lwres/man/lwres_noop.html

	lwres_noop.html revision 1969ab5360417d374547a8b51c78acfa1e9202ba
98N/A<!--
98N/A - Copyright (C) 2001  Internet Software Consortium.
967N/A -
98N/A - Permission to use, copy, modify, and distribute this software for any
98N/A - purpose with or without fee is hereby granted, provided that the above
919N/A - copyright notice and this permission notice appear in all copies.
919N/A -
919N/A - THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM
919N/A - DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
919N/A - IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
919N/A - INTERNET SOFTWARE CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT,
919N/A - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
919N/A - FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
919N/A - NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
919N/A - WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
919N/A-->
919N/A
919N/A<!-- $Id: lwres_noop.html,v 1.4 2001/05/30 20:27:45 bwelling Exp $ -->
919N/A
919N/A<HTML
919N/A><HEAD
919N/A><TITLE
98N/A>lwres_noop</TITLE
98N/A><META
98N/ANAME="GENERATOR"
98N/ACONTENT="Modular DocBook HTML Stylesheet Version 1.61
810N/A"></HEAD
810N/A><BODY
810N/ACLASS="REFENTRY"
810N/ABGCOLOR="#FFFFFF"
354N/ATEXT="#000000"
354N/ALINK="#0000FF"
354N/AVLINK="#840084"
354N/AALINK="#0000FF"
354N/A><H1
354N/A><A
354N/ANAME="AEN1"
354N/A>lwres_noop</A
606N/A></H1
810N/A><DIV
606N/ACLASS="REFNAMEDIV"
606N/A><A
354N/ANAME="AEN8"
810N/A></A
824N/A><H2
810N/A>Name</H2
830N/A>lwres_nooprequest_render, lwres_noopresponse_render, lwres_nooprequest_parse, lwres_noopresponse_parse, lwres_noopresponse_free, lwres_nooprequest_free&nbsp;--&nbsp;lightweight resolver no-op message handling</DIV
1026N/A><DIV
810N/ACLASS="REFSYNOPSISDIV"
810N/A><A
810N/ANAME="AEN16"
810N/A></A
810N/A><H2
810N/A>Synopsis</H2
851N/A><DIV
851N/ACLASS="FUNCSYNOPSIS"
810N/A><A
810N/ANAME="AEN17"
810N/A></A
810N/A><P
810N/A></P
851N/A><PRE
810N/ACLASS="FUNCSYNOPSISINFO"
851N/A>#include &lt;lwres/lwres.h&gt;</PRE
810N/A><P
810N/A><CODE
810N/A><CODE
810N/ACLASS="FUNCDEF"
810N/A>lwres_result_t
810N/Alwres_nooprequest_render</CODE
851N/A>(lwres_context_t *ctx, lwres_nooprequest_t *req, lwres_lwpacket_t *pkt, lwres_buffer_t *b);</CODE
810N/A></P
851N/A><P
1010N/A><CODE
851N/A><CODE
810N/ACLASS="FUNCDEF"
810N/A>lwres_result_t
810N/Alwres_noopresponse_render</CODE
810N/A>(lwres_context_t *ctx, lwres_noopresponse_t *req, lwres_lwpacket_t *pkt, lwres_buffer_t *b);</CODE
810N/A></P
810N/A><P
810N/A><CODE
810N/A><CODE
851N/ACLASS="FUNCDEF"
851N/A>lwres_result_t
851N/Alwres_nooprequest_parse</CODE
851N/A>(lwres_context_t *ctx, lwres_buffer_t *b, lwres_lwpacket_t *pkt, lwres_nooprequest_t **structp);</CODE
851N/A></P
98N/A><P
824N/A><CODE
98N/A><CODE
98N/ACLASS="FUNCDEF"
830N/A>lwres_result_t
1026N/Alwres_noopresponse_parse</CODE
851N/A>(lwres_context_t *ctx, lwres_buffer_t *b, lwres_lwpacket_t *pkt, lwres_noopresponse_t **structp);</CODE
824N/A></P
571N/A><P
98N/A><CODE
98N/A><CODE
98N/ACLASS="FUNCDEF"
341N/A>void
366N/Alwres_noopresponse_free</CODE
354N/A>(lwres_context_t *ctx, lwres_noopresponse_t **structp);</CODE
425N/A></P
325N/A><P
456N/A><CODE
577N/A><CODE
325N/ACLASS="FUNCDEF"
354N/A>void
278N/Alwres_nooprequest_free</CODE
98N/A>(lwres_context_t *ctx, lwres_nooprequest_t **structp);</CODE
543N/A></P
98N/A><P
749N/A></P
749N/A></DIV
98N/A></DIV
151N/A><DIV
137N/ACLASS="REFSECT1"
153N/A><A
210N/ANAME="AEN57"
366N/A></A
98N/A><H2
179N/A>DESCRIPTION</H2
269N/A><P
126N/A>These are low-level routines for creating and parsing
98N/Alightweight resolver no-op request and response messages.</P
98N/A><P
287N/A>The no-op message is analogous to a <B
366N/ACLASS="COMMAND"
499N/A>ping</B
123N/A> packet:
98N/Aa packet is sent to the resolver daemon and is simply echoed back.
98N/AThe opcode is intended to allow a client to determine if the server is
98N/Aoperational or not.</P
98N/A><P
851N/A>There are four main functions for the no-op opcode.
577N/AOne render function converts a no-op request structure &mdash;
498N/A<SPAN
98N/ACLASS="TYPE"
98N/A>lwres_nooprequest_t</SPAN
98N/A> &mdash;
851N/Ato the lighweight resolver's canonical format.
98N/AIt is complemented by a parse function that converts a packet in this
744N/Acanonical format to a no-op request structure.
747N/AAnother render function converts the no-op response structure &mdash;
744N/A<SPAN
744N/ACLASS="TYPE"
744N/A>lwres_noopresponse_t</SPAN
493N/A>
967N/Ato the canonical format.
98N/AThis is complemented by a parse function which converts a packet in
493N/Acanonical format to a no-op response structure.</P
493N/A><P
967N/A>These structures are defined in
810N/A<TT
CLASS="FILENAME"
>lwres/lwres.h</TT
>.

