NAME

res_mkquery − Make query messages for name servers

SYNOPSIS

#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <resolv.h> int res_mkquery(
        int query_type,
        const u_char ∗domain_name,
        int class,
        int type,
        const char ∗data,
        int data_length,
        const u_char ∗reserved,
        u_char ∗buffer,
        int buf_length );

LIBRARY

Standard C Library (libc)

PARAMETERS

query_type
Specifies a query type.  The usual type is QUERY, but the parameter can be set to any of the query types defined in the arpa/nameser.h file. 

domain_name
Points to the name of the domain.  If the domain_name parameter points to a single label and the RES_DEFNAMES bit is set, as it is by default, the function appends domain_name to the current domain name.  The current domain name is defined by the name server in use or in the /etc/resolv.conf file. 

class
Specifies one of the following parameters:

C_INSpecifies the ARPA Internet. 

C_CHAOS
Specifies the Chaos network at MIT.

typeRequires one of the following values:

T_AHost address

T_NSAuthoritative server

T_MDMail destination

T_MFMail forwarder

T_CNAME
Canonical name

T_SOAStart of authority zone

T_MBMailbox domain name

T_MGMail group member

T_MRMail rename name

T_NULL
NULL resource record

T_WKSWell known service

T_PTRDomain name pointer

T_HINFO
Host information

T_MINFO
Mailbox information

T_MXMail routing information

T_UINFO
User (finger) information

T_UIDUser ID

T_GIDGroup ID

dataPoints to the data that is sent to the name server as a search key.  The data is stored as a character array. 

data_length
Defines the size of the array pointed to by the data parameter. 

reserved
Specifies a reserved and currently unused parameter.

buffer
Points to a location containing the query message.

buf_length
Specifies the length of the message pointed to by the buffer parameter. 

DESCRIPTION

The res_mkquery() function makes packets for name servers in the Internet domain.  The res_mkquery() function makes a standard query message and places it in the location pointed to by the buffer parameter. 

The res_mkquery() function is one of a set of subroutines that form the resolver, a set of functions that resolve domain names.  Global information that is used by the resolver functions is kept in the _res data structure. The /include/resolv.h file contains the _res data structure definition. 

RETURN VALUES

Upon successful completion, the res_mkquery() function returns the size of the query. If the query is larger than the value of the buf_length parameter, the function fails and returns a value of -1. 

ERRORS

If an error occurs during a resolver operation, the h_errno external variable is set.  Error code values and reasons are defined in <netdb.h>. 

FILES

/etc/resolv.conf
Contains the name server and domain name.

SEE ALSO

Functions: dn_comp(3), dn_expand(3), dn_find(3), dn_skipname(3), _getlong(3), _getshort(3), putlong(3), putshort(3), res_init(3), res_query(3), res_search(3), res_send(3).