299 lines
10 KiB
HTML
299 lines
10 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<!--
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- Copyright (C) 2000, 2001, 2004, 2005, 2007, 2014-2016 Internet Systems Consortium, Inc. ("ISC")
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-
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- This Source Code Form is subject to the terms of the Mozilla Public
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- License, v. 2.0. If a copy of the MPL was not distributed with this
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- file, You can obtain one at http://mozilla.org/MPL/2.0/.
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-->
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<html lang="en">
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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 V1.78.1">
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</head>
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry">
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<a name="id-1"></a><div class="titlepage"></div>
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<div class="refnamediv">
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<h2>Name</h2>
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<p>
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lwres_nooprequest_render,
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lwres_noopresponse_render,
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lwres_nooprequest_parse,
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lwres_noopresponse_parse,
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lwres_noopresponse_free,
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lwres_nooprequest_free
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— lightweight resolver no-op message handling
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</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" class="funcprototype-table" summary="Function synopsis" style="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_nooprequest_render</b>(</code></td>
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<td>lwres_context_t *<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 *<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 *<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 *<var class="pdparam">b</var><code>)</code>;</td>
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</tr>
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</table>
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<div class="funcprototype-spacer"> </div>
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<table border="0" class="funcprototype-table" summary="Function synopsis" style="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_noopresponse_render</b>(</code></td>
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<td>lwres_context_t *<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 *<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 *<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 *<var class="pdparam">b</var><code>)</code>;</td>
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</tr>
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</table>
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<div class="funcprototype-spacer"> </div>
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<table border="0" class="funcprototype-table" summary="Function synopsis" style="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_nooprequest_parse</b>(</code></td>
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<td>lwres_context_t *<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 *<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 *<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 **<var class="pdparam">structp</var><code>)</code>;</td>
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</tr>
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</table>
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<div class="funcprototype-spacer"> </div>
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<table border="0" class="funcprototype-table" summary="Function synopsis" style="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_noopresponse_parse</b>(</code></td>
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<td>lwres_context_t *<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 *<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 *<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 **<var class="pdparam">structp</var><code>)</code>;</td>
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</tr>
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</table>
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<div class="funcprototype-spacer"> </div>
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<table border="0" class="funcprototype-table" summary="Function synopsis" style="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_noopresponse_free</b>(</code></td>
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<td>lwres_context_t *<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 **<var class="pdparam">structp</var><code>)</code>;</td>
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</tr>
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</table>
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<div class="funcprototype-spacer"> </div>
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<table border="0" class="funcprototype-table" summary="Function synopsis" style="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 *<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 **<var class="pdparam">structp</var><code>)</code>;</td>
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</tr>
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</table>
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<div class="funcprototype-spacer"> </div>
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</div>
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</div>
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<div class="refsection">
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<a name="id-1.7"></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 class="command"><strong>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="refsection">
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<a name="id-1.8"></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="refsection">
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<a name="id-1.9"></a><h2>SEE ALSO</h2>
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<p><span class="citerefentry">
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<span class="refentrytitle">lwres_packet</span>(3)
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</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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