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<head><title>dkim_dns_set_query_start()</title></head>
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<h1>dkim_dns_set_query_start()</h1>
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<!---------- Synopsis ----------->
<tr><th valign="top" align=left width=150>SYNOPSIS</th><td>
<pre>
#include <dkim.h>
<tt>void</tt> dkim_dns_set_query_start(
<a href="dkim_lib.html"><tt>DKIM_LIB</tt></a> *libopendkim,
<tt>int</tt> (*func)(<tt>void *, int, u_char *, u_char *, size_t,
void **</tt>)
);
</pre>
Declares the function to be used by a libopendkim instance when it needs to
start a DNS query. By default, a stub function that calls the standard
UNIX resolver library is set.<p>
The function will be passed the following arguments:
<ol>
<li> An opaque DNS service handle as previously specified by a call to
<a href="dkim_dns_set_query_service.html"><tt>dkim_dns_set_query_service()</tt></a>
<li> The DNS query type (e.g., <tt>ns_t_txt</tt> or the older <tt>T_TXT</tt>)
<li> A NULL-terminated string containing the name to be queried
<li> The address of a buffer into which the result should be written
<li> The length of that buffer
<li> The address of a <tt>void *</tt> that should be updated to contain an
opaque handle for the started query
</ol>
The function is expected to return one of the following:
<ul>
<li><tt>DKIM_DNS_SUCCESS</tt> -- query was successfully initiated
<li><tt>DKIM_DNS_ERROR</tt> -- an error occurred
</ul>
<p> The query type should be a DNS resource record type as registered with
IANA (<a href="http://www.iana.org/assignments/dns-parameters">here</a>).
The constants are typically given names for use in source code via the
include file <tt><arpa/nameser.h></tt>. </p>
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<!----------- Description ---------->
<tr><th valign="top" align=left>DESCRIPTION</th><td>
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<th width="80">Called When</th>
<td><tt>dkim_dns_set_query_start()</tt> can be called at any time, but is
presumably most useful prior to doing any DNS operations such as are done
during <a href="dkim_eoh.html"><tt>dkim_eoh()</tt></a> when verifying. </td>
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<!----------- Arguments ---------->
<tr><th valign="top" align=left>ARGUMENTS</th><td>
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<tr bgcolor="#dddddd"><th>Argument</th><th>Description</th></tr>
<tr valign="top"><td>libopendkim</td>
<td>The library instantiation handle, returned by
<a href="dkim_init.html"><tt>dkim_init()</tt></a>.
</td></tr>
<tr valign="top"><td>func</td>
<td>A pointer to a function that should be used to initiate
DNS queries.
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<!----------- Return Values ---------->
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<th valign="top" align=left>RETURN VALUES</th>
<td>
<ul>
<li>None.
</ul>
</td>
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<!----------- Notes ---------->
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<th valign="top" align=left>NOTES</th>
<td>
<ul>
<li>None.
</ul>
</td>
</tr>
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<hr size="1">
<font size="-1">
Copyright (c) 2007 Sendmail, Inc. and its suppliers.
All rights reserved.
<br>
Copyright (c) 2011, The OpenDKIM Project. All rights reserved.
<br>
By using this file, you agree to the terms and conditions set
forth in the respective licenses.
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