PPSRATECHECK(9)              OpenBSD Kernel Manual             PPSRATECHECK(9)

NAME
     ppsratecheck - function to help implement rate-limited actions

SYNOPSIS
     #include <sys/time.h>

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

DESCRIPTION
     The ppsratecheck() function provides easy way to perform packet-per-sec,
     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 possi-
     bilities.

     maxpps specifies maximum permitted packets, or events, per second.  If
     ppsratecheck() is called more than maxpps times in a given one second pe-
     riod, 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
     log(9), printf(9), ratecheck(9), time(9)

HISTORY
     The ppsratecheck() function appeared in NetBSD 1.5.

OpenBSD 2.8                     August 3, 2000                               1
