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<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>
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