They are shown below.
<PRE
CLASS="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;</PRE
>
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.</P
><P
><TT
CLASS="FUNCTION"
>lwres_nooprequest_render()</TT
>
uses resolver context
<TT
CLASS="PARAMETER"
><I
>ctx</I
></TT
>
to convert no-op request structure
<TT
CLASS="PARAMETER"
><I
>req</I
></TT
>
to canonical format.
The packet header structure
<TT
CLASS="PARAMETER"
><I
>pkt</I
></TT
>
is initialised and transferred to
buffer
<TT
CLASS="PARAMETER"
><I
>b</I
></TT
>.

The contents of
<TT
CLASS="PARAMETER"
><I
>*req</I
></TT
>
are then appended to the buffer in canonical format.
<TT
CLASS="FUNCTION"
>lwres_noopresponse_render()</TT
>
performs the same task, except it converts a no-op response structure
<SPAN
CLASS="TYPE"
>lwres_noopresponse_t</SPAN
>
to the lightweight resolver's canonical format.</P
><P
><TT
CLASS="FUNCTION"
>lwres_nooprequest_parse()</TT
>
uses context
<TT
CLASS="PARAMETER"
><I
>ctx</I
></TT
>
to convert the contents of packet
<TT
CLASS="PARAMETER"
><I
>pkt</I
></TT
>
to a
<SPAN
CLASS="TYPE"
>lwres_nooprequest_t</SPAN
>
structure.
Buffer
<TT
CLASS="PARAMETER"
><I
>b</I
></TT
>
provides space to be used for storing this structure.
When the function succeeds, the resulting
<SPAN
CLASS="TYPE"
>lwres_nooprequest_t</SPAN
>
is made available through
<TT
CLASS="PARAMETER"
><I
>*structp</I
></TT
>.

<TT
CLASS="FUNCTION"
>lwres_noopresponse_parse()</TT
>
offers the same semantics as
<TT
CLASS="FUNCTION"
>lwres_nooprequest_parse()</TT
>
except it yields a
<SPAN
CLASS="TYPE"
>lwres_noopresponse_t</SPAN
>
structure.</P
><P
><TT
CLASS="FUNCTION"
>lwres_noopresponse_free()</TT
>
and
<TT
CLASS="FUNCTION"
>lwres_nooprequest_free()</TT
>
release the memory in resolver context
<TT
CLASS="PARAMETER"
><I
>ctx</I
></TT
>
that was allocated to the
<SPAN
CLASS="TYPE"
>lwres_noopresponse_t</SPAN
>
or
<SPAN
CLASS="TYPE"
>lwres_nooprequest_t</SPAN
>
structures referenced via
<TT
CLASS="PARAMETER"
><I
>structp</I
></TT
>.&#13;</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN95"
></A
><H2
>RETURN VALUES</H2
><P
>The no-op opcode functions
<TT
CLASS="FUNCTION"
>lwres_nooprequest_render()</TT
>,

<TT
CLASS="FUNCTION"
>lwres_noopresponse_render()</TT
>
<TT
CLASS="FUNCTION"
>lwres_nooprequest_parse()</TT
>
and
<TT
CLASS="FUNCTION"
>lwres_noopresponse_parse()</TT
>
all return
<SPAN
CLASS="ERRORCODE"
>LWRES_R_SUCCESS</SPAN
>
on success.
They return
<SPAN
CLASS="ERRORCODE"
>LWRES_R_NOMEMORY</SPAN
>
if memory allocation fails.
<SPAN
CLASS="ERRORCODE"
>LWRES_R_UNEXPECTEDEND</SPAN
>
is returned if the available space in the buffer
<TT
CLASS="PARAMETER"
><I
>b</I
></TT
>
is too small to accommodate the packet header or the
<SPAN
CLASS="TYPE"
>lwres_nooprequest_t</SPAN
>
and
<SPAN
CLASS="TYPE"
>lwres_noopresponse_t</SPAN
>
structures.
<TT
CLASS="FUNCTION"
>lwres_nooprequest_parse()</TT
>
and
<TT
CLASS="FUNCTION"
>lwres_noopresponse_parse()</TT
>
will return
<SPAN
CLASS="ERRORCODE"
>LWRES_R_UNEXPECTEDEND</SPAN
>
if the buffer is not empty after decoding the received packet.
These functions will return
<SPAN
CLASS="ERRORCODE"
>LWRES_R_FAILURE</SPAN
>
if
<TT
CLASS="CONSTANT"
>pktflags</TT
>
in the packet header structure
<SPAN
CLASS="TYPE"
>lwres_lwpacket_t</SPAN
>
indicate that the packet is not a response to an earlier query.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN114"
></A
><H2
>SEE ALSO</H2
><P
><SPAN
CLASS="CITEREFENTRY"
><SPAN
CLASS="REFENTRYTITLE"
>lwres_packet</SPAN
>(3)</SPAN
></P
></DIV
></BODY
></HTML
>