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      1 /*	$NetBSD: kern_rate.c,v 1.2 2012/12/12 11:10:56 pooka Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2000, 2004, 2005, 2007, 2008 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Christopher G. Demetriou.
      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  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 #include <sys/cdefs.h>
     33 __KERNEL_RCSID(0, "$NetBSD: kern_rate.c,v 1.2 2012/12/12 11:10:56 pooka Exp $");
     34 
     35 #include <sys/param.h>
     36 #include <sys/time.h>
     37 
     38 /*
     39  * ratecheck(): simple time-based rate-limit checking.  see ratecheck(9)
     40  * for usage and rationale.
     41  */
     42 int
     43 ratecheck(struct timeval *lasttime, const struct timeval *mininterval)
     44 {
     45 	struct timeval tv, delta;
     46 	int rv = 0;
     47 
     48 	getmicrouptime(&tv);
     49 	timersub(&tv, lasttime, &delta);
     50 
     51 	/*
     52 	 * check for 0,0 is so that the message will be seen at least once,
     53 	 * even if interval is huge.
     54 	 */
     55 	if (timercmp(&delta, mininterval, >=) ||
     56 	    (lasttime->tv_sec == 0 && lasttime->tv_usec == 0)) {
     57 		*lasttime = tv;
     58 		rv = 1;
     59 	}
     60 
     61 	return (rv);
     62 }
     63 
     64 /*
     65  * ppsratecheck(): packets (or events) per second limitation.
     66  */
     67 int
     68 ppsratecheck(struct timeval *lasttime, int *curpps, int maxpps)
     69 {
     70 	struct timeval tv, delta;
     71 	int rv;
     72 
     73 	getmicrouptime(&tv);
     74 	timersub(&tv, lasttime, &delta);
     75 
     76 	/*
     77 	 * check for 0,0 is so that the message will be seen at least once.
     78 	 * if more than one second have passed since the last update of
     79 	 * lasttime, reset the counter.
     80 	 *
     81 	 * we do increment *curpps even in *curpps < maxpps case, as some may
     82 	 * try to use *curpps for stat purposes as well.
     83 	 */
     84 	if ((lasttime->tv_sec == 0 && lasttime->tv_usec == 0) ||
     85 	    delta.tv_sec >= 1) {
     86 		*lasttime = tv;
     87 		*curpps = 0;
     88 	}
     89 	if (maxpps < 0)
     90 		rv = 1;
     91 	else if (*curpps < maxpps)
     92 		rv = 1;
     93 	else
     94 		rv = 0;
     95 
     96 #if 1 /*DIAGNOSTIC?*/
     97 	/* be careful about wrap-around */
     98 	if (__predict_true(*curpps != INT_MAX))
     99 		*curpps = *curpps + 1;
    100 #else
    101 	/*
    102 	 * assume that there's not too many calls to this function.
    103 	 * not sure if the assumption holds, as it depends on *caller's*
    104 	 * behavior, not the behavior of this function.
    105 	 * IMHO it is wrong to make assumption on the caller's behavior,
    106 	 * so the above #if is #if 1, not #ifdef DIAGNOSTIC.
    107 	 */
    108 	*curpps = *curpps + 1;
    109 #endif
    110 
    111 	return (rv);
    112 }
    113