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117 lines
3.1 KiB
117 lines
3.1 KiB
.\" $Id$ |
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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_SEND 3 "25 July 1998" |
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.SH NAME |
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ares_send \- Initiate a DNS query |
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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 |
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void ares_send(ares_channel \fIchannel\fP, const unsigned char *\fIqbuf\fP, |
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.B int \fIqlen\fP, ares_callback \fIcallback\fP, 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_send |
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function initiates a DNS query on the name service channel identified |
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by |
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.IR channel . |
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The parameters |
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.I qbuf |
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and |
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.I qlen |
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give the DNS query, which should already have been formatted according |
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to the DNS protocol. When the query is complete or has failed, the |
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ares library will invoke |
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.IR callback . |
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Completion or failure of the query may happen immediately, or may |
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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_send |
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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 succeeded and, if not, how it failed. It |
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may have any of the following values: |
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.TP 19 |
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.B ARES_SUCCESS |
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The query completed. |
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.TP 19 |
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.B ARES_EBADQUERY |
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The query buffer was poorly formed (was not long enough for a DNS |
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header or was too long for TCP transmission). |
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.TP 19 |
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.B ARES_ETIMEOUT |
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No name servers responded 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 the query completed, 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, |
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.I abuf |
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will be NULL and |
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.I alen |
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will be 0. |
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.PP |
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Unless the flag |
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.B ARES_FLAG_NOCHECKRESP |
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was set at channel initialization time, |
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.B ares_send |
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will normally ignore responses whose questions do not match the |
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questions in |
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.IR qbuf , |
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as well as responses with reply codes of |
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.BR SERVFAIL , |
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.BR NOTIMP , |
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and |
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.BR REFUSED . |
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Unlike other query functions in the ares library, however, |
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.B ares_send |
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does not inspect the header of the reply packet to determine the error |
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status, so a callback status of |
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.B ARES_SUCCESS |
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does not reflect as much about the response as for other query |
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functions. |
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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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