res_mkquery()

The res_mkquery() call makes a query message for the name servers in the internet domain.

Syntax

#include <types.h>
#include <netinet\in.h>
#include <arpa\nameser.h>
#include <resolv.h>
int res_mkquery(op, dname, class, type, data, datalen, newrr,
            buf, buflen)
int op;
char *dname;
int class;
int type;
char *data;
int datalen;
struct rrec *newrr;
char *buf;
int buflen;

Parameters

op

The usual type is QUERY, but you can set the parameter to any query type defined in the <ARPA\NAMESER.H> header file.

Pointer to the domain name. If dname points to a single label and the RES_DEFNAMES bit in the _res data structure (see The _res Data Structure) defined in the <RESOLV.H> header file is set, the call appends dname to the current domain name. The current domain name is defined in the ETC\RESOLV file.

One of the following values:

C_IN

ARPA Internet
C_CHAOS
Chaos network at MIT
type
One of the following type values for resources and queries:

T_A

Host address
T_NS
Authoritative server
T_MD
Mail destination
T_MF
Mail forwarder
T_CNAME
Canonical name
T_SOA
Start of authority zone
T_MB
Mailbox domain name
T_MG
Mail group member
T_MR
Mail rename name
T_NULL
Null resource record
T_WKS
Well-known service
T_PTR
Domain name pointer
T_HINFO
Host information
T_MINFO
Mailbox information
T_MX
Mail routing information
T_UINFO
User information
T_UID
User ID
T_GID
Group ID
data
Pointer to the data sent to the name server as a search key.
datalen
Size of the data parameter in bytes.
newrr
Reserved. Unused parameter.
buf
Pointer to the query message.
buflen
Length of the buffer in bytes pointed to by the buf parameter.

Description

This call creates packets for name servers in the internet domain. The call makes a query message for the name servers and puts that query message in the location pointed to by the buf parameter.

The res_mkquery() call is one of a group of calls that form the resolver. The resolver is a set of functions that perform a translation between domain names and network addresses. Global information used by the resolver calls resides in the _res data structure. The <RESOLV.H> file contains the _res data structure definition. (See The _res Data Structure for more on the _res data structure.)

Return Values

When successful, the res_mkquery() call returns the size of the query. When the query is larger than the value of buflen, the call fails and returns a value of -1.

Related Calls

dn_comp() dn_expand()
dn_find()
dn_skipname()


• getlong()
  
• getshort()
  putlong()
  putshort()
  res_init()
  res_query()
  res_search()
  res_send()

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