Date: Thu, 8 May 2014 18:29:18 +0200 From: Luigi Rizzo <rizzo@iet.unipi.it> To: bycn82 <bycn82@gmail.com> Cc: "freebsd-ipfw@freebsd.org" <freebsd-ipfw@freebsd.org>, Freddie Cash <fjwcash@gmail.com> Subject: Re: feature of `packet per second` Message-ID: <20140508162918.GA68254@onelab2.iet.unipi.it> In-Reply-To: <536BACA4.7010702@gmail.com> References: <53611738.8010103@gmail.com> <CAOjFWZ4zRUmcjG-r--OqoGEWcSZoWhtTykgAAHzCjoEWsMVS9g@mail.gmail.com> <53611EB1.4000406@gmail.com> <CA%2BhQ2%2BhjjS=AXVdnaEdFOKY1DqiLuX9iP0gy3wo6FbwnEdq_Qw@mail.gmail.com> <5364E097.9020106@gmail.com> <CA%2BhQ2%2BgXC9uNdtH1VCGa%2Bs1dPNWjErC9qfgXmEnfQ4SQ6Rnz_g@mail.gmail.com> <536AD13B.6080907@gmail.com> <536AD941.9090102@gmail.com> <20140508073816.GB64368@onelab2.iet.unipi.it> <536BACA4.7010702@gmail.com>
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On Fri, May 09, 2014 at 12:11:16AM +0800, bycn82 wrote:
> On 5/8/14 15:38, Luigi Rizzo wrote:
...
> >>>>> If i were to implement the feature i would add two parameters
> >>>>> (burst, I_max) with reasonable defaults and compute the internal
> >>>>> interval and max_count as follows
> >>>>> if (burst> max_pps * I_max)
> >>>>> burst = max_pps * I_max; // make sure it is not too large
> >>>>> else if (burst< max_pps / HZ)
> >>>>> burst = max_pps * HZ; // nor too small
> >>>>> max_count = max_pps / burst;
> >>>>> interval = HZ * burst / max_pps;
> >>>>> count = 0; // actual counter
> >>>>>
> >>>>> then add { max_count, interval, timestamp, count } to the rule
> >>>>> descriptor.
> >>>>> On incoming packets:
> >>>>>
> >>>>> if (ticks>= r->interval + r->timestamp) {
> >>>>> r->timestamp = r->ticks;
> >>>>> r->count = 1;
> >>>>> return ACCEPT;
> >>>>> }
> >>>>> if (r->count> r->max_count)
> >>>>> return DENY;
> >>>>> r->count++;
> >>>>> return ACCEPT;
> >>>>>
> >>>>> cheers
> >>>>> luigi
> >>>>>
> >>>> Hi Luigi,
> >>>> You are right, it will be more generic if provide two parameters
> >>>> as you described,
> >>>> But this PPS feature should not be used to control the traffic
> >>>> rate, the dummynet you provided is the correct way.
> >>>> So I am thinking in what kind of scenario, people need this PPS
> >>>> feature?
> >>>> in my opinion, people will use PPS only when they want to limit
> >>>> the connections/transactions numbers. ( already have limit
> >>>> command to limit the connections)
> >>>> So I think provide a simple PPS feature is good enough, and we
> >>>> can improve it if someone complaint on this.
...
> Man page patch for PPS
>
> .It Cm pps Ar limit duration
> Rule with the
> .Cm pps
> keyword will allow the first
> .Ar limit
> packets in each
> .Ar duration
> milliseconds.
>
> and it will be like blow
> pps _limit duration_
> Rule with the pps keyword will allow the first _limit
> _packets in
> each _duration _milliseconds.
>
> is that OK?
looks good to me.
Just remember that the value of HZ may be quite low (e.g. HZ=100
or less in some cases) so internally the code should round up
the intervals as needed.
cheers
luigi
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