280 lines
10 KiB
HTML
280 lines
10 KiB
HTML
<!--
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- Permission to use, copy, modify, and/or distribute this software for any
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<!-- $Id: lwres_getipnode.html,v 1.25.418.1.10.1 2010/03/03 22:06:39 marka Exp $ -->
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<title>lwres_getipnode</title>
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<meta name="generator" content="DocBook XSL Stylesheets V1.71.1">
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</head>
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en">
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<a name="id2476267"></a><div class="titlepage"></div>
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<div class="refnamediv">
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<h2>Name</h2>
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<p>lwres_getipnodebyname, lwres_getipnodebyaddr, lwres_freehostent — lightweight resolver nodename / address translation API</p>
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</div>
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<div class="refsynopsisdiv">
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<h2>Synopsis</h2>
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<div class="funcsynopsis">
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<pre class="funcsynopsisinfo">#include <lwres/netdb.h></pre>
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<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
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<tr>
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<td><code class="funcdef">
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struct hostent *
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<b class="fsfunc">lwres_getipnodebyname</b>(</code></td>
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<td>const char * </td>
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<td>
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<var class="pdparam">name</var>, </td>
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</tr>
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<tr>
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<td> </td>
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<td>int </td>
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<td>
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<var class="pdparam">af</var>, </td>
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</tr>
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<tr>
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<td> </td>
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<td>int </td>
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<td>
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<var class="pdparam">flags</var>, </td>
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</tr>
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<tr>
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<td> </td>
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<td>int * </td>
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<td>
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<var class="pdparam">error_num</var><code>)</code>;</td>
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</tr>
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</table>
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<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
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<tr>
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<td><code class="funcdef">
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struct hostent *
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<b class="fsfunc">lwres_getipnodebyaddr</b>(</code></td>
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<td>const void * </td>
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<td>
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<var class="pdparam">src</var>, </td>
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</tr>
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<tr>
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<td> </td>
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<td>size_t </td>
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<td>
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<var class="pdparam">len</var>, </td>
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</tr>
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<tr>
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<td> </td>
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<td>int </td>
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<td>
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<var class="pdparam">af</var>, </td>
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</tr>
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<tr>
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<td> </td>
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<td>int * </td>
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<td>
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<var class="pdparam">error_num</var><code>)</code>;</td>
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</tr>
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</table>
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<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr>
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<td><code class="funcdef">
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void
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<b class="fsfunc">lwres_freehostent</b>(</code></td>
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<td>struct hostent * </td>
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<td>
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<var class="pdparam">he</var><code>)</code>;</td>
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</tr></table>
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</div>
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</div>
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<div class="refsect1" lang="en">
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<a name="id2543429"></a><h2>DESCRIPTION</h2>
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<p>
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These functions perform thread safe, protocol independent
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nodename-to-address and address-to-nodename
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translation as defined in RFC2553.
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</p>
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<p>
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They use a
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<span class="type">struct hostent</span>
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which is defined in
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<code class="filename">namedb.h</code>:
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</p>
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<pre class="programlisting">
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struct hostent {
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char *h_name; /* official name of host */
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char **h_aliases; /* alias list */
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int h_addrtype; /* host address type */
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int h_length; /* length of address */
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char **h_addr_list; /* list of addresses from name server */
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};
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#define h_addr h_addr_list[0] /* address, for backward compatibility */
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</pre>
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<p>
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</p>
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<p>
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The members of this structure are:
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</p>
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<div class="variablelist"><dl>
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<dt><span class="term"><code class="constant">h_name</code></span></dt>
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<dd><p>
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The official (canonical) name of the host.
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</p></dd>
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<dt><span class="term"><code class="constant">h_aliases</code></span></dt>
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<dd><p>
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A NULL-terminated array of alternate names (nicknames) for the
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host.
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</p></dd>
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<dt><span class="term"><code class="constant">h_addrtype</code></span></dt>
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<dd><p>
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The type of address being returned - usually
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<span class="type">PF_INET</span>
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or
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<span class="type">PF_INET6</span>.
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</p></dd>
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<dt><span class="term"><code class="constant">h_length</code></span></dt>
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<dd><p>
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The length of the address in bytes.
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</p></dd>
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<dt><span class="term"><code class="constant">h_addr_list</code></span></dt>
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<dd><p>
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A
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<span class="type">NULL</span>
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terminated array of network addresses for the host.
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Host addresses are returned in network byte order.
