From a3836d52413e6e2a83b3409b93cb7c3b9539a65a Mon Sep 17 00:00:00 2001
From: "Johan T. Halseth" <johanth@gmail.com>
Date: Fri, 14 Jul 2017 20:28:40 +0200
Subject: [PATCH] lnwire: add update_fee message type.

---
 lnwire/lnwire_test.go |  6 ++++
 lnwire/message.go     |  3 ++
 lnwire/update_fee.go  | 69 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 78 insertions(+)
 create mode 100644 lnwire/update_fee.go

diff --git a/lnwire/lnwire_test.go b/lnwire/lnwire_test.go
index b171bf8e..ebfefcfc 100644
--- a/lnwire/lnwire_test.go
+++ b/lnwire/lnwire_test.go
@@ -523,6 +523,12 @@ func TestLightningWireProtocol(t *testing.T) {
 				return mainScenario(&m)
 			},
 		},
+		{
+			msgType: MsgUpdateFee,
+			scenario: func(m UpdateFee) bool {
+				return mainScenario(&m)
+			},
+		},
 		{
 			msgType: MsgChannelAnnouncement,
 			scenario: func(m ChannelAnnouncement) bool {
diff --git a/lnwire/message.go b/lnwire/message.go
index e58384c9..f92705d9 100644
--- a/lnwire/message.go
+++ b/lnwire/message.go
@@ -39,6 +39,7 @@ const (
 	MsgUpdateFailHTLC                        = 131
 	MsgCommitSig                             = 132
 	MsgRevokeAndAck                          = 133
+	MsgUpdateFee                             = 137
 	MsgChannelAnnouncement                   = 256
 	MsgNodeAnnouncement                      = 257
 	MsgChannelUpdate                         = 258
@@ -149,6 +150,8 @@ func makeEmptyMessage(msgType MessageType) (Message, error) {
 		msg = &CommitSig{}
 	case MsgRevokeAndAck:
 		msg = &RevokeAndAck{}
+	case MsgUpdateFee:
+		msg = &UpdateFee{}
 	case MsgError:
 		msg = &Error{}
 	case MsgChannelAnnouncement:
diff --git a/lnwire/update_fee.go b/lnwire/update_fee.go
new file mode 100644
index 00000000..cbf21b61
--- /dev/null
+++ b/lnwire/update_fee.go
@@ -0,0 +1,69 @@
+package lnwire
+
+import (
+	"io"
+
+	"github.com/roasbeef/btcutil"
+)
+
+// UpdateFee is the message the channel initiator sends to the other peer if
+// the channel commitment fee needs to be updated.
+type UpdateFee struct {
+	// ChanID is the channel that this UpdateFee is meant for.
+	ChanID ChannelID
+
+	// FeePerKw is the fee-per-kw on commit transactions that the sender of
+	// this message wants to use for this channel.
+	FeePerKw btcutil.Amount
+}
+
+// NewUpdateFee creates a new UpdateFee message.
+func NewUpdateFee(chanID ChannelID, feePerKw btcutil.Amount) *UpdateFee {
+	return &UpdateFee{
+		ChanID:   chanID,
+		FeePerKw: feePerKw,
+	}
+}
+
+// A compile time check to ensure UpdateFee implements the lnwire.Message
+// interface.
+var _ Message = (*UpdateFee)(nil)
+
+// Decode deserializes a serialized UpdateFee message stored in the
+// passed io.Reader observing the specified protocol version.
+//
+// This is part of the lnwire.Message interface.
+func (c *UpdateFee) Decode(r io.Reader, pver uint32) error {
+	return readElements(r,
+		&c.ChanID,
+		&c.FeePerKw,
+	)
+}
+
+// Encode serializes the target UpdateFee into the passed io.Writer
+// observing the protocol version specified.
+//
+// This is part of the lnwire.Message interface.
+func (c *UpdateFee) Encode(w io.Writer, pver uint32) error {
+	return writeElements(w,
+		c.ChanID,
+		c.FeePerKw,
+	)
+}
+
+// MsgType returns the integer uniquely identifying this message type on the
+// wire.
+//
+// This is part of the lnwire.Message interface.
+func (c *UpdateFee) MsgType() MessageType {
+	return MsgUpdateFee
+}
+
+// MaxPayloadLength returns the maximum allowed payload size for a
+// UpdateFee complete message observing the specified protocol version.
+//
+// This is part of the lnwire.Message interface.
+func (c *UpdateFee) MaxPayloadLength(uint32) uint32 {
+	// 32 + 8
+	return 40
+}