94 lines
2.7 KiB
Groff
94 lines
2.7 KiB
Groff
.\"-
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.\" Copyright (c) 2017 Dag-Erling Smørgrav
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd September 25, 2017
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.Dt RATECHECK 9
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.Os
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.Sh NAME
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.Nm ratecheck ,
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.Nm ppsratecheck
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.Nd "event rate limiting"
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.Sh SYNOPSIS
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.In sys/time.h
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.Ft int
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.Fn ratecheck "struct timeval *lasttime" "struct timeval *mininterval"
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.Ft int
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.Fn ppsratecheck "struct timeval *lasttime" "int *curpps" "int maxpps"
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.Sh DESCRIPTION
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The
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.Nm ratecheck
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and
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.Nm ppsratecheck
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functions facilitate rate-limiting of arbitrary events.
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The former enforces a minimum interval between events while the latter
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enforces a maximum number of events per second.
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.Pp
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The
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.Nm ratecheck
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function compares the current time to the value pointed to by
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.Fa lasttime .
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If the difference is equal to or greater than
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.Fa mininterval ,
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it returns a non-zero value and updates
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.Fa lasttime
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to the current time.
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Otherwise, it returns zero.
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.Pp
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The
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.Nm ppsratecheck
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function first compares the current time
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to
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.Fa lasttime .
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If at least a full second has passed, the value pointed to by the
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.Fa curpps
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argument is reset to 1 and
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.Fa lasttime
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is updated to the current time.
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Otherwise,
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.Fa curpps
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is incremented and
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.Fa lasttime
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is left untouched.
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In either case,
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.Nm ppsratecheck
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returns a non-zero value if and only if the updated
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.Fa curpps
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is less than or equal to
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.Fa maxpps
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or
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.Fa maxpps
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is negative.
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.Sh SEE ALSO
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.Xr counter 9
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.Sh HISTORY
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The
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.Nm ratecheck
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and
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.Nm ppsratecheck
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functions first appeared in
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.Fx 5.1 .
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