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NetBSD 6.1.5 - man page for ppsratecheck (netbsd section 9)

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PPSRATECHECK(9) 		  BSD Kernel Developer's 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 possibili-
     ties.

     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 incre-
     mented every time ppsratecheck() is called, and will be reset whenever necessary.

SEE ALSO
     log(9), printf(9), ratecheck(9), time_second(9)

HISTORY
     The ppsratecheck() function appeared in NetBSD 1.5.

BSD					  August 3, 2000				      BSD
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