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<title>dn_expand()--Expand Domain Name</title>
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<h2>dn_expand()--Expand Domain Name</h2>
<div class="box" style="width: 70%;">
<br>
&nbsp;&nbsp;Syntax<br>
<pre>
#include &lt;sys/types.h&gt;
#include &lt;netinet/in.h&gt;
#include &lt;arpa/nameser.h&gt;
#include &lt;resolv.h&gt;
int dn_expand(unsigned char *<em>message_pointer</em>,
unsigned char *<em>end_of_message</em>,
unsigned char *<em>compressed_domain_name</em>,
unsigned char *<em>expanded_domain_name</em>,
int <em>answer_buffer_length</em>)
</pre>
<br>
&nbsp;&nbsp;Service Program Name: QSOSRV2<br>
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<br>
&nbsp;&nbsp;Default Public Authority: *USE<br>
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&nbsp;&nbsp;Threadsafe: Yes<br>
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<p>The <em>dn_expand()</em> function is used to expand a compressed domain
name.</p>
<br>
<!-- Please NOTE: DO NOT DELETE THIS SECTION if this API has no authorities and locks. -->
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<h3>Authorities and Locks</h3>
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<p>None.</p>
<br>
<h3>Parameters</h3>
<dl>
<dt><strong>message_pointer</strong></dt>
<dd>(Input) The pointer to the beginning of a DNS packet.<br>
<br>
</dd>
<dt><strong>end_of_message</strong></dt>
<dd>(Input) The pointer to the end of the DNS packet.<br>
<br>
</dd>
<dt><strong>compressed_domain_name</strong></dt>
<dd>(Input) The pointer to the compressed domain name within the DNS
packet.<br>
<br>
</dd>
<dt><strong>expanded_domain_name</strong></dt>
<dd>(Output) The pointer to the expanded domain name.<br>
<br>
</dd>
<dt><strong>answer_buffer_length</strong></dt>
<dd>(Input) The size of the <em>expanded_domain_name</em> buffer.</dd>
</dl>
<br>
<h3>Return Value</h3>
<p><em>dn_expand()</em> returns an integer. Possible values are:</p>
<ul>
<li>-1 (unsuccessful)<br>
<br>
</li>
<li>n (successful), where n is the size of the compressed domain name.
<p>The <em>dn_expand()</em> routine expands the domain name pointed to by
<em>compressed_domain_name</em>. The result is placed in
<em>expanded_domain_name</em>.</p>
</li>
</ul>
<br>
<h3>Error Conditions</h3>
<p>When the <em>dn_expand()</em> function fails, it does not set specific
<em>errno</em> or <em>h_errno</em> values. An error occurs under the following
conditions:</p>
<ul>
<li>NULL pointer(s) passed to the function.<br><br></li>
<li>Invalid pointer(s) passed to the function.<br><br></li>
<li><em>expanded_domain_name</em> too small for the expanded domain name.<br><br></li>
<li><em>end_of_message</em> reached before the domain name could be
expanded.</li>
</ul>
<br>
<h3>Usage Notes</h3>
<ol>
<li>The compressed domain name size is returned rather than the expanded domain
name size because it is used to parse through the DNS packet.<br>
<br>
</li>
<li><em>dn_expand()</em> uses <em>end_of_message</em> to insure that it doesn't
run past the end of the DNS packet.<br>
<br>
</li>
<li><em>dn_expand()</em> expects EBCDIC data as input. The output from
<em>dn_expand()</em> is also EBCDIC.</li>
</ol>
<br>
<h3>Related Information</h3>
<ul>
<li><a href="dncomp.htm">dn_comp()</a>--Compress Domain Name<br>
<br>
</li>
<li><a href="dnfind.htm">dn_find()</a>--Search for Compressed Domain Name<br>
<br>
</li>
<li><a href="dnsknm.htm">dn_skipname()</a>--Skip over Compressed Domain
Name</li>
</ul>
<br>
<hr>
API introduced: V3R1
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