00b67f09dd
Also known as ISC bind. This import adds utilities such as host(1), dig(1), and nslookup(1), as well as many other tools and libraries. Change-Id: I035ca46e64f1965d57019e773f4ff0ef035e4aa3
318 lines
10 KiB
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318 lines
10 KiB
HTML
<!--
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- Copyright (C) 2004, 2005, 2007, 2014 Internet Systems Consortium, Inc. ("ISC")
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- Copyright (C) 2000, 2001 Internet Software Consortium.
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- Permission to use, copy, modify, and/or distribute this software for any
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- THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
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- PERFORMANCE OF THIS SOFTWARE.
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<!-- Id -->
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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_noop</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="id2476275"></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_nooprequest_render, lwres_noopresponse_render, lwres_nooprequest_parse, lwres_noopresponse_parse, lwres_noopresponse_free, lwres_nooprequest_free — lightweight resolver no-op message handling</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">
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#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_nooprequest_render</b>(</code></td>
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<td>lwres_context_t * </td>
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<td>
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<var class="pdparam">ctx</var>, </td>
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</tr>
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<tr>
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<td> </td>
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<td>lwres_nooprequest_t * </td>
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<td>
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<var class="pdparam">req</var>, </td>
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</tr>
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<tr>
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<td> </td>
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<td>lwres_lwpacket_t * </td>
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<td>
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<var class="pdparam">pkt</var>, </td>
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</tr>
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<tr>
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<td> </td>
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<td>lwres_buffer_t * </td>
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<td>
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<var class="pdparam">b</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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lwres_result_t
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<b class="fsfunc">lwres_noopresponse_render</b>(</code></td>
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<td>lwres_context_t * </td>
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<td>
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<var class="pdparam">ctx</var>, </td>
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</tr>
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<tr>
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<td> </td>
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<td>lwres_noopresponse_t * </td>
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<td>
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<var class="pdparam">req</var>, </td>
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</tr>
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<tr>
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<td> </td>
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<td>lwres_lwpacket_t * </td>
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<td>
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<var class="pdparam">pkt</var>, </td>
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</tr>
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<tr>
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<td> </td>
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<td>lwres_buffer_t * </td>
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<td>
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<var class="pdparam">b</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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lwres_result_t
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<b class="fsfunc">lwres_nooprequest_parse</b>(</code></td>
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<td>lwres_context_t * </td>
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<td>
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<var class="pdparam">ctx</var>, </td>
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</tr>
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<tr>
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<td> </td>
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<td>lwres_buffer_t * </td>
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<td>
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<var class="pdparam">b</var>, </td>
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</tr>
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<tr>
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<td> </td>
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<td>lwres_lwpacket_t * </td>
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<td>
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<var class="pdparam">pkt</var>, </td>
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</tr>
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<tr>
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<td> </td>
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<td>lwres_nooprequest_t ** </td>
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<td>
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<var class="pdparam">structp</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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lwres_result_t
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<b class="fsfunc">lwres_noopresponse_parse</b>(</code></td>
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<td>lwres_context_t * </td>
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<td>
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<var class="pdparam">ctx</var>, </td>
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</tr>
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<tr>
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<td> </td>
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<td>lwres_buffer_t * </td>
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<td>
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<var class="pdparam">b</var>, </td>
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</tr>
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<tr>
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<td> </td>
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<td>lwres_lwpacket_t * </td>
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<td>
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<var class="pdparam">pkt</var>, </td>
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</tr>
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<tr>
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<td> </td>
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<td>lwres_noopresponse_t ** </td>
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<td>
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<var class="pdparam">structp</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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void
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<b class="fsfunc">lwres_noopresponse_free</b>(</code></td>
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<td>lwres_context_t * </td>
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<td>
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<var class="pdparam">ctx</var>, </td>
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</tr>
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<tr>
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<td> </td>
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<td>lwres_noopresponse_t ** </td>
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<td>
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<var class="pdparam">structp</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">
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<tr>
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<td><code class="funcdef">
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void
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<b class="fsfunc">lwres_nooprequest_free</b>(</code></td>
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<td>lwres_context_t * </td>
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<td>
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<var class="pdparam">ctx</var>, </td>
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</tr>
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<tr>
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<td> </td>
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<td>lwres_nooprequest_t ** </td>
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<td>
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<var class="pdparam">structp</var><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="id2543531"></a><h2>DESCRIPTION</h2>
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<p>
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These are low-level routines for creating and parsing
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lightweight resolver no-op request and response messages.
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</p>
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<p>
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The no-op message is analogous to a <span><strong class="command">ping</strong></span>
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packet:
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a packet is sent to the resolver daemon and is simply echoed back.
