sys/kern/kern_rate.c

   1 /*      $NetBSD: kern_time.c,v 1.151 2008/08/08 16:44:52 christos 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_time.c,v 1.151 2008/08/08 16:44:52 christos 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 (*curpps + 1 > *curpps)
  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 }