<!-- - Copyright (C) 2004, 2005, 2007, 2012 Internet Systems Consortium, Inc. ("ISC") - Copyright (C) 2000, 2001 Internet Software Consortium. - - Permission to use, copy, modify, and/or distribute this software for any - purpose with or without fee is hereby granted, provided that the above - copyright notice and this permission notice appear in all copies. - - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY - AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE - OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR - PERFORMANCE OF THIS SOFTWARE. --> <!-- $Id$ --> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>lwres_noop</title> <meta name="generator" content="DocBook XSL Stylesheets V1.71.1"> </head> <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en"> <a name="id2476275"></a><div class="titlepage"></div> <div class="refnamediv"> <h2>Name</h2> <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> </div> <div class="refsynopsisdiv"> <h2>Synopsis</h2> <div class="funcsynopsis"> <pre class="funcsynopsisinfo"> #include <lwres/lwres.h></pre> <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em"> <tr> <td><code class="funcdef"> lwres_result_t <b class="fsfunc">lwres_nooprequest_render</b>(</code></td> <td>lwres_context_t * </td> <td> <var class="pdparam">ctx</var>, </td> </tr> <tr> <td> </td> <td>lwres_nooprequest_t * </td> <td> <var class="pdparam">req</var>, </td> </tr> <tr> <td> </td> <td>lwres_lwpacket_t * </td> <td> <var class="pdparam">pkt</var>, </td> </tr> <tr> <td> </td> <td>lwres_buffer_t * </td> <td> <var class="pdparam">b</var><code>)</code>;</td> </tr> </table> <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em"> <tr> <td><code class="funcdef"> lwres_result_t <b class="fsfunc">lwres_noopresponse_render</b>(</code></td> <td>lwres_context_t * </td> <td> <var class="pdparam">ctx</var>, </td> </tr> <tr> <td> </td> <td>lwres_noopresponse_t * </td> <td> <var class="pdparam">req</var>, </td> </tr> <tr> <td> </td> <td>lwres_lwpacket_t * </td> <td> <var class="pdparam">pkt</var>, </td> </tr> <tr> <td> </td> <td>lwres_buffer_t * </td> <td> <var class="pdparam">b</var><code>)</code>;</td> </tr> </table> <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em"> <tr> <td><code class="funcdef"> lwres_result_t <b class="fsfunc">lwres_nooprequest_parse</b>(</code></td> <td>lwres_context_t * </td> <td> <var class="pdparam">ctx</var>, </td> </tr> <tr> <td> </td> <td>lwres_buffer_t * </td> <td> <var class="pdparam">b</var>, </td> </tr> <tr> <td> </td> <td>lwres_lwpacket_t * </td> <td> <var class="pdparam">pkt</var>, </td> </tr> <tr> <td> </td> <td>lwres_nooprequest_t ** </td> <td> <var class="pdparam">structp</var><code>)</code>;</td> </tr> </table> <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em"> <tr> <td><code class="funcdef"> lwres_result_t <b class="fsfunc">lwres_noopresponse_parse</b>(</code></td> <td>lwres_context_t * </td> <td> <var class="pdparam">ctx</var>, </td> </tr> <tr> <td> </td> <td>lwres_buffer_t * </td> <td> <var class="pdparam">b</var>, </td> </tr> <tr> <td> </td> <td>lwres_lwpacket_t * </td> <td> <var class="pdparam">pkt</var>, </td> </tr> <tr> <td> </td> <td>lwres_noopresponse_t ** </td> <td> <var class="pdparam">structp</var><code>)</code>;</td> </tr> </table> <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em"> <tr> <td><code class="funcdef"> void <b class="fsfunc">lwres_noopresponse_free</b>(</code></td> <td>lwres_context_t * </td> <td> <var class="pdparam">ctx</var>, </td> </tr> <tr> <td> </td> <td>lwres_noopresponse_t ** </td> <td> <var class="pdparam">structp</var><code>)</code>;</td> </tr> </table> <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"> <tr> <td><code class="funcdef"> void <b class="fsfunc">lwres_nooprequest_free</b>(</code></td> <td>lwres_context_t * </td> <td> <var class="pdparam">ctx</var>, </td> </tr> <tr> <td> </td> <td>lwres_nooprequest_t ** </td> <td> <var class="pdparam">structp</var><code>)</code>;</td> </tr> </table> </div> </div> <div class="refsect1" lang="en"> <a name="id2543526"></a><h2>DESCRIPTION</h2> <p> These are low-level routines for creating and parsing lightweight resolver no-op request and response messages. </p> <p> The no-op message is analogous to a <span><strong class="command">ping</strong></span> packet: a packet is sent to the resolver daemon and is simply echoed back. The opcode is intended to allow a client to determine if the server is operational or not. </p> <p> There are four main functions for the no-op opcode. One render function converts