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151 lines
5.5 KiB
C
151 lines
5.5 KiB
C
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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef NET_DNS_DNS_PROTOCOL_H_
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#define NET_DNS_DNS_PROTOCOL_H_
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#include <stdint.h>
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#include "net/base/net_export.h"
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namespace net {
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namespace dns_protocol {
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static const uint16_t kDefaultPort = 53;
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static const uint16_t kDefaultPortMulticast = 5353;
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// DNS packet consists of a header followed by questions and/or answers.
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// For the meaning of specific fields, please see RFC 1035 and 2535
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// Header format.
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// 1 1 1 1 1 1
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// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
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// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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// | ID |
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// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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// |QR| Opcode |AA|TC|RD|RA| Z|AD|CD| RCODE |
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// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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// | QDCOUNT |
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// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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// | ANCOUNT |
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// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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// | NSCOUNT |
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// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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// | ARCOUNT |
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// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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// Question format.
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// 1 1 1 1 1 1
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// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
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// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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// | |
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// / QNAME /
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// / /
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// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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// | QTYPE |
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// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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// | QCLASS |
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// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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// Answer format.
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// 1 1 1 1 1 1
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// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
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// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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// | |
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// / /
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// / NAME /
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// | |
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// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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// | TYPE |
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// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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// | CLASS |
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// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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// | TTL |
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// | |
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// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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// | RDLENGTH |
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// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
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// / RDATA /
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// / /
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// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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#pragma pack(push)
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#pragma pack(1)
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// On-the-wire header. All uint16_t are in network order.
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struct NET_EXPORT Header {
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uint16_t id;
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uint16_t flags;
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uint16_t qdcount;
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uint16_t ancount;
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uint16_t nscount;
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uint16_t arcount;
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};
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#pragma pack(pop)
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static const uint8_t kLabelMask = 0xc0;
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static const uint8_t kLabelPointer = 0xc0;
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static const uint8_t kLabelDirect = 0x0;
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static const uint16_t kOffsetMask = 0x3fff;
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// In MDns the most significant bit of the rrclass is designated as the
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// "cache-flush bit", as described in http://www.rfc-editor.org/rfc/rfc6762.txt
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// section 10.2.
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static const uint16_t kMDnsClassMask = 0x7FFF;
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// RFC 1035, section 3.1: To simplify implementations, the total length of
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// a domain name (i.e., label octets and label length octets) is restricted
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// to 255 octets or less.
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static const int kMaxNameLength = 255;
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// RFC 1035, section 4.2.1: Messages carried by UDP are restricted to 512
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// bytes (not counting the IP nor UDP headers).
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static const int kMaxUDPSize = 512;
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// RFC 6762, section 17: Messages over the local link are restricted by the
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// medium's MTU, and must be under 9000 bytes
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static const int kMaxMulticastSize = 9000;
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// DNS class types.
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//
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// https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-2
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static const uint16_t kClassIN = 1;
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// DNS resource record types.
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//
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// https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-4
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static const uint16_t kTypeA = 1;
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static const uint16_t kTypeCNAME = 5;
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static const uint16_t kTypePTR = 12;
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static const uint16_t kTypeTXT = 16;
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static const uint16_t kTypeAAAA = 28;
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static const uint16_t kTypeSRV = 33;
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static const uint16_t kTypeOPT = 41;
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static const uint16_t kTypeNSEC = 47;
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// DNS reply codes (RCODEs).
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//
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// https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-6
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static const uint8_t kRcodeNOERROR = 0;
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static const uint8_t kRcodeFORMERR = 1;
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static const uint8_t kRcodeSERVFAIL = 2;
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static const uint8_t kRcodeNXDOMAIN = 3;
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static const uint8_t kRcodeNOTIMP = 4;
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static const uint8_t kRcodeREFUSED = 5;
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// DNS header flags.
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//
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// https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-12
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static const uint16_t kFlagResponse = 0x8000;
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static const uint16_t kFlagRD = 0x100; // Recursion Desired - query flag.
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static const uint16_t kFlagTC = 0x200; // Truncated - server flag.
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} // namespace dns_protocol
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} // namespace net
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#endif // NET_DNS_DNS_PROTOCOL_H_
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