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The opcode is intended to allow a client to determine if the server is
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operational or not.
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</p>
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<p>
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There are four main functions for the no-op opcode.
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One render function converts a no-op request structure —
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<span class="type">lwres_nooprequest_t</span> —
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to the lightweight resolver's canonical format.
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It is complemented by a parse function that converts a packet in this
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canonical format to a no-op request structure.
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Another render function converts the no-op response structure —
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<span class="type">lwres_noopresponse_t</span>
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to the canonical format.
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This is complemented by a parse function which converts a packet in
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canonical format to a no-op response structure.
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</p>
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<p>
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These structures are defined in
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<code class="filename">lwres/lwres.h</code>.
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They are shown below.
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</p>
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<pre class="programlisting">
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#define LWRES_OPCODE_NOOP 0x00000000U
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</pre>
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<p>
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</p>
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<pre class="programlisting">
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typedef struct {
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lwres_uint16_t datalength;
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unsigned char *data;
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} lwres_nooprequest_t;
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</pre>
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<p>
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</p>
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<pre class="programlisting">
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typedef struct {
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lwres_uint16_t datalength;
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unsigned char *data;
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} lwres_noopresponse_t;
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</pre>
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<p>
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</p>
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<p>
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Although the structures have different types, they are identical.
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This is because the no-op opcode simply echos whatever data was sent:
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the response is therefore identical to the request.
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</p>
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<p><code class="function">lwres_nooprequest_render()</code>
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uses resolver context <em class="parameter"><code>ctx</code></em> to convert
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no-op request structure <em class="parameter"><code>req</code></em> to canonical
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format. The packet header structure <em class="parameter"><code>pkt</code></em>
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is initialised and transferred to buffer
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<em class="parameter"><code>b</code></em>. The contents of
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<em class="parameter"><code>*req</code></em> are then appended to the buffer in
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canonical format.
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<code class="function">lwres_noopresponse_render()</code> performs the
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same task, except it converts a no-op response structure
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<span class="type">lwres_noopresponse_t</span> to the lightweight resolver's
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canonical format.
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</p>
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<p><code class="function">lwres_nooprequest_parse()</code>
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uses context <em class="parameter"><code>ctx</code></em> to convert the contents
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of packet <em class="parameter"><code>pkt</code></em> to a
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<span class="type">lwres_nooprequest_t</span> structure. Buffer
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<em class="parameter"><code>b</code></em> provides space to be used for storing
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this structure. When the function succeeds, the resulting
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<span class="type">lwres_nooprequest_t</span> is made available through
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<em class="parameter"><code>*structp</code></em>.
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<code class="function">lwres_noopresponse_parse()</code> offers the same
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semantics as <code class="function">lwres_nooprequest_parse()</code>
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except it yields a <span class="type">lwres_noopresponse_t</span> structure.
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</p>
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<p><code class="function">lwres_noopresponse_free()</code>
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and <code class="function">lwres_nooprequest_free()</code> release the
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memory in resolver context <em class="parameter"><code>ctx</code></em> that was
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allocated to the <span class="type">lwres_noopresponse_t</span> or
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<span class="type">lwres_nooprequest_t</span> structures referenced via
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<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="id2543682"></a><h2>RETURN VALUES</h2>
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<p>
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The no-op opcode functions
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<code class="function">lwres_nooprequest_render()</code>,
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<code class="function">lwres_noopresponse_render()</code>
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<code class="function">lwres_nooprequest_parse()</code>
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and
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<code class="function">lwres_noopresponse_parse()</code>
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all return
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<span class="errorcode">LWRES_R_SUCCESS</span>
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on success.
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They return
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<span class="errorcode">LWRES_R_NOMEMORY</span>
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if memory allocation fails.
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<span class="errorcode">LWRES_R_UNEXPECTEDEND</span>
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is returned if the available space in the buffer
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<em class="parameter"><code>b</code></em>
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is too small to accommodate the packet header or the
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<span class="type">lwres_nooprequest_t</span>
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and
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<span class="type">lwres_noopresponse_t</span>
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structures.
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<code class="function">lwres_nooprequest_parse()</code>
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and
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<code class="function">lwres_noopresponse_parse()</code>
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will return
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<span class="errorcode">LWRES_R_UNEXPECTEDEND</span>
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if the buffer is not empty after decoding the received packet.
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These functions will return
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<span class="errorcode">LWRES_R_FAILURE</span>
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if
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<code class="constant">pktflags</code>
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in the packet header structure
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<span class="type">lwres_lwpacket_t</span>
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indicate that the packet is not a response to an earlier query.
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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="id2543748"></a><h2>SEE ALSO</h2>
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<p><span class="citerefentry"><span class="refentrytitle">lwres_packet</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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