ares_create_query(3) [centos man page]

ARES_CREATE_QUERY(3)					     Library Functions Manual					      ARES_CREATE_QUERY(3)

NAME

       ares_create_query - Compose a single-question DNS query buffer

SYNOPSIS

       #include <ares.h>

       int ares_create_query(const char *name, int dnsclass, int type,
	     unsigned short id, int rd, unsigned char **buf,
	     int *buflen, int max_udp_size)

DESCRIPTION

       The  ares_create_query function composes a DNS query with a single question.  The parameter name gives the query name as a NUL-terminated C
       string of period-separated labels optionally ending with a period; periods and backslashes within a label must be escaped with a  backlash.
       The parameters dnsclass and type give the class and type of the query using the values defined in <arpa/nameser.h>.  The parameter id gives
       a 16-bit identifier for the query.  The parameter rd should be nonzero if recursion is desired, zero if not.  The query will be	placed	in
       an  allocated  buffer,  a  pointer to which will be stored in the variable pointed to by buf, and the length of which will be stored in the
       variable pointed to by buflen.  It is the caller's responsibility to free this buffer  using  ares_free_string(3)  when	it  is	no  longer
       needed.	 The  parameter  max_udp_size  should  be nonzero to activate EDNS. Usage of ares_create_query(3) with max_udp_size set to zero is
       equivalent to ares_mkquery(3).

RETURN VALUES

       ares_create_query can return any of the following values:

       ARES_SUCCESS   Construction of the DNS query succeeded.

       ARES_EBADNAME  The query name name could not be encoded as a domain name, either because it contained a zero-length  label  or  because	it
		      contained a label of more than 63 characters.

       ARES_ENOMEM    Memory was exhausted.

AVAILABILITY

       Added in c-ares 1.10.0

SEE ALSO

       ares_expand_name(3), ares_free_string(3)

AUTHOR

								    17 Aug 2012 					      ARES_CREATE_QUERY(3)

ARES_SEND(3)						     Library Functions Manual						      ARES_SEND(3)

NAME

       ares_send - Initiate a DNS query

SYNOPSIS

       #include <ares.h>

       typedef void (*ares_callback)(void *arg, int status,
       int timeouts, unsigned char *abuf, int alen)

       void ares_send(ares_channel channel, const unsigned char *qbuf,
	    int qlen, ares_callback callback, void *arg)

DESCRIPTION

       The  ares_send function initiates a DNS query on the name service channel identified by channel.  The parameters qbuf and qlen give the DNS
       query, which should already have been formatted according to the DNS protocol.  When the query is complete or has failed, the ares  library
       will  invoke  callback.	Completion or failure of the query may happen immediately, or may happen during a later call to ares_process(3) or
       ares_destroy(3).

       The callback argument arg is copied from the ares_send argument arg.  The callback argument status indicates whether  the  query  succeeded
       and, if not, how it failed.  It may have any of the following values:

       ARES_SUCCESS	  The query completed.

       ARES_EBADQUERY	  The query buffer was poorly formed (was not long enough for a DNS header or was too long for TCP transmission).

       ARES_ETIMEOUT	  No name servers responded within the timeout period.

       ARES_ECONNREFUSED  No name servers could be contacted.

       ARES_ENOMEM	  Memory was exhausted.

       ARES_EDESTRUCTION  The name service channel channel is being destroyed; the query will not be completed.

       The callback argument timeouts reports how many times a query timed out during the execution of the given request.

       If  the	query completed, the callback argument abuf points to a result buffer of length alen.  If the query did not complete, abuf will be
       NULL and alen will be 0.

       Unless the flag ARES_FLAG_NOCHECKRESP was set at channel initialization time, ares_send will normally ignore responses whose  questions	do
       not  match  the questions in qbuf, as well as responses with reply codes of SERVFAIL, NOTIMP, and REFUSED.  Unlike other query functions in
       the ares library, however, ares_send does not inspect the header of the reply packet to determine the error status, so a callback status of
       ARES_SUCCESS does not reflect as much about the response as for other query functions.

SEE ALSO

       ares_process(3)

AUTHOR

       Greg Hudson, MIT Information Systems
       Copyright 1998 by the Massachusetts Institute of Technology.

								   25 July 1998 						      ARES_SEND(3)