145 строки
4.4 KiB
Groff
145 строки
4.4 KiB
Groff
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.\" $Id$
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.\"
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.\" Copyright 1998 by the Massachusetts Institute of Technology.
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.\"
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.\" Permission to use, copy, modify, and distribute this
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.\" software and its documentation for any purpose and without
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.\" fee is hereby granted, provided that the above copyright
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.\" notice appear in all copies and that both that copyright
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.\" notice and this permission notice appear in supporting
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.\" documentation, and that the name of M.I.T. not be used in
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.\" advertising or publicity pertaining to distribution of the
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.\" software without specific, written prior permission.
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.\" M.I.T. makes no representations about the suitability of
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.\" this software for any purpose. It is provided "as is"
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.\" without express or implied warranty.
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.\"
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.TH ARES_SEARCH 3 "24 July 1998"
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.SH NAME
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ares_search \- Initiate a DNS query with domain search
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.SH SYNOPSIS
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.nf
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.B #include <ares.h>
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.PP
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.B typedef void (*ares_callback)(void *\fIarg\fP, int \fIstatus\fP,
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.B unsigned char *\fIabuf\fP, int \fIalen\fP)
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.PP
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.B void ares_search(ares_channel \fIchannel\fP, const char *\fIname\fP,
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.B int \fIdnsclass\fP, int \fItype\fP, ares_callback \fIcallback\fP,
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.B void *\fIarg\fP)
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.fi
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.SH DESCRIPTION
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The
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.B ares_search
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function initiates a series of single-question DNS queries on the name
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service channel identified by
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.IR channel ,
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using the channel's search domains as well as a host alias file given
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by the HOSTALIAS environment variable. The parameter
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.I name
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gives the alias name or the base of the query name as a NUL-terminated
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C string of period-separated labels; if it ends with a period, the
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channel's search domains will not be used. Periods and backslashes
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within a label must be escaped with a backslash. The parameters
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.I dnsclass
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and
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.I type
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give the class and type of the query using the values defined in
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.BR <arpa/nameser.h> .
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When the query sequence is complete or has failed, the ares library
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will invoke
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.IR callback .
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Completion or failure of the query sequence may happen immediately, or
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may happen during a later call to
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.BR ares_process (3)
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or
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.BR ares_destroy (3).
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.PP
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The callback argument
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.I arg
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is copied from the
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.B ares_search
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argument
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.IR arg .
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The callback argument
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.I status
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indicates whether the query sequence ended with a successful query
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and, if not, how the query sequence failed. It may have any of the
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following values:
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.TP 19
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.B ARES_SUCCESS
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A query completed successfully.
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.TP 19
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.B ARES_ENODATA
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No query completed successfully; when the query was tried without a
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search domain appended, a response was returned with no answers.
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.TP 19
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.B ARES_EFORMERR
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A query completed but the server claimed that the query was
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malformatted.
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.TP 19
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.B ARES_ESERVFAIL
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No query completed successfully; when the query was tried without a
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search domain appended, the server claimed to have experienced a
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failure. (This code can only occur if the
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.B ARES_FLAG_NOCHECKRESP
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flag was specified at channel initialization time; otherwise, such
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responses are ignored at the
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.BR ares_send (3)
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level.)
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.TP 19
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.B ARES_ENOTFOUND
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No query completed successfully; when the query was tried without a
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search domain appended, the server reported that the queried-for
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domain name was not found.
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.TP 19
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.B ARES_ENOTIMP
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A query completed but the server does not implement the operation
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requested by the query. (This code can only occur if the
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.B ARES_FLAG_NOCHECKRESP
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flag was specified at channel initialization time; otherwise, such
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responses are ignored at the
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.BR ares_send (3)
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level.)
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.TP 19
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.B ARES_EREFUSED
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A query completed but the server refused the query. (This code can
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only occur returned if the
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.B ARES_FLAG_NOCHECKRESP
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flag was specified at channel initialization time; otherwise, such
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responses are ignored at the
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.BR ares_send (3)
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level.)
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.TP 19
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.B ARES_TIMEOUT
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No name servers responded to a query within the timeout period.
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.TP 19
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.B ARES_ECONNREFUSED
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No name servers could be contacted.
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.TP 19
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.B ARES_ENOMEM
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Memory was exhausted.
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.TP 19
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.B ARES_EDESTRUCTION
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The name service channel
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.I channel
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is being destroyed; the query will not be completed.
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.PP
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If a query completed successfully, the callback argument
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.I abuf
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points to a result buffer of length
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.IR alen .
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If the query did not complete successfully,
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.I abuf
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will usually be NULL and
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.I alen
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will usually be 0, but in some cases an unsuccessful query result may
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be placed in
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.IR abuf .
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.SH SEE ALSO
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.BR ares_process (3)
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.SH AUTHOR
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Greg Hudson, MIT Information Systems
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.br
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Copyright 1998 by the Massachusetts Institute of Technology.
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