DWORD SetResolverOptions(
	DWORD dwOptions
);

The SetResolverOptions method changes the resolver options for the client session.

Parameters

hClient

Handle to the client session.

dwOptions

An unsigned integer that specifies one or more resolver options. This parameter is constructed by using a bitwise operator with any of the following values:

Constant	Description
DNS_OPTION_NONE	No additional resolver options specified. This is the default value, and it is recommended that most applications do not specify additional options unless the implications of doing so are understood.
DNS_OPTION_PROMOTE	Promotes the server that successfully completed the last query to the first server that will be used to resolve subsequent queries. This option can improve performance in some cases where one or more of the registered servers are non-responsive. This option takes precedence over the DNS_OPTION_ROTATE option.
DNS_OPTION_ROTATE	Enables a round-robin selection of nameservers when performing queries. Normally each nameserver is queried in the same order. This option rotates the available nameservers so a different server is used with each query.
DNS_OPTION_AUTHONLY	Require the answer from the nameserver to be authoritative, not from the server's cache. This option is included for future expansion as most servers do not support this feature and will ignore it.
DNS_OPTION_PRIMARY	Queries are only accepted from the primary nameserver. This option is included for future expansion as most servers do not support this feature and will ignore it.
DNS_OPTION_NORECURSE	Disable the sending of recursive queries to the nameserver. Specifying this option will disable the bit in the DNS request header that specifies recursion is desired.
DNS_OPTION_NOSEARCH	Disable additional queries of higher domains in the search list if the host name cannot be resolved. If this option is specified, and the host name cannot be resolved using the local domain name an error is returned immediately. This option is ignored if no local domain has been specified or if the DNS_OPTION_NOSUFFIX option has been specified.
DNS_OPTION_NOSUFFIX	Disable additional queries using the local domain name if the host name is not a fully qualified domain name and cannot be resolved. This option is ignored if no local domain has been specified.
DNS_OPTION_NONAMECHECK	Disable checking the host name for invalid characters, such as the underscore and control characters. By default, host names are checked to ensure they're valid before submitting a query to the nameserver.

Return Value

If the method succeeds, the return value is non-zero. If the method fails, the return value is zero. To get extended error information, call GetLastError.

Remarks

The SetResolverOptions method changes the resolver options for the specified client session, modifying how nameserver queries are processed. It is recommended that most applications do not specify any resolver options and use the default behavior. Specifying these options without understanding how they can affect standard queries can result in unexpected failures. In particular, caution should be used when specifying the DNS_OPTION_NORECURSE and DNS_OPTION_NOSEARCH options as they change the normal process of resolving a host name.

Requirements

Client: Requires Windows 7, Windows Vista or Windows XP.
Server: Requires Windows Server 2008 or Windows Server 2003.
Header: Include cstools7.h.
Library: Use csdnsav7.lib.

See Also

CDnsClient, GetResolverOptions

Copyright © 2012 Catalyst Development Corporation. All rights reserved.