1// Copyright (c) 2012 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef NET_DNS_DNS_PROTOCOL_H_
6#define NET_DNS_DNS_PROTOCOL_H_
7
8#include "base/basictypes.h"
9#include "net/base/net_export.h"
10
11namespace net {
12
13namespace dns_protocol {
14
15static const uint16 kDefaultPort = 53;
16static const uint16 kDefaultPortMulticast = 5353;
17
18// DNS packet consists of a header followed by questions and/or answers.
19// For the meaning of specific fields, please see RFC 1035 and 2535
20
21// Header format.
22//                                  1  1  1  1  1  1
23//    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
24//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
25//  |                      ID                       |
26//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
27//  |QR|   Opcode  |AA|TC|RD|RA| Z|AD|CD|   RCODE   |
28//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
29//  |                    QDCOUNT                    |
30//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
31//  |                    ANCOUNT                    |
32//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
33//  |                    NSCOUNT                    |
34//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
35//  |                    ARCOUNT                    |
36//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
37
38// Question format.
39//                                  1  1  1  1  1  1
40//    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
41//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
42//  |                                               |
43//  /                     QNAME                     /
44//  /                                               /
45//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
46//  |                     QTYPE                     |
47//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
48//  |                     QCLASS                    |
49//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
50
51// Answer format.
52//                                  1  1  1  1  1  1
53//    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
54//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
55//  |                                               |
56//  /                                               /
57//  /                      NAME                     /
58//  |                                               |
59//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
60//  |                      TYPE                     |
61//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
62//  |                     CLASS                     |
63//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
64//  |                      TTL                      |
65//  |                                               |
66//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
67//  |                   RDLENGTH                    |
68//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
69//  /                     RDATA                     /
70//  /                                               /
71//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
72
73#pragma pack(push)
74#pragma pack(1)
75
76// On-the-wire header. All uint16 are in network order.
77// Used internally in DnsQuery and DnsResponseParser.
78struct NET_EXPORT_PRIVATE Header {
79  uint16 id;
80  uint16 flags;
81  uint16 qdcount;
82  uint16 ancount;
83  uint16 nscount;
84  uint16 arcount;
85};
86
87#pragma pack(pop)
88
89static const uint8 kLabelMask = 0xc0;
90static const uint8 kLabelPointer = 0xc0;
91static const uint8 kLabelDirect = 0x0;
92static const uint16 kOffsetMask = 0x3fff;
93
94// In MDns the most significant bit of the rrclass is designated as the
95// "cache-flush bit", as described in http://www.rfc-editor.org/rfc/rfc6762.txt
96// section 10.2.
97static const uint16 kMDnsClassMask = 0x7FFF;
98
99static const int kMaxNameLength = 255;
100
101// RFC 1035, section 4.2.1: Messages carried by UDP are restricted to 512
102// bytes (not counting the IP nor UDP headers).
103static const int kMaxUDPSize = 512;
104
105// RFC 6762, section 17: Messages over the local link are restricted by the
106// medium's MTU, and must be under 9000 bytes
107static const int kMaxMulticastSize = 9000;
108
109// DNS class types.
110static const uint16 kClassIN = 1;
111
112// DNS resource record types. See
113// http://www.iana.org/assignments/dns-parameters
114static const uint16 kTypeA = 1;
115static const uint16 kTypeCNAME = 5;
116static const uint16 kTypePTR = 12;
117static const uint16 kTypeTXT = 16;
118static const uint16 kTypeAAAA = 28;
119static const uint16 kTypeSRV = 33;
120static const uint16 kTypeNSEC = 47;
121
122
123// DNS rcode values.
124static const uint8 kRcodeMask = 0xf;
125static const uint8 kRcodeNOERROR = 0;
126static const uint8 kRcodeFORMERR = 1;
127static const uint8 kRcodeSERVFAIL = 2;
128static const uint8 kRcodeNXDOMAIN = 3;
129static const uint8 kRcodeNOTIMP = 4;
130static const uint8 kRcodeREFUSED = 5;
131
132// DNS flags.
133static const uint16 kFlagResponse = 0x8000;
134static const uint16 kFlagRA = 0x80;
135static const uint16 kFlagRD = 0x100;
136static const uint16 kFlagTC = 0x200;
137static const uint16 kFlagAA = 0x400;
138
139}  // namespace dns_protocol
140
141}  // namespace net
142
143#endif  // NET_DNS_DNS_PROTOCOL_H_
144