From e3b9e70d93bf8206f4852ff4455a7bcd3a282720 Mon Sep 17 00:00:00 2001
From: Mikio Hara <mikioh.mikioh@gmail.com>
Date: Wed, 7 Jan 2015 12:10:14 +0900
Subject: [PATCH] icmp: add support for multi-part messages

ICMP extension structures allow a few existing ICMP error messages to
convey extra information for troubleshooting; especially the root cause
of why the original datagram could not be delivered.

This CL adds generic support for ICMP extension stuructures to
DstUnreach, TimeExceeded and ParamProb structs. Specific extensions such
as MPLS label-stack, interface and next-hop identification will be
inplemneted in separate followup CLs.

Change-Id: I90798c135bdf76b806e2dde2bdd57c2c11d7e7e9
---
 icmp/dstunreach.go   |  3 ++-
 icmp/extension.go    | 16 ++++++++++++++++
 icmp/message.go      |  1 +
 icmp/paramprob.go    |  5 +++--
 icmp/timeexceeded.go |  3 ++-
 5 files changed, 24 insertions(+), 4 deletions(-)
 create mode 100644 icmp/extension.go

diff --git a/icmp/dstunreach.go b/icmp/dstunreach.go
index 3f843cd4..d1905a94 100644
--- a/icmp/dstunreach.go
+++ b/icmp/dstunreach.go
@@ -7,7 +7,8 @@ package icmp
 // A DstUnreach represents an ICMP destination unreachable message
 // body.
 type DstUnreach struct {
-	Data []byte // data
+	Data       []byte      // data, known as original datagram field
+	Extensions []Extension // extensions
 }
 
 // Len implements the Len method of MessageBody interface.
diff --git a/icmp/extension.go b/icmp/extension.go
new file mode 100644
index 00000000..7575f026
--- /dev/null
+++ b/icmp/extension.go
@@ -0,0 +1,16 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package icmp
+
+// An Extension represents an ICMP extension.
+type Extension interface {
+	// Len returns the length of ICMP extension.
+	Len() int
+
+	// Marshal returns the binary enconding of ICMP extension.
+	Marshal() ([]byte, error)
+}
+
+const extensionVersion = 2
diff --git a/icmp/message.go b/icmp/message.go
index 13398a00..4e6bec7d 100644
--- a/icmp/message.go
+++ b/icmp/message.go
@@ -7,6 +7,7 @@
 // ICMPv4 and ICMPv6.
 //
 // ICMPv4 and ICMPv6 are defined in RFC 792 and RFC 4443.
+// Multi-part message support for ICMP is defined in RFC 4884.
 package icmp // import "golang.org/x/net/icmp"
 
 import (
diff --git a/icmp/paramprob.go b/icmp/paramprob.go
index ecf80ec9..48ae6019 100644
--- a/icmp/paramprob.go
+++ b/icmp/paramprob.go
@@ -8,8 +8,9 @@ import "golang.org/x/net/internal/iana"
 
 // A ParamProb represents an ICMP parameter problem message body.
 type ParamProb struct {
-	Pointer uintptr // offset within the data where the error was detected
-	Data    []byte  // data
+	Pointer    uintptr     // offset within the data where the error was detected
+	Data       []byte      // data, known as original datagram field
+	Extensions []Extension // extensions
 }
 
 // Len implements the Len method of MessageBody interface.
diff --git a/icmp/timeexceeded.go b/icmp/timeexceeded.go
index 0f0bb913..f61f4314 100644
--- a/icmp/timeexceeded.go
+++ b/icmp/timeexceeded.go
@@ -6,7 +6,8 @@ package icmp
 
 // A TimeExceeded represents an ICMP time exceeded message body.
 type TimeExceeded struct {
-	Data []byte // data
+	Data       []byte      // data, known as original datagram field
+	Extensions []Extension // extensions
 }
 
 // Len implements the Len method of MessageBody interface.