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.\" Copyright (C) 2000, 2001 Internet Software Consortium.
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.\" $Id: lwres_noop.3,v 1.14.2.1.8.5 2005/10/13 02:33:54 marka Exp $
.\"
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.TH "LWRES_NOOP" "3" "Jun 30, 2000" "BIND9" "BIND9"
.\" disable hyphenation
.nh
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.ad l
.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"
.nf
#include <lwres/lwres.h>
.fi
.HP 40
\fBlwres_result_t\ \fBlwres_nooprequest_render\fR\fR\fB(\fR\fBlwres_context_t\ *ctx\fR\fB, \fR\fBlwres_nooprequest_t\ *req\fR\fB, \fR\fBlwres_lwpacket_t\ *pkt\fR\fB, \fR\fBlwres_buffer_t\ *b\fR\fB);\fR
.HP 41
\fBlwres_result_t\ \fBlwres_noopresponse_render\fR\fR\fB(\fR\fBlwres_context_t\ *ctx\fR\fB, \fR\fBlwres_noopresponse_t\ *req\fR\fB, \fR\fBlwres_lwpacket_t\ *pkt\fR\fB, \fR\fBlwres_buffer_t\ *b\fR\fB);\fR
.HP 39
\fBlwres_result_t\ \fBlwres_nooprequest_parse\fR\fR\fB(\fR\fBlwres_context_t\ *ctx\fR\fB, \fR\fBlwres_buffer_t\ *b\fR\fB, \fR\fBlwres_lwpacket_t\ *pkt\fR\fB, \fR\fBlwres_nooprequest_t\ **structp\fR\fB);\fR
.HP 40
\fBlwres_result_t\ \fBlwres_noopresponse_parse\fR\fR\fB(\fR\fBlwres_context_t\ *ctx\fR\fB, \fR\fBlwres_buffer_t\ *b\fR\fB, \fR\fBlwres_lwpacket_t\ *pkt\fR\fB, \fR\fBlwres_noopresponse_t\ **structp\fR\fB);\fR
.HP 29
\fBvoid\ \fBlwres_noopresponse_free\fR\fR\fB(\fR\fBlwres_context_t\ *ctx\fR\fB, \fR\fBlwres_noopresponse_t\ **structp\fR\fB);\fR
.HP 28
\fBvoid\ \fBlwres_nooprequest_free\fR\fR\fB(\fR\fBlwres_context_t\ *ctx\fR\fB, \fR\fBlwres_nooprequest_t\ **structp\fR\fB);\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;
.fi
.sp
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
\fBLWRES_R_SUCCESS\fR
on success. They return
\fBLWRES_R_NOMEMORY\fR
if memory allocation fails.
\fBLWRES_R_UNEXPECTEDEND\fR
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
\fBLWRES_R_UNEXPECTEDEND\fR
if the buffer is not empty after decoding the received packet. These functions will return
\fBLWRES_R_FAILURE\fR
if
\fBpktflags\fR
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 )