channeldb: add optional TapscriptRoot field + feature bit

channeldb/channel.go

@@ -252,6 +252,10 @@ type openChannelTlvData struct {
 	// memo is an optional text field that gives context to the user about
 	// the channel.
 	memo tlv.OptionalRecordT[tlv.TlvType5, []byte]
+
+	// tapscriptRoot is the optional Tapscript root the channel funding
+	// output commits to.
+	tapscriptRoot tlv.OptionalRecordT[tlv.TlvType6, [32]byte]
 }
 
 // encode serializes the openChannelTlvData to the given io.Writer.
@@ -265,6 +269,11 @@ func (c *openChannelTlvData) encode(w io.Writer) error {
 	c.memo.WhenSome(func(memo tlv.RecordT[tlv.TlvType5, []byte]) {
 		tlvRecords = append(tlvRecords, memo.Record())
 	})
+	c.tapscriptRoot.WhenSome(
+		func(root tlv.RecordT[tlv.TlvType6, [32]byte]) {
+			tlvRecords = append(tlvRecords, root.Record())
+		},
+	)
 
 	// Create the tlv stream.
 	tlvStream, err := tlv.NewStream(tlvRecords...)
@@ -278,6 +287,7 @@ func (c *openChannelTlvData) encode(w io.Writer) error {
 // decode deserializes the openChannelTlvData from the given io.Reader.
 func (c *openChannelTlvData) decode(r io.Reader) error {
 	memo := c.memo.Zero()
+	tapscriptRoot := c.tapscriptRoot.Zero()
 
 	// Create the tlv stream.
 	tlvStream, err := tlv.NewStream(
@@ -286,6 +296,7 @@ func (c *openChannelTlvData) decode(r io.Reader) error {
 		c.initialRemoteBalance.Record(),
 		c.realScid.Record(),
 		memo.Record(),
+		tapscriptRoot.Record(),
 	)
 	if err != nil {
 		return err
@@ -299,6 +310,9 @@ func (c *openChannelTlvData) decode(r io.Reader) error {
 	if _, ok := tlvs[memo.TlvType()]; ok {
 		c.memo = tlv.SomeRecordT(memo)
 	}
+	if _, ok := tlvs[tapscriptRoot.TlvType()]; ok {
+		c.tapscriptRoot = tlv.SomeRecordT(tapscriptRoot)
+	}
 
 	return nil
 }
@@ -380,6 +394,11 @@ const (
 	// SimpleTaprootFeatureBit indicates that the simple-taproot-chans
 	// feature bit was negotiated during the lifetime of the channel.
 	SimpleTaprootFeatureBit ChannelType = 1 << 10
+
+	// TapscriptRootBit indicates that this is a MuSig2 channel with a top
+	// level tapscript commitment. This MUST be set along with the
+	// SimpleTaprootFeatureBit.
+	TapscriptRootBit ChannelType = 1 << 11
 )
 
 // IsSingleFunder returns true if the channel type if one of the known single
@@ -450,6 +469,12 @@ func (c ChannelType) IsTaproot() bool {
 	return c&SimpleTaprootFeatureBit == SimpleTaprootFeatureBit
 }
 
+// HasTapscriptRoot returns true if the channel is using a top level tapscript
+// root commitment.
+func (c ChannelType) HasTapscriptRoot() bool {
+	return c&TapscriptRootBit == TapscriptRootBit
+}
+
 // ChannelStateBounds are the parameters from OpenChannel and AcceptChannel
 // that are responsible for providing bounds on the state space of the abstract
 // channel state. These values must be remembered for normal channel operation
@@ -1098,6 +1123,9 @@ func (c *OpenChannel) amendTlvData(auxData openChannelTlvData) {
 	auxData.memo.WhenSomeV(func(memo []byte) {
 		c.Memo = memo
 	})
+	auxData.tapscriptRoot.WhenSomeV(func(h [32]byte) {
+		c.TapscriptRoot = fn.Some[chainhash.Hash](h)
+	})
 }
 
 // extractTlvData creates a new openChannelTlvData from the given channel.
@@ -1122,6 +1150,11 @@ func (c *OpenChannel) extractTlvData() openChannelTlvData {
 			tlv.NewPrimitiveRecord[tlv.TlvType5](c.Memo),
 		)
 	}
+	c.TapscriptRoot.WhenSome(func(h chainhash.Hash) {
+		auxData.tapscriptRoot = tlv.SomeRecordT(
+			tlv.NewPrimitiveRecord[tlv.TlvType6, [32]byte](h),
+		)
+	})
 
 	return auxData
 }