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17 <!-- $Id: lwres_noop.html,v 1.25.214.1 2009/07/11 01:43:34 tbox Exp $ -->
18 <html>
19 <head>
20 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
21 <title>lwres_noop</title>
22 <meta name="generator" content="DocBook XSL Stylesheets V1.71.1">
23 </head>
24 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en">
25 <a name="id2476275"></a><div class="titlepage"></div>
26 <div class="refnamediv">
27 <h2>Name</h2>
28 <p>lwres_nooprequest_render, lwres_noopresponse_render, lwres_nooprequest_parse, lwres_noopresponse_parse, lwres_noopresponse_free, lwres_nooprequest_free &#8212; lightweight resolver no-op message handling</p>
29 </div>
30 <div class="refsynopsisdiv">
31 <h2>Synopsis</h2>
32 <div class="funcsynopsis">
33 <pre class="funcsynopsisinfo">
34 #include &lt;lwres/lwres.h&gt;</pre>
35 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
36 <tr>
37 <td><code class="funcdef">
38 lwres_result_t
39 <b class="fsfunc">lwres_nooprequest_render</b>(</code></td>
40 <td>lwres_context_t * </td>
41 <td>
42 <var class="pdparam">ctx</var>, </td>
43 </tr>
44 <tr>
45 <td> </td>
46 <td>lwres_nooprequest_t * </td>
47 <td>
48 <var class="pdparam">req</var>, </td>
49 </tr>
50 <tr>
51 <td> </td>
52 <td>lwres_lwpacket_t * </td>
53 <td>
54 <var class="pdparam">pkt</var>, </td>
55 </tr>
56 <tr>
57 <td> </td>
58 <td>lwres_buffer_t * </td>
59 <td>
60 <var class="pdparam">b</var><code>)</code>;</td>
61 </tr>
62 </table>
63 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
64 <tr>
65 <td><code class="funcdef">
66 lwres_result_t
67 <b class="fsfunc">lwres_noopresponse_render</b>(</code></td>
68 <td>lwres_context_t * </td>
69 <td>
70 <var class="pdparam">ctx</var>, </td>
71 </tr>
72 <tr>
73 <td> </td>
74 <td>lwres_noopresponse_t * </td>
75 <td>
76 <var class="pdparam">req</var>, </td>
77 </tr>
78 <tr>
79 <td> </td>
80 <td>lwres_lwpacket_t * </td>
81 <td>
82 <var class="pdparam">pkt</var>, </td>
83 </tr>
84 <tr>
85 <td> </td>
86 <td>lwres_buffer_t * </td>
87 <td>
88 <var class="pdparam">b</var><code>)</code>;</td>
89 </tr>
90 </table>
91 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
92 <tr>
93 <td><code class="funcdef">
94 lwres_result_t
95 <b class="fsfunc">lwres_nooprequest_parse</b>(</code></td>
96 <td>lwres_context_t * </td>
97 <td>
98 <var class="pdparam">ctx</var>, </td>
99 </tr>
100 <tr>
101 <td> </td>
102 <td>lwres_buffer_t * </td>
103 <td>
104 <var class="pdparam">b</var>, </td>
105 </tr>
106 <tr>
107 <td> </td>
108 <td>lwres_lwpacket_t * </td>
109 <td>
110 <var class="pdparam">pkt</var>, </td>
111 </tr>
112 <tr>
113 <td> </td>
114 <td>lwres_nooprequest_t ** </td>
115 <td>
116 <var class="pdparam">structp</var><code>)</code>;</td>
117 </tr>
118 </table>
119 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
120 <tr>
121 <td><code class="funcdef">
122 lwres_result_t
123 <b class="fsfunc">lwres_noopresponse_parse</b>(</code></td>
124 <td>lwres_context_t * </td>
125 <td>
126 <var class="pdparam">ctx</var>, </td>
127 </tr>
128 <tr>
129 <td> </td>
130 <td>lwres_buffer_t * </td>
131 <td>
132 <var class="pdparam">b</var>, </td>
133 </tr>
134 <tr>
135 <td> </td>
136 <td>lwres_lwpacket_t * </td>
137 <td>
138 <var class="pdparam">pkt</var>, </td>
139 </tr>
140 <tr>
141 <td> </td>
142 <td>lwres_noopresponse_t ** </td>
143 <td>
144 <var class="pdparam">structp</var><code>)</code>;</td>
145 </tr>
146 </table>
147 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
148 <tr>
149 <td><code class="funcdef">
150 void
151 <b class="fsfunc">lwres_noopresponse_free</b>(</code></td>
152 <td>lwres_context_t * </td>
153 <td>
154 <var class="pdparam">ctx</var>, </td>
