lnwire: add wire types for dynamic commitments

docs/release-notes/release-notes-0.18.0.md

@@ -62,6 +62,11 @@
 
 # Technical and Architectural Updates
 ## BOLT Spec Updates
+
+* [Add Dynamic Commitment Wire Types](https://github.com/lightningnetwork/lnd/pull/8026).
+  This change begins the development of Dynamic Commitments allowing for the
+  negotiation of new channel parameters and the upgrading of channel types.
+
 ## Testing
 ## Database
 ## Code Health
@@ -71,4 +76,5 @@
 
 * Carla Kirk-Cohen
 * Elle Mouton
+* Keagan McClelland
 * Yong Yu

fn/option.go

@@ -0,0 +1,149 @@
+package fn
+
+// Option[A] represents a value which may or may not be there. This is very
+// often preferable to nil-able pointers.
+type Option[A any] struct {
+	isSome bool
+	some   A
+}
+
+// Some trivially injects a value into an optional context.
+//
+// Some : A -> Option[A].
+func Some[A any](a A) Option[A] {
+	return Option[A]{
+		isSome: true,
+		some:   a,
+	}
+}
+
+// None trivially constructs an empty option
+//
+// None : Option[A].
+func None[A any]() Option[A] {
+	return Option[A]{}
+}
+
+// ElimOption is the universal Option eliminator. It can be used to safely
+// handle all possible values inside the Option by supplying two continuations.
+//
+// ElimOption : (Option[A], () -> B, A -> B) -> B.
+func ElimOption[A, B any](o Option[A], b func() B, f func(A) B) B {
+	if o.isSome {
+		return f(o.some)
+	}
+
+	return b()
+}
+
+// UnwrapOr is used to extract a value from an option, and we supply the default
+// value in the case when the Option is empty.
+//
+// UnwrapOr : (Option[A], A) -> A.
+func (o Option[A]) UnwrapOr(a A) A {
+	if o.isSome {
+		return o.some
+	}
+
+	return a
+}
+
+// WhenSome is used to conditionally perform a side-effecting function that
+// accepts a value of the type that parameterizes the option. If this function
+// performs no side effects, WhenSome is useless.
+//
+// WhenSome : (Option[A], A -> ()) -> ().
+func (o Option[A]) WhenSome(f func(A)) {
+	if o.isSome {
+		f(o.some)
+	}
+}
+
+// IsSome returns true if the Option contains a value
+//
+// IsSome : Option[A] -> bool.
+func (o Option[A]) IsSome() bool {
+	return o.isSome
+}
+
+// IsNone returns true if the Option is empty
+//
+// IsNone : Option[A] -> bool.
+func (o Option[A]) IsNone() bool {
+	return !o.isSome
+}
+
+// FlattenOption joins multiple layers of Options together such that if any of
+// the layers is None, then the joined value is None. Otherwise the innermost
+// Some value is returned.
+//
+// FlattenOption : Option[Option[A]] -> Option[A].
+func FlattenOption[A any](oo Option[Option[A]]) Option[A] {
+	if oo.IsNone() {
+		return None[A]()
+	}
+	if oo.some.IsNone() {
+		return None[A]()
+	}
+
+	return oo.some
+}
+
+// ChainOption transforms a function A -> Option[B] into one that accepts an
+// Option[A] as an argument.
+//
+// ChainOption : (A -> Option[B]) -> Option[A] -> Option[B].
+func ChainOption[A, B any](f func(A) Option[B]) func(Option[A]) Option[B] {
+	return func(o Option[A]) Option[B] {
+		if o.isSome {
+			return f(o.some)
+		}
+
+		return None[B]()
+	}
+}
+
+// MapOption transforms a pure function A -> B into one that will operate
+// inside the Option context.
+//
+// MapOption : (A -> B) -> Option[A] -> Option[B].
+func MapOption[A, B any](f func(A) B) func(Option[A]) Option[B] {
+	return func(o Option[A]) Option[B] {
+		if o.isSome {
+			return Some(f(o.some))
+		}
+
+		return None[B]()
+	}
+}
+
+// LiftA2Option transforms a pure function (A, B) -> C into one that will
+// operate in an Option context. For the returned function, if either of its
+// arguments are None, then the result will be None.
+//
+// LiftA2Option : ((A, B) -> C) -> (Option[A], Option[B]) -> Option[C].
+func LiftA2Option[A, B, C any](
+	f func(A, B) C,
+) func(Option[A], Option[B]) Option[C] {
+
+	return func(o1 Option[A], o2 Option[B]) Option[C] {
+		if o1.isSome && o2.isSome {
+			return Some(f(o1.some, o2.some))
+		}
+
+		return None[C]()
+	}
+}
+
+// Alt chooses the left Option if it is full, otherwise it chooses the right
+// option. This can be useful in a long chain if you want to choose between
+// many different ways of producing the needed value.
+//
+// Alt : Option[A] -> Option[A] -> Option[A].
+func (o Option[A]) Alt(o2 Option[A]) Option[A] {
+	if o.isSome {
+		return o
+	}
+
+	return o2
+}

