/contrib/bind9/lib/lwres/man/lwres_noop.3

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  2.\" Copyright (C) 2000, 2001 Internet Software Consortium.
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 16.\" $Id$
 17.\"
 18.hy 0
 19.ad l
 20.\"     Title: lwres_noop
 21.\"    Author: 
 22.\" Generator: DocBook XSL Stylesheets v1.71.1 <http://docbook.sf.net/>
 23.\"      Date: Jun 30, 2000
 24.\"    Manual: BIND9
 25.\"    Source: BIND9
 26.\"
 27.TH "LWRES_NOOP" "3" "Jun 30, 2000" "BIND9" "BIND9"
 28.\" disable hyphenation
 29.nh
 30.\" disable justification (adjust text to left margin only)
 31.ad l
 32.SH "NAME"
 33lwres_nooprequest_render, lwres_noopresponse_render, lwres_nooprequest_parse, lwres_noopresponse_parse, lwres_noopresponse_free, lwres_nooprequest_free \- lightweight resolver no\-op message handling
 34.SH "SYNOPSIS"
 35.nf
 36#include <lwres/lwres.h>
 37.fi
 38.HP 40
 39.BI "lwres_result_t lwres_nooprequest_render(lwres_context_t\ *" "ctx" ", lwres_nooprequest_t\ *" "req" ", lwres_lwpacket_t\ *" "pkt" ", lwres_buffer_t\ *" "b" ");"
 40.HP 41
 41.BI "lwres_result_t lwres_noopresponse_render(lwres_context_t\ *" "ctx" ", lwres_noopresponse_t\ *" "req" ", lwres_lwpacket_t\ *" "pkt" ", lwres_buffer_t\ *" "b" ");"
 42.HP 39
 43.BI "lwres_result_t lwres_nooprequest_parse(lwres_context_t\ *" "ctx" ", lwres_buffer_t\ *" "b" ", lwres_lwpacket_t\ *" "pkt" ", lwres_nooprequest_t\ **" "structp" ");"
 44.HP 40
 45.BI "lwres_result_t lwres_noopresponse_parse(lwres_context_t\ *" "ctx" ", lwres_buffer_t\ *" "b" ", lwres_lwpacket_t\ *" "pkt" ", lwres_noopresponse_t\ **" "structp" ");"
 46.HP 29
 47.BI "void lwres_noopresponse_free(lwres_context_t\ *" "ctx" ", lwres_noopresponse_t\ **" "structp" ");"
 48.HP 28
 49.BI "void lwres_nooprequest_free(lwres_context_t\ *" "ctx" ", lwres_nooprequest_t\ **" "structp" ");"
 50.SH "DESCRIPTION"
 51.PP
 52These are low\-level routines for creating and parsing lightweight resolver no\-op request and response messages.
 53.PP
 54The no\-op message is analogous to a
 55\fBping\fR
 56packet: 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.
 57.PP
 58There are four main functions for the no\-op opcode. One render function converts a no\-op request structure \(em
 59\fBlwres_nooprequest_t\fR
 60\(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
 61\fBlwres_noopresponse_t\fR
 62to the canonical format. This is complemented by a parse function which converts a packet in canonical format to a no\-op response structure.
 63.PP
 64These structures are defined in
 65\fIlwres/lwres.h\fR. They are shown below.
 66.PP
 67.RS 4
 68.nf
 69#define LWRES_OPCODE_NOOP       0x00000000U
 70.fi
 71.RE
 72.sp
 73.PP
 74.RS 4
 75.nf
 76typedef struct {
 77        lwres_uint16_t  datalength;
 78        unsigned char   *data;
 79} lwres_nooprequest_t;
 80.fi
 81.RE
 82.sp
 83.PP
 84.RS 4
 85.nf
 86typedef struct {
 87        lwres_uint16_t  datalength;
 88        unsigned char   *data;
 89} lwres_noopresponse_t;
 90.fi
 91.RE
 92.sp
 93.PP
 94Although 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.
 95.PP
 96\fBlwres_nooprequest_render()\fR
 97uses resolver context
 98\fIctx\fR
 99to convert no\-op request structure
100\fIreq\fR
101to canonical format. The packet header structure
102\fIpkt\fR
103is initialised and transferred to buffer
104\fIb\fR. The contents of
105\fI*req\fR
106are then appended to the buffer in canonical format.
107\fBlwres_noopresponse_render()\fR
108performs the same task, except it converts a no\-op response structure
109\fBlwres_noopresponse_t\fR
110to the lightweight resolver's canonical format.
111.PP
112\fBlwres_nooprequest_parse()\fR
113uses context
114\fIctx\fR
115to convert the contents of packet
116\fIpkt\fR
117to a
118\fBlwres_nooprequest_t\fR
119structure. Buffer
120\fIb\fR
121provides space to be used for storing this structure. When the function succeeds, the resulting
122\fBlwres_nooprequest_t\fR
123is made available through
124\fI*structp\fR.
125\fBlwres_noopresponse_parse()\fR
126offers the same semantics as
127\fBlwres_nooprequest_parse()\fR
128except it yields a
129\fBlwres_noopresponse_t\fR
130structure.
131.PP
132\fBlwres_noopresponse_free()\fR
133and
134\fBlwres_nooprequest_free()\fR
135release the memory in resolver context
136\fIctx\fR
137that was allocated to the
138\fBlwres_noopresponse_t\fR
139or
140\fBlwres_nooprequest_t\fR
141structures referenced via
142\fIstructp\fR.
143.SH "RETURN VALUES"
144.PP
145The no\-op opcode functions
146\fBlwres_nooprequest_render()\fR,
147\fBlwres_noopresponse_render()\fR
148\fBlwres_nooprequest_parse()\fR
149and
150\fBlwres_noopresponse_parse()\fR
151all return
152\fBLWRES_R_SUCCESS\fR
153on success. They return
154\fBLWRES_R_NOMEMORY\fR
155if memory allocation fails.
156\fBLWRES_R_UNEXPECTEDEND\fR
157is returned if the available space in the buffer
158\fIb\fR
159is too small to accommodate the packet header or the
160\fBlwres_nooprequest_t\fR
161and
162\fBlwres_noopresponse_t\fR
163structures.
164\fBlwres_nooprequest_parse()\fR
165and
166\fBlwres_noopresponse_parse()\fR
167will return
168\fBLWRES_R_UNEXPECTEDEND\fR
169if the buffer is not empty after decoding the received packet. These functions will return
170\fBLWRES_R_FAILURE\fR
171if
172\fBpktflags\fR
173in the packet header structure
174\fBlwres_lwpacket_t\fR
175indicate that the packet is not a response to an earlier query.
176.SH "SEE ALSO"
177.PP
178\fBlwres_packet\fR(3)
179.SH "COPYRIGHT"
180Copyright \(co 2004, 2005, 2007, 2012 Internet Systems Consortium, Inc. ("ISC")
181.br
182Copyright \(co 2000, 2001 Internet Software Consortium.
183.br