dn_expand()

The dn_expand() call expands a compressed domain name to a full domain name.

Syntax

#include <types.h>
#include <netinet\in.h>
#include <arpa\nameser.h>
#include <resolv.h>
int dn_expand(msg, eomorig, comp_dn, exp_dn, length)
u_char *msg;
u_char *eomorig;
u_char *comp_dn;
u_char *exp_dn;
int length;

Parameters

msg

Pointer to the beginning of a message.

Pointer to the end of the original message that contains the compressed domain name.

Pointer to the compressed domain name.

Pointer to a buffer that holds the resulting expanded domain name.

Length of the buffer in bytes pointed to by the exp_dn parameter.

Description

The dn_expand() call expands a compressed domain name to a full domain name, converting the expanded names to all uppercase letters. A client process compresses domain names to conserve space. Compression consists of removing the longest possible previously occurring suffixes. The dn_expand() call restores a domain name compressed by the dn_comp() call to its full size.

The dn_expand() call is one of a set of calls that form the resolver. The resolver is a group 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 dn_expand() call returns the size of the expanded domain name. When unsuccessful, the call returns a value of -1.

Related Calls

dn_comp() dn_find()
dn_skipname()


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