96 lines
3.4 KiB
Groff
96 lines
3.4 KiB
Groff
.\" $NetBSD: ppsratecheck.9,v 1.2 2001/09/04 02:51:16 wiz Exp $
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.\"
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.\" Copyright (c) 2000 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Jun-ichiro itojun Hagino.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the NetBSD
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.\" Foundation, Inc. and its contributors.
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.\" 4. Neither the name of The NetBSD Foundation nor the names of its
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.\" contributors may be used to endorse or promote products derived
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.\" from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd August 3, 2000
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.Dt PPSRATECHECK 9
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.Os
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.Sh NAME
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.Nm ppsratecheck
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.Nd function to help implement rate-limited actions
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.Sh SYNOPSIS
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.Fd #include <sys/time.h>
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.Ft int
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.Fn ppsratecheck "struct timeval *lasttime" "int *curpps" "int maxpps"
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.Sh DESCRIPTION
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The
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.Fn ppsratecheck
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function provides easy way to perform packet-per-sec,
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or event-per-sec, rate limitation.
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The motivation for implementing
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.Fn ppsratecheck
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was to provide a mechanism that could be used to add rate limitation to
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network packet output.
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For certain network packets, we may want to impose rate limitation,
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to avoid denial-of-service attack possibilities.
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.Pp
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.Fa maxpps
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specifies maximum permitted packets, or events, per second.
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If
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.Fn ppsratecheck
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is called more than
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.Fa maxpps
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times in a given one second period,
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the function will return 0, indicating that we exceeded the limit.
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If we are below the limit, the function will return 1.
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If
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.Fa maxpps
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is set to 0, the function will always return 0
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.Pq no packets/events are permitted .
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Negative
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.Fa maxpps
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indicates that rate limitation is disabled, and
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.Fa ppsratecheck
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will always return 1.
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.Pp
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.Fa curpps
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and
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.Fa lasttime
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are used to maintain the number of recent calls.
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.Fa curpps
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will be incremented every time
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.Fn ppsratecheck
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is called, and will be reset whenever necessary.
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.Sh SEE ALSO
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.Xr log 9 ,
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.Xr printf 9 ,
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.Xr ratecheck 9 ,
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.Xr time 9
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.Sh HISTORY
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The
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.Fn ppsratecheck
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function appeared in
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.Nx 1.5 .
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