DNS Constants

The following constants are defined for DNS in host byte order.

DNS Record Types

Constant Value
DNS_TYPE_A 0x0001
DNS_TYPE_NS 0x0002
DNS_TYPE_MD 0x0003
DNS_TYPE_MF 0x0004
DNS_TYPE_CNAME 0x0005
DNS_TYPE_SOA 0x0006
DNS_TYPE_MB 0x0007
DNS_TYPE_MG 0x0008
DNS_TYPE_MR 0x0009
DNS_TYPE_NULL 0x000a
DNS_TYPE_WKS 0x000b
DNS_TYPE_PTR 0x000c
DNS_TYPE_HINFO 0x000d
DNS_TYPE_MINFO 0x000e
DNS_TYPE_MX 0x000f
DNS_TYPE_TEXT 0x0010
DNS_TYPE_RP 0x0011
DNS_TYPE_AFSDB 0x0012
DNS_TYPE_X25 0x0013
DNS_TYPE_ISDN 0x0014
DNS_TYPE_RT 0x0015
DNS_TYPE_NSAP 0x0016
DNS_TYPE_NSAPPTR 0x0017
DNS_TYPE_SIG 0x0018
DNS_TYPE_KEY 0x0019
DNS_TYPE_PX 0x001a
DNS_TYPE_GPOS 0x001b
DNS_TYPE_AAAA 0x001c
DNS_TYPE_LOC 0x001d
DNS_TYPE_NXT 0x001e
DNS_TYPE_EID 0x001f
DNS_TYPE_NIMLOC 0x0020
DNS_TYPE_SRV 0x0021
DNS_TYPE_ATMA 0x0022
DNS_TYPE_NAPTR 0x0023
DNS_TYPE_KX 0x0024
DNS_TYPE_CERT 0x0025
DNS_TYPE_A6 0x0026
DNS_TYPE_DNAME 0x0027
DNS_TYPE_SINK 0x0028
DNS_TYPE_OPT 0x0029
DNS_TYPE_DS 0x002B
DNS_TYPE_RRSIG 0x002E
DNS_TYPE_NSEC 0x002F
DNS_TYPE_DNSKEY 0x0030
DNS_TYPE_DHCID 0x0031
DNS_TYPE_UINFO 0x0064
DNS_TYPE_UID 0x0065
DNS_TYPE_GID 0x0066
DNS_TYPE_UNSPEC 0x0067
DNS_TYPE_ADDRS 0x00f8
DNS_TYPE_TKEY 0x00f9
DNS_TYPE_TSIG 0x00fa
DNS_TYPE_IXFR 0x00fb
DNS_TYPE_AXFR 0x00fc
DNS_TYPE_MAILB 0x00fd
DNS_TYPE_MAILA 0x00fe
DNS_TYPE_ALL 0x00ff
DNS_TYPE_ANY 0x00ff
DNS_TYPE_WINS 0xff01
DNS_TYPE_WINSR 0xff02
DNS_TYPE_NBSTAT DNS_TYPE_WINSR

DNS Class Types

Constant Value
DNS_CLASS_INTERNET 0x0001
DNS_CLASS_CSNET 0x0002
DNS_CLASS_CHAOS 0x0003
DNS_CLASS_HESIOD 0x0004
DNS_CLASS_NONE 0x00fe
DNS_CLASS_ALL 0x00ff
DNS_CLASS_ANY 0x00ff

DNS Query Types

Constant Value
DNS_OPCODE_QUERY 0x0000
DNS_OPCODE_IQUERY 0x0001
DNS_OPCODE_SERVER_STATUS 0x0002
DNS_OPCODE_UNKNOWN 0x0003
DNS_OPCODE_NOTIFY 0x0004
DNS_OPCODE_UPDATE 0x0005

DNS Record Flags

The following flags refer to a resource record's (RR) section within a DNS message:

Constant Value Meaning
DNSREC_QUESTION 0x00000000 RR is in the question section
DNSREC_ANSWER 0x00000001 RR is in the answer section
DNSREC_AUTHORITY 0x00000002 RR is in the authority section
DNSREC_ADDITIONAL 0x00000003 RR is in the additional section

The following flags refer to a RR's section within an update DNS message per RFC 2136:

Constant Value Meaning
DNSREC_ZONE 0x00000000 RR is in the zone section
DNSREC_PREREQ 0x00000001 RR is in the prerequisite section
DNSREC_UPDATE 0x00000002 RR is in the update section

The following flags are mutually exclusive:

Constant Value Meaning
DNSREC_DELETE 0x00000004 Delete a RR. Used in conjunction with DNSREC_UPDATE
DNSREC_NOEXIST 0x00000004 RR does not exist. Used in conjunction with DNSREC_PREREQ

