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20 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
21 <title>lwres_noop</title>
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24 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en">
25 <a name="id2476274"></a><div class="titlepage"></div>
26 <div class="refnamediv">
28 <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>
30 <div class="refsynopsisdiv">
32 <div class="funcsynopsis">
33 <pre class="funcsynopsisinfo">
34 #include <lwres/lwres.h></pre>
35 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
37 <td><code class="funcdef">
39 <b class="fsfunc">lwres_nooprequest_render</b>(</code></td>
40 <td>lwres_context_t * </td>
42 <var class="pdparam">ctx</var>, </td>
46 <td>lwres_nooprequest_t * </td>
48 <var class="pdparam">req</var>, </td>
52 <td>lwres_lwpacket_t * </td>
54 <var class="pdparam">pkt</var>, </td>
58 <td>lwres_buffer_t * </td>
60 <var class="pdparam">b</var><code>)</code>;</td>
63 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
65 <td><code class="funcdef">
67 <b class="fsfunc">lwres_noopresponse_render</b>(</code></td>
68 <td>lwres_context_t * </td>
70 <var class="pdparam">ctx</var>, </td>
74 <td>lwres_noopresponse_t * </td>
76 <var class="pdparam">req</var>, </td>
80 <td>lwres_lwpacket_t * </td>
82 <var class="pdparam">pkt</var>, </td>
86 <td>lwres_buffer_t * </td>
88 <var class="pdparam">b</var><code>)</code>;</td>
91 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
93 <td><code class="funcdef">
95 <b class="fsfunc">lwres_nooprequest_parse</b>(</code></td>
96 <td>lwres_context_t * </td>
98 <var class="pdparam">ctx</var>, </td>
102 <td>lwres_buffer_t * </td>
104 <var class="pdparam">b</var>, </td>
108 <td>lwres_lwpacket_t * </td>
110 <var class="pdparam">pkt</var>, </td>
114 <td>lwres_nooprequest_t ** </td>
116 <var class="pdparam">structp</var><code>)</code>;</td>
119 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
121 <td><code class="funcdef">
123 <b class="fsfunc">lwres_noopresponse_parse</b>(</code></td>
124 <td>lwres_context_t * </td>
126 <var class="pdparam">ctx</var>, </td>
130 <td>lwres_buffer_t * </td>
132 <var class="pdparam">b</var>, </td>
136 <td>lwres_lwpacket_t * </td>
138 <var class="pdparam">pkt</var>, </td>
142 <td>lwres_noopresponse_t ** </td>
144 <var class="pdparam">structp</var><code>)</code>;</td>
147 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
149 <td><code class="funcdef">
151 <b class="fsfunc">lwres_noopresponse_free</b>(</code></td>
152 <td>lwres_context_t * </td>
154 <var class="pdparam">ctx</var>, </td>
158 <td>lwres_noopresponse_t ** </td>
160 <var class="pdparam">structp</var><code>)</code>;</td>
163 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0">
165 <td><code class="funcdef">
167 <b class="fsfunc">lwres_nooprequest_free</b>(</code></td>
168 <td>lwres_context_t * </td>
170 <var class="pdparam">ctx</var>, </td>
174 <td>lwres_nooprequest_t ** </td>
176 <var class="pdparam">structp</var><code>)</code>;</td>
181 <div class="refsect1" lang="en">
182 <a name="id2543524"></a><h2>DESCRIPTION</h2>
184 These are low-level routines for creating and parsing
185 lightweight resolver no-op request and response messages.
188 The no-op message is analogous to a <span><strong class="command">ping</strong></span>
190 a packet is sent to the resolver daemon and is simply echoed back.
191 The opcode is intended to allow a client to determine if the server is
195 There are four main functions for the no-op opcode.
196 One render function converts a no-op request structure —
197 <span class="type">lwres_nooprequest_t</span> —
198 to the lighweight resolver's canonical format.
199 It is complemented by a parse function that converts a packet in this
200 canonical format to a no-op request structure.
201 Another render function converts the no-op response structure —
202 <span class="type">lwres_noopresponse_t</span>
203 to the canonical format.
