<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V4.1//EN"><!-- - Copyright (C) 2004  Internet Systems Consortium, Inc. ("ISC") - Copyright (C) 2001  Internet Software Consortium. - - Permission to use, copy, modify, and distribute this software for any - purpose with or without fee is hereby granted, provided that the above - copyright notice and this permission notice appear in all copies. - - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY - AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE - OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR - PERFORMANCE OF THIS SOFTWARE.--><!-- $Id: lwres_noop.docbook,v 1.2 2004/09/20 18:00:50 mcr Exp $ --><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 parsinglightweight 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 isoperational 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 thiscanonical 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 incanonical 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       0x00000000Utypedef 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 resolvercontext <parameter>ctx</parameter> to convert no-op request structure<parameter>req</parameter> to canonical format.  The packet headerstructure <parameter>pkt</parameter> is initialised and transferred tobuffer <parameter>b</parameter>.  The contents of<parameter>*req</parameter> are then appended to the buffer incanonical 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'scanonical 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 usedfor 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 samesemantics as <function>lwres_nooprequest_parse()</function> except ityields a <type>lwres_noopresponse_t</type> structure.</para><para><function>lwres_noopresponse_free()</function> and<function>lwres_nooprequest_free()</function> release the memory inresolver 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>