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<title>lwres_gnba</title>
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry">
<a name="id-1"></a><div class="titlepage"></div>
<div class="refnamediv">
<h2>Name</h2>
<p>lwres_gnbarequest_render, lwres_gnbaresponse_render, lwres_gnbarequest_parse, lwres_gnbaresponse_parse, lwres_gnbaresponse_free, lwres_gnbarequest_free — lightweight resolver getnamebyaddress message handling</p>
</div>
<div class="refsynopsisdiv">
<h2>Synopsis</h2>
<div class="funcsynopsis">
<pre class="funcsynopsisinfo">
#include <lwres/lwres.h>
</pre>
<table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;">
<tr>
<td><code class="funcdef">
lwres_result_t
<b class="fsfunc">lwres_gnbarequest_render</b>
(</code></td>
<td>lwres_context_t *<var class="pdparam">ctx</var>, </td>
</tr>
<tr>
<td> </td>
<td>lwres_gnbarequest_t *<var class="pdparam">req</var>, </td>
</tr>
<tr>
<td> </td>
<td>lwres_lwpacket_t *<var class="pdparam">pkt</var>, </td>
</tr>
<tr>
<td> </td>
<td>lwres_buffer_t *<var class="pdparam">b</var><code>)</code>;</td>
</tr>
</table>
<div class="funcprototype-spacer"> </div>
<table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;">
<tr>
<td><code class="funcdef">
lwres_result_t
<b class="fsfunc">lwres_gnbaresponse_render</b>
(</code></td>
<td>lwres_context_t *<var class="pdparam">ctx</var>, </td>
</tr>
<tr>
<td> </td>
<td>lwres_gnbaresponse_t *<var class="pdparam">req</var>, </td>
</tr>
<tr>
<td> </td>
<td>lwres_lwpacket_t *<var class="pdparam">pkt</var>, </td>
</tr>
<tr>
<td> </td>
<td>lwres_buffer_t *<var class="pdparam">b</var><code>)</code>;</td>
</tr>
</table>
<div class="funcprototype-spacer"> </div>
<table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;">
<tr>
<td><code class="funcdef">
lwres_result_t
<b class="fsfunc">lwres_gnbarequest_parse</b>(</code></td>
<td>lwres_context_t *<var class="pdparam">ctx</var>, </td>
</tr>
<tr>
<td> </td>
<td>lwres_buffer_t *<var class="pdparam">b</var>, </td>
</tr>
<tr>
<td> </td>
<td>lwres_lwpacket_t *<var class="pdparam">pkt</var>, </td>
</tr>
<tr>
<td> </td>
<td>lwres_gnbarequest_t **<var class="pdparam">structp</var><code>)</code>;</td>
</tr>
</table>
<div class="funcprototype-spacer"> </div>
<table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;">
<tr>
<td><code class="funcdef">
lwres_result_t
<b class="fsfunc">lwres_gnbaresponse_parse</b>(</code></td>
<td>lwres_context_t *<var class="pdparam">ctx</var>, </td>
</tr>
<tr>
<td> </td>
<td>lwres_buffer_t *<var class="pdparam">b</var>, </td>
</tr>
<tr>
<td> </td>
<td>lwres_lwpacket_t *<var class="pdparam">pkt</var>, </td>
</tr>
<tr>
<td> </td>
<td>lwres_gnbaresponse_t **<var class="pdparam">structp</var><code>)</code>;</td>
</tr>
</table>
<div class="funcprototype-spacer"> </div>
<table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;">
<tr>
<td><code class="funcdef">
void
<b class="fsfunc">lwres_gnbaresponse_free</b>
(</code></td>
<td>lwres_context_t *<var class="pdparam">ctx</var>, </td>
</tr>
<tr>
<td> </td>
<td>lwres_gnbaresponse_t **<var class="pdparam">structp</var><code>)</code>;</td>
</tr>
</table>
<div class="funcprototype-spacer"> </div>
<table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;">
<tr>
<td><code class="funcdef">
void
<b class="fsfunc">lwres_gnbarequest_free</b>(</code></td>
<td>lwres_context_t *<var class="pdparam">ctx</var>, </td>
</tr>
<tr>
<td> </td>
<td>lwres_gnbarequest_t **<var class="pdparam">structp</var><code>)</code>;</td>
</tr>
</table>
<div class="funcprototype-spacer"> </div>
</div>
</div>
<div class="refsection">
<a name="id-1.7"></a><h2>DESCRIPTION</h2>
<p>
These are low-level routines for creating and parsing
lightweight resolver address-to-name lookup request and
response messages.
