net/dns/dns_protocol.h

   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
  11 namespace net {
  12
  13 namespace dns_protocol {
  14
  15 static const uint16 kDefaultPort = 53;
  16
  17 // DNS packet consists of a header followed by questions and/or answers.
  18 // For the meaning of specific fields, please see RFC 1035 and 2535
  19
  20 // Header format.
  21 //                                  1  1  1  1  1  1
  22 //    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
  23 //  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  24 //  |                      ID                       |
  25 //  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  26 //  |QR|   Opcode  |AA|TC|RD|RA| Z|AD|CD|   RCODE   |
  27 //  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  28 //  |                    QDCOUNT                    |
  29 //  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  30 //  |                    ANCOUNT                    |
  31 //  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  32 //  |                    NSCOUNT                    |
  33 //  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  34 //  |                    ARCOUNT                    |
  35 //  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  36
  37 // Question format.
  38 //                                  1  1  1  1  1  1
  39 //    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
  40 //  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  41 //  |                                               |
  42 //  /                     QNAME                     /
  43 //  /                                               /
  44 //  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  45 //  |                     QTYPE                     |
  46 //  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  47 //  |                     QCLASS                    |
  48 //  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  49
  50 // Answer format.
  51 //                                  1  1  1  1  1  1
  52 //    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
  53 //  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  54 //  |                                               |
  55 //  /                                               /
  56 //  /                      NAME                     /
  57 //  |                                               |
  58 //  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  59 //  |                      TYPE                     |
  60 //  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  61 //  |                     CLASS                     |
  62 //  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  63 //  |                      TTL                      |
  64 //  |                                               |
  65 //  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  66 //  |                   RDLENGTH                    |
  67 //  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
  68 //  /                     RDATA                     /
  69 //  /                                               /
  70 //  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  71
  72 #pragma pack(push)
  73 #pragma pack(1)
  74
  75 // On-the-wire header. All uint16 are in network order.
  76 // Used internally in DnsQuery and DnsResponseParser.
  77 struct NET_EXPORT_PRIVATE Header {
  78   uint16 id;
  79   uint16 flags;
  80   uint16 qdcount;
  81   uint16 ancount;
  82   uint16 nscount;
  83   uint16 arcount;
  84 };
  85
  86 #pragma pack(pop)
  87
  88 static const uint8 kLabelMask = 0xc0;
  89 static const uint8 kLabelPointer = 0xc0;
  90 static const uint8 kLabelDirect = 0x0;
  91 static const uint16 kOffsetMask = 0x3fff;
  92
  93 static const int kMaxNameLength = 255;
  94
  95 // RFC 1035, section 4.2.1: Messages carried by UDP are restricted to 512
  96 // bytes (not counting the IP nor UDP headers).
  97 static const int kMaxUDPSize = 512;
  98
  99 // DNS class types.
 100 static const uint16 kClassIN = 1;
 101
 102 // DNS resource record types. See
 103 // http://www.iana.org/assignments/dns-parameters
 104 static const uint16 kTypeA = 1;
 105 static const uint16 kTypeCNAME = 5;
 106 static const uint16 kTypeTXT = 16;
 107 static const uint16 kTypeAAAA = 28;
 108
 109 // DNS rcode values.
 110 static const uint8 kRcodeMask = 0xf;
 111 static const uint8 kRcodeNOERROR = 0;
 112 static const uint8 kRcodeFORMERR = 1;
 113 static const uint8 kRcodeSERVFAIL = 2;
 114 static const uint8 kRcodeNXDOMAIN = 3;
 115 static const uint8 kRcodeNOTIMP = 4;
 116 static const uint8 kRcodeREFUSED = 5;
 117
 118 // DNS flags.
 119 static const uint16 kFlagResponse = 0x8000;
 120 static const uint16 kFlagRA = 0x80;
 121 static const uint16 kFlagRD = 0x100;
 122 static const uint16 kFlagTC = 0x200;
 123 static const uint16 kFlagAA = 0x400;
 124
 125 }  // namespace dns_protocol
 126
 127 }  // namespace net
 128
 129 #endif  // NET_DNS_DNS_PROTOCOL_H_
 130