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 18<html>
 19<head>
 20<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
 21<title>lwres_getipnode</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_getipnodebyname, lwres_getipnodebyaddr, lwres_freehostent &#8212; lightweight resolver nodename / address translation API</p>
 29</div>
 30<div class="refsynopsisdiv">
 31<h2>Synopsis</h2>
 32<div class="funcsynopsis">
 33<pre class="funcsynopsisinfo">#include &lt;lwres/netdb.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">
 37struct hostent *
 38<b class="fsfunc">lwres_getipnodebyname</b>(</code></td>
 39<td>const char * </td>
 40<td>
 41<var class="pdparam">name</var>, </td>
 42</tr>
 43<tr>
 44<td> </td>
 45<td>int  </td>
 46<td>
 47<var class="pdparam">af</var>, </td>
 48</tr>
 49<tr>
 50<td> </td>
 51<td>int  </td>
 52<td>
 53<var class="pdparam">flags</var>, </td>
 54</tr>
 55<tr>
 56<td> </td>
 57<td>int * </td>
 58<td>
 59<var class="pdparam">error_num</var><code>)</code>;</td>
 60</tr>
 61</table>
 62<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
 63<tr>
 64<td><code class="funcdef">
 65struct hostent *
 66<b class="fsfunc">lwres_getipnodebyaddr</b>(</code></td>
 67<td>const void * </td>
 68<td>
 69<var class="pdparam">src</var>, </td>
 70</tr>
 71<tr>
 72<td> </td>
 73<td>size_t  </td>
 74<td>
 75<var class="pdparam">len</var>, </td>
 76</tr>
 77<tr>
 78<td> </td>
 79<td>int  </td>
 80<td>
 81<var class="pdparam">af</var>, </td>
 82</tr>
 83<tr>
 84<td> </td>
 85<td>int * </td>
 86<td>
 87<var class="pdparam">error_num</var><code>)</code>;</td>
 88</tr>
 89</table>
 90<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr>
 91<td><code class="funcdef">
 92void
 93<b class="fsfunc">lwres_freehostent</b>(</code></td>
 94<td>struct hostent * </td>
 95<td>
 96<var class="pdparam">he</var><code>)</code>;</td>
 97</tr></table>
 98</div>
 99</div>
100<div class="refsect1" lang="en">
101<a name="id2543435"></a><h2>DESCRIPTION</h2>
102<p>
103      These functions perform thread safe, protocol independent
104      nodename-to-address and address-to-nodename
105      translation as defined in RFC2553.
106    </p>
107<p>
108      They use a
109      <span class="type">struct hostent</span>
110      which is defined in
111      <code class="filename">namedb.h</code>:
112    </p>
113<pre class="programlisting">
114struct  hostent {
115        char    *h_name;        /* official name of host */
116        char    **h_aliases;    /* alias list */
117        int     h_addrtype;     /* host address type */
118        int     h_length;       /* length of address */
119        char    **h_addr_list;  /* list of addresses from name server */
120};
121#define h_addr  h_addr_list[0]  /* address, for backward compatibility */
122</pre>
123<p>
124    </p>
125<p>
126      The members of this structure are:
127      </p>
128<div class="variablelist"><dl>
129<dt><span class="term"><code class="constant">h_name</code></span></dt>
130<dd><p>
131              The official (canonical) name of the host.
132            </p></dd>
133<dt><span class="term"><code class="constant">h_aliases</code></span></dt>
134<dd><p>
135              A NULL-terminated array of alternate names (nicknames) for the
136              host.
137            </p></dd>
138<dt><span class="term"><code class="constant">h_addrtype</code></span></dt>
139<dd><p>
140              The type of address being returned - usually
141              <span class="type">PF_INET</span>
142              or
143              <span class="type">PF_INET6</span>.
144
145            </p></dd>
146<dt><span class="term"><code class="constant">h_length</code></span></dt>
147<dd><p>
148              The length of the address in bytes.
149            </p></dd>
150<dt><span class="term"><code class="constant">h_addr_list</code></span></dt>
151<dd><p>
152              A
153              <span class="type">NULL</span>
154              terminated array of network addresses for the host.
155              Host addresses are returned in network byte order.
156            </p></dd>
157</dl></div>
158<p>
159    </p>
160<p><code class="function">lwres_getipnodebyname()</code>
161      looks up addresses of protocol family <em class="parameter"><code>af</code></em>
162      for the hostname <em class="parameter"><code>name</code></em>.  The
163      <em class="parameter"><code>flags</code></em> parameter contains ORed flag bits
164      to specify the types of addresses that are searched for, and the
165      types of addresses that are returned.  The flag bits are:
166
167      </p>
168<div class="variablelist"><dl>
169<dt><span class="term"><code class="constant">AI_V4MAPPED</code></span></dt>
170<dd><p>
171              This is used with an
172              <em class="parameter"><code>af</code></em>
173              of AF_INET6, and causes IPv4 addresses to be returned as
174              IPv4-mapped
175              IPv6 addresses.
176            </p></dd>
177<dt><span class="term"><code class="constant">AI_ALL</code></span></dt>
178<dd><p>
179              This is used with an
180              <em class="parameter"><code>af</code></em>
181              of AF_INET6, and causes all known addresses (IPv6 and IPv4) to
182              be returned.
