feature of `packet per second`

[bycn82]

On 5/4/14 1:19, Luigi Rizzo wrote:
>
>
>
> On Sat, May 3, 2014 at 2:27 PM, bycn82 <bycn82 at gmail.com 
> <mailto:bycn82 at gmail.com>> wrote:
>
>     On 5/2/14 16:59, Luigi Rizzo wrote:
>>
>>
>>
>>     On Wed, Apr 30, 2014 at 6:02 PM, bycn82 <bycn82 at gmail.com
>>     <mailto:bycn82 at gmail.com>> wrote:
>>
>>
>>             fjwcash at gmail.com <mailto:fjwcash at gmail.com>
>>             <mailto:fjwcash at gmail.com <mailto:fjwcash at gmail.com>>
>>
>>         Thanks for your reply,  and it is good to know the sysctl for
>>         ICMP.
>>
>>         finally it works.I just added a new `action` in firewall and
>>         it is called `pps`,  that means it can be generic purpose
>>         while the net.inet.icmp.icmplim is only for ICMP traffic.
>>
>>         the usage will be like below
>>
>>         root at F10:/usr/src/sbin/ipfw # .*/ipfw add pps 1 icmp from any
>>         to any*
>>         00100 pps 1 icmp from any to any
>>         root at F10:/usr/src/sbin/ipfw # ./ipfw show
>>         00100     9     540 pps 1 icmp from any to any
>>         65535 13319 1958894 allow ip from any to any
>>         root at F10:/usr/src/sbin/ipfw #
>>
>>
>>     ​hi,
>>     as julian said it would be great if you would like to share your code
>>     so we can integrate it in future ipfw releases.
>>     Once again citing Julian, dummynet is a bit of a superset of pps but
>>     not exactly, so i see value in the additional feature.
>>
>>     One thing  ​to keep in mind in the implementation:
>>
>>     the burst size used for limiting is an important parameter that
>>     everyone forgets. 1 pps is basically "don't bother me".
>>     1000 pps could be "1000 packets every fixed 1-sec interval"
>>     or "1 packet every ms" or (this is more difficult)
>>     "20 pkt in the last 50ms interval".
>>
>>     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.
>
>
> ​pps has a strong reason to exist because it is a lot cheaper
> than a dummynet pipe, and given its pur​pose is to police
> traffic (icmp, dns requests, etc) which should not even
> get close to the limit which is set, I think it is
> a completely reasonable feature to have.
>
> Given that the above code is the complete implementation
> with the two parameters (burst and interval) there is no
> reason not to use them, at least internally.
>
> Then you could choose not to expose them as part of the
> user interface (though since you are implementing a new
> option from scratch, it is completely trivial to
> parse 1, 2 or 3 arguments and set defaults for the others).
>
> cheers
> luigi
OK, PPS with 2 parameters , it is done,
But how to get the current time in millisecond?
any recommendation?