ares_process(3) [centos man page]

ARES_PROCESS(3) 					     Library Functions Manual						   ARES_PROCESS(3)

NAME

       ares_process - Process events for name resolution

SYNOPSIS

       #include <ares.h>

       void ares_process(ares_channel channel, fd_set *read_fds,
       fd_set *write_fds)

       void ares_process_fd(ares_channel channel, ares_socket_t read_fd, ares_socket_t write_fd)

DESCRIPTION

       The  ares_process(3)  function handles input/output events and timeouts associated with queries pending on the name service channel identi-
       fied by channel.  The file descriptor sets pointed to by read_fds and write_fds should have file  descriptors  set  in  them  according	to
       whether the file descriptors specified by ares_fds(3) are ready for reading and writing.  (The easiest way to determine this information is
       to invoke select with a timeout no greater than the timeout given by ares_timeout(3) ).

       The ares_process function will invoke callbacks for pending queries if they complete successfully or fail.

       ares_process_fd(3) works the same way but acts and operates only on the specific file descriptors (sockets) you pass in	to  the  function.
       Use  ARES_SOCKET_BAD  for  "no action". This function is of course provided to allow users of c-ares to void select() in their applications
       and within c-ares.

   EXAMPLE
       The following code fragment waits for all pending queries on a channel to complete:

	      int nfds, count;
	      fd_set readers, writers;
	      struct timeval tv, *tvp;

	      while (1)
		{
		  FD_ZERO(&readers);
		  FD_ZERO(&writers);
		  nfds = ares_fds(channel, &readers, &writers);
		  if (nfds == 0)
		    break;
		  tvp = ares_timeout(channel, NULL, &tv);
		  count = select(nfds, &readers, &writers, NULL, tvp);
		  ares_process(channel, &readers, &writers);
		}

SEE ALSO

       ares_fds(3), ares_timeout(3)

AUTHOR

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

								   25 July 1998 						   ARES_PROCESS(3)

ARES_QUERY(3)						     Library Functions Manual						     ARES_QUERY(3)

NAME

       ares_query - Initiate a single-question DNS query

SYNOPSIS

       #include <ares.h>

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

       void ares_query(ares_channel channel, const char *name,
	    int dnsclass, int type, ares_callback callback,
       void *arg)

DESCRIPTION

       The  ares_query function initiates a single-question DNS query on the name service channel identified by channel.  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 backslash.  The parameters dnsclass and type give the class and type of the query using the values defined in
       <arpa/nameser.h>.  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_query 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 successfully.

       ARES_ENODATA	  The query completed but contains no answers.

       ARES_EFORMERR	  The query completed but the server claims that the query was malformatted.

       ARES_ESERVFAIL	  The query completed but the  server  claims  to  have  experienced  a  failure.   (This  code  can  only  occur  if  the
			  ARES_FLAG_NOCHECKRESP  flag  was  specified at channel initialization time; otherwise, such responses are ignored at the
			  ares_send(3) level.)

       ARES_ENOTFOUND	  The query completed but the queried-for domain name was not found.

       ARES_ENOTIMP	  The query completed but the server does not implement the operation requested by the query.  (This code can  only  occur
			  if the ARES_FLAG_NOCHECKRESP flag was specified at channel initialization time; otherwise, such responses are ignored at
			  the ares_send(3) level.)

       ARES_EREFUSED	  The query completed but the server refused the query.  (This code can only occur if the ARES_FLAG_NOCHECKRESP  flag  was
			  specified at channel initialization time; otherwise, such responses are ignored at the ares_send(3) level.)

       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_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 (even if there was something wrong with it, as indicated by some of the above error codes),  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.

SEE ALSO

       ares_process(3)

AUTHOR

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

								   24 July 1998 						     ARES_QUERY(3)