183              If AI_V4MAPPED is also set, the IPv4 addresses are return as
184              mapped
185              IPv6 addresses.
186            </p></dd>
187<dt><span class="term"><code class="constant">AI_ADDRCONFIG</code></span></dt>
188<dd><p>
189              Only return an IPv6 or IPv4 address if here is an active network
190              interface of that type.  This is not currently implemented
191              in the BIND 9 lightweight resolver, and the flag is ignored.
192            </p></dd>
193<dt><span class="term"><code class="constant">AI_DEFAULT</code></span></dt>
194<dd><p>
195              This default sets the
196              <code class="constant">AI_V4MAPPED</code>
197              and
198              <code class="constant">AI_ADDRCONFIG</code>
199              flag bits.
200            </p></dd>
201</dl></div>
202<p>
203    </p>
204<p><code class="function">lwres_getipnodebyaddr()</code>
205      performs a reverse lookup of address <em class="parameter"><code>src</code></em>
206      which is <em class="parameter"><code>len</code></em> bytes long.
207      <em class="parameter"><code>af</code></em> denotes the protocol family, typically
208      <span class="type">PF_INET</span> or <span class="type">PF_INET6</span>.
209    </p>
210<p><code class="function">lwres_freehostent()</code>
211      releases all the memory associated with the <span class="type">struct
212      hostent</span> pointer <em class="parameter"><code>he</code></em>.  Any memory
213      allocated for the <code class="constant">h_name</code>,
214      <code class="constant">h_addr_list</code> and
215      <code class="constant">h_aliases</code> is freed, as is the memory for
216      the <span class="type">hostent</span> structure itself.
217    </p>
218</div>
219<div class="refsect1" lang="en">
220<a name="id2543693"></a><h2>RETURN VALUES</h2>
221<p>
222      If an error occurs,
223      <code class="function">lwres_getipnodebyname()</code>
224      and
225      <code class="function">lwres_getipnodebyaddr()</code>
226      set
227      <em class="parameter"><code>*error_num</code></em>
228      to an appropriate error code and the function returns a
229      <span class="type">NULL</span>
230      pointer.
231      The error codes and their meanings are defined in
232      <code class="filename">&lt;lwres/netdb.h&gt;</code>:
233      </p>
234<div class="variablelist"><dl>
235<dt><span class="term"><code class="constant">HOST_NOT_FOUND</code></span></dt>
236<dd><p>
237              No such host is known.
238            </p></dd>
239<dt><span class="term"><code class="constant">NO_ADDRESS</code></span></dt>
240<dd><p>
241              The server recognised the request and the name but no address is
242              available.  Another type of request to the name server for the
243              domain might return an answer.
244            </p></dd>
245<dt><span class="term"><code class="constant">TRY_AGAIN</code></span></dt>
246<dd><p>
247              A temporary and possibly transient error occurred, such as a
248              failure of a server to respond.  The request may succeed if
249              retried.
250            </p></dd>
251<dt><span class="term"><code class="constant">NO_RECOVERY</code></span></dt>
252<dd><p>
253              An unexpected failure occurred, and retrying the request
254              is pointless.
255            </p></dd>
256</dl></div>
257<p>
258    </p>
259<p><span class="citerefentry"><span class="refentrytitle">lwres_hstrerror</span>(3)</span>
260      translates these error codes to suitable error messages.
261    </p>
262</div>
263<div class="refsect1" lang="en">
264<a name="id2543790"></a><h2>SEE ALSO</h2>
265<p><span class="citerefentry"><span class="refentrytitle">RFC2553</span></span>,
266
267      <span class="citerefentry"><span class="refentrytitle">lwres</span>(3)</span>,
268
269      <span class="citerefentry"><span class="refentrytitle">lwres_gethostent</span>(3)</span>,
270
271      <span class="citerefentry"><span class="refentrytitle">lwres_getaddrinfo</span>(3)</span>,
272
273      <span class="citerefentry"><span class="refentrytitle">lwres_getnameinfo</span>(3)</span>,
274
275      <span class="citerefentry"><span class="refentrytitle">lwres_hstrerror</span>(3)</span>.
276    </p>
277</div>
278</div></body>
279</html>