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)