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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>
<year>2007</year>
<year>2012</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 <lwres/lwres.h></funcsynopsisinfo>
<funcprototype>
<funcdef>
lwres_result_t
<function>lwres_gabnrequest_render</function></funcdef>
<paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>
<paramdef>lwres_gabnrequest_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_gabnresponse_render</function></funcdef>
<paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>
<paramdef>lwres_gabnresponse_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_gabnrequest_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_gabnrequest_t **<parameter>structp</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>
lwres_result_t
<function>lwres_gabnresponse_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_gabnresponse_t **<parameter>structp</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>
void
<function>lwres_gabnresponse_free</function></funcdef>
<paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>
<paramdef>lwres_gabnresponse_t **<parameter>structp</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>
void
<function>lwres_gabnrequest_free</function></funcdef>
<paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>
<paramdef>lwres_gabnrequest_t **<parameter>structp</parameter></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 —
<type>lwres_gabnrequest_t</type> —
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
— <type>lwres_gabnresponse_t</type> —
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><lwres/lwres.h></filename>.
They are shown below.
</para>
<para><programlisting>
#define LWRES_OPCODE_GETADDRSBYNAME 0x00010001U
</programlisting>
</para>
<para><programlisting>
typedef struct lwres_addr lwres_addr_t;
typedef LWRES_LIST(lwres_addr_t) lwres_addrlist_t;
</programlisting>
</para>
<para><programlisting>
typedef struct {
lwres_uint32_t flags;
lwres_uint32_t addrtypes;
lwres_uint16_t namelen;
char *name;
} lwres_gabnrequest_t;
</programlisting>
</para>
<para><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;
</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>
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