multi: add new NoRevLogAmtData config option

In this commit, a new `--db.no-rev-log-amt-data` flag is added. The
config option is passed though to everywhere that it will be used. Note
that it is still a no-op in this commit. An upcoming commit will make
use of the flag.

channeldb/channel.go

@@ -2657,8 +2657,8 @@ func (c *OpenChannel) AdvanceCommitChainTail(fwdPkg *FwdPkg,
 		// With the commitment pointer swapped, we can now add the
 		// revoked (prior) state to the revocation log.
 		err = putRevocationLog(
-			logBucket, &c.RemoteCommitment,
+			logBucket, &c.RemoteCommitment, ourOutputIndex,
-			ourOutputIndex, theirOutputIndex,
+			theirOutputIndex, c.Db.parent.noRevLogAmtData,
 		)
 		if err != nil {
 			return err

channeldb/db.go

@@ -324,6 +324,10 @@ type DB struct {
 	dryRun                    bool
 	keepFailedPaymentAttempts bool
 	storeFinalHtlcResolutions bool
+
+	// noRevLogAmtData if true, means that commitment transaction amount
+	// data should not be stored in the revocation log.
+	noRevLogAmtData bool
 }
 
 // Open opens or creates channeldb. Any necessary schemas migrations due
@@ -382,6 +386,7 @@ func CreateWithBackend(backend kvdb.Backend,
 		dryRun:                    opts.dryRun,
 		keepFailedPaymentAttempts: opts.keepFailedPaymentAttempts,
 		storeFinalHtlcResolutions: opts.storeFinalHtlcResolutions,
+		noRevLogAmtData:           opts.NoRevLogAmtData,
 	}
 
 	// Set the parent pointer (only used in tests).
@@ -1562,7 +1567,9 @@ func (d *DB) applyOptionalVersions(cfg OptionalMiragtionConfig) error {
 	log.Infof("Performing database optional migration: %s", version.name)
 
 	migrationCfg := &MigrationConfigImpl{
-		migration30.MigrateRevLogConfigImpl{},
+		migration30.MigrateRevLogConfigImpl{
+			NoAmountData: d.noRevLogAmtData,
+		},
 	}
 
 	// Migrate the data.

channeldb/migration30/revocation_log.go

@@ -223,7 +223,7 @@ type RevocationLog struct {
 // disk. It also saves our output index and their output index, which are
 // useful when creating breach retribution.
 func putRevocationLog(bucket kvdb.RwBucket, commit *mig.ChannelCommitment,
-	ourOutputIndex, theirOutputIndex uint32) error {
+	ourOutputIndex, theirOutputIndex uint32, noAmtData bool) error {
 
 	// Sanity check that the output indexes can be safely converted.
 	if ourOutputIndex > math.MaxUint16 {

channeldb/migration30/test_utils.go

@@ -306,7 +306,7 @@ func setupTestLogs(db kvdb.Backend, c *mig26.OpenChannel,
 		}
 
 		// Create new logs.
-		return writeNewRevocationLogs(chanBucket, newLogs)
+		return writeNewRevocationLogs(chanBucket, newLogs, !withAmtData)
 	}, func() {})
 }
 
@@ -460,7 +460,7 @@ func writeOldRevocationLogs(chanBucket kvdb.RwBucket,
 
 // writeNewRevocationLogs saves a new revocation log to db.
 func writeNewRevocationLogs(chanBucket kvdb.RwBucket,
-	oldLogs []mig.ChannelCommitment) error {
+	oldLogs []mig.ChannelCommitment, noAmtData bool) error {
 
 	// Don't bother continue if the logs are empty.
 	if len(oldLogs) == 0 {
@@ -480,7 +480,7 @@ func writeNewRevocationLogs(chanBucket kvdb.RwBucket,
 		// old commit tx. We do this intentionally so we can
 		// distinguish a newly created log from an already saved one.
 		err := putRevocationLog(
-			logBucket, &c, testOurIndex, testTheirIndex,
+			logBucket, &c, testOurIndex, testTheirIndex, noAmtData,
 		)
 		if err != nil {
 			return err

channeldb/options.go

@@ -64,6 +64,10 @@ type Options struct {
 	// applications that use the channeldb package as a library.
 	NoMigration bool
 
+	// NoRevLogAmtData when set to true, indicates that amount data should
+	// not be stored in the revocation log.
+	NoRevLogAmtData bool
+
 	// clock is the time source used by the database.
 	clock clock.Clock
 
@@ -130,6 +134,14 @@ func OptionSetUseGraphCache(use bool) OptionModifier {
 	}
 }
 
+// OptionNoRevLogAmtData sets the NoRevLogAmtData option to the given value. If
+// it is set to true then amount data will not be stored in the revocation log.
+func OptionNoRevLogAmtData(noAmtData bool) OptionModifier {
+	return func(o *Options) {
+		o.NoRevLogAmtData = noAmtData
+	}
+}
+
 // OptionSetSyncFreelist allows the database to sync its freelist.
 func OptionSetSyncFreelist(b bool) OptionModifier {
 	return func(o *Options) {

channeldb/revocation_log.go

@@ -211,7 +211,7 @@ type RevocationLog struct {
 // disk. It also saves our output index and their output index, which are
 // useful when creating breach retribution.
 func putRevocationLog(bucket kvdb.RwBucket, commit *ChannelCommitment,
-	ourOutputIndex, theirOutputIndex uint32) error {
+	ourOutputIndex, theirOutputIndex uint32, noAmtData bool) error {
 
