<!DOCTYPE book [

<!ENTITY mdash "&#8212;">]>

<refentry xmlns:db="http://docbook.org/ns/docbook" version="5.0">

<info>

<date>2007-06-18</date>

</info>

<refentryinfo>

<corpname>ISC</corpname>

<corpauthor>Internet Systems Consortium, Inc.</corpauthor>

</refentryinfo>

<refmeta>

<refentrytitle>lwres_gnba</refentrytitle>

<manvolnum>3</manvolnum>

<refmiscinfo>BIND9</refmiscinfo>

</refmeta>

<docinfo>

<copyright>

<year>2000</year>

<year>2001</year>

<year>2004</year>

<year>2005</year>

<year>2007</year>

<year>2014</year>

<year>2015</year>

<year>2016</year>

<holder>Internet Systems Consortium, Inc. ("ISC")</holder>

</copyright>

</docinfo>

<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 *<parameter>ctx</parameter></paramdef>

<paramdef>lwres_gnbaresponse_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_gnbarequest_parse</function></funcdef>

<paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>

<paramdef>lwres_buffer_t *<parameter>b</parameter></paramdef>

<paramdef>lwres_lwpacket_t *<parameter>pkt</parameter></paramdef>

<paramdef>lwres_gnbarequest_t **<parameter>structp</parameter></paramdef>

</funcprototype>

<funcprototype>

<funcdef>

lwres_result_t

<function>lwres_gnbaresponse_parse</function></funcdef>

<paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>

<paramdef>lwres_buffer_t *<parameter>b</parameter></paramdef>

<paramdef>lwres_lwpacket_t *<parameter>pkt</parameter></paramdef>

<paramdef>lwres_gnbaresponse_t **<parameter>structp</parameter></paramdef>

</funcprototype>

<funcprototype>

<funcdef>

void

<function>lwres_gnbaresponse_free</function>

</funcdef>

<paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>

<paramdef>lwres_gnbaresponse_t **<parameter>structp</parameter></paramdef>

</funcprototype>

<funcprototype>

<funcdef>

void

<function>lwres_gnbarequest_free</function></funcdef>

<paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>

<paramdef>lwres_gnbarequest_t **<parameter>structp</parameter></paramdef>

</funcprototype>

</funcsynopsis>

</refsynopsisdiv>

<refsection><info><title>DESCRIPTION</title></info>

<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.

</para>

<para><programlisting>

#define LWRES_OPCODE_GETNAMEBYADDR 0x00010002U

</programlisting>

</para>

<para><programlisting>

typedef struct {

lwres_uint32_t flags;

lwres_addr_t addr;

} lwres_gnbarequest_t;

</programlisting>

</para>

<para><programlisting>

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>

</refsection>

<refsection><info><title>RETURN VALUES</title></info>

<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

<varname remap="structfield">pktflags</varname>

in the packet header structure

<type>lwres_lwpacket_t</type>

indicate that the packet is not a response to an earlier query.

</para>

</refsection>

<refsection><info><title>SEE ALSO</title></info>

<para><citerefentry>

<refentrytitle>lwres_packet</refentrytitle><manvolnum>3</manvolnum>

</citerefentry>.

</para>

</refsection>

</refentry>