lnwire/channel_reestablish.go

@@ -5,9 +5,24 @@ import (
 	"io"
 
 	"github.com/btcsuite/btcd/btcec/v2"
+	"github.com/lightningnetwork/lnd/fn"
 	"github.com/lightningnetwork/lnd/tlv"
 )
 
+const (
+	CRDynHeight tlv.Type = 20
+)
+
+// DynHeight is a newtype wrapper to get the proper RecordProducer instance
+// to smoothly integrate with the ChannelReestablish Message instance.
+type DynHeight uint64
+
+// Record implements the RecordProducer interface, allowing a full tlv.Record
+// object to be constructed from a DynHeight.
+func (d *DynHeight) Record() tlv.Record {
+	return tlv.MakePrimitiveRecord(CRDynHeight, (*uint64)(d))
+}
+
 // ChannelReestablish is a message sent between peers that have an existing
 // open channel upon connection reestablishment. This message allows both sides
 // to report their local state, and their current knowledge of the state of the
@@ -70,6 +85,11 @@ type ChannelReestablish struct {
 	// TODO(roasbeef): rename to verification nonce
 	LocalNonce *Musig2Nonce
 
+	// DynHeight is an optional field that stores the dynamic commitment
+	// negotiation height that is incremented upon successful completion of
+	// a dynamic commitment negotiation
+	DynHeight fn.Option[DynHeight]
+
 	// ExtraData is the set of data that was appended to this message to
 	// fill out the full maximum transport message size. These fields can
 	// be used to specify optional data such as custom TLV fields.
@@ -121,6 +141,10 @@ func (a *ChannelReestablish) Encode(w *bytes.Buffer, pver uint32) error {
 	if a.LocalNonce != nil {
 		recordProducers = append(recordProducers, a.LocalNonce)
 	}
+	a.DynHeight.WhenSome(func(h DynHeight) {
+		recordProducers = append(recordProducers, &h)
+	})
+
 	err := EncodeMessageExtraData(&a.ExtraData, recordProducers...)
 	if err != nil {
 		return err
@@ -180,8 +204,9 @@ func (a *ChannelReestablish) Decode(r io.Reader, pver uint32) error {
 	}
 
 	var localNonce Musig2Nonce
+	var dynHeight DynHeight
 	typeMap, err := tlvRecords.ExtractRecords(
-		&localNonce,
+		&localNonce, &dynHeight,
 	)
 	if err != nil {
 		return err
@@ -190,6 +215,9 @@ func (a *ChannelReestablish) Decode(r io.Reader, pver uint32) error {
 	if val, ok := typeMap[NonceRecordType]; ok && val == nil {
 		a.LocalNonce = &localNonce
 	}
+	if val, ok := typeMap[CRDynHeight]; ok && val == nil {
+		a.DynHeight = fn.Some(dynHeight)
+	}
 