204 This is complemented by a parse function which converts a packet in
205 canonical format to a no-op response structure.
208 These structures are defined in
209 <code class="filename">lwres/lwres.h</code>.
211 They are shown below.
213 <pre class="programlisting">
214 #define LWRES_OPCODE_NOOP 0x00000000U
218 <pre class="programlisting">
220 lwres_uint16_t datalength;
222 } lwres_nooprequest_t;
226 <pre class="programlisting">
228 lwres_uint16_t datalength;
230 } lwres_noopresponse_t;
235 Although the structures have different types, they are identical.
236 This is because the no-op opcode simply echos whatever data was sent:
237 the response is therefore identical to the request.
239 <p><code class="function">lwres_nooprequest_render()</code>
240 uses resolver context <em class="parameter"><code>ctx</code></em> to convert
241 no-op request structure <em class="parameter"><code>req</code></em> to canonical
242 format. The packet header structure <em class="parameter"><code>pkt</code></em>
243 is initialised and transferred to buffer
244 <em class="parameter"><code>b</code></em>. The contents of
245 <em class="parameter"><code>*req</code></em> are then appended to the buffer in
247 <code class="function">lwres_noopresponse_render()</code> performs the
248 same task, except it converts a no-op response structure
249 <span class="type">lwres_noopresponse_t</span> to the lightweight resolver's
252 <p><code class="function">lwres_nooprequest_parse()</code>
253 uses context <em class="parameter"><code>ctx</code></em> to convert the contents
254 of packet <em class="parameter"><code>pkt</code></em> to a
255 <span class="type">lwres_nooprequest_t</span> structure. Buffer
256 <em class="parameter"><code>b</code></em> provides space to be used for storing
257 this structure. When the function succeeds, the resulting
258 <span class="type">lwres_nooprequest_t</span> is made available through
259 <em class="parameter"><code>*structp</code></em>.
260 <code class="function">lwres_noopresponse_parse()</code> offers the same
261 semantics as <code class="function">lwres_nooprequest_parse()</code>
262 except it yields a <span class="type">lwres_noopresponse_t</span> structure.
264 <p><code class="function">lwres_noopresponse_free()</code>
265 and <code class="function">lwres_nooprequest_free()</code> release the
266 memory in resolver context <em class="parameter"><code>ctx</code></em> that was
267 allocated to the <span class="type">lwres_noopresponse_t</span> or
268 <span class="type">lwres_nooprequest_t</span> structures referenced via
269 <em class="parameter"><code>structp</code></em>.
272 <div class="refsect1" lang="en">
273 <a name="id2543674"></a><h2>RETURN VALUES</h2>
275 The no-op opcode functions
276 <code class="function">lwres_nooprequest_render()</code>,
278 <code class="function">lwres_noopresponse_render()</code>
279 <code class="function">lwres_nooprequest_parse()</code>
281 <code class="function">lwres_noopresponse_parse()</code>
283 <span class="errorcode">LWRES_R_SUCCESS</span>
286 <span class="errorcode">LWRES_R_NOMEMORY</span>
287 if memory allocation fails.
288 <span class="errorcode">LWRES_R_UNEXPECTEDEND</span>
289 is returned if the available space in the buffer
290 <em class="parameter"><code>b</code></em>
291 is too small to accommodate the packet header or the
292 <span class="type">lwres_nooprequest_t</span>
294 <span class="type">lwres_noopresponse_t</span>
296 <code class="function">lwres_nooprequest_parse()</code>
298 <code class="function">lwres_noopresponse_parse()</code>
300 <span class="errorcode">LWRES_R_UNEXPECTEDEND</span>
301 if the buffer is not empty after decoding the received packet.
302 These functions will return
303 <span class="errorcode">LWRES_R_FAILURE</span>
305 <code class="constant">pktflags</code>
306 in the packet header structure
307 <span class="type">lwres_lwpacket_t</span>
308 indicate that the packet is not a response to an earlier query.
311 <div class="refsect1" lang="en">
312 <a name="id2543740"></a><h2>SEE ALSO</h2>
313 <p><span class="citerefentry"><span class="refentrytitle">lwres_packet</span>(3)</span>