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<refentry>

<refentryinfo>
<date>Jun 30, 2000</date>
</refentryinfo>

<refmeta>
<refentrytitle>lwres_gnba</refentrytitle>
<manvolnum>3</manvolnum>
<refmiscinfo>BIND9</refmiscinfo>
</refmeta>

<refnamediv>
<refname>lwres_gnbarequest_render</refname>
<refname>lwres_gnbaresponse_render</refname>
<refname>lwres_gnbarequest_parse</refname>
<refname>lwres_gnbaresponse_parse</refname>
<refname>lwres_gnbaresponse_free</refname>
<refname>lwres_gnbarequest_free</refname>
<refpurpose>lightweight resolver getnamebyaddress message handling</refpurpose>
</refnamediv>

<refsynopsisdiv>

<funcsynopsis>
<funcsynopsisinfo>
#include &lt;lwres/lwres.h&gt;
</funcsynopsisinfo>

<funcprototype>
<funcdef>
lwres_result_t
<function>lwres_gnbarequest_render</function>
</funcdef>
<paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>
<paramdef>lwres_gnbarequest_t *<parameter>req</parameter></paramdef>
<paramdef>lwres_lwpacket_t *<parameter>pkt</parameter></paramdef>
<paramdef>lwres_buffer_t *<parameter>b</parameter></paramdef>
</funcprototype>

<funcprototype>
<funcdef>
lwres_result_t
<function>lwres_gnbaresponse_render</function>
</funcdef>
<paramdef>lwres_context_t *ctx</paramdef>
<paramdef>lwres_gnbaresponse_t *req</paramdef>
<paramdef>lwres_lwpacket_t *pkt</paramdef>
<paramdef>lwres_buffer_t *b</paramdef>
</funcprototype>
<funcprototype>
<funcdef>
lwres_result_t
<function>lwres_gnbarequest_parse</function></funcdef>
<paramdef>lwres_context_t *ctx</paramdef>
<paramdef>lwres_buffer_t *b</paramdef>
<paramdef>lwres_lwpacket_t *pkt</paramdef>
<paramdef>lwres_gnbarequest_t **structp</paramdef>
</funcprototype>
<funcprototype>
<funcdef>
lwres_result_t
<function>lwres_gnbaresponse_parse</function></funcdef>
<paramdef>lwres_context_t *ctx</paramdef>
<paramdef>lwres_buffer_t *b</paramdef>
<paramdef>lwres_lwpacket_t *pkt</paramdef>
<paramdef>lwres_gnbaresponse_t **structp</paramdef>
</funcprototype>

<funcprototype>
<funcdef>
void
<function>lwres_gnbaresponse_free</function>
</funcdef>
<paramdef>lwres_context_t *ctx</paramdef>
<paramdef>lwres_gnbaresponse_t **structp</paramdef>
</funcprototype>
<funcprototype>
<funcdef>
void
<function>lwres_gnbarequest_free</function></funcdef>
<paramdef>lwres_context_t *ctx</paramdef>
<paramdef>lwres_gnbarequest_t **structp</paramdef>
</funcprototype>
</funcsynopsis>

</refsynopsisdiv>

<refsect1>
<title>DESCRIPTION</title>
<para>
These are low-level routines for creating and parsing
lightweight resolver address-to-name lookup request and 
response messages.
</para>
<para>
There are four main functions for the getnamebyaddr opcode.
One render function converts a getnamebyaddr request structure &mdash;
<type>lwres_gnbarequest_t</type> &mdash;
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 &mdash;
<type>lwres_gnbaresponse_t</type>
to the canonical format.
This is complemented by a parse function which converts a packet in
canonical format to a getnamebyaddr response structure.
</para>
<para>
These structures are defined in
<filename>lwres/lwres.h</filename>.
They are shown below.
<programlisting>
#define LWRES_OPCODE_GETNAMEBYADDR      0x00010002U

typedef struct {
        lwres_uint32_t  flags;
        lwres_addr_t    addr;
} lwres_gnbarequest_t;

typedef struct {
        lwres_uint32_t  flags;
        lwres_uint16_t  naliases;
        char           *realname;
        char          **aliases;
        lwres_uint16_t  realnamelen;
        lwres_uint16_t *aliaslen;
        void           *base;
        size_t          baselen;
} lwres_gnbaresponse_t;
</programlisting>
</para>
<para>
<function>lwres_gnbarequest_render()</function>
uses resolver context
<varname>ctx</varname>
to convert getnamebyaddr request structure
<varname>req</varname>
to canonical format.
The packet header structure
<varname>pkt</varname>
is initialised and transferred to
buffer
<varname>b</varname>.
The contents of
<varname>*req</varname>
are then appended to the buffer in canonical format.
<function>lwres_gnbaresponse_render()</function>
performs the same task, except it converts a getnamebyaddr response structure
<type>lwres_gnbaresponse_t</type>
to the lightweight resolver's canonical format.
</para>
<para>
<function>lwres_gnbarequest_parse()</function>
uses context
<varname>ctx</varname>
to convert the contents of packet
<varname>pkt</varname>
to a
<type>lwres_gnbarequest_t</type>
structure.
Buffer
<varname>b</varname>
provides space to be used for storing this structure.
When the function succeeds, the resulting
<type>lwres_gnbarequest_t</type>
is made available through
<varname>*structp</varname>.
<function>lwres_gnbaresponse_parse()</function>
offers the same semantics as
<function>lwres_gnbarequest_parse()</function>
except it yields a
<type>lwres_gnbaresponse_t</type>
structure.
</para>
<para>
<function>lwres_gnbaresponse_free()</function>
and
<function>lwres_gnbarequest_free()</function>
release the memory in resolver context
<varname>ctx</varname>
that was allocated to the
<type>lwres_gnbaresponse_t</type>
or
<type>lwres_gnbarequest_t</type>
structures referenced via
<varname>structp</varname>.
Any memory associated with ancillary buffers and strings for those
structures is also discarded.
</para>
</refsect1>
<refsect1>
<title>RETURN VALUES</title>
<para>
The getnamebyaddr opcode functions
<function>lwres_gnbarequest_render()</function>,
<function>lwres_gnbaresponse_render()</function>
<function>lwres_gnbarequest_parse()</function>
and
<function>lwres_gnbaresponse_parse()</function>
all return
<errorcode>LWRES_R_SUCCESS</errorcode>
on success.
They return
<errorcode>LWRES_R_NOMEMORY</errorcode>
if memory allocation fails.
<errorcode>LWRES_R_UNEXPECTEDEND</errorcode>
is returned if the available space in the buffer
<varname>b</varname>
is too small to accommodate the packet header or the
<type>lwres_gnbarequest_t</type>
and
<type>lwres_gnbaresponse_t</type>
structures.
<function>lwres_gnbarequest_parse()</function>
and
<function>lwres_gnbaresponse_parse()</function>
will return
<errorcode>LWRES_R_UNEXPECTEDEND</errorcode>
if the buffer is not empty after decoding the received packet.
These functions will return
<errorcode>LWRES_R_FAILURE</errorcode>
if
<structfield>pktflags</structfield>
in the packet header structure
<type>lwres_lwpacket_t</type>
indicate that the packet is not a response to an earlier query.
</para>
</refsect1>
<refsect1>
<title>SEE ALSO</title>
<para>
<citerefentry>
<refentrytitle>lwres_packet</refentrytitle>
<manvolnum>3</manvolnum>
</citerefentry>.
</para>
</refsect1>
</refentry>