<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V4.1//EN">

<refentry>

<refentryinfo>

<date>Jun 30, 2000</date>

</refentryinfo>

<refmeta>

<refentrytitle>lwres_noop</refentrytitle>

<manvolnum>3</manvolnum>

<refmiscinfo>BIND9</refmiscinfo>

</refmeta>

<refnamediv>

<refname>lwres_nooprequest_render</refname>

<refname>lwres_noopresponse_render</refname>

<refname>lwres_nooprequest_parse</refname>

<refname>lwres_noopresponse_parse</refname>

<refname>lwres_noopresponse_free</refname>

<refname>lwres_nooprequest_free</refname>

<refpurpose>lightweight resolver no-op message handling</refpurpose>

</refnamediv>

<refsynopsisdiv>

<funcsynopsis>

<funcsynopsisinfo>

#include &lt;lwres/lwres.h&gt;</funcsynopsisinfo>

<funcprototype>

<funcdef>

lwres_result_t

<function>lwres_nooprequest_render</function></funcdef>

<paramdef>lwres_context_t *ctx</paramdef>

<paramdef>lwres_nooprequest_t *req</paramdef>

<paramdef>lwres_lwpacket_t *pkt</paramdef>

<paramdef>lwres_buffer_t *b</paramdef>

</funcprototype>

<funcprototype>

<funcdef>

lwres_result_t

<function>lwres_noopresponse_render</function></funcdef>

<paramdef>lwres_context_t *ctx</paramdef>

<paramdef>lwres_noopresponse_t *req</paramdef>

<paramdef>lwres_lwpacket_t *pkt</paramdef>

<paramdef>lwres_buffer_t *b</paramdef>

</funcprototype>

<funcprototype>

<funcdef>

lwres_result_t

<function>lwres_nooprequest_parse</function></funcdef>

<paramdef>lwres_context_t *ctx</paramdef>

<paramdef>lwres_buffer_t *b</paramdef>

<paramdef>lwres_lwpacket_t *pkt</paramdef>

<paramdef>lwres_nooprequest_t **structp</paramdef>

</funcprototype>

<funcprototype>

<funcdef>

lwres_result_t

<function>lwres_noopresponse_parse</function></funcdef>

<paramdef>lwres_context_t *ctx</paramdef>

<paramdef>lwres_buffer_t *b</paramdef>

<paramdef>lwres_lwpacket_t *pkt</paramdef>

<paramdef>lwres_noopresponse_t **structp</paramdef>

</funcprototype>

<funcprototype>

<funcdef>

void

<function>lwres_noopresponse_free</function></funcdef>

<paramdef>lwres_context_t *ctx</paramdef>

<paramdef>lwres_noopresponse_t **structp</paramdef>

</funcprototype>

<funcprototype>

<funcdef>

void

<function>lwres_nooprequest_free</function></funcdef>

<paramdef>lwres_context_t *ctx</paramdef>

<paramdef>lwres_nooprequest_t **structp</paramdef>

</funcprototype>

</funcsynopsis>

</refsynopsisdiv>

<refsect1>

<title>DESCRIPTION</title>

<para>

These are low-level routines for creating and parsing

lightweight resolver no-op request and response messages.

</para>

<para>

The no-op message is analogous to a <command>ping</command> packet:

a packet is sent to the resolver daemon and is simply echoed back.

The opcode is intended to allow a client to determine if the server is

operational or not.

</para>

<para>

There are four main functions for the no-op opcode.

One render function converts a no-op request structure &mdash;

<type>lwres_nooprequest_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 no-op request structure.

Another render function converts the no-op response structure &mdash;

<type>lwres_noopresponse_t</type>

to the canonical format.

This is complemented by a parse function which converts a packet in

canonical format to a no-op response structure.

</para>

<para>

These structures are defined in

<filename>lwres/lwres.h</filename>.

They are shown below.

<programlisting>

#define LWRES_OPCODE_NOOP 0x00000000U

typedef struct {

lwres_uint16_t datalength;

unsigned char *data;

} lwres_nooprequest_t;

typedef struct {

lwres_uint16_t datalength;

unsigned char *data;

} lwres_noopresponse_t;

</programlisting>

Although the structures have different types, they are identical.

This is because the no-op opcode simply echos whatever data was sent:

the response is therefore identical to the request.

</para>

<para>

<function>lwres_nooprequest_render()</function>

uses resolver context

<parameter>ctx</parameter>

to convert no-op 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_noopresponse_render()</function>

performs the same task, except it converts a no-op response structure

<type>lwres_noopresponse_t</type>

to the lightweight resolver's canonical format.

</para>

<para>

<function>lwres_nooprequest_parse()</function>

uses context

<parameter>ctx</parameter>

to convert the contents of packet

<parameter>pkt</parameter>

to a

<type>lwres_nooprequest_t</type>

structure.

Buffer

<parameter>b</parameter>

provides space to be used for storing this structure.

When the function succeeds, the resulting

<type>lwres_nooprequest_t</type>

is made available through

<parameter>*structp</parameter>.

<function>lwres_noopresponse_parse()</function>

offers the same semantics as

<function>lwres_nooprequest_parse()</function>

except it yields a

<type>lwres_noopresponse_t</type>

structure.

</para>

<para>

<function>lwres_noopresponse_free()</function>

and

<function>lwres_nooprequest_free()</function>

release the memory in resolver context

<parameter>ctx</parameter>

that was allocated to the

<type>lwres_noopresponse_t</type>

or

<type>lwres_nooprequest_t</type>

structures referenced via

<parameter>structp</parameter>.

</para>

</refsect1>

<refsect1>

<title>RETURN VALUES</title>

<para>

The no-op opcode functions

<function>lwres_nooprequest_render()</function>,

<function>lwres_noopresponse_render()</function>

<function>lwres_nooprequest_parse()</function>

and

<function>lwres_noopresponse_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_nooprequest_t</type>

and

<type>lwres_noopresponse_t</type>

structures.

<function>lwres_nooprequest_parse()</function>

and

<function>lwres_noopresponse_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

<constant>pktflags</constant>

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>