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ARES_QUERY(3)         DragonFly 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_ECANCELLED    The query was cancelled.

       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)

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