NAME    [Toc]    [Back]

     ppsratecheck - function to help implement  rate-limited  actions

SYNOPSIS    [Toc]    [Back]

     #include <sys/time.h>

     int
     ppsratecheck(struct  timeval  *lasttime,  int  *curpps,  int
maxpps);

DESCRIPTION    [Toc]    [Back]

     The ppsratecheck() function provides an easy way to  perform
packet-persec,
  or event-per-sec, rate limitation.  The motivation for
implementing
     ppsratecheck() was to provide a mechanism that could be used
to add rate
     limitation  to  network  packet output.  For certain network
packets, we may
     want to impose rate limitation, to  avoid  denial-of-service
attack possibilities.


     maxpps  specifies  maximum permitted packets, or events, per
second.  If
     ppsratecheck() is called more than maxpps times in  a  given
one second period,
 the function will return 0, indicating that we exceeded the limit.
     If we are below the limit, the function will return  1.   If
maxpps is set
     to  0,  the function will always return 0 (no packets/events
are
     permitted).  Negative maxpps indicates that rate  limitation
is disabled,
     and ppsratecheck() will always return 1.

     curpps  and  lasttime are used to maintain the number of recent calls.
     curpps will be  incremented  every  time  ppsratecheck()  is
called, and will
     be reset whenever necessary.

SEE ALSO    [Toc]    [Back]

     log(9), printf(9), ratecheck(9), time(9)

HISTORY    [Toc]    [Back]

     The ppsratecheck() function appeared in NetBSD 1.5.

OpenBSD      3.6                          August      3,     2000