/contrib/bind9/lib/lwres/man/lwres_resutil.html
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1<!-- 2 - Copyright (C) 2004, 2005, 2007, 2012 Internet Systems Consortium, Inc. ("ISC") 3 - Copyright (C) 2000, 2001 Internet Software Consortium. 4 - 5 - Permission to use, copy, modify, and/or distribute this software for any 6 - purpose with or without fee is hereby granted, provided that the above 7 - copyright notice and this permission notice appear in all copies. 8 - 9 - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH 10 - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY 11 - AND FITNESS. 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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->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->address</code> and 156 <code class="constant">addr->length</code> indicates the size in bytes 157 of the address that was copied. 158 <code class="constant">b->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"> 167typedef 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="id2543609"></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="id2543681"></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>