icmpv4.go raw
1 // Copyright 2018 The gVisor Authors.
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 package header
16
17 import (
18 "encoding/binary"
19
20 "gvisor.dev/gvisor/pkg/tcpip"
21 "gvisor.dev/gvisor/pkg/tcpip/checksum"
22 )
23
24 // ICMPv4 represents an ICMPv4 header stored in a byte array.
25 type ICMPv4 []byte
26
27 const (
28 // ICMPv4PayloadOffset defines the start of ICMP payload.
29 ICMPv4PayloadOffset = 8
30
31 // ICMPv4MinimumSize is the minimum size of a valid ICMP packet.
32 ICMPv4MinimumSize = 8
33
34 // ICMPv4MinimumErrorPayloadSize Is the smallest number of bytes of an
35 // errant packet's transport layer that an ICMP error type packet should
36 // attempt to send as per RFC 792 (see each type) and RFC 1122
37 // section 3.2.2 which states:
38 // Every ICMP error message includes the Internet header and at
39 // least the first 8 data octets of the datagram that triggered
40 // the error; more than 8 octets MAY be sent; this header and data
41 // MUST be unchanged from the received datagram.
42 //
43 // RFC 792 shows:
44 // 0 1 2 3
45 // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
46 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
47 // | Type | Code | Checksum |
48 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
49 // | unused |
50 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
51 // | Internet Header + 64 bits of Original Data Datagram |
52 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
53 ICMPv4MinimumErrorPayloadSize = 8
54
55 // ICMPv4ProtocolNumber is the ICMP transport protocol number.
56 ICMPv4ProtocolNumber tcpip.TransportProtocolNumber = 1
57
58 // icmpv4ChecksumOffset is the offset of the checksum field
59 // in an ICMPv4 message.
60 icmpv4ChecksumOffset = 2
61
62 // icmpv4MTUOffset is the offset of the MTU field
63 // in an ICMPv4FragmentationNeeded message.
64 icmpv4MTUOffset = 6
65
66 // icmpv4IdentOffset is the offset of the ident field
67 // in an ICMPv4EchoRequest/Reply message.
68 icmpv4IdentOffset = 4
69
70 // icmpv4PointerOffset is the offset of the pointer field
71 // in an ICMPv4ParamProblem message.
72 icmpv4PointerOffset = 4
73
74 // icmpv4SequenceOffset is the offset of the sequence field
75 // in an ICMPv4EchoRequest/Reply message.
76 icmpv4SequenceOffset = 6
77 )
78
79 // ICMPv4Type is the ICMP type field described in RFC 792.
80 type ICMPv4Type byte
81
82 // ICMPv4Code is the ICMP code field described in RFC 792.
83 type ICMPv4Code byte
84
85 // Typical values of ICMPv4Type defined in RFC 792.
86 const (
87 ICMPv4EchoReply ICMPv4Type = 0
88 ICMPv4DstUnreachable ICMPv4Type = 3
89 ICMPv4SrcQuench ICMPv4Type = 4
90 ICMPv4Redirect ICMPv4Type = 5
91 ICMPv4Echo ICMPv4Type = 8
92 ICMPv4TimeExceeded ICMPv4Type = 11
93 ICMPv4ParamProblem ICMPv4Type = 12
94 ICMPv4Timestamp ICMPv4Type = 13
95 ICMPv4TimestampReply ICMPv4Type = 14
96 ICMPv4InfoRequest ICMPv4Type = 15
97 ICMPv4InfoReply ICMPv4Type = 16
98 )
99
100 // ICMP codes for ICMPv4 Time Exceeded messages as defined in RFC 792.
101 const (
102 ICMPv4TTLExceeded ICMPv4Code = 0
103 ICMPv4ReassemblyTimeout ICMPv4Code = 1
104 )
105
106 // ICMP codes for ICMPv4 Destination Unreachable messages as defined in RFC 792,
107 // RFC 1122 section 3.2.2.1 and RFC 1812 section 5.2.7.1.
108 const (
109 ICMPv4NetUnreachable ICMPv4Code = 0
110 ICMPv4HostUnreachable ICMPv4Code = 1
111 ICMPv4ProtoUnreachable ICMPv4Code = 2
112 ICMPv4PortUnreachable ICMPv4Code = 3
113 ICMPv4FragmentationNeeded ICMPv4Code = 4
114 ICMPv4SourceRouteFailed ICMPv4Code = 5
115 ICMPv4DestinationNetworkUnknown ICMPv4Code = 6
116 ICMPv4DestinationHostUnknown ICMPv4Code = 7
117 ICMPv4SourceHostIsolated ICMPv4Code = 8
118 ICMPv4NetProhibited ICMPv4Code = 9
119 ICMPv4HostProhibited ICMPv4Code = 10
120 ICMPv4NetUnreachableForTos ICMPv4Code = 11
121 ICMPv4HostUnreachableForTos ICMPv4Code = 12
122 ICMPv4AdminProhibited ICMPv4Code = 13
123 ICMPv4HostPrecedenceViolation ICMPv4Code = 14
124 ICMPv4PrecedenceCutInEffect ICMPv4Code = 15
125 )
126
127 // ICMPv4UnusedCode is a code to use in ICMP messages where no code is needed.