a no-op request structure — <span class="type">lwres_nooprequest_t</span> — to the lighweight resolver's canonical format. It is complemented by a parse function that converts a packet in this canonical format to a no-op request structure. Another render function converts the no-op response structure — <span class="type">lwres_noopresponse_t</span> to the canonical format. This is complemented by a parse function which converts a packet in canonical format to a no-op response structure. </p> <p> These structures are defined in <code class="filename">lwres/lwres.h</code>. They are shown below. </p> <pre class="programlisting"> #define LWRES_OPCODE_NOOP 0x00000000U </pre> <p> </p> <pre class="programlisting"> typedef struct { lwres_uint16_t datalength; unsigned char *data; } lwres_nooprequest_t; </pre> <p> </p> <pre class="programlisting"> typedef struct { lwres_uint16_t datalength; unsigned char *data; } lwres_noopresponse_t; </pre> <p> </p> <p> Although the structures have different types, they are identical. This is because the no-op opcode simply echos whatever data was sent: the response is therefore identical to the request. </p> <p><code class="function">lwres_nooprequest_render()</code> uses resolver context <em class="parameter"><code>ctx</code></em> to convert no-op request structure <em class="parameter"><code>req</code></em> to canonical format. The packet header structure <em class="parameter"><code>pkt</code></em> is initialised and transferred to buffer <em class="parameter"><code>b</code></em>. The contents of <em class="parameter"><code>*req</code></em> are then appended to the buffer in canonical format. <code class="function">lwres_noopresponse_render()</code> performs the same task, except it converts a no-op response structure <span class="type">lwres_noopresponse_t</span> to the lightweight resolver's canonical format. </p> <p><code class="function">lwres_nooprequest_parse()</code> uses context <em class="parameter"><code>ctx</code></em> to convert the contents of packet <em class="parameter"><code>pkt</code></em> to a <span class="type">lwres_nooprequest_t</span> structure. Buffer <em class="parameter"><code>b</code></em> provides space to be used for storing this structure. When the function succeeds, the resulting <span class="type">lwres_nooprequest_t</span> is made available through <em class="parameter"><code>*structp</code></em>. <code class="function">lwres_noopresponse_parse()</code> offers the same semantics as <code class="function">lwres_nooprequest_parse()</code> except it yields a <span class="type">lwres_noopresponse_t</span> structure. </p> <p><code class="function">lwres_noopresponse_free()</code> and <code class="function">lwres_nooprequest_free()</code> release the memory in resolver context <em class="parameter"><code>ctx</code></em> that was allocated to the <span class="type">lwres_noopresponse_t</span> or <span class="type">lwres_nooprequest_t</span> structures referenced via <em class="parameter"><code>structp</code></em>. </p> </div> <div class="refsect1" lang="en"> <a name="id2543676"></a><h2>RETURN VALUES</h2> <p> The no-op opcode functions <code class="function">lwres_nooprequest_render()</code>, <code class="function">lwres_noopresponse_render()</code> <code class="function">lwres_nooprequest_parse()</code> and <code class="function">lwres_noopresponse_parse()</code> all return <span class="errorcode">LWRES_R_SUCCESS</span> on success. They return <span class="errorcode">LWRES_R_NOMEMORY</span> if memory allocation fails. <span class="errorcode">LWRES_R_UNEXPECTEDEND</span> is returned if the available space in the buffer <em class="parameter"><code>b</code></em> is too small to accommodate the packet header or the <span class="type">lwres_nooprequest_t</span> and <span class="type">lwres_noopresponse_t</span> structures. <code class="function">lwres_nooprequest_parse()</code> and <code class="function">lwres_noopresponse_parse()</code> will return <span class="errorcode">LWRES_R_UNEXPECTEDEND</span> if the buffer is not empty after decoding the received packet. These functions will return <span class="errorcode">LWRES_R_FAILURE</span> if <code class="constant">pktflags</code> in the packet header structure <span class="type">lwres_lwpacket_t</span> indicate that the packet is not a response to an earlier query. </p> </div> <div class="refsect1" lang="en"> <a name="id2543742"></a><h2>SEE ALSO</h2> <p><span class="citerefentry"><span class="refentrytitle">lwres_packet</span>(3)</span> </p> </div> </div></body> </html>