper.Start()
+	if err := subSwapper.Start(); err != nil {
+		t.Fatalf("unable to start swapper: %v", err)
+	}
+
+	// The swapper should write the initial channel state as soon as it's
+	// active.
+	backupSet := make(map[wire.OutPoint]Single)
+	assertExpectedBackupSwap(t, swapper, subSwapper, keyRing, backupSet)
+
 	subSwapper.Start()
 
 	subSwapper.Stop()
@@ -188,6 +194,10 @@ func TestSubSwapperUpdater(t *testing.T) {
 	}
 	defer subSwapper.Stop()
 
+	// The swapper should write the initial channel state as soon as it's
+	// active.
+	assertExpectedBackupSwap(t, swapper, subSwapper, keyRing, backupSet)
+
 	// Now that the sub-swapper is active, we'll notify to add a brand new
 	// channel to the channel state.
 	newChannel, err := genRandomOpenChannelShell()