netdev - Re: tc filter u32 match

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Date:	Thu, 24 May 2012 06:04:38 -0400
From:	Jamal Hadi Salim <jhs@...atatu.com>
To:	adam.niescierowicz@...tnet.pl
Cc:	netdev@...r.kernel.org
Subject: Re: tc filter u32 match

On Tue, 2012-05-22 at 15:42 +0200, Nieścierowicz Adam wrote:
> Hello,
> 
> I'm in the process of building a new shaper, when adding support for 
> 802.1q
> vlan noticed that u32 can catch network traffic without giving 4 bytes
> offset. How is this possible?
> 

Because we look at where the network header starts?
Why do you expect 4 bytes to be counted? 

> My environment:
> 
> eth2 - network card
> eth2.200 - vlan
> 
> /sbin/tc filter add dev eth2 parent 1:0 prio 5 handle 35: protocol ip 
> u32 divisor 256
> /sbin/tc filter add dev eth2 protocol ip parent 1:0 prio 5 u32 ht 800:: 
> match ip dst 31.41.208.32/27 hashkey mask 0x000000ff at 16 link 35:
> /sbin/tc filter add dev eth2 protocol ip parent 1: prio 1 u32 ht 35:24: 
> match ip dst 31.41.208.36 flowid 1:2e5
> 
> Here you can see the hits in the rule
> filter parent 1: protocol ip pref 5 u32 fh 35:24:800 order 2048 key ht 
> 35 bkt 24 flowid 1:2e5  (rule hit 44037 success 44037)
>    match 1f29d024/ffffffff at 16 (success 44037 )

I dont see an issue. This looks correct.

> 
> I found a similar question here 
> http://serverfault.com/questions/370795/tc-u32-how-to-match-l2-protocols-in-recent-kernels
> 

There may have been bugs in the past that someone missed or didnt
report here (likely around the time there was a lot of changes
happening with vlan offloading). Try the latest kernel and 
if it behaves badly, send a report and a reproducible test case.

cheers,
jamal

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