 	// Sanity check that the output indexes can be safely converted.
 	if ourOutputIndex > math.MaxUint16 {

channeldb/revocation_log_test.go

@@ -368,6 +368,7 @@ func TestPutRevocationLog(t *testing.T) {
 		commit      ChannelCommitment
 		ourIndex    uint32
 		theirIndex  uint32
+		noAmtData   bool
 		expectedErr error
 		expectedLog RevocationLog
 	}{
@@ -435,6 +436,7 @@ func TestPutRevocationLog(t *testing.T) {
 			// Save the log.
 			err = putRevocationLog(
 				bucket, &tc.commit, tc.ourIndex, tc.theirIndex,
+				tc.noAmtData,
 			)
 			if err != nil {
 				return RevocationLog{}, err
@@ -542,7 +544,7 @@ func TestFetchRevocationLogCompatible(t *testing.T) {
 				require.NoError(t, err)
 
 				err = putRevocationLog(
-					lb, &testChannelCommit, 0, 1,
+					lb, &testChannelCommit, 0, 1, false,
 				)
 				require.NoError(t, err)
 			}

config.go

@@ -981,6 +981,13 @@ func ValidateConfig(cfg Config, interceptor signal.Interceptor, fileParser,
 		)
 	}
 
+	// Ensure that the amount data for revoked commitment transactions is
+	// stored if the watchtower client is active.
+	if cfg.DB.NoRevLogAmtData && cfg.WtClient.Active {
+		return nil, mkErr("revocation log amount data must be stored " +
+			"if the watchtower client is active")
+	}
+
 	// Ensure a valid max channel fee allocation was set.
 	if cfg.MaxChannelFeeAllocation <= 0 || cfg.MaxChannelFeeAllocation > 1 {
 		return nil, mkErr("invalid max channel fee allocation: %v, "+

config_builder.go

@@ -867,15 +867,22 @@ func (d *DefaultDatabaseBuilder) BuildDatabase(
 
 	dbOptions := []channeldb.OptionModifier{
 		channeldb.OptionSetRejectCacheSize(cfg.Caches.RejectCacheSize),
-		channeldb.OptionSetChannelCacheSize(cfg.Caches.ChannelCacheSize),
+		channeldb.OptionSetChannelCacheSize(
-		channeldb.OptionSetBatchCommitInterval(cfg.DB.BatchCommitInterval),
+			cfg.Caches.ChannelCacheSize,
+		),
+		channeldb.OptionSetBatchCommitInterval(
+			cfg.DB.BatchCommitInterval,
+		),
 		channeldb.OptionDryRunMigration(cfg.DryRunMigration),
 		channeldb.OptionSetUseGraphCache(!cfg.DB.NoGraphCache),
-		channeldb.OptionKeepFailedPaymentAttempts(cfg.KeepFailedPaymentAttempts),
+		channeldb.OptionKeepFailedPaymentAttempts(
+			cfg.KeepFailedPaymentAttempts,
+		),
 		channeldb.OptionStoreFinalHtlcResolutions(
 			cfg.StoreFinalHtlcResolutions,
 		),
 		channeldb.OptionPruneRevocationLog(cfg.DB.PruneRevocation),
+		channeldb.OptionNoRevLogAmtData(cfg.DB.NoRevLogAmtData),
 	}
 
 	// We want to pre-allocate the channel graph cache according to what we

lncfg/db.go

@@ -85,6 +85,8 @@ type DB struct {
 	NoGraphCache bool `long:"no-graph-cache" description:"Don't use the in-memory graph cache for path finding. Much slower but uses less RAM. Can only be used with a bolt database backend."`
 
 	PruneRevocation bool `long:"prune-revocation" description:"Run the optional migration that prunes the revocation logs to save disk space."`
+
+	NoRevLogAmtData bool `long:"no-rev-log-amt-data" description:"If set, the to-local and to-remote output amounts of revoked commitment transactions will not be stored in the revocation log. Note that once this data is lost, a watchtower client will not be able to back up the revoked state."`
 }
 
 // DefaultDB creates and returns a new default DB config.

sample-lnd.conf

@@ -1241,6 +1241,12 @@ litecoin.node=ltcd
 ; channels prior to lnd@v0.15.0.
 ; db.prune-revocation=false
 
+; If set to true, then the to-local and to-remote output amount data of revoked
+; commitment transactions will not be stored in the revocation log. Note that
+; this flag can only be set if --wtclient.active is not set. It is not
+; recommended to set this flag if you plan on ever setting wtclient.active in
+; the future.
+; db.no-rev-log-amt-data=false
 
 [etcd]