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<title>lwres_resutil</title>
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en">
<a name="id2463721"></a><div class="titlepage"></div>
<div class="refnamediv">
<h2>Name</h2>
<p>lwres_string_parse, lwres_addr_parse, lwres_getaddrsbyname, lwres_getnamebyaddr — lightweight resolver utility functions</p>
</div>
<div class="refsynopsisdiv">
<h2>Synopsis</h2>
<div class="funcsynopsis">
<pre class="funcsynopsisinfo">#include <lwres/lwres.h></pre>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
<tr>
<td><code class="funcdef">
lwres_result_t
<b class="fsfunc">lwres_string_parse</b>(</code></td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>
<code>)</code>;</td>
</tr>
</table>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
<tr>
<td><code class="funcdef">
lwres_result_t
<b class="fsfunc">lwres_addr_parse</b>(</code></td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>
<code>)</code>;</td>
</tr>
</table>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
<tr>
<td><code class="funcdef">
lwres_result_t
<b class="fsfunc">lwres_getaddrsbyname</b>(</code></td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>
<code>)</code>;</td>
</tr>
</table>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0">
<tr>
<td><code class="funcdef">
lwres_result_t
<b class="fsfunc">lwres_getnamebyaddr</b>(</code></td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>
<code>)</code>;</td>
</tr>
</table>
</div>
</div>
<div class="refsect1" lang="en">
<a name="id2525921"></a><h2>DESCRIPTION</h2>
<p>
<code class="function">lwres_string_parse()</code> retrieves a DNS-encoded
string starting the current pointer of lightweight resolver buffer
<em class="parameter"><code>b</code></em>: i.e. <code class="constant">b->current</code>.
When the function returns, the address of the first byte of the
encoded string is returned via <em class="parameter"><code>*c</code></em> and the
length of that string is given by <em class="parameter"><code>*len</code></em>. The
buffer's current pointer is advanced to point at the character
following the string length, the encoded string, and the trailing
<span class="type">NULL</span> character.
</p>
<p>
<code class="function">lwres_addr_parse()</code> extracts an address from the
buffer <em class="parameter"><code>b</code></em>. The buffer's current pointer
<code class="constant">b->current</code> is presumed to point at an encoded
address: the address preceded by a 32-bit protocol family identifier
and a 16-bit length field. The encoded address is copied to
<code class="constant">addr->address</code> and
<code class="constant">addr->length</code> indicates the size in bytes of
the address that was copied. <code class="constant">b->current</code> is
advanced to point at the next byte of available data in the buffer
following the encoded address.
</p>
<p>
<code class="function">lwres_getaddrsbyname()</code>
and
<code class="function">lwres_getnamebyaddr()</code>
use the
<span class="type">lwres_gnbaresponse_t</span>
structure defined below:
</p>
<pre class="programlisting">
typedef struct {
lwres_uint32_t flags;
lwres_uint16_t naliases;
lwres_uint16_t naddrs;
char *realname;
char **aliases;
lwres_uint16_t realnamelen;
lwres_uint16_t *aliaslen;
lwres_addrlist_t addrs;
void *base;
size_t baselen;
} lwres_gabnresponse_t;
</pre>
<p>
The contents of this structure are not manipulated directly but
they are controlled through the
<span class="citerefentry"><span class="refentrytitle">lwres_gabn</span>(3
)</span>
functions.
</p>
<p>
The lightweight resolver uses
<code class="function">lwres_getaddrsbyname()</code> to perform foward lookups.
Hostname <em class="parameter"><code>name</code></em> is looked up using the resolver
context <em class="parameter"><code>ctx</code></em> for memory allocation.
<em class="parameter"><code>addrtypes</code></em> is a bitmask indicating which type of
addresses are to be looked up. Current values for this bitmask are
<span class="type">LWRES_ADDRTYPE_V4</span> for IPv4 addresses and
<span class="type">LWRES_ADDRTYPE_V6</span> for IPv6 addresses. Results of the
lookup are returned in <em class="parameter"><code>*structp</code></em>.
</p>
<p>
<code class="function">lwres_getnamebyaddr()</code> performs reverse lookups.
Resolver context <em class="parameter"><code>ctx</code></em> is used for memory
allocation. The address type is indicated by
<em class="parameter"><code>addrtype</code></em>: <span class="type">LWRES_ADDRTYPE_V4</span> or
<span class="type">LWRES_ADDRTYPE_V6</span>. The address to be looked up is given
by <em class="parameter"><code>addr</code></em> and its length is
<em class="parameter"><code>addrlen</code></em> bytes. The result of the function call
is made available through <em class="parameter"><code>*structp</code></em>.
</p>
</div>
<div class="refsect1" lang="en">
<a name="id2526060"></a><h2>RETURN VALUES</h2>
<p>
Successful calls to
<code class="function">lwres_string_parse()</code>
and
<code class="function">lwres_addr_parse()</code>
return
<span class="errorcode">LWRES_R_SUCCESS.</span>
Both functions return
<span class="errorcode">LWRES_R_FAILURE</span>
if the buffer is corrupt or
<span class="errorcode">LWRES_R_UNEXPECTEDEND</span>
if the buffer has less space than expected for the components of the
encoded string or address.
</p>
<p>
<code class="function">lwres_getaddrsbyname()</code>
returns
<span class="errorcode">LWRES_R_SUCCESS</span>
on success and it returns
<span class="errorcode">LWRES_R_NOTFOUND</span>
if the hostname
<em class="parameter"><code>name</code></em>
could not be found.
</p>
<p>
<span class="errorcode">LWRES_R_SUCCESS</span>
is returned by a successful call to
<code class="function">lwres_getnamebyaddr()</code>.
</p>
<p>
Both
<code class="function">lwres_getaddrsbyname()</code>
and
<code class="function">lwres_getnamebyaddr()</code>
return
<span class="errorcode">LWRES_R_NOMEMORY</span>
when memory allocation requests fail and
<span class="errorcode">LWRES_R_UNEXPECTEDEND</span>
if the buffers used for sending queries and receiving replies are too
small.
</p>
</div>
<div class="refsect1" lang="en">
<a name="id2526130"></a><h2>SEE ALSO</h2>
<p>
<span class="citerefentry"><span class="refentrytitle">lwres_buffer</span>(3)</span>,
<span class="citerefentry"><span class="refentrytitle">lwres_gabn</span>(3)</span>.
</p>
</div>
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