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<head><title>dkim_set_dns_callback()</title></head>
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<h1>dkim_set_dns_callback()</h1>
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<!---------- Synopsis ----------->
<tr><th valign="top" align=left width=150>SYNOPSIS</th><td>
<pre>
#include <dkim.h>
<a href="dkim_stat.html"><tt>DKIM_STAT</tt></a> dkim_set_dns_callback(
<a href="dkim_lib.html"><tt>DKIM_LIB</tt></a> *libopendkim,
void (*func)(const void *context),
unsigned int interval);
);
</pre>
Define a function which should be called from time to time while waiting
for a DNS response to become available. This is particularly meant for
use when libopendkim is being used by an application which is timeout-sensitive
where a heartbeat ("still alive, operation in progress") message is
desirable. <p>
When defined, the specified function will be called at the specified interval
even if the DNS response has not yet arrived, using the caller-specific
context pointer set by the
<a href="dkim_set_user_context.html"><tt>dkim_set_user_context()</tt></a>
function (if any) as the parameter to that function.
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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_set_dns_callback()</tt> can called at any time. </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>Library-specific 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 which takes a single void pointer
which should be called at the requested interval while waiting
for a DNS reply. If NULL, no callback will be used.
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<tr valign="top"><td>interval</td>
<td>Desired interval, in seconds, between calls to <tt>func</tt>.
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<!----------- Return Values ---------->
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<th valign="top" align=left>RETURN VALUES</th>
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<ul>
<li>DKIM_STAT_OK -- the callback and interval were successfully registered
<li>DKIM_STAT_NOTIMPLEMENT -- the underlying DNS resolution service does not
provide a callback facility
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Copyright (c) 2007 Sendmail, Inc. and its suppliers.
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Copyright (c) 2009, 2010, The OpenDKIM Project. All rights reserved.
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