lnwire: rename CommitRevocation to RevokeAndAck

This commit renames the prior CommitRevocation message to RevokeAndAck
in order to better align the set of wire messages implemented by the
`lnwire` message with those currently defined within the specification.

lnwire/revoke_and_ack.go

@@ -0,0 +1,120 @@
+package lnwire
+
+import (
+	"io"
+
+	"github.com/roasbeef/btcd/btcec"
+	"github.com/roasbeef/btcd/wire"
+)
+
+// RevokeAndAck is sent by either side once a CommitSig message has been
+// received, and validated. This message serves to revoke the prior commitment
+// transaction, which was the most up to date version until a CommitSig message
+// referencing the specified ChannelPoint was received.  Additionally, this
+// message also piggyback's the next revocation hash that Alice should use when
+// constructing the Bob's version of the next commitment transaction (which
+// would be done before sending a CommitSig message).  This piggybacking allows
+// Alice to send the next CommitSig message modifying Bob's commitment
+// transaction without first asking for a revocation hash initially.
+type RevokeAndAck struct {
+	// ChannelPoint uniquely identifies to which currently active channel
+	// this RevokeAndAck applies to.
+	ChannelPoint wire.OutPoint
+
+	// Revocation is the preimage to the revocation hash of the now prior
+	// commitment transaction.
+	//
+	// If the received revocation is the all zeroes hash ('0' * 32), then
+	// this RevokeAndAck is being sent in order to build up the sender's
+	// initial revocation window (IRW). In this case, the RevokeAndAck
+	// should be added to the receiver's queue of unused revocations to be
+	// used to construct future commitment transactions.
+	Revocation [32]byte
+
+	// NextRevocationKey is the next revocation key which should be added
+	// to the queue of unused revocation keys for the remote peer. This key
+	// will be used within the revocation clause for any new commitment
+	// transactions created for the remote peer.
+	NextRevocationKey *btcec.PublicKey
+
+	// NextRevocationHash is the next revocation hash which should be added
+	// to the queue on unused revocation hashes for the remote peer. This
+	// revocation hash will be used within any HTLCs included within this
+	// next commitment transaction.
+	NextRevocationHash [32]byte
+}
+
+// NewRevokeAndAck creates a new RevokeAndAck message.
+func NewRevokeAndAck() *RevokeAndAck {
+	return &RevokeAndAck{}
+}
+
+// A compile time check to ensure RevokeAndAck implements the lnwire.Message
+// interface.
+var _ Message = (*RevokeAndAck)(nil)
+
+// Decode deserializes a serialized RevokeAndAck message stored in the
+// passed io.Reader observing the specified protocol version.
+//
+// This is part of the lnwire.Message interface.
+func (c *RevokeAndAck) Decode(r io.Reader, pver uint32) error {
+	// ChannelPoint (8)
+	// Revocation (32)
+	// NextRevocationKey (33)
+	// NextRevocationHash (32)
+	err := readElements(r,
+		&c.ChannelPoint,
+		c.Revocation[:],
+		&c.NextRevocationKey,
+		c.NextRevocationHash[:],
+	)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// Encode serializes the target RevokeAndAck into the passed io.Writer
+// observing the protocol version specified.
+//
+// This is part of the lnwire.Message interface.
+func (c *RevokeAndAck) Encode(w io.Writer, pver uint32) error {
+	err := writeElements(w,
+		c.ChannelPoint,
+		c.Revocation[:],
+		c.NextRevocationKey,
+		c.NextRevocationHash[:],
+	)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// Command returns the integer uniquely identifying this message type on the
+// wire.
+//
+// This is part of the lnwire.Message interface.
+func (c *RevokeAndAck) Command() uint32 {
+	return CmdRevokeAndAck
+}
+
+// MaxPayloadLength returns the maximum allowed payload size for a
+// RevokeAndAck complete message observing the specified protocol version.
+//
+// This is part of the lnwire.Message interface.
+func (c *RevokeAndAck) MaxPayloadLength(uint32) uint32 {
+	// 36 + 32 + 33 + 32
+	return 133
+}
+
+// Validate performs any necessary sanity checks to ensure all fields present
+// on the RevokeAndAck are valid.
+//
+// This is part of the lnwire.Message interface.
+func (c *RevokeAndAck) Validate() error {
+	// We're good!
+	return nil
+}