276 lines
8.2 KiB
HTML
276 lines
8.2 KiB
HTML
<!--
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- Copyright (C) 2004, 2005 Internet Systems Consortium, Inc. ("ISC")
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- Copyright (C) 2000, 2001 Internet Software Consortium.
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-
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- Permission to use, copy, modify, and distribute this software for any
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- purpose with or without fee is hereby granted, provided that the above
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- copyright notice and this permission notice appear in all copies.
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-
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- THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
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- REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
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- OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
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- PERFORMANCE OF THIS SOFTWARE.
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-->
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<!-- $Id: lwres_resutil.html,v 1.8.2.1.4.11 2006/06/29 13:02:31 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_resutil</title>
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<meta name="generator" content="DocBook XSL Stylesheets V1.70.1">
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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="id2482688"></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_string_parse, lwres_addr_parse, lwres_getaddrsbyname, lwres_getnamebyaddr — lightweight resolver utility functions</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/lwres.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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lwres_result_t
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<b class="fsfunc">lwres_string_parse</b>(</code></td>
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<td> </td>
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<td>, </td>
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</tr>
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<tr>
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<td> </td>
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<td>, </td>
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<td>, </td>
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<tr>
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<td> </td>
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<td> </td>
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<td>
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<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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lwres_result_t
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<b class="fsfunc">lwres_addr_parse</b>(</code></td>
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<td> </td>
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<td>, </td>
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</tr>
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<tr>
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<td>, </td>
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<td> </td>
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<td> </td>
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<td>
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<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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lwres_result_t
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<b class="fsfunc">lwres_getaddrsbyname</b>(</code></td>
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<td> </td>
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<td>, </td>
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</tr>
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<tr>
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<td> </td>
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<td>, </td>
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<td>, </td>
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<td>, </td>
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</tr>
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<tr>
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<td> </td>
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<td> </td>
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<td>
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<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">
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<tr>
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<td><code class="funcdef">
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lwres_result_t
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<b class="fsfunc">lwres_getnamebyaddr</b>(</code></td>
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<td> </td>
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<td>, </td>
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</tr>
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<tr>
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<td> </td>
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<td> </td>
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<td>, </td>
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</tr>
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<td> </td>
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<td> </td>
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<td>, </td>
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<td> </td>
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<td>, </td>
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</tr>
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<td> </td>
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<td> </td>
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<td>, </td>
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<tr>
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<td> </td>
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<td> </td>
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<td>
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<code>)</code>;</td>
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</tr>
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</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="id2549485"></a><h2>DESCRIPTION</h2>
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<p>
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<code class="function">lwres_string_parse()</code> retrieves a DNS-encoded
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string starting the current pointer of lightweight resolver buffer
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<em class="parameter"><code>b</code></em>: i.e. <code class="constant">b->current</code>.
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When the function returns, the address of the first byte of the
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encoded string is returned via <em class="parameter"><code>*c</code></em> and the
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length of that string is given by <em class="parameter"><code>*len</code></em>. The
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buffer's current pointer is advanced to point at the character
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following the string length, the encoded string, and the trailing
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<span class="type">NULL</span> character.
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</p>
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<p>
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<code class="function">lwres_addr_parse()</code> extracts an address from the
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buffer <em class="parameter"><code>b</code></em>. The buffer's current pointer
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<code class="constant">b->current</code> is presumed to point at an encoded
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address: the address preceded by a 32-bit protocol family identifier
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and a 16-bit length field. The encoded address is copied to
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<code class="constant">addr->address</code> and
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<code class="constant">addr->length</code> indicates the size in bytes of
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the address that was copied. <code class="constant">b->current</code> is
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advanced to point at the next byte of available data in the buffer
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following the encoded address.
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</p>
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<p>
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<code class="function">lwres_getaddrsbyname()</code>
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and
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<code class="function">lwres_getnamebyaddr()</code>
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use the
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<span class="type">lwres_gnbaresponse_t</span>
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structure defined below:
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</p>
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<pre class="programlisting">
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typedef struct {
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lwres_uint32_t flags;
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lwres_uint16_t naliases;
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lwres_uint16_t naddrs;
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char *realname;
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char **aliases;
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lwres_uint16_t realnamelen;
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lwres_uint16_t *aliaslen;
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lwres_addrlist_t addrs;
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void *base;
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size_t baselen;
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} lwres_gabnresponse_t;
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</pre>
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<p>
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The contents of this structure are not manipulated directly but
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they are controlled through the
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<span class="citerefentry"><span class="refentrytitle">lwres_gabn</span>(3
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)</span>
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functions.
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</p>
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<p>
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The lightweight resolver uses
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<code class="function">lwres_getaddrsbyname()</code> to perform foward lookups.
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Hostname <em class="parameter"><code>name</code></em> is looked up using the resolver
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context <em class="parameter"><code>ctx</code></em> for memory allocation.
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<em class="parameter"><code>addrtypes</code></em> is a bitmask indicating which type of
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addresses are to be looked up. Current values for this bitmask are
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<span class="type">LWRES_ADDRTYPE_V4</span> for IPv4 addresses and
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<span class="type">LWRES_ADDRTYPE_V6</span> for IPv6 addresses. Results of the
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lookup are returned in <em class="parameter"><code>*structp</code></em>.
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</p>
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<p>
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<code class="function">lwres_getnamebyaddr()</code> performs reverse lookups.
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Resolver context <em class="parameter"><code>ctx</code></em> is used for memory
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allocation. The address type is indicated by
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<em class="parameter"><code>addrtype</code></em>: <span class="type">LWRES_ADDRTYPE_V4</span> or
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<span class="type">LWRES_ADDRTYPE_V6</span>. The address to be looked up is given
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by <em class="parameter"><code>addr</code></em> and its length is
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<em class="parameter"><code>addrlen</code></em> bytes. The result of the function call
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is made available through <em class="parameter"><code>*structp</code></em>.
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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="id2549693"></a><h2>RETURN VALUES</h2>
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<p>
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Successful calls to
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<code class="function">lwres_string_parse()</code>
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and
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<code class="function">lwres_addr_parse()</code>
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return
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<span class="errorcode">LWRES_R_SUCCESS.</span>
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Both functions return
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<span class="errorcode">LWRES_R_FAILURE</span>
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if the buffer is corrupt or
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<span class="errorcode">LWRES_R_UNEXPECTEDEND</span>
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if the buffer has less space than expected for the components of the
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encoded string or address.
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</p>
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<p>
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<code class="function">lwres_getaddrsbyname()</code>
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returns
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<span class="errorcode">LWRES_R_SUCCESS</span>
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on success and it returns
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<span class="errorcode">LWRES_R_NOTFOUND</span>
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if the hostname
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<em class="parameter"><code>name</code></em>
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could not be found.
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</p>
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<p>
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<span class="errorcode">LWRES_R_SUCCESS</span>
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is returned by a successful call to
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<code class="function">lwres_getnamebyaddr()</code>.
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</p>
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<p>
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Both
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<code class="function">lwres_getaddrsbyname()</code>
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and
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<code class="function">lwres_getnamebyaddr()</code>
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return
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<span class="errorcode">LWRES_R_NOMEMORY</span>
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when memory allocation requests fail and
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<span class="errorcode">LWRES_R_UNEXPECTEDEND</span>
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if the buffers used for sending queries and receiving replies are too
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small.
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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="id2549763"></a><h2>SEE ALSO</h2>
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<p>
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<span class="citerefentry"><span class="refentrytitle">lwres_buffer</span>(3)</span>,
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<span class="citerefentry"><span class="refentrytitle">lwres_gabn</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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