155 </tr>
156 <tr>
157 <td> </td>
158 <td>lwres_noopresponse_t ** </td>
159 <td>
160 <var class="pdparam">structp</var><code>)</code>;</td>
161 </tr>
162 </table>
163 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0">
164 <tr>
165 <td><code class="funcdef">
166 void
167 <b class="fsfunc">lwres_nooprequest_free</b>(</code></td>
168 <td>lwres_context_t * </td>
169 <td>
170 <var class="pdparam">ctx</var>, </td>
171 </tr>
172 <tr>
173 <td> </td>
174 <td>lwres_nooprequest_t ** </td>
175 <td>
176 <var class="pdparam">structp</var><code>)</code>;</td>
177 </tr>
178 </table>
179 </div>
180 </div>
181 <div class="refsect1" lang="en">
182 <a name="id2543522"></a><h2>DESCRIPTION</h2>
183 <p>
184       These are low-level routines for creating and parsing
185       lightweight resolver no-op request and response messages.
186     </p>
187 <p>
188       The no-op message is analogous to a <span><strong class="command">ping</strong></span>
189       packet:
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
192       operational or not.
193     </p>
194 <p>
195       There are four main functions for the no-op opcode.
196       One render function converts a no-op request structure &#8212;
197       <span class="type">lwres_nooprequest_t</span> &#8212;
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 &#8212;
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.
206     </p>
207 <p>
208       These structures are defined in
209       <code class="filename">lwres/lwres.h</code>.
210
211       They are shown below.
212     </p>
213 <pre class="programlisting">
214 #define LWRES_OPCODE_NOOP       0x00000000U
215 </pre>
216 <p>
217     </p>
218 <pre class="programlisting">
219 typedef struct {
220         lwres_uint16_t  datalength;
221         unsigned char   *data;
222 } lwres_nooprequest_t;
223 </pre>
224 <p>
225     </p>
226 <pre class="programlisting">
227 typedef struct {
228         lwres_uint16_t  datalength;
229         unsigned char   *data;
230 } lwres_noopresponse_t;
231 </pre>
232 <p>
233     </p>
234 <p>
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.
238     </p>
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
246       canonical format.
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
250       canonical format.
251     </p>
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.
263     </p>
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>.
270     </p>
271 </div>
272 <div class="refsect1" lang="en">
273 <a name="id2543672"></a><h2>RETURN VALUES</h2>
274 <p>
275       The no-op opcode functions
276       <code class="function">lwres_nooprequest_render()</code>,
277
278       <code class="function">lwres_noopresponse_render()</code>
279       <code class="function">lwres_nooprequest_parse()</code>
280       and
281       <code class="function">lwres_noopresponse_parse()</code>
282       all return
283       <span class="errorcode">LWRES_R_SUCCESS</span>
284       on success.
285       They return
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>
293       and
294       <span class="type">lwres_noopresponse_t</span>
295       structures.
296       <code class="function">lwres_nooprequest_parse()</code>
297       and
298       <code class="function">lwres_noopresponse_parse()</code>
299       will return
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>
304       if
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.
309     </p>
310 </div>
311 <div class="refsect1" lang="en">
312 <a name="id2543738"></a><h2>SEE ALSO</h2>
313 <p><span class="citerefentry"><span class="refentrytitle">lwres_packet</span>(3)</span>
314     </p>
315 </div>
316 </div></body>
317 </html>