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18 <html>
19 <head>
20 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
21 <title>lwres_resutil</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_string_parse, lwres_addr_parse, lwres_getaddrsbyname, lwres_getnamebyaddr &#8212; lightweight resolver utility functions</p>
29 </div>
30 <div class="refsynopsisdiv">
31 <h2>Synopsis</h2>
32 <div class="funcsynopsis">
33 <pre class="funcsynopsisinfo">#include &lt;lwres/lwres.h&gt;</pre>
34 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
35 <tr>
36 <td><code class="funcdef">
37 lwres_result_t
38 <b class="fsfunc">lwres_string_parse</b>(</code></td>
39 <td>lwres_buffer_t * </td>
40 <td>
41 <var class="pdparam">b</var>, </td>
42 </tr>
43 <tr>
44 <td> </td>
45 <td>char ** </td>
46 <td>
47 <var class="pdparam">c</var>, </td>
48 </tr>
49 <tr>
50 <td> </td>
51 <td>lwres_uint16_t * </td>
52 <td>
53 <var class="pdparam">len</var><code>)</code>;</td>
54 </tr>
55 </table>
56 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
57 <tr>
58 <td><code class="funcdef">
59 lwres_result_t
60 <b class="fsfunc">lwres_addr_parse</b>(</code></td>
61 <td>lwres_buffer_t * </td>
62 <td>
63 <var class="pdparam">b</var>, </td>
64 </tr>
65 <tr>
66 <td> </td>
67 <td>lwres_addr_t * </td>
68 <td>
69 <var class="pdparam">addr</var><code>)</code>;</td>
70 </tr>
71 </table>
72 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
73 <tr>
74 <td><code class="funcdef">
75 lwres_result_t
76 <b class="fsfunc">lwres_getaddrsbyname</b>(</code></td>
77 <td>lwres_context_t * </td>
78 <td>
79 <var class="pdparam">ctx</var>, </td>
80 </tr>
81 <tr>
82 <td> </td>
83 <td>const char * </td>
84 <td>
85 <var class="pdparam">name</var>, </td>
86 </tr>
87 <tr>
88 <td> </td>
89 <td>lwres_uint32_t  </td>
90 <td>
91 <var class="pdparam">addrtypes</var>, </td>
92 </tr>
93 <tr>
94 <td> </td>
95 <td>lwres_gabnresponse_t ** </td>
96 <td>
97 <var class="pdparam">structp</var><code>)</code>;</td>
98 </tr>
99 </table>
100 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0">
101 <tr>
102 <td><code class="funcdef">
103 lwres_result_t
104 <b class="fsfunc">lwres_getnamebyaddr</b>(</code></td>
105 <td>lwres_context_t * </td>
106 <td>
107 <var class="pdparam">ctx</var>, </td>
108 </tr>
109 <tr>
110 <td> </td>
111 <td>lwres_uint32_t  </td>
112 <td>
113 <var class="pdparam">addrtype</var>, </td>
114 </tr>
115 <tr>
116 <td> </td>
117 <td>lwres_uint16_t  </td>
118 <td>
119 <var class="pdparam">addrlen</var>, </td>
120 </tr>
121 <tr>
122 <td> </td>
123 <td>const unsigned char * </td>
124 <td>
125 <var class="pdparam">addr</var>, </td>
126 </tr>
127 <tr>
128 <td> </td>
129 <td>lwres_gnbaresponse_t ** </td>
130 <td>
131 <var class="pdparam">structp</var><code>)</code>;</td>
132 </tr>
133 </table>
134 </div>
135 </div>
136 <div class="refsect1" lang="en">
137 <a name="id2543466"></a><h2>DESCRIPTION</h2>
138 <p><code class="function">lwres_string_parse()</code>
139       retrieves a DNS-encoded string starting the current pointer of
140       lightweight resolver buffer <em class="parameter"><code>b</code></em>: i.e.
141       <code class="constant">b-&gt;current</code>.  When the function returns,
142       the address of the first byte of the encoded string is returned
143       via <em class="parameter"><code>*c</code></em> and the length of that string is
144       given by <em class="parameter"><code>*len</code></em>.  The buffer's current
145       pointer is advanced to point at the character following the
146       string length, the encoded string, and the trailing
147       <span class="type">NULL</span> character.
148     </p>
149 <p><code class="function">lwres_addr_parse()</code>
150       extracts an address from the buffer <em class="parameter"><code>b</code></em>.
151       The buffer's current pointer <code class="constant">b-&gt;current</code>
152       is presumed to point at an encoded address: the address preceded
153       by a 32-bit protocol family identifier and a 16-bit length
154       field.  The encoded address is copied to
155       <code class="constant">addr-&gt;address</code> and
156       <code class="constant">addr-&gt;length</code> indicates the size in bytes
157       of the address that was copied.
