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<refentry>
<refentryinfo>


<date>Jun 30, 2000</date>
</refentryinfo>
<refmeta>
<refentrytitle>lwres_gabn</refentrytitle>
<manvolnum>3</manvolnum>
<refmiscinfo>BIND9</refmiscinfo>
</refmeta>

  <docinfo>
    <copyright>
      <year>2004</year>
      <year>2005</year>
      <holder>Internet Systems Consortium, Inc. ("ISC")</holder>
    </copyright>
    <copyright>
      <year>2000</year>
      <year>2001</year>
      <holder>Internet Software Consortium.</holder>
    </copyright>
  </docinfo>

<refnamediv>
<refname>lwres_gabnrequest_render</refname>
<refname>lwres_gabnresponse_render</refname>
<refname>lwres_gabnrequest_parse</refname>
<refname>lwres_gabnresponse_parse</refname>
<refname>lwres_gabnresponse_free</refname>
<refname>lwres_gabnrequest_free</refname>
<refpurpose>lightweight resolver getaddrbyname message handling</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include &lt;lwres/lwres.h&gt;</funcsynopsisinfo>
<funcprototype>
<funcdef>
lwres_result_t
<function>lwres_gabnrequest_render</function></funcdef>
<paramdef>lwres_context_t *ctx</paramdef>
<paramdef>lwres_gabnrequest_t *req</paramdef>
<paramdef>lwres_lwpacket_t *pkt</paramdef>
<paramdef>lwres_buffer_t *b</paramdef>
</funcprototype>
<funcprototype>
<funcdef>
lwres_result_t
<function>lwres_gabnresponse_render</function></funcdef>
<paramdef>lwres_context_t *ctx</paramdef>
<paramdef>lwres_gabnresponse_t *req</paramdef>
<paramdef>lwres_lwpacket_t *pkt</paramdef>
<paramdef>lwres_buffer_t *b</paramdef>
</funcprototype>
<funcprototype>
<funcdef>
lwres_result_t
<function>lwres_gabnrequest_parse</function></funcdef>
<paramdef>lwres_context_t *ctx</paramdef>
<paramdef>lwres_buffer_t *b</paramdef>
<paramdef>lwres_lwpacket_t *pkt</paramdef>
<paramdef>lwres_gabnrequest_t **structp</paramdef>
</funcprototype>
<funcprototype>
<funcdef>
lwres_result_t
<function>lwres_gabnresponse_parse</function></funcdef>
<paramdef>lwres_context_t *ctx</paramdef>
<paramdef>lwres_buffer_t *b</paramdef>
<paramdef>lwres_lwpacket_t *pkt</paramdef>
<paramdef>lwres_gabnresponse_t **structp</paramdef>
</funcprototype>
<funcprototype>
<funcdef>
void
<function>lwres_gabnresponse_free</function></funcdef>
<paramdef>lwres_context_t *ctx</paramdef>
<paramdef>lwres_gabnresponse_t **structp</paramdef>
</funcprototype>
<funcprototype>
<funcdef>
void
<function>lwres_gabnrequest_free</function></funcdef>
<paramdef>lwres_context_t *ctx</paramdef>
<paramdef>lwres_gabnrequest_t **structp</paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>DESCRIPTION</title>
<para>
These are low-level routines for creating and parsing
lightweight resolver name-to-address lookup request and 
response messages.
</para><para>
There are four main functions for the getaddrbyname opcode.
One render function converts a getaddrbyname request structure &mdash;
<type>lwres_gabnrequest_t</type> &mdash;
to the lighweight resolver's canonical format.
It is complemented by a parse function that converts a packet in this
canonical format to a getaddrbyname request structure.
Another render function converts the getaddrbyname response structure &mdash;
<type>lwres_gabnresponse_t</type> &mdash;
to the canonical format.
This is complemented by a parse function which converts a packet in
canonical format to a getaddrbyname response structure.
</para>
<para>
These structures are defined in
<filename>&lt;lwres/lwres.h&gt;</filename>.
They are shown below.
<programlisting>
#define LWRES_OPCODE_GETADDRSBYNAME     0x00010001U

typedef struct lwres_addr lwres_addr_t;
typedef LWRES_LIST(lwres_addr_t) lwres_addrlist_t;

typedef struct {
        lwres_uint32_t  flags;
        lwres_uint32_t  addrtypes;
        lwres_uint16_t  namelen;
        char           *name;
} lwres_gabnrequest_t;

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;
</programlisting>
</para>
<para>
<function>lwres_gabnrequest_render()</function>
uses resolver context
<parameter>ctx</parameter>
to convert getaddrbyname request structure
<parameter>req</parameter>
to canonical format.
The packet header structure
<parameter>pkt</parameter>
is initialised and transferred to
buffer
<parameter>b</parameter>.

The contents of
<parameter>*req</parameter>
are then appended to the buffer in canonical format.
<function>lwres_gabnresponse_render()</function>
performs the same task, except it converts a getaddrbyname response structure
<type>lwres_gabnresponse_t</type>
to the lightweight resolver's canonical format.
</para>
<para>
<function>lwres_gabnrequest_parse()</function>
uses context
<parameter>ctx</parameter>
to convert the contents of packet
<parameter>pkt</parameter>
to a
<type>lwres_gabnrequest_t</type>
structure.
Buffer
<parameter>b</parameter>
provides space to be used for storing this structure.
When the function succeeds, the resulting
<type>lwres_gabnrequest_t</type>
is made available through
<parameter>*structp</parameter>.

<function>lwres_gabnresponse_parse()</function>
offers the same semantics as
<function>lwres_gabnrequest_parse()</function>
except it yields a
<type>lwres_gabnresponse_t</type>
structure.
</para>
<para>
<function>lwres_gabnresponse_free()</function>
and
<function>lwres_gabnrequest_free()</function>
release the memory in resolver context
<parameter>ctx</parameter>
that was allocated to the
<type>lwres_gabnresponse_t</type>
or
<type>lwres_gabnrequest_t</type>
structures referenced via
<parameter>structp</parameter>.

Any memory associated with ancillary buffers and strings for those
structures is also discarded.
</para>
</refsect1>
<refsect1>
<title>RETURN VALUES</title>
<para>
The getaddrbyname opcode functions
<function>lwres_gabnrequest_render()</function>, 
<function>lwres_gabnresponse_render()</function>
<function>lwres_gabnrequest_parse()</function>
and
<function>lwres_gabnresponse_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
<parameter>b</parameter>
is too small to accommodate the packet header or the
<type>lwres_gabnrequest_t</type>
and
<type>lwres_gabnresponse_t</type>
structures.
<function>lwres_gabnrequest_parse()</function>
and
<function>lwres_gabnresponse_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>
