ares_query(3)

1ARES_QUERY(3)              Library Functions Manual              ARES_QUERY(3)
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NAME

6       ares_query - Initiate a single-question DNS query
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SYNOPSIS

9       #include <ares.h>
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11       typedef void (*ares_callback)(void *arg, int status,
12                                     int timeouts, unsigned char *abuf,
13                                     int alen)
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15       void ares_query(ares_channel channel, const char *name,
16                       int dnsclass, int type,
17                       ares_callback callback, void *arg)
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DESCRIPTION

20       The  ares_query  function  initiates a single-question DNS query on the
21       name service channel identified by channel.  The parameter  name  gives
22       the  query name as a NUL-terminated C string of period-separated labels
23       optionally ending with a period; periods and backslashes within a label
24       must  be  escaped  with  a backslash.  The parameters dnsclass and type
25       give the class and type of  the  query  using  the  values  defined  in
26       <arpa/nameser.h>.   When  the query is complete or has failed, the ares
27       library will invoke callback.  Completion or failure of the  query  may
28       happen   immediately,   or   may   happen   during   a  later  call  to
29       ares_process(3) or ares_destroy(3).
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31       The callback argument arg is copied from the ares_query  argument  arg.
32       The callback argument status indicates whether the query succeeded and,
33       if not, how it failed.  It may have any of the following values:
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35       ARES_SUCCESS       The query completed successfully.
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37       ARES_ENODATA       The query completed but contains no answers.
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39       ARES_EFORMERR      The query completed but the server claims  that  the
40                          query was malformatted.
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42       ARES_ESERVFAIL     The  query  completed  but the server claims to have
43                          experienced a failure.  (This code can only occur if
44                          the  ARES_FLAG_NOCHECKRESP  flag  was  specified  at
45                          channel initialization  time;  otherwise,  such  re‐
46                          sponses are ignored at the ares_send(3) level.)
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48       ARES_ENOTFOUND     The  query completed but the queried-for domain name
49                          was not found.
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51       ARES_ENOTIMP       The query completed but the server does  not  imple‐
52                          ment  the  operation  requested by the query.  (This
53                          code can only  occur  if  the  ARES_FLAG_NOCHECKRESP
54                          flag  was  specified at channel initialization time;
55                          otherwise,  such  responses  are  ignored   at   the
56                          ares_send(3) level.)
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58       ARES_EREFUSED      The  query  completed  but  the  server  refused the
59                          query.   (This  code   can   only   occur   if   the
60                          ARES_FLAG_NOCHECKRESP  flag was specified at channel
61                          initialization time; otherwise, such  responses  are
62                          ignored at the ares_send(3) level.)
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64       ARES_EBADNAME      The query name name could not be encoded as a domain
65                          name, either because it contained a zero-length  la‐
66                          bel  or because it contained a label of more than 63
67                          characters.
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69       ARES_ETIMEOUT      No name servers responded within the timeout period.
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71       ARES_ECONNREFUSED  No name servers could be contacted.
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73       ARES_ENOMEM        Memory was exhausted.
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75       ARES_ECANCELLED    The query was cancelled.
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77       ARES_EDESTRUCTION  The name service channel channel is being destroyed;
78                          the query will not be completed.
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80       The callback argument timeouts reports how many times a query timed out
81       during the execution of the given request.
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83       If the query completed (even if there was something wrong with  it,  as
84       indicated by some of the above error codes), the callback argument abuf
85       points to a result buffer of length alen.  If the query  did  not  com‐
86       plete, abuf will be NULL and alen will be 0.
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AUTHOR

92       Greg Hudson, MIT Information Systems
93       Copyright 1998 by the Massachusetts Institute of Technology.
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97                                 24 July 1998                    ARES_QUERY(3)

NAME

SYNOPSIS

DESCRIPTION

SEE ALSO

AUTHOR