158       <code class="constant">b-&gt;current</code> is advanced to point at the
159       next byte of available data in the buffer following the encoded
160       address.
161     </p>
162 <p><code class="function">lwres_getaddrsbyname()</code>
163       and <code class="function">lwres_getnamebyaddr()</code> use the
164       <span class="type">lwres_gnbaresponse_t</span> structure defined below:
165     </p>
166 <pre class="programlisting">
167 typedef struct {
168         lwres_uint32_t          flags;
169         lwres_uint16_t          naliases;
170         lwres_uint16_t          naddrs;
171         char                   *realname;
172         char                  **aliases;
173         lwres_uint16_t          realnamelen;
174         lwres_uint16_t         *aliaslen;
175         lwres_addrlist_t        addrs;
176         void                   *base;
177         size_t                  baselen;
178 } lwres_gabnresponse_t;
179 </pre>
180 <p>
181       The contents of this structure are not manipulated directly but
182       they are controlled through the
183       <span class="citerefentry"><span class="refentrytitle">lwres_gabn</span>(3)</span>
184       functions.
185     </p>
186 <p>
187       The lightweight resolver uses
188       <code class="function">lwres_getaddrsbyname()</code> to perform
189       foward lookups.
190       Hostname <em class="parameter"><code>name</code></em> is looked up using the
191       resolver
192       context <em class="parameter"><code>ctx</code></em> for memory allocation.
193       <em class="parameter"><code>addrtypes</code></em> is a bitmask indicating
194       which type of
195       addresses are to be looked up.  Current values for this bitmask are
196       <span class="type">LWRES_ADDRTYPE_V4</span> for IPv4 addresses and
197       <span class="type">LWRES_ADDRTYPE_V6</span> for IPv6 addresses.  Results of the
198       lookup are returned in <em class="parameter"><code>*structp</code></em>.
199     </p>
200 <p><code class="function">lwres_getnamebyaddr()</code>
201       performs reverse lookups.  Resolver context
202       <em class="parameter"><code>ctx</code></em> is used for memory allocation.  The
203       address type is indicated by <em class="parameter"><code>addrtype</code></em>:
204       <span class="type">LWRES_ADDRTYPE_V4</span> or
205       <span class="type">LWRES_ADDRTYPE_V6</span>.  The address to be looked up is
206       given by <em class="parameter"><code>addr</code></em> and its length is
207       <em class="parameter"><code>addrlen</code></em> bytes.  The result of the
208       function call is made available through
209       <em class="parameter"><code>*structp</code></em>.
210     </p>
211 </div>
212 <div class="refsect1" lang="en">
213 <a name="id2543605"></a><h2>RETURN VALUES</h2>
214 <p>
215       Successful calls to
216       <code class="function">lwres_string_parse()</code>
217       and
218       <code class="function">lwres_addr_parse()</code>
219       return
220       <span class="errorcode">LWRES_R_SUCCESS.</span>
221       Both functions return
222       <span class="errorcode">LWRES_R_FAILURE</span>
223       if the buffer is corrupt or
224       <span class="errorcode">LWRES_R_UNEXPECTEDEND</span>
225       if the buffer has less space than expected for the components of the
226       encoded string or address.
227     </p>
228 <p><code class="function">lwres_getaddrsbyname()</code>
229       returns <span class="errorcode">LWRES_R_SUCCESS</span> on success and it
230       returns <span class="errorcode">LWRES_R_NOTFOUND</span> if the hostname
231       <em class="parameter"><code>name</code></em> could not be found.
232     </p>
233 <p><span class="errorcode">LWRES_R_SUCCESS</span>
234       is returned by a successful call to
235       <code class="function">lwres_getnamebyaddr()</code>.
236     </p>
237 <p>
238       Both
239       <code class="function">lwres_getaddrsbyname()</code>
240       and
241       <code class="function">lwres_getnamebyaddr()</code>
242       return
243       <span class="errorcode">LWRES_R_NOMEMORY</span>
244       when memory allocation requests fail and
245       <span class="errorcode">LWRES_R_UNEXPECTEDEND</span>
246       if the buffers used for sending queries and receiving replies are too
247       small.
248     </p>
249 </div>
250 <div class="refsect1" lang="en">
251 <a name="id2543676"></a><h2>SEE ALSO</h2>
252 <p><span class="citerefentry"><span class="refentrytitle">lwres_buffer</span>(3)</span>,
253
254       <span class="citerefentry"><span class="refentrytitle">lwres_gabn</span>(3)</span>.
255     </p>
256 </div>
257 </div></body>
258 </html>