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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef NET_DNS_DNS_PROTOCOL_H_
#define NET_DNS_DNS_PROTOCOL_H_
#include "base/basictypes.h"
#include "net/base/net_export.h"
namespace net {
namespace dns_protocol {
static const uint16 kDefaultPort = 53;
static const uint16 kDefaultPortMulticast = 5353;
// DNS packet consists of a header followed by questions and/or answers.
// For the meaning of specific fields, please see RFC 1035 and 2535
// Header format.
// 1 1 1 1 1 1
// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// | ID |
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// |QR| Opcode |AA|TC|RD|RA| Z|AD|CD| RCODE |
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// | QDCOUNT |
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// | ANCOUNT |
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// | NSCOUNT |
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// | ARCOUNT |
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// Question format.
// 1 1 1 1 1 1
// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// | |
// / QNAME /
// / /
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// | QTYPE |
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// | QCLASS |
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// Answer format.
// 1 1 1 1 1 1
// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// | |
// / /
// / NAME /
// | |
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// | TYPE |
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// | CLASS |
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// | TTL |
// | |
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// | RDLENGTH |
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
// / RDATA /
// / /
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
#pragma pack(push)
#pragma pack(1)
// On-the-wire header. All uint16 are in network order.
// Used internally in DnsQuery and DnsResponseParser.
struct NET_EXPORT_PRIVATE Header {
uint16 id;
uint16 flags;
uint16 qdcount;
uint16 ancount;
uint16 nscount;
uint16 arcount;
};
#pragma pack(pop)
static const uint8 kLabelMask = 0xc0;
static const uint8 kLabelPointer = 0xc0;
static const uint8 kLabelDirect = 0x0;
static const uint16 kOffsetMask = 0x3fff;
// In MDns the most significant bit of the rrclass is designated as the
// "cache-flush bit", as described in http://www.rfc-editor.org/rfc/rfc6762.txt
// section 10.2.
static const uint16 kMDnsClassMask = 0x7FFF;
static const int kMaxNameLength = 255;
// RFC 1035, section 4.2.1: Messages carried by UDP are restricted to 512
// bytes (not counting the IP nor UDP headers).
static const int kMaxUDPSize = 512;
// RFC 6762, section 17: Messages over the local link are restricted by the
// medium's MTU, and must be under 9000 bytes
static const int kMaxMulticastSize = 9000;
// DNS class types.
static const uint16 kClassIN = 1;
// DNS resource record types. See
// http://www.iana.org/assignments/dns-parameters
static const uint16 kTypeA = 1;
static const uint16 kTypeCNAME = 5;
static const uint16 kTypePTR = 12;
static const uint16 kTypeTXT = 16;
static const uint16 kTypeAAAA = 28;
static const uint16 kTypeSRV = 33;
static const uint16 kTypeNSEC = 47;
// DNS rcode values.
static const uint8 kRcodeMask = 0xf;
static const uint8 kRcodeNOERROR = 0;
static const uint8 kRcodeFORMERR = 1;
static const uint8 kRcodeSERVFAIL = 2;
static const uint8 kRcodeNXDOMAIN = 3;
static const uint8 kRcodeNOTIMP = 4;
static const uint8 kRcodeREFUSED = 5;
// DNS flags.
static const uint16 kFlagResponse = 0x8000;
static const uint16 kFlagRA = 0x80;
static const uint16 kFlagRD = 0x100;
static const uint16 kFlagTC = 0x200;
static const uint16 kFlagAA = 0x400;
} // namespace dns_protocol
} // namespace net
#endif // NET_DNS_DNS_PROTOCOL_H_
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