manpagez: man pages & more
man ares_search(3)
Home | html | info | man
ares_search(3)             Library Functions Manual             ares_search(3)


NAME

       ares_search - Initiate a DNS query with domain search


SYNOPSIS

       #include <ares.h>

       typedef void (*ares_callback_dnsrec)(void *arg,
                                            ares_status_t status,
                                            size_t timeouts,
                                            const ares_dns_record_t *dnsrec);

       void ares_search_dnsrec(ares_channel_t *channel,
                               const ares_dns_record_t *dnsrec,
                               ares_callback_dnsrec callback, void *arg);

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

       void ares_search(ares_channel_t *channel, const char *name,
                        int dnsclass, int type,
                        ares_callback callback, void *arg);



DESCRIPTION

       The ares_search function initiates a series of single-question DNS
       queries on the name service channel identified by channel, using the
       channel's search domains as well as a host alias file given by the
       HOSTALIAS environment variable.  The parameter name gives the alias
       name or the base of the query name as a NUL-terminated C string of
       period-separated labels; if it ends with a period, the channel's search
       domains will not be used.  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 sequence is complete or has failed,
       the ares library will invoke callback.  Completion or failure of the
       query sequence may happen immediately, or may happen during a later
       call to ares_process(3) or ares_destroy(3).

       If this is called from a thread other than which the main program event
       loop is running, care needs to be taken to ensure any file descriptor
       lists are updated immediately within the eventloop.  When the
       associated callback is called, it is called with a channel lock so care
       must be taken to ensure any processing is minimal to prevent DNS
       channel stalls.

       The callback argument arg is copied from the ares_search argument arg.
       The callback argument status indicates whether the query sequence ended
       with a successful query and, if not, how the query sequence failed.  It
       may have any of the following values:

       ARES_SUCCESS       A query completed successfully.

       ARES_ENODATA       No query completed successfully; when the query was
                          tried without a search domain appended, a response
                          was returned with no answers.

       ARES_EFORMERR      A query completed but the server claimed that the
                          query was malformatted.

       ARES_ESERVFAIL     No query completed successfully; when the query was
                          tried without a search domain appended, the server
                          claimed 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     No query completed successfully; when the query was
                          tried without a search domain appended, the server
                          reported that the queried-for domain name was not
                          found.

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

       ARES_TIMEOUT       No name servers responded to a query 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.

       ARES_ENOSERVER     No query completed successfully; no DNS servers were
                          configured on the channel.

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

       If a query completed successfully, the callback argument abuf points to
       a result buffer of length alen.  If the query did not complete
       successfully, abuf will usually be NULL and alen will usually be 0, but
       in some cases an unsuccessful query result may be placed in abuf.

       The ares_search_dnsrec(3) function behaves identically to
       ares_search(3), but takes an initialized and filled DNS record object
       to use for queries as the second argument dnsrec instead of a name,
       class and type.  This object is used as the base for the queries and
       must itself represent a valid query for a single name.  Note that the
       search domains will only be appended to the name in the question
       section; RRs on the DNS record object will not be affected.  Moreover,
       the callback argument is of type ares_callback_dnsrec.  This callback
       behaves identically to ares_callback, but is invoked with a parsed DNS
       record object dnsrec rather than a raw buffer with length.  Note that
       this object is read-only.

       The ares_search_dnsrec(3) function returns an ares_status_t response
       code.  This may be useful to know that the query was enqueued properly.
       The response code does not reflect the result of the query, just the
       result of the enqueuing of the query.



AVAILABILITY

       ares_search_dnsrec(3) was introduced in c-ares 1.28.0.



SEE ALSO

       ares_process(3), ares_dns_record(3)

                                 24 July 1998                   ares_search(3)

c-ares 1.30.0 - Generated Thu Jun 13 11:49:46 CDT 2024
© manpagez.com 2000-2024
Individual documents may contain additional copyright information.