1.\" $OpenBSD: ppsratecheck.9,v 1.1 2000/10/10 13:40:46 itojun Exp $ 2.\" $NetBSD: ppsratecheck.9,v 1.1 2000/08/03 00:09:39 itojun Exp $ 3.\" 4.\" Copyright (c) 2000 The NetBSD Foundation, Inc. 5.\" All rights reserved. 6.\" 7.\" This code is derived from software contributed to The NetBSD Foundation 8.\" by Jun-ichiro itojun Hagino. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 3. All advertising materials mentioning features or use of this software 19.\" must display the following acknowledgement: 20.\" This product includes software developed by the NetBSD 21.\" Foundation, Inc. and its contributors. 22.\" 4. Neither the name of The NetBSD Foundation nor the names of its 23.\" contributors may be used to endorse or promote products derived 24.\" from this software without specific prior written permission. 25.\" 26.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 27.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 28.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 29.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 30.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 31.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 32.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 33.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 34.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 35.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 36.\" POSSIBILITY OF SUCH DAMAGE. 37.\" 38.Dd August 3, 2000 39.Dt PPSRATECHECK 9 40.Os 41.Sh NAME 42.Nm ppsratecheck 43.Nd function to help implement rate-limited actions 44.Sh SYNOPSIS 45.Fd #include <sys/time.h> 46.Ft int 47.Fn ppsratecheck "struct timeval *lasttime" "int *curpps" "int maxpps" 48.Sh DESCRIPTION 49The 50.Fn ppsratecheck 51function provides easy way to perform packet-per-sec, 52or event-per-sec, rate limitation. 53The motivation for implementing 54.Fn ppsratecheck 55was to provide a mechanism that could be used to add rate limitation to 56network packet output. 57For certain network packets, we may want to impose rate limitation, 58to avoid denial-of-service attack possibilities. 59.Pp 60.Fa maxpps 61specifies maximum permitted packets, or events, per second. 62If 63.Fn ppsratecheck 64is called more than 65.Fa maxpps 66times in a given one second period, 67the function will return 0, indicating that we exceeded the limit. 68If we are below the limit, the function will return 1. 69If 70.Fa maxpps 71is set to 0, the function will always return 0 72.Pq no packets/events are permitted . 73Negative 74.Fa maxpps 75indicates that rate limitation is disabled, and 76.Fa ppsratecheck 77will always return 1. 78.Pp 79.Fa curpps 80and 81.Fa lasttime 82are used to maintain the number of recent calls. 83.Fa curpps 84will be incremented every time 85.Fn ppsratecheck 86is called, and will be reset whenever necessary. 87.Sh SEE ALSO 88.Xr log 9 , 89.Xr printf 9 , 90.Xr ratecheck 9 , 91.Xr time 9 92.Sh HISTORY 93The 94.Fn ppsratecheck 95function appeared in 96.Nx 1.5 . 97