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bind9/lib/lwres/man/lwres_noop.html
Andreas Gustafsson ac299c4f5c Removed statements to the effect that certain functions 
perform assertion checks.  Such statements are inappropriate as they
document the implementation rather than the public interface.  The
functions are not required to perform assertion checks, but the caller
is required to pass arguments that conform to the API requirements.
2001-06-18 22:56:35 +00:00

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<HTML
><HEAD
><TITLE
>lwres_noop</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.61
"></HEAD
><BODY
CLASS="REFENTRY"
BGCOLOR="#FFFFFF"
TEXT="#000000"
LINK="#0000FF"
VLINK="#840084"
ALINK="#0000FF"
><H1
><A
NAME="AEN1"
>lwres_noop</A
></H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN8"
></A
><H2
>Name</H2
>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
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN16"
></A
><H2
>Synopsis</H2
><DIV
CLASS="FUNCSYNOPSIS"
><A
NAME="AEN17"
></A
><P
></P
><PRE
CLASS="FUNCSYNOPSISINFO"
>#include &lt;lwres/lwres.h&gt;</PRE
><P
><CODE
><CODE
CLASS="FUNCDEF"
>lwres_result_t
lwres_nooprequest_render</CODE
>(lwres_context_t *ctx, lwres_nooprequest_t *req, lwres_lwpacket_t *pkt, lwres_buffer_t *b);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>lwres_result_t
lwres_noopresponse_render</CODE
>(lwres_context_t *ctx, lwres_noopresponse_t *req, lwres_lwpacket_t *pkt, lwres_buffer_t *b);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>lwres_result_t
lwres_nooprequest_parse</CODE
>(lwres_context_t *ctx, lwres_buffer_t *b, lwres_lwpacket_t *pkt, lwres_nooprequest_t **structp);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>lwres_result_t
lwres_noopresponse_parse</CODE
>(lwres_context_t *ctx, lwres_buffer_t *b, lwres_lwpacket_t *pkt, lwres_noopresponse_t **structp);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void
lwres_noopresponse_free</CODE
>(lwres_context_t *ctx, lwres_noopresponse_t **structp);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void
lwres_nooprequest_free</CODE
>(lwres_context_t *ctx, lwres_nooprequest_t **structp);</CODE
></P
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN57"
></A
><H2
>DESCRIPTION</H2
><P
>These are low-level routines for creating and parsing
lightweight resolver no-op request and response messages.</P
><P
>The no-op message is analogous to a <B
CLASS="COMMAND"
>ping</B
> 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.</P
><P
>There are four main functions for the no-op opcode.
One render function converts a no-op request structure &mdash;
<SPAN
CLASS="TYPE"
>lwres_nooprequest_t</SPAN
> &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;
<SPAN
CLASS="TYPE"
>lwres_noopresponse_t</SPAN
>
to the canonical format.
This is complemented by a parse function which converts a packet in
canonical format to a no-op response structure.</P
><P
>These structures are defined in
<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
>.</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
>
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