lwres_noop.3

bind 9.3结合mysql数据库

.\" Copyright (C) 2004  Internet Systems Consortium, Inc. ("ISC")
.\" Copyright (C) 2000, 2001  Internet Software Consortium.
.\"
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.\" PERFORMANCE OF THIS SOFTWARE.
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.\" $Id: lwres_noop.3,v 1.14.2.1.8.1 2004/03/06 07:41:44 marka Exp $
.\"
.TH "LWRES_NOOP" "3" "Jun 30, 2000" "BIND9" ""
.SH NAME
lwres_nooprequest_render, lwres_noopresponse_render, lwres_nooprequest_parse, lwres_noopresponse_parse, lwres_noopresponse_free, lwres_nooprequest_free \- lightweight resolver no-op message handling
.SH SYNOPSIS
\fB#include <lwres/lwres.h>
.sp
.na
lwres_result_t
lwres_nooprequest_render(lwres_context_t *ctx, lwres_nooprequest_t *req, lwres_lwpacket_t *pkt, lwres_buffer_t *b);
.ad
.sp
.na
lwres_result_t
lwres_noopresponse_render(lwres_context_t *ctx, lwres_noopresponse_t *req, lwres_lwpacket_t *pkt, lwres_buffer_t *b);
.ad
.sp
.na
lwres_result_t
lwres_nooprequest_parse(lwres_context_t *ctx, lwres_buffer_t *b, lwres_lwpacket_t *pkt, lwres_nooprequest_t **structp);
.ad
.sp
.na
lwres_result_t
lwres_noopresponse_parse(lwres_context_t *ctx, lwres_buffer_t *b, lwres_lwpacket_t *pkt, lwres_noopresponse_t **structp);
.ad
.sp
.na
void
lwres_noopresponse_free(lwres_context_t *ctx, lwres_noopresponse_t **structp);
.ad
.sp
.na
void
lwres_nooprequest_free(lwres_context_t *ctx, lwres_nooprequest_t **structp);
.ad
\fR
.SH "DESCRIPTION"
.PP
These are low-level routines for creating and parsing
lightweight resolver no-op request and response messages.
.PP
The no-op message is analogous to a \fBping\fR 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.
.PP
There are four main functions for the no-op opcode.
One render function converts a no-op request structure \(em
\fBlwres_nooprequest_t\fR \(em
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 \(em
\fBlwres_noopresponse_t\fR
to the canonical format.
This is complemented by a parse function which converts a packet in
canonical format to a no-op response structure.
.PP
These structures are defined in
\fIlwres/lwres.h\fR.
They are shown below.
.sp
.nf
#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;
.sp
.fi
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.
.PP
\fBlwres_nooprequest_render()\fR uses resolver
context \fIctx\fR to convert no-op request structure
\fIreq\fR to canonical format. The packet header
structure \fIpkt\fR is initialised and transferred to
buffer \fIb\fR. The contents of
\fI*req\fR are then appended to the buffer in
canonical format. \fBlwres_noopresponse_render()\fR
performs the same task, except it converts a no-op response structure
\fBlwres_noopresponse_t\fR to the lightweight resolver's
canonical format.
.PP
\fBlwres_nooprequest_parse()\fR uses context
\fIctx\fR to convert the contents of packet
\fIpkt\fR to a \fBlwres_nooprequest_t\fR
structure. Buffer \fIb\fR provides space to be used
for storing this structure. When the function succeeds, the resulting
\fBlwres_nooprequest_t\fR is made available through
\fI*structp\fR.
\fBlwres_noopresponse_parse()\fR offers the same
semantics as \fBlwres_nooprequest_parse()\fR except it
yields a \fBlwres_noopresponse_t\fR structure.
.PP
\fBlwres_noopresponse_free()\fR and
\fBlwres_nooprequest_free()\fR release the memory in
resolver context \fIctx\fR that was allocated to the
\fBlwres_noopresponse_t\fR or \fBlwres_nooprequest_t\fR
structures referenced via \fIstructp\fR.
.SH "RETURN VALUES"
.PP
The no-op opcode functions
\fBlwres_nooprequest_render()\fR,
\fBlwres_noopresponse_render()\fR
\fBlwres_nooprequest_parse()\fR
and
\fBlwres_noopresponse_parse()\fR
all return
LWRES_R_SUCCESS
on success.
They return
LWRES_R_NOMEMORY
if memory allocation fails.
LWRES_R_UNEXPECTEDEND
is returned if the available space in the buffer
\fIb\fR
is too small to accommodate the packet header or the
\fBlwres_nooprequest_t\fR
and
\fBlwres_noopresponse_t\fR
structures.
\fBlwres_nooprequest_parse()\fR
and
\fBlwres_noopresponse_parse()\fR
will return
LWRES_R_UNEXPECTEDEND
if the buffer is not empty after decoding the received packet.
These functions will return
LWRES_R_FAILURE
if
pktflags
in the packet header structure
\fBlwres_lwpacket_t\fR
indicate that the packet is not a response to an earlier query.
.SH "SEE ALSO"
.PP
\fBlwres_packet\fR(3)