multi: add new SCB version for the taproot chan type

chanbackup/single.go

@@ -48,6 +48,10 @@ const (
 	// commitment and HTLC outputs that pay directly to the channel
 	// initiator.
 	ScriptEnforcedLeaseVersion = 4
+
+	// SimpleTaprootVersion is a version that denotes this channel is using
+	// the musig2 based taproot commitment format.
+	SimpleTaprootVersion = 5
 )
 
 // Single is a static description of an existing channel that can be used for
@@ -213,6 +217,9 @@ func NewSingle(channel *channeldb.OpenChannel,
 	}
 
 	switch {
+	case channel.ChanType.IsTaproot():
+		single.Version = SimpleTaprootVersion
+
 	case channel.ChanType.HasLeaseExpiration():
 		single.Version = ScriptEnforcedLeaseVersion
 		single.LeaseExpiry = channel.ThawHeight
@@ -244,6 +251,7 @@ func (s *Single) Serialize(w io.Writer) error {
 	case AnchorsCommitVersion:
 	case AnchorsZeroFeeHtlcTxCommitVersion:
 	case ScriptEnforcedLeaseVersion:
+	case SimpleTaprootVersion:
 	default:
 		return fmt.Errorf("unable to serialize w/ unknown "+
 			"version: %v", s.Version)
@@ -420,6 +428,7 @@ func (s *Single) Deserialize(r io.Reader) error {
 	case AnchorsCommitVersion:
 	case AnchorsZeroFeeHtlcTxCommitVersion:
 	case ScriptEnforcedLeaseVersion:
+	case SimpleTaprootVersion:
 	default:
 		return fmt.Errorf("unable to de-serialize w/ unknown "+
 			"version: %v", s.Version)

chanrestore.go

@@ -154,6 +154,12 @@ func (c *chanDBRestorer) openChannelShell(backup chanbackup.Single) (
 		chanType |= channeldb.AnchorOutputsBit
 		chanType |= channeldb.SingleFunderTweaklessBit
 
+	case chanbackup.SimpleTaprootVersion:
+		chanType = channeldb.ZeroHtlcTxFeeBit
+		chanType |= channeldb.AnchorOutputsBit
+		chanType |= channeldb.SingleFunderTweaklessBit
+		chanType |= channeldb.SimpleTaprootFeatureBit
+
 	default:
 		return nil, fmt.Errorf("unknown Single version: %v", err)
 	}

itest/lnd_channel_backup_test.go

@@ -107,6 +107,13 @@ func newChanRestoreScenario(ht *lntest.HarnessTest, ct lnrpc.CommitmentType,
 	// with a portion pushed.
 	ht.ConnectNodes(dave, carol)
 
+	// If the commitment type is taproot, then the channel must also be
+	// private.
+	var privateChan bool
+	if ct == lnrpc.CommitmentType_SIMPLE_TAPROOT {
+		privateChan = true
+	}
+
 	return &chanRestoreScenario{
 		carol:    carol,
 		dave:     dave,
@@ -117,6 +124,7 @@ func newChanRestoreScenario(ht *lntest.HarnessTest, ct lnrpc.CommitmentType,
 			PushAmt:        pushAmt,
 			ZeroConf:       zeroConf,
 			CommitmentType: ct,
+			Private:        privateChan,
 		},
 	}
 }
@@ -564,6 +572,21 @@ func testChannelBackupRestoreCommitTypes(ht *lntest.HarnessTest) {
 			ct:       lnrpc.CommitmentType_SCRIPT_ENFORCED_LEASE,
 			zeroConf: true,
 		},
+
+		// Restore a channel back up of a taproot channel that was
+		// confirmed.
+		{
+			name:     "restore from backup taproot",
+			ct:       lnrpc.CommitmentType_SIMPLE_TAPROOT,
+			zeroConf: false,
+		},
+
+		// Restore a chanenl back up of an unconfirmed taproot channel.
+		{
+			name:     "restore from backup taproot zero conf",
+			ct:       lnrpc.CommitmentType_SIMPLE_TAPROOT,
+			zeroConf: true,
+		},
 	}
 
 	for _, testCase := range testCases {
@@ -626,6 +649,13 @@ func runChanRestoreScenarioCommitTypes(ht *lntest.HarnessTest,
 	multi, err := ioutil.ReadFile(backupFilePath)
 	require.NoError(ht, err)
 
+	// If this was a zero conf taproot channel, then since it's private,
+	// we'll need to mine an extra block (framework won't mine extra blocks
+	// otherwise).
+	if ct == lnrpc.CommitmentType_SIMPLE_TAPROOT && zeroConf {
+		ht.MineBlocksAndAssertNumTxes(1, 1)
+	}
+
 	// Now that we have Dave's backup file, we'll create a new nodeRestorer
 	// that we'll restore using the on-disk channels.backup.
 	restoredNodeFunc := chanRestoreViaRPC(