// Copyright 2012 The Chromium Authors // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. #ifndef NET_DNS_PUBLIC_DNS_PROTOCOL_H_ #define NET_DNS_PUBLIC_DNS_PROTOCOL_H_ #include <stdint.h> #include "net/base/net_export.h" namespace net { // General constants and structs defined by the DNS and MDNS protocols. // // Direct interaction with DNS and MDNS, as well as parsing DNS and MDNS // messages, should generally only be done within network stack code. // Network-stack-external code should interact indirectly through network // service APIs, e.g. NetworkContext::ResolveHost(). But these constants may // still be useful for other minor purposes. namespace dns_protocol { static const uint16_t kDefaultPort = …; // RFC 5353. static const uint16_t kDefaultPortMulticast = …; // https://www.iana.org/assignments/multicast-addresses/multicast-addresses.xhtml#multicast-addresses-1 static const char kMdnsMulticastGroupIPv4[] = …; // https://www.iana.org/assignments/ipv6-multicast-addresses/ipv6-multicast-addresses.xhtml#link-local static const char kMdnsMulticastGroupIPv6[] = …; // 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_t are in network order. struct NET_EXPORT Header { … }; #pragma pack(pop) static const uint8_t kLabelMask = …; static const uint8_t kLabelPointer = …; static const uint8_t kLabelDirect = …; static const uint16_t kOffsetMask = …; // 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_t kMDnsClassMask = …; // RFC 1035, section 3.1: To simplify implementations, the total length of // a domain name in wire form (i.e., label octets and label length octets) is // restricted to 255 octets or less. // // Note that RFC 1035 is ambiguous over whether or not this limit includes the // final zero-length terminating label, but RFC 6762 unambiguously uses the // more permissive interpretation of not including the terminating label against // the limit for mDNS and argues in RFC 6762 Appendix C that that is the correct // interpretation for unicast DNS. To avoid overcomplicating logic, Chrome // universally uses the more permissive RFC 6762 interpretation for all parsing. static const int kMaxNameLength = …; // The maximum number of ASCII characters allowed in a domain in dotted form, // derived from `kMaxNameLength` above by subtracting one from the count to // correspond to the first byte, which is not available to encode characters and // does not correspond to a dot after conversion. static const uint16_t kMaxCharNameLength = …; // RFC 1035, section 2.3.4: labels 63 octets or less. // Section 3.1: Each label is represented as a one octet length field followed // by that number of octets. const int kMaxLabelLength = …; // 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 = …; // 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 = …; // RFC 1035, Section 4.1.3. // TYPE (2 bytes) + CLASS (2 bytes) + TTL (4 bytes) + RDLENGTH (2 bytes) static const int kResourceRecordSizeInBytesWithoutNameAndRData = …; // DNS class types. // // https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-2 static const uint16_t kClassIN = …; // RFC 6762, Section 10.2. // // For resource records sent through mDNS, the top bit of the class field in a // resource record is repurposed to the cache-flush bit. This bit should only be // used in mDNS transactions. static const uint16_t kFlagCacheFlush = …; // DNS resource record types. // // https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-4 static const uint16_t kTypeA = …; static const uint16_t kTypeCNAME = …; static const uint16_t kTypeSOA = …; static const uint16_t kTypePTR = …; static const uint16_t kTypeTXT = …; static const uint16_t kTypeAAAA = …; static const uint16_t kTypeSRV = …; static const uint16_t kTypeOPT = …; static const uint16_t kTypeNSEC = …; static const uint16_t kTypeHttps = …; static const uint16_t kTypeANY = …; // DNS reply codes (RCODEs). // // https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-6 static const uint8_t kRcodeNOERROR = …; static const uint8_t kRcodeFORMERR = …; static const uint8_t kRcodeSERVFAIL = …; static const uint8_t kRcodeNXDOMAIN = …; static const uint8_t kRcodeNOTIMP = …; static const uint8_t kRcodeREFUSED = …; // DNS EDNS(0) option codes (OPT) // // https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-11 static constexpr uint16_t kEdnsPadding = …; static constexpr uint16_t kEdnsExtendedDnsError = …; // DNS header flags. // // https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-12 static const uint16_t kFlagResponse = …; static const uint16_t kFlagAA = …; // Authoritative Answer - response flag. static const uint16_t kFlagRD = …; // Recursion Desired - query flag. static const uint16_t kFlagTC = …; // Truncated - server flag. // SVCB/HTTPS ServiceParamKey // // IANA registration pending. Values from draft-ietf-dnsop-svcb-https-08. static constexpr uint16_t kHttpsServiceParamKeyMandatory = …; static constexpr uint16_t kHttpsServiceParamKeyAlpn = …; static constexpr uint16_t kHttpsServiceParamKeyNoDefaultAlpn = …; static constexpr uint16_t kHttpsServiceParamKeyPort = …; static constexpr uint16_t kHttpsServiceParamKeyIpv4Hint = …; static constexpr uint16_t kHttpsServiceParamKeyEchConfig = …; static constexpr uint16_t kHttpsServiceParamKeyIpv6Hint = …; // draft-ietf-dnsop-svcb-https-08#section-9 inline constexpr char kHttpsServiceDefaultAlpn[] = …; } // namespace dns_protocol } // namespace net #endif // NET_DNS_PUBLIC_DNS_PROTOCOL_H_
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