1// Copyright 2018 GoPacket Authors. All rights reserved.
2//
3// Use of this source code is governed by a BSD-style license
4// that can be found in the LICENSE file in the root of the source
5// tree.
6
7package layers
8
9import (
10	"encoding/binary"
11	"errors"
12	"fmt"
13	"math"
14	"net"
15	"time"
16
17	"github.com/google/gopacket"
18)
19
20// MLDv1Message represents the common structure of all MLDv1 messages
21type MLDv1Message struct {
22	BaseLayer
23	// 3.4. Maximum Response Delay
24	MaximumResponseDelay time.Duration
25	// 3.6. Multicast Address
26	// Zero in general query
27	// Specific IPv6 multicast address otherwise
28	MulticastAddress net.IP
29}
30
31// DecodeFromBytes decodes the given bytes into this layer.
32func (m *MLDv1Message) DecodeFromBytes(data []byte, df gopacket.DecodeFeedback) error {
33	if len(data) < 20 {
34		df.SetTruncated()
35		return errors.New("ICMP layer less than 20 bytes for Multicast Listener Query Message V1")
36	}
37
38	m.MaximumResponseDelay = time.Duration(binary.BigEndian.Uint16(data[0:2])) * time.Millisecond
39	// data[2:4] is reserved and not used in mldv1
40	m.MulticastAddress = data[4:20]
41
42	return nil
43}
44
45// NextLayerType returns the layer type contained by this DecodingLayer.
46func (*MLDv1Message) NextLayerType() gopacket.LayerType {
47	return gopacket.LayerTypeZero
48}
49
50// SerializeTo writes the serialized form of this layer into the
51// SerializationBuffer, implementing gopacket.SerializableLayer.
52// See the docs for gopacket.SerializableLayer for more info.
53func (m *MLDv1Message) SerializeTo(b gopacket.SerializeBuffer, opts gopacket.SerializeOptions) error {
54	buf, err := b.PrependBytes(20)
55	if err != nil {
56		return err
57	}
58
59	if m.MaximumResponseDelay < 0 {
60		return errors.New("maximum response delay must not be negative")
61	}
62	dms := m.MaximumResponseDelay / time.Millisecond
63	if dms > math.MaxUint16 {
64		return fmt.Errorf("maximum response delay %dms is more than the allowed 65535ms", dms)
65	}
66	binary.BigEndian.PutUint16(buf[0:2], uint16(dms))
67
68	copy(buf[2:4], []byte{0x0, 0x0})
69
70	ma16 := m.MulticastAddress.To16()
71	if ma16 == nil {
72		return fmt.Errorf("invalid multicast address '%s'", m.MulticastAddress)
73	}
74	copy(buf[4:20], ma16)
75
76	return nil
77}
78
79// Sums this layer up nicely formatted
80func (m *MLDv1Message) String() string {
81	return fmt.Sprintf(
82		"Maximum Response Delay: %dms, Multicast Address: %s",
83		m.MaximumResponseDelay/time.Millisecond,
84		m.MulticastAddress)
85}
86
87// MLDv1MulticastListenerQueryMessage are sent by the router to determine
88// whether there are multicast listeners on the link.
89// https://tools.ietf.org/html/rfc2710 Page 5
90type MLDv1MulticastListenerQueryMessage struct {
91	MLDv1Message
92}
93
94// DecodeFromBytes decodes the given bytes into this layer.
95func (m *MLDv1MulticastListenerQueryMessage) DecodeFromBytes(data []byte, df gopacket.DecodeFeedback) error {
96	err := m.MLDv1Message.DecodeFromBytes(data, df)
97	if err != nil {
98		return err
99	}
100
101	if len(data) > 20 {
102		m.Payload = data[20:]
103	}
104
105	return nil
106}
107
108// LayerType returns LayerTypeMLDv1MulticastListenerQuery.
109func (*MLDv1MulticastListenerQueryMessage) LayerType() gopacket.LayerType {
110	return LayerTypeMLDv1MulticastListenerQuery
111}
112
113// CanDecode returns the set of layer types that this DecodingLayer can decode.
114func (*MLDv1MulticastListenerQueryMessage) CanDecode() gopacket.LayerClass {
115	return LayerTypeMLDv1MulticastListenerQuery
116}
117
118// IsGeneralQuery is true when this is a general query.
119// In a Query message, the Multicast Address field is set to zero when
120// sending a General Query.
121// https://tools.ietf.org/html/rfc2710#section-3.6
122func (m *MLDv1MulticastListenerQueryMessage) IsGeneralQuery() bool {
123	return net.IPv6zero.Equal(m.MulticastAddress)
124}
125
126// IsSpecificQuery is true when this is not a general query.
127// In a Query message, the Multicast Address field is set to a specific
128// IPv6 multicast address when sending a Multicast-Address-Specific Query.
129// https://tools.ietf.org/html/rfc2710#section-3.6
130func (m *MLDv1MulticastListenerQueryMessage) IsSpecificQuery() bool {
131	return !m.IsGeneralQuery()
132}
133
134// MLDv1MulticastListenerReportMessage is sent by a client listening on
135// a specific multicast address to indicate that it is (still) listening
136// on the specific multicast address.
137// https://tools.ietf.org/html/rfc2710 Page 6
138type MLDv1MulticastListenerReportMessage struct {
139	MLDv1Message
140}
141
142// LayerType returns LayerTypeMLDv1MulticastListenerReport.
143func (*MLDv1MulticastListenerReportMessage) LayerType() gopacket.LayerType {
144	return LayerTypeMLDv1MulticastListenerReport
145}
146
147// CanDecode returns the set of layer types that this DecodingLayer can decode.
148func (*MLDv1MulticastListenerReportMessage) CanDecode() gopacket.LayerClass {
149	return LayerTypeMLDv1MulticastListenerReport
150}
151
152// MLDv1MulticastListenerDoneMessage should be sent by a client when it ceases
153// to listen to a multicast address on an interface.
154// https://tools.ietf.org/html/rfc2710 Page 7
155type MLDv1MulticastListenerDoneMessage struct {
156	MLDv1Message
157}
158
159// LayerType returns LayerTypeMLDv1MulticastListenerDone.
160func (*MLDv1MulticastListenerDoneMessage) LayerType() gopacket.LayerType {
161	return LayerTypeMLDv1MulticastListenerDone
162}
163
164// CanDecode returns the set of layer types that this DecodingLayer can decode.
165func (*MLDv1MulticastListenerDoneMessage) CanDecode() gopacket.LayerClass {
166	return LayerTypeMLDv1MulticastListenerDone
167}
168
169func decodeMLDv1MulticastListenerReport(data []byte, p gopacket.PacketBuilder) error {
170	m := &MLDv1MulticastListenerReportMessage{}
171	return decodingLayerDecoder(m, data, p)
172}
173
174func decodeMLDv1MulticastListenerQuery(data []byte, p gopacket.PacketBuilder) error {
175	m := &MLDv1MulticastListenerQueryMessage{}
176	return decodingLayerDecoder(m, data, p)
177}
178
179func decodeMLDv1MulticastListenerDone(data []byte, p gopacket.PacketBuilder) error {
180	m := &MLDv1MulticastListenerDoneMessage{}
181	return decodingLayerDecoder(m, data, p)
182}
183