128 const ICMPv4UnusedCode ICMPv4Code = 0
129
130 // Type is the ICMP type field.
131 func (b ICMPv4) Type() ICMPv4Type { return ICMPv4Type(b[0]) }
132
133 // SetType sets the ICMP type field.
134 func (b ICMPv4) SetType(t ICMPv4Type) { b[0] = byte(t) }
135
136 // Code is the ICMP code field. Its meaning depends on the value of Type.
137 func (b ICMPv4) Code() ICMPv4Code { return ICMPv4Code(b[1]) }
138
139 // SetCode sets the ICMP code field.
140 func (b ICMPv4) SetCode(c ICMPv4Code) { b[1] = byte(c) }
141
142 // Pointer returns the pointer field in a Parameter Problem packet.
143 func (b ICMPv4) Pointer() byte { return b[icmpv4PointerOffset] }
144
145 // SetPointer sets the pointer field in a Parameter Problem packet.
146 func (b ICMPv4) SetPointer(c byte) { b[icmpv4PointerOffset] = c }
147
148 // Checksum is the ICMP checksum field.
149 func (b ICMPv4) Checksum() uint16 {
150 return binary.BigEndian.Uint16(b[icmpv4ChecksumOffset:])
151 }
152
153 // SetChecksum sets the ICMP checksum field.
154 func (b ICMPv4) SetChecksum(cs uint16) {
155 checksum.Put(b[icmpv4ChecksumOffset:], cs)
156 }
157
158 // SourcePort implements Transport.SourcePort.
159 func (ICMPv4) SourcePort() uint16 {
160 return 0
161 }
162
163 // DestinationPort implements Transport.DestinationPort.
164 func (ICMPv4) DestinationPort() uint16 {
165 return 0
166 }
167
168 // SetSourcePort implements Transport.SetSourcePort.
169 func (ICMPv4) SetSourcePort(uint16) {
170 }
171
172 // SetDestinationPort implements Transport.SetDestinationPort.
173 func (ICMPv4) SetDestinationPort(uint16) {
174 }
175
176 // Payload implements Transport.Payload.
177 func (b ICMPv4) Payload() []byte {
178 return b[ICMPv4PayloadOffset:]
179 }
180
181 // MTU retrieves the MTU field from an ICMPv4 message.
182 func (b ICMPv4) MTU() uint16 {
183 return binary.BigEndian.Uint16(b[icmpv4MTUOffset:])
184 }
185
186 // SetMTU sets the MTU field from an ICMPv4 message.
187 func (b ICMPv4) SetMTU(mtu uint16) {
188 binary.BigEndian.PutUint16(b[icmpv4MTUOffset:], mtu)
189 }
190
191 // Ident retrieves the Ident field from an ICMPv4 message.
192 func (b ICMPv4) Ident() uint16 {
193 return binary.BigEndian.Uint16(b[icmpv4IdentOffset:])
194 }
195
196 // SetIdent sets the Ident field from an ICMPv4 message.
197 func (b ICMPv4) SetIdent(ident uint16) {
198 binary.BigEndian.PutUint16(b[icmpv4IdentOffset:], ident)
199 }
200
201 // SetIdentWithChecksumUpdate sets the Ident field and updates the checksum.
202 func (b ICMPv4) SetIdentWithChecksumUpdate(new uint16) {
203 old := b.Ident()
204 b.SetIdent(new)
205 b.SetChecksum(^checksumUpdate2ByteAlignedUint16(^b.Checksum(), old, new))
206 }
207
208 // Sequence retrieves the Sequence field from an ICMPv4 message.
209 func (b ICMPv4) Sequence() uint16 {
210 return binary.BigEndian.Uint16(b[icmpv4SequenceOffset:])
211 }
212
213 // SetSequence sets the Sequence field from an ICMPv4 message.
214 func (b ICMPv4) SetSequence(sequence uint16) {
215 binary.BigEndian.PutUint16(b[icmpv4SequenceOffset:], sequence)
216 }
217
218 // ICMPv4Checksum calculates the ICMP checksum over the provided ICMP header,
219 // and payload.
220 func ICMPv4Checksum(h ICMPv4, payloadCsum uint16) uint16 {
221 xsum := payloadCsum
222
223 // h[2:4] is the checksum itself, skip it to avoid checksumming the checksum.
224 xsum = checksum.Checksum(h[:2], xsum)
225 xsum = checksum.Checksum(h[4:], xsum)
226
227 return ^xsum
228 }
229