.\" Copyright (C) 2000, 2001, 2004, 2005, 2007, 2014-2016, 2018-2021 Internet Systems Consortium, Inc. ("ISC")
.\" 
.\" This Source Code Form is subject to the terms of the Mozilla Public
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.\"     Title: lwres_noop
.\"    Author: 
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: 2007-06-18
.\"    Manual: BIND9
.\"    Source: ISC
.\"  Language: English
.\"
.TH "LWRES_NOOP" "3" "2007\-06\-18" "ISC" "BIND9"
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.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"
.sp
.ft B
.nf
#include <lwres/lwres\&.h>
.fi
.ft
.HP \w'lwres_result_t\ lwres_nooprequest_render('u
.BI "lwres_result_t lwres_nooprequest_render(lwres_context_t\ *" "ctx" ", lwres_nooprequest_t\ *" "req" ", lwres_lwpacket_t\ *" "pkt" ", lwres_buffer_t\ *" "b" ");"
.HP \w'lwres_result_t\ lwres_noopresponse_render('u
.BI "lwres_result_t lwres_noopresponse_render(lwres_context_t\ *" "ctx" ", lwres_noopresponse_t\ *" "req" ", lwres_lwpacket_t\ *" "pkt" ", lwres_buffer_t\ *" "b" ");"
.HP \w'lwres_result_t\ lwres_nooprequest_parse('u
.BI "lwres_result_t lwres_nooprequest_parse(lwres_context_t\ *" "ctx" ", lwres_buffer_t\ *" "b" ", lwres_lwpacket_t\ *" "pkt" ", lwres_nooprequest_t\ **" "structp" ");"
.HP \w'lwres_result_t\ lwres_noopresponse_parse('u
.BI "lwres_result_t lwres_noopresponse_parse(lwres_context_t\ *" "ctx" ", lwres_buffer_t\ *" "b" ", lwres_lwpacket_t\ *" "pkt" ", lwres_noopresponse_t\ **" "structp" ");"
.HP \w'void\ lwres_noopresponse_free('u
.BI "void lwres_noopresponse_free(lwres_context_t\ *" "ctx" ", lwres_noopresponse_t\ **" "structp" ");"
.HP \w'void\ lwres_nooprequest_free('u
.BI "void lwres_nooprequest_free(lwres_context_t\ *" "ctx" ", lwres_nooprequest_t\ **" "structp" ");"
.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 lightweight resolver\*(Aqs 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
lwres/lwres\&.h\&. They are shown below\&.
.PP
.if n \{\
.RS 4
.\}
.nf
#define LWRES_OPCODE_NOOP       0x00000000U
.fi
.if n \{\
.RE
.\}
.PP
.if n \{\
.RS 4
.\}
.nf
typedef struct {
        uint16_t  datalength;
        unsigned char   *data;
} lwres_nooprequest_t;
.fi
.if n \{\
.RE
.\}
.PP
.if n \{\
.RS 4
.\}
.nf
typedef struct {
        uint16_t  datalength;
        unsigned char   *data;
} lwres_noopresponse_t;
.fi
.if n \{\
.RE
.\}
.PP
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\*(Aqs 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)
.SH "AUTHOR"
.PP
\fBInternet Systems Consortium, Inc\&.\fR
.SH "COPYRIGHT"
.br
Copyright \(co 2000, 2001, 2004, 2005, 2007, 2014-2016, 2018-2021 Internet Systems Consortium, Inc. ("ISC")
.br
