* Jitter phenomenon in the netfilter infrastructure
@ 2003-10-16 7:42 Mike-Ro-Chanel
2003-10-16 12:30 ` Harald Welte
0 siblings, 1 reply; 2+ messages in thread
From: Mike-Ro-Chanel @ 2003-10-16 7:42 UTC (permalink / raw)
To: netfilter-devel
Hi All,
Inspired by ipt_limit module I've written a token bucket module as a
iptables module extension.
I've observed a strange behaviour:
In the linux kernel 2.4.21 input ethernet frames are sent to the IPv4
layer by "process_backlog()" function, this one pass to ip_rcv()
hundreds of SKB elements in a single burst, its execution is limited (in
time) by 1 jiffy.
As result a regular IPv4 input traffic is looked by PREROUTING hook as
an irregular flow of packets.
Looking this phenomenon I think: an ingress bandwidth filter as
netfilter module is unfeasible.
Is my opinion wrong?
Any suggestions?
Thanks
Mike-Ro-Chanel
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: Jitter phenomenon in the netfilter infrastructure
2003-10-16 7:42 Jitter phenomenon in the netfilter infrastructure Mike-Ro-Chanel
@ 2003-10-16 12:30 ` Harald Welte
0 siblings, 0 replies; 2+ messages in thread
From: Harald Welte @ 2003-10-16 12:30 UTC (permalink / raw)
To: Mike-Ro-Chanel; +Cc: netfilter-devel
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On Thu, Oct 16, 2003 at 09:42:53AM +0200, Mike-Ro-Chanel wrote:
> Hi All,
> Inspired by ipt_limit module I've written a token bucket module as a
> iptables module extension.
>
> I've observed a strange behaviour:
> In the linux kernel 2.4.21 input ethernet frames are sent to the IPv4
> layer by "process_backlog()" function, this one pass to ip_rcv()
> hundreds of SKB elements in a single burst, its execution is limited (in
> time) by 1 jiffy.
> As result a regular IPv4 input traffic is looked by PREROUTING hook as
> an irregular flow of packets.
yes, but you have an skb receive timestamp, which tells you the exact
jiffies at which the skb came in from the wire.
> Thanks
> Mike-Ro-Chanel
--
- Harald Welte <laforge@netfilter.org> http://www.netfilter.org/
============================================================================
"Fragmentation is like classful addressing -- an interesting early
architectural error that shows how much experimentation was going
on while IP was being designed." -- Paul Vixie
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2003-10-16 7:42 Jitter phenomenon in the netfilter infrastructure Mike-Ro-Chanel
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