lwres_gnba.docbook [plain text]
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<refentry>
<refentryinfo>
<date>Jun 30, 2000</date>
</refentryinfo>
<refmeta>
<refentrytitle>lwres_gnba</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_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 <lwres/lwres.h>
</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>
<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 —
<type>lwres_gnbarequest_t</type> —
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
—
<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>
</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>
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