</p>
<p>
There are four main functions for the getnamebyaddr opcode.
One render function converts a getnamebyaddr request structure —
<span class="type">lwres_gnbarequest_t</span> —
to the lightweight resolver's canonical format.
It is complemented by a parse function that converts a packet in this
canonical format to a getnamebyaddr request structure.
Another render function converts the getnamebyaddr response structure
—
<span class="type">lwres_gnbaresponse_t</span>
to the canonical format.
This is complemented by a parse function which converts a packet in
canonical format to a getnamebyaddr response structure.
</p>
<p>
These structures are defined in
<code class="filename">lwres/lwres.h</code>.
They are shown below.
</p>
<pre class="programlisting">
#define LWRES_OPCODE_GETNAMEBYADDR 0x00010002U
</pre>
<p>
</p>
<pre class="programlisting">
typedef struct {
uint32_t flags;
lwres_addr_t addr;
} lwres_gnbarequest_t;
</pre>
<p>
</p>
<pre class="programlisting">
typedef struct {
uint32_t flags;
uint16_t naliases;
char *realname;
char **aliases;
uint16_t realnamelen;
uint16_t *aliaslen;
void *base;
size_t baselen;
} lwres_gnbaresponse_t;
</pre>
<p>
</p>
<p><code class="function">lwres_gnbarequest_render()</code>
uses resolver context <code class="varname">ctx</code> to convert
getnamebyaddr request structure <code class="varname">req</code> to
canonical format. The packet header structure
<code class="varname">pkt</code> is initialised and transferred to buffer
<code class="varname">b</code>. The contents of <code class="varname">*req</code>
are then appended to the buffer in canonical format.
<code class="function">lwres_gnbaresponse_render()</code> performs the
same task, except it converts a getnamebyaddr response structure
<span class="type">lwres_gnbaresponse_t</span> to the lightweight resolver's
canonical format.
</p>
<p><code class="function">lwres_gnbarequest_parse()</code>
uses context <code class="varname">ctx</code> to convert the contents of
packet <code class="varname">pkt</code> to a
<span class="type">lwres_gnbarequest_t</span> structure. Buffer
<code class="varname">b</code> provides space to be used for storing this
structure. When the function succeeds, the resulting
<span class="type">lwres_gnbarequest_t</span> is made available through
<code class="varname">*structp</code>.
<code class="function">lwres_gnbaresponse_parse()</code> offers the same
semantics as <code class="function">lwres_gnbarequest_parse()</code>
except it yields a <span class="type">lwres_gnbaresponse_t</span> structure.
</p>
<p><code class="function">lwres_gnbaresponse_free()</code>
and <code class="function">lwres_gnbarequest_free()</code> release the
memory in resolver context <code class="varname">ctx</code> that was
allocated to the <span class="type">lwres_gnbaresponse_t</span> or
<span class="type">lwres_gnbarequest_t</span> structures referenced via
<code class="varname">structp</code>. Any memory associated with
ancillary buffers and strings for those structures is also
discarded.
</p>
</div>
<div class="refsection">
<a name="id-1.8"></a><h2>RETURN VALUES</h2>
<p>
The getnamebyaddr opcode functions
<code class="function">lwres_gnbarequest_render()</code>,
<code class="function">lwres_gnbaresponse_render()</code>
<code class="function">lwres_gnbarequest_parse()</code>
and
<code class="function">lwres_gnbaresponse_parse()</code>
all return
<span class="errorcode">LWRES_R_SUCCESS</span>
on success.
They return
<span class="errorcode">LWRES_R_NOMEMORY</span>
if memory allocation fails.
<span class="errorcode">LWRES_R_UNEXPECTEDEND</span>
is returned if the available space in the buffer
<code class="varname">b</code>
is too small to accommodate the packet header or the
<span class="type">lwres_gnbarequest_t</span>
and
<span class="type">lwres_gnbaresponse_t</span>
structures.
<code class="function">lwres_gnbarequest_parse()</code>
and
<code class="function">lwres_gnbaresponse_parse()</code>
will return
<span class="errorcode">LWRES_R_UNEXPECTEDEND</span>
if the buffer is not empty after decoding the received packet.
These functions will return
<span class="errorcode">LWRES_R_FAILURE</span>
if
<code class="varname">pktflags</code>
in the packet header structure
<span class="type">lwres_lwpacket_t</span>
indicate that the packet is not a response to an earlier query.
</p>
</div>
<div class="refsection">
<a name="id-1.9"></a><h2>SEE ALSO</h2>
<p><span class="citerefentry"><span class="refentrytitle">lwres_packet</span>(3)</span>.
</p>
</div>
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