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.Dd August 3, 2000 .Dt PPSRATECHECK 9 .Os .Sh NAME .Nm ppsratecheck .Nd function to help implement rate-limited actions .Sh SYNOPSIS n sys/time.h .Ft int .Fn ppsratecheck "struct timeval *lasttime" "int *curpps" "int maxpps" .Sh DESCRIPTION The .Fn ppsratecheck function provides easy way to perform packet-per-sec, or event-per-sec, rate limitation. The motivation for implementing .Fn 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.
p .Fa maxpps specifies maximum permitted packets, or events, per second. If .Fn ppsratecheck is called more than .Fa 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 .Fa maxpps is set to 0, the function will always return 0
q no packets/events are permitted . Negative .Fa maxpps indicates that rate limitation is disabled, and .Fa ppsratecheck will always return 1.
p .Fa curpps and .Fa lasttime are used to maintain the number of recent calls. .Fa curpps will be incremented every time .Fn ppsratecheck is called, and will be reset whenever necessary. .Sh SEE ALSO .Xr log 9 , .Xr printf 9 , .Xr ratecheck 9 , .Xr time_second 9 .Sh HISTORY The .Fn ppsratecheck function appeared in .Nx 1.5 .
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