 	if len(tlvRecords) != 0 {
 		a.ExtraData = tlvRecords

lnwire/dyn_ack.go

@@ -0,0 +1,138 @@
+package lnwire
+
+import (
+	"bytes"
+	"io"
+
+	"github.com/btcsuite/btcd/btcec/v2/schnorr/musig2"
+	"github.com/lightningnetwork/lnd/fn"
+	"github.com/lightningnetwork/lnd/tlv"
+)
+
+const (
+	// DALocalMusig2Pubnonce is the TLV type number that identifies the
+	// musig2 public nonce that we need to verify the commitment transaction
+	// signature.
+	DALocalMusig2Pubnonce tlv.Type = 0
+)
+
+// DynAck is the message used to accept the parameters of a dynamic commitment
+// negotiation. Additional optional parameters will need to be present depending
+// on the details of the dynamic commitment upgrade.
+type DynAck struct {
+	// ChanID is the ChannelID of the channel that is currently undergoing
+	// a dynamic commitment negotiation
+	ChanID ChannelID
+
+	// LocalNonce is an optional field that is transmitted when accepting
+	// a dynamic commitment upgrade to Taproot Channels. This nonce will be
+	// used to verify the first commitment transaction signature. This will
+	// only be populated if the DynPropose we are responding to specifies
+	// taproot channels in the ChannelType field.
+	LocalNonce fn.Option[Musig2Nonce]
+
+	// ExtraData is the set of data that was appended to this message to
+	// fill out the full maximum transport message size. These fields can
+	// be used to specify optional data such as custom TLV fields.
+	ExtraData ExtraOpaqueData
+}
+
+// A compile time check to ensure DynAck implements the lnwire.Message
+// interface.
+var _ Message = (*DynAck)(nil)
+
+// Encode serializes the target DynAck into the passed io.Writer. Serialization
+// will observe the rules defined by the passed protocol version.
+//
+// This is a part of the lnwire.Message interface.
+func (da *DynAck) Encode(w *bytes.Buffer, _ uint32) error {
+	if err := WriteChannelID(w, da.ChanID); err != nil {
+		return err
+	}
+
+	var tlvRecords []tlv.Record
+	da.LocalNonce.WhenSome(func(nonce Musig2Nonce) {
+		tlvRecords = append(
+			tlvRecords, tlv.MakeStaticRecord(
+				DALocalMusig2Pubnonce, &nonce,
+				musig2.PubNonceSize, nonceTypeEncoder,
+				nonceTypeDecoder,
+			),
+		)
+	})
+	tlv.SortRecords(tlvRecords)
+
+	tlvStream, err := tlv.NewStream(tlvRecords...)
+	if err != nil {
+		return err
+	}
+
+	var extraBytesWriter bytes.Buffer
+	if err := tlvStream.Encode(&extraBytesWriter); err != nil {
+		return err
+	}
+
+	da.ExtraData = ExtraOpaqueData(extraBytesWriter.Bytes())
+
+	return WriteBytes(w, da.ExtraData)
+}
+
+// Decode deserializes the serialized DynAck stored in the passed io.Reader into
+// the target DynAck using the deserialization rules defined by the passed
+// protocol version.
+//
+// This is a part of the lnwire.Message interface.
+func (da *DynAck) Decode(r io.Reader, _ uint32) error {
+	// Parse out main message.
+	if err := ReadElements(r, &da.ChanID); err != nil {
+		return err
+	}
+
+	// Parse out TLV records.
+	var tlvRecords ExtraOpaqueData
+	if err := ReadElement(r, &tlvRecords); err != nil {
+		return err
+	}
+
+	// Prepare receiving buffers to be filled by TLV extraction.
+	var localNonceScratch Musig2Nonce
+	localNonce := tlv.MakeStaticRecord(
+		DALocalMusig2Pubnonce, &localNonceScratch, musig2.PubNonceSize,
+		nonceTypeEncoder, nonceTypeDecoder,
+	)
+
+	// Create set of Records to read TLV bytestream into.
+	records := []tlv.Record{localNonce}
+	tlv.SortRecords(records)
+
+	// Read TLV stream into record set.
+	extraBytesReader := bytes.NewReader(tlvRecords)
+	tlvStream, err := tlv.NewStream(records...)
+	if err != nil {
+		return err
+	}
+	typeMap, err := tlvStream.DecodeWithParsedTypesP2P(extraBytesReader)
+	if err != nil {
+		return err
+	}
+
+	// Check the results of the TLV Stream decoding and appropriately set
+	// message fields.
+	if val, ok := typeMap[DALocalMusig2Pubnonce]; ok && val == nil {
+		da.LocalNonce = fn.Some(localNonceScratch)
+	}
+
+	if len(tlvRecords) != 0 {
+		da.ExtraData = tlvRecords
+	}
+
+	return nil
+}
+
+// MsgType returns the MessageType code which uniquely identifies this message
+// as a DynAck on the wire.
+//
+// This is part of the lnwire.Message interface.
+func (da *DynAck) MsgType() MessageType {
+	return MsgDynAck
+}