Home | History | Annotate | Download | only in dns 
      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 DnsResponseParser.
     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_
    144