ARES_SEARCH
Section: C Library Functions (3)
Updated: 24 July 1998
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NAME
ares_search - Initiate a DNS query with domain search
SYNOPSIS
#include <ares.h>
typedef void (*ares_callback)(void *arg, int status,
void ares_search(ares_channel channel, const char *name,
int dnsclass, int type, ares_callback callback,
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).
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.
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.
SEE ALSO
ares_process(3)
AUTHOR
Greg Hudson, MIT Information Systems
Copyright 1998 by the Massachusetts Institute of Technology.