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</p></dd>
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</dl></div>
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<p>
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</p>
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<p><code class="function">lwres_getipnodebyname()</code>
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looks up addresses of protocol family <em class="parameter"><code>af</code></em>
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for the hostname <em class="parameter"><code>name</code></em>. The
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<em class="parameter"><code>flags</code></em> parameter contains ORed flag bits
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to specify the types of addresses that are searched for, and the
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types of addresses that are returned. The flag bits are:
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</p>
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<div class="variablelist"><dl>
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<dt><span class="term"><code class="constant">AI_V4MAPPED</code></span></dt>
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<dd><p>
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This is used with an
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<em class="parameter"><code>af</code></em>
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of AF_INET6, and causes IPv4 addresses to be returned as
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IPv4-mapped
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IPv6 addresses.
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</p></dd>
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<dt><span class="term"><code class="constant">AI_ALL</code></span></dt>
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<dd><p>
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This is used with an
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<em class="parameter"><code>af</code></em>
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of AF_INET6, and causes all known addresses (IPv6 and IPv4) to
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be returned.
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If AI_V4MAPPED is also set, the IPv4 addresses are return as
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mapped
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IPv6 addresses.
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</p></dd>
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<dt><span class="term"><code class="constant">AI_ADDRCONFIG</code></span></dt>
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<dd><p>
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Only return an IPv6 or IPv4 address if here is an active network
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interface of that type. This is not currently implemented
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in the BIND 9 lightweight resolver, and the flag is ignored.
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</p></dd>
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<dt><span class="term"><code class="constant">AI_DEFAULT</code></span></dt>
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<dd><p>
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This default sets the
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<code class="constant">AI_V4MAPPED</code>
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and
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<code class="constant">AI_ADDRCONFIG</code>
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flag bits.
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</p></dd>
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</dl></div>
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<p>
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</p>
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<p><code class="function">lwres_getipnodebyaddr()</code>
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performs a reverse lookup of address <em class="parameter"><code>src</code></em>
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which is <em class="parameter"><code>len</code></em> bytes long.
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<em class="parameter"><code>af</code></em> denotes the protocol family, typically
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<span class="type">PF_INET</span> or <span class="type">PF_INET6</span>.
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</p>
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<p><code class="function">lwres_freehostent()</code>
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releases all the memory associated with the <span class="type">struct
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hostent</span> pointer <em class="parameter"><code>he</code></em>. Any memory
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allocated for the <code class="constant">h_name</code>,
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<code class="constant">h_addr_list</code> and
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<code class="constant">h_aliases</code> is freed, as is the memory for
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the <span class="type">hostent</span> structure itself.
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</p>
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</div>
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<div class="refsect1" lang="en">
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<a name="id2543687"></a><h2>RETURN VALUES</h2>
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<p>
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If an error occurs,
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<code class="function">lwres_getipnodebyname()</code>
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and
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<code class="function">lwres_getipnodebyaddr()</code>
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set
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<em class="parameter"><code>*error_num</code></em>
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to an appropriate error code and the function returns a
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<span class="type">NULL</span>
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pointer.
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The error codes and their meanings are defined in
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<code class="filename"><lwres/netdb.h></code>:
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</p>
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<div class="variablelist"><dl>
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<dt><span class="term"><code class="constant">HOST_NOT_FOUND</code></span></dt>
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<dd><p>
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No such host is known.
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</p></dd>
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<dt><span class="term"><code class="constant">NO_ADDRESS</code></span></dt>
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<dd><p>
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The server recognised the request and the name but no address is
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available. Another type of request to the name server for the
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domain might return an answer.
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</p></dd>
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<dt><span class="term"><code class="constant">TRY_AGAIN</code></span></dt>
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<dd><p>
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A temporary and possibly transient error occurred, such as a
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failure of a server to respond. The request may succeed if
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retried.
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</p></dd>
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<dt><span class="term"><code class="constant">NO_RECOVERY</code></span></dt>
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<dd><p>
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An unexpected failure occurred, and retrying the request
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is pointless.
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</p></dd>
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</dl></div>
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<p>
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</p>
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<p><span class="citerefentry"><span class="refentrytitle">lwres_hstrerror</span>(3)</span>
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translates these error codes to suitable error messages.
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</p>
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</div>
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<div class="refsect1" lang="en">
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<a name="id2543784"></a><h2>SEE ALSO</h2>
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<p><span class="citerefentry"><span class="refentrytitle">RFC2553</span></span>,
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<span class="citerefentry"><span class="refentrytitle">lwres</span>(3)</span>,
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<span class="citerefentry"><span class="refentrytitle">lwres_gethostent</span>(3)</span>,
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<span class="citerefentry"><span class="refentrytitle">lwres_getaddrinfo</span>(3)</span>,
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<span class="citerefentry"><span class="refentrytitle">lwres_getnameinfo</span>(3)</span>,
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<span class="citerefentry"><span class="refentrytitle">lwres_hstrerror</span>(3)</span>.
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</p>
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</div>
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</div></body>
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</html>
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