1// Copyright 2014 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package icmp
6
7import "encoding/binary"
8
9// A PacketTooBig represents an ICMP packet too big message body.
10type PacketTooBig struct {
11	MTU  int    // maximum transmission unit of the nexthop link
12	Data []byte // data, known as original datagram field
13}
14
15// Len implements the Len method of MessageBody interface.
16func (p *PacketTooBig) Len(proto int) int {
17	if p == nil {
18		return 0
19	}
20	return 4 + len(p.Data)
21}
22
23// Marshal implements the Marshal method of MessageBody interface.
24func (p *PacketTooBig) Marshal(proto int) ([]byte, error) {
25	b := make([]byte, 4+len(p.Data))
26	binary.BigEndian.PutUint32(b[:4], uint32(p.MTU))
27	copy(b[4:], p.Data)
28	return b, nil
29}
30
31// parsePacketTooBig parses b as an ICMP packet too big message body.
32func parsePacketTooBig(proto int, _ Type, b []byte) (MessageBody, error) {
33	bodyLen := len(b)
34	if bodyLen < 4 {
35		return nil, errMessageTooShort
36	}
37	p := &PacketTooBig{MTU: int(binary.BigEndian.Uint32(b[:4]))}
38	if bodyLen > 4 {
39		p.Data = make([]byte, bodyLen-4)
40		copy(p.Data, b[4:])
41	}
42	return p, nil
43}
44