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DNS_HEADER structure (windns.h)

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The DNS_HEADER structure contains DNS header information used when sending DNS messages as specified in section 4.1.1 of RFC 1035.

Syntax

typedef struct _DNS_HEADER {
  WORD Xid;
  WORD Flags;
  BYTE RecursionDesired : 1;
  BYTE Truncation : 1;
  BYTE Authoritative : 1;
  BYTE Opcode : 4;
  BYTE IsResponse : 1;
  BYTE ResponseCode : 4;
  BYTE CheckingDisabled : 1;
  BYTE AuthenticatedData : 1;
  BYTE Reserved : 1;
  BYTE RecursionAvailable : 1;
  WORD QuestionCount;
  WORD AnswerCount;
  WORD NameServerCount;
  WORD AdditionalCount;
} DNS_HEADER, *PDNS_HEADER;

Members

Xid

A value that specifies the unique DNS message identifier.

Flags

RecursionDesired

A value that specifies whether recursive name query should be used by the DNS name server.

Value Meaning
0x00
 Do not use recursive name query.
0x01
 Use recursive name query.

Truncation

A value that specifies whether the DNS message has been truncated.

Value Meaning
0x00
 The message is not truncated.
0x01
 The message is truncated.

Authoritative

A value that specifies whether the DNS server from which the DNS message is being sent is authoritative for the domain name's zone.

Value Meaning
0x00
 The DNS server is not authoritative in the zone.
0x01
 The DNS server is authoritative in the zone.

Opcode

A value that specifies the operation code to be taken on the DNS message as defined in section 4.1.1 of RFC 1035 as the OPCODE field.

IsResponse

A value that specifies whether the DNS message is a query or a response message.

Value Meaning
0x00
 The DNS message is a query.
0x01
 The DNS message is a response.

ResponseCode

The DNS Response Code of the message.

CheckingDisabled

Windows 7 or later: A value that specifies whether checking is supported by the DNS resolver.

Value Meaning
0x00
 Checking is enabled on the DNS resolver.
0x01
 Checking is disabled on the DNS resolver.

AuthenticatedData

Windows 7 or later: A value that specifies whether the DNS data following the DNS_HEADER is authenticated by the DNS server.

Value Meaning
0x00
 The DNS data is not authenticated.
0x01
 The DNS data is authenticated.

Reserved

Reserved. Do not use.

RecursionAvailable

A value that specifies whether recursive name query is supported by the DNS name server.

Value Meaning
0x00
 Recursive name query is not supported.
0x01
 Recursive name query is supported.

QuestionCount

The number of queries contained in the question section of the DNS message.

AnswerCount

The number of resource records (RRs) contained in the answer section of the DNS message.

NameServerCount

The number of DNS name server RRs contained in the authority section of the DNS message. This value is the number of DNS name servers the message has traversed in its search for resolution.

AdditionalCount

Reserved. Do not use.

Requirements

Requirement Value
Minimum supported client Windows 2000 Professional [desktop apps only]
Minimum supported server Windows 2000 Server [desktop apps only]
Header windns.h

See also

DNS_RECORD