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 static 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 DnsResponse.
  78 struct 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
  89 static const uint8 kLabelMask = 0xc0;
  90 static const uint8 kLabelPointer = 0xc0;
  91 static const uint8 kLabelDirect = 0x0;
  92 static 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.
  97 static const uint16 kMDnsClassMask = 0x7FFF;
  98
  99 static 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).
 103 static 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
 107 static const int kMaxMulticastSize = 9000;
 108
 109 // DNS class types.
 110 static const uint16 kClassIN = 1;
 111
 112 // DNS resource record types. See
 113 // http://www.iana.org/assignments/dns-parameters
 114 static const uint16 kTypeA = 1;
 115 static const uint16 kTypeCNAME = 5;
 116 static const uint16 kTypePTR = 12;
 117 static const uint16 kTypeTXT = 16;
 118 static const uint16 kTypeAAAA = 28;
 119 static const uint16 kTypeSRV = 33;
 120 static const uint16 kTypeNSEC = 47;
 121
 122
 123 // DNS rcode values.
 124 static const uint8 kRcodeMask = 0xf;
 125 static const uint8 kRcodeNOERROR = 0;
 126 static const uint8 kRcodeFORMERR = 1;
 127 static const uint8 kRcodeSERVFAIL = 2;
 128 static const uint8 kRcodeNXDOMAIN = 3;
 129 static const uint8 kRcodeNOTIMP = 4;
 130 static const uint8 kRcodeREFUSED = 5;
 131
 132 // DNS flags.
 133 static const uint16 kFlagResponse = 0x8000;
 134 static const uint16 kFlagRA = 0x80;
 135 static const uint16 kFlagRD = 0x100;
 136 static const uint16 kFlagTC = 0x200;
 137 static const uint16 kFlagAA = 0x400;
 138
 139 }  // namespace dns_protocol
 140
 141 }  // namespace net
 142
 143 #endif  // NET_DNS_DNS_PROTOCOL_H_