DNS Query Options

Constant Value Meaning
DNS_QUERY_STANDARD 0x00000000 Standard query.
DNS_QUERY_ACCEPT_TRUNCATED_RESPONSE 0x00000001 Returns truncated results. Does not retry under TCP.
DNS_QUERY_USE_TCP_ONLY 0x00000002 Uses TCP only for the query.
DNS_QUERY_NO_RECURSION 0x00000004 Directs the DNS server to perform an iterative query (specifically directs the DNS server not to perform recursive resolution to resolve the query).
DNS_QUERY_BYPASS_CACHE 0x00000008 Bypasses the resolver cache on the lookup.
DNS_QUERY_NO_WIRE_QUERY 0x00000010 Directs DNS to perform a query on the local cache only.Windows 2000 Server and Windows 2000 Professional: This value is not supported. For similar functionality, use DNS_QUERY_CACHE_ONLY.
DNS_QUERY_NO_LOCAL_NAME 0x00000020 Directs DNS to ignore the local name.Windows 2000 Server and Windows 2000 Professional: This value is not supported.
DNS_QUERY_NO_HOSTS_FILE 0x00000040 Prevents the DNS query from consulting the HOSTS file.Windows 2000 Server and Windows 2000 Professional: This value is not supported.
DNS_QUERY_NO_NETBT 0x00000080 Prevents the DNS query from using NetBT for resolution.Windows 2000 Server and Windows 2000 Professional: This value is not supported.
DNS_QUERY_WIRE_ONLY 0x00000100 Directs DNS to perform a query using the network only, bypassing local information.Windows 2000 Server and Windows 2000 Professional: This value is not supported.
DNS_QUERY_RETURN_MESSAGE 0x00000200 Directs DNS to return the entire DNS response message.Windows 2000 Server and Windows 2000 Professional: This value is not supported.
DNS_QUERY_MULTICAST_ONLY 0x00000400 Prevents the query from using DNS and uses only Local Link Multicast Name Resolution (LLMNR).Windows Vista and Windows Server 2008 or later.: This value is supported.
DNS_QUERY_NO_MULTICAST 0x00000800
DNS_QUERY_TREAT_AS_FQDN 0x00001000 Prevents the DNS response from attaching suffixes to the submitted name in a name resolution process.
DNS_QUERY_ADDRCONFIG 0x00002000 Windows 7 only: Do not send A type queries if IPv4 addresses are not available on an interface and do not send AAAA type queries if IPv6 addresses are not available.
DNS_QUERY_DUAL_ADDR 0x00004000 Windows 7 only: Query both AAAA and A type records and return results for each. Results for A type records are mapped into AAAA type.
DNS_QUERY_MULTICAST_WAIT 0x00020000 Waits for a full timeout to collect all the responses from the Local Link. If not set, the default behavior is to return with the first response.Windows Vista and Windows Server 2008 or later.: This value is supported.
DNS_QUERY_MULTICAST_VERIFY 0x00040000 Directs a test using the local machine hostname to verify name uniqueness on the same Local Link. Collects all responses even if normal LLMNR Sender behavior is not enabled.Windows Vista and Windows Server 2008 or later.: This value is supported.
DNS_QUERY_DONT_RESET_TTL_VALUES 0x00100000 If set, and if the response contains multiple records, records are stored with the TTL corresponding to the minimum value TTL from among all records. When this option is set, "Do not change the TTL of individual records" in the returned record set is not modified.
DNS_QUERY_DISABLE_IDN_ENCODING 0x00200000 Disables International Domain Name (IDN) encoding support in the DnsQuery, DnsQueryEx, DnsModifyRecordsInSet, and DnsReplaceRecordSet APIs. All punycode names are treated as ASCII and will be ASCII encoded on the wire. All non-ASCII names are encoded in UTF8 on the wire. Windows 8 or later.: This value is supported.
DNS_QUERY_APPEND_MULTILABEL 0x00800000
DNS_QUERY_RESERVED 0xf0000000 Reserved.

DNS Update Options

Constant Value Meaning
DNS_UPDATE_SECURITY_USE_DEFAULT 0x00000000 Uses the default behavior, which is specified in the registry, for secure dynamic DNS updates.
DNS_UPDATE_SECURITY_OFF 0x00000010 Does not attempt secure dynamic updates.
DNS_UPDATE_SECURITY_ON 0x00000020 Attempts non-secure dynamic update; if refused, attempts secure dynamic update.
DNS_UPDATE_SECURITY_ONLY 0x00000100 Attempts secure dynamic updates only.
DNS_UPDATE_CACHE_SECURITY_CONTEXT 0x00000200 Caches the security context for use in future transactions.
DNS_UPDATE_TEST_USE_LOCAL_SYS_ACCT 0x00000400 Uses credentials of the local computer account.
DNS_UPDATE_FORCE_SECURITY_NEGO 0x00000800 Does not use cached security context.
DNS_UPDATE_TRY_ALL_MASTER_SERVERS 0x00001000 Sends DNS updates to all multi-master DNS servers.
DNS_UPDATE_SKIP_NO_UPDATE_ADAPTERS 0x00002000 Do not update adapters where dynamic DNS updates are disabled.Windows 2000 Server with SP2 or later.: This value is supported.
DNS_UPDATE_REMOTE_SERVER 0x00004000 Register CNAME records on a remote server in addition to the local DNS server.Windows 2000 Server with SP2 or later.: This value is supported.
DNS_UPDATE_RESERVED 0xffff0000 Reserved for future use.

DNS Response Codes

Error Meaning
DNS_RCODE_NOERROR No error
DNS_RCODE_FORMERR Format error
DNS_RCODE_SERVFAIL Server failure
DNS_RCODE_NXDOMAIN Name error
DNS_RCODE_NOTIMPL Not implemented
DNS_RCODE_REFUSED Connection refused
DNS_RCODE_YXDOMAIN Domain name should not exist
DNS_RCODE_YXRRSET Resource Record (RR) set should not exist
DNS_RCODE_NXRRSET RR set does not exist
DNS_RCODE_NOTAUTH Not authoritative for zone
DNS_RCODE_NOTZONE Name not in zone
DNS_RCODE_BADVERS Bad Extension Mechanism for DNS (EDNS) version
DNS_RCODE_BADSIG Bad signature
DNS_RCODE_BADKEY Bad key
DNS_RCODE_BADTIME Bad timestamp