lnwire: adjusted coop close messages to comply with spec

Removed close_request and close_complete and replaced with shutdown and
closing_signed.

lnwire/closing_signed.go

@@ -0,0 +1,88 @@
+package lnwire
+
+import (
+	"io"
+
+	"github.com/roasbeef/btcd/btcec"
+)
+
+// ClosingSigned is sent by both parties to a channel once the channel is clear
+// of HTLCs, and is primarily concerned with negotiating fees for the close
+// transaction. Each party provides a signature for a transaction with a fee
+// that they believe is fair. The process terminates when both sides agree on
+// the same fee, or when one side force closes the channel.
+//
+// NOTE: The responder is able to send a signature without any additional
+// messages as all transactions are assembled observing BIP 69 which defines a
+// cannonical ordering for input/outputs. Therefore, both sides are able to
+// arrive at an identical closure transaction as they know the order of the
+// inputs/outputs.
+type ClosingSigned struct {
+	// ChannelID serves to identify which channel is to be closed.
+	ChannelID ChannelID
+
+	// FeeSatoshis is the fee that the party to the channel would like to
+	// propose for the close transaction.
+	FeeSatoshis uint64
+
+	// Signature is for the proposed channel close transaction.
+	Signature *btcec.Signature
+}
+
+// NewClosingSigned creates a new empty ClosingSigned message.
+func NewClosingSigned(cid ChannelID, fs uint64,
+	sig *btcec.Signature) *ClosingSigned {
+
+	return &ClosingSigned{
+		ChannelID:   cid,
+		FeeSatoshis: fs,
+		Signature:   sig,
+	}
+}
+
+// A compile time check to ensure ClosingSigned implements the lnwire.Message
+// interface.
+var _ Message = (*ClosingSigned)(nil)
+
+// Decode deserializes a serialized ClosingSigned message stored in the passed
+// io.Reader observing the specified protocol version.
+//
+// This is part of the lnwire.Message interface.
+func (c *ClosingSigned) Decode(r io.Reader, pver uint32) error {
+	return readElements(r, &c.ChannelID, &c.FeeSatoshis, &c.Signature)
+}
+
+// Encode serializes the target ClosingSigned into the passed io.Writer
+// observing the protocol version specified.
+//
+// This is part of the lnwire.Message interface.
+func (c *ClosingSigned) Encode(w io.Writer, pver uint32) error {
+	return writeElements(w, c.ChannelID, c.FeeSatoshis, c.Signature)
+}
+
+// MsgType returns the integer uniquely identifying this message type on the
+// wire.
+//
+// This is part of the lnwire.Message interface.
+func (c *ClosingSigned) MsgType() MessageType {
+	return MsgClosingSigned
+}
+
+// MaxPayloadLength returns the maximum allowed payload size for a
+// ClosingSigned complete message observing the specified protocol version.
+//
+// This is part of the lnwire.Message interface.
+func (c *ClosingSigned) MaxPayloadLength(uint32) uint32 {
+	var length uint32
+
+	// ChannelID - 32 bytes
+	length += 32
+
+	// FeeSatoshis - 8 bytes
+	length += 8
+
+	// Signature - 64 bytes
+	length += 64
+
+	return length
+}