netdev - Re: Optimizing tc filters

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Date:	Sat, 10 Dec 2011 14:58:00 -0500
From:	"John A. Sullivan III" <jsullivan@...nsourcedevel.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: Optimizing tc filters

On Sat, 2011-12-10 at 20:41 +0100, Eric Dumazet wrote:
> Le samedi