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<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_packet</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>
<year>2018</year>
<year>2019</year>
<year>2020</year>
<holder>Internet Systems Consortium, Inc. ("ISC")</holder>
</copyright>
</docinfo>
<refnamediv>
<refname>lwres_lwpacket_renderheader</refname>
<refname>lwres_lwpacket_parseheader</refname>
<refpurpose>lightweight resolver packet handling functions</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include <lwres/lwpacket.h></funcsynopsisinfo>
<funcprototype>
<funcdef>
lwres_result_t
<function>lwres_lwpacket_renderheader</function></funcdef>
<paramdef>lwres_buffer_t *<parameter>b</parameter></paramdef>
<paramdef>lwres_lwpacket_t *<parameter>pkt</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>
lwres_result_t
<function>lwres_lwpacket_parseheader</function></funcdef>
<paramdef>lwres_buffer_t *<parameter>b</parameter></paramdef>
<paramdef>lwres_lwpacket_t *<parameter>pkt</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsection><info><title>DESCRIPTION</title></info>
<para>
These functions rely on a
<type>struct lwres_lwpacket</type>
which is defined in
<filename>lwres/lwpacket.h</filename>.
</para>
<para><programlisting>
typedef struct lwres_lwpacket lwres_lwpacket_t;
</programlisting>
</para>
<para><programlisting>
struct lwres_lwpacket {
uint32_t length;
uint16_t version;
uint16_t pktflags;
uint32_t serial;
uint32_t opcode;
uint32_t result;
uint32_t recvlength;
uint16_t authtype;
uint16_t authlength;
};
</programlisting>
</para>
<para>
The elements of this structure are:
<variablelist>
<varlistentry>
<term><constant>length</constant></term>
<listitem>
<para>
the overall packet length, including the entire packet header.
This field is filled in by the lwres_gabn_*() and lwres_gnba_*()
calls.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>version</constant></term>
<listitem>
<para>
the header format. There is currently only one format,
<type>LWRES_LWPACKETVERSION_0</type>.
This field is filled in by the lwres_gabn_*() and lwres_gnba_*()
calls.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>pktflags</constant></term>
<listitem>
<para>
library-defined flags for this packet: for instance whether the
packet
is a request or a reply. Flag values can be set, but not defined
by
the caller.
This field is filled in by the application with the exception of
the
LWRES_LWPACKETFLAG_RESPONSE bit, which is set by the library in
the
lwres_gabn_*() and lwres_gnba_*() calls.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>serial</constant></term>
<listitem>
<para>
is set by the requestor and is returned in all replies. If two
or more
packets from the same source have the same serial number and are
from
the same source, they are assumed to be duplicates and the
latter ones
may be dropped.
This field must be set by the application.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>opcode</constant></term>
<listitem>
<para>
indicates the operation.
Opcodes between 0x00000000 and 0x03ffffff are
reserved for use by the lightweight resolver library. Opcodes
between
0x04000000 and 0xffffffff are application defined.
This field is filled in by the lwres_gabn_*() and lwres_gnba_*()
calls.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>result</constant></term>
<listitem>
<para>
is only valid for replies.
Results between 0x04000000 and 0xffffffff are application
defined.
Results between 0x00000000 and 0x03ffffff are reserved for
library use.
This field is filled in by the lwres_gabn_*() and lwres_gnba_*()
calls.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>recvlength</constant></term>
<listitem>
<para>
is the maximum buffer size that the receiver can handle on
requests
and the size of the buffer needed to satisfy a request when the
buffer
is too large for replies.
This field is supplied by the application.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>authtype</constant></term>
<listitem>
<para>
defines the packet level authentication that is used.
Authorisation types between 0x1000 and 0xffff are application
defined
and types between 0x0000 and 0x0fff are reserved for library
use.
Currently these are not used and must be zero.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>authlen</constant></term>
<listitem>
<para>
gives the length of the authentication data.
Since packet authentication is currently not used, this must be
zero.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
<para>
The following opcodes are currently defined:
<variablelist>
<varlistentry>
<term><constant>NOOP</constant></term>
<listitem>
<para>
Success is always returned and the packet contents are echoed.
The lwres_noop_*() functions should be used for this type.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GETADDRSBYNAME</constant></term>
<listitem>
<para>
returns all known addresses for a given name.
The lwres_gabn_*() functions should be used for this type.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GETNAMEBYADDR</constant></term>
<listitem>
<para>
return the hostname for the given address.
The lwres_gnba_*() functions should be used for this type.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
<para><function>lwres_lwpacket_renderheader()</function>
transfers the contents of lightweight resolver packet structure
<type>lwres_lwpacket_t</type> <parameter>*pkt</parameter> in
network byte order to the lightweight resolver buffer,
<parameter>*b</parameter>.
</para>
<para><function>lwres_lwpacket_parseheader()</function>
performs the converse operation. It transfers data in network
byte order from buffer <parameter>*b</parameter> to resolver
packet <parameter>*pkt</parameter>. The contents of the buffer
<parameter>b</parameter> should correspond to a
<type>lwres_lwpacket_t</type>.
</para>
</refsection>
<refsection><info><title>RETURN VALUES</title></info>
<para>
Successful calls to
<function>lwres_lwpacket_renderheader()</function> and
<function>lwres_lwpacket_parseheader()</function> return
<errorcode>LWRES_R_SUCCESS</errorcode>. If there is insufficient
space to copy data between the buffer <parameter>*b</parameter> and
lightweight resolver packet <parameter>*pkt</parameter> both
functions
return <errorcode>LWRES_R_UNEXPECTEDEND</errorcode>.
</para>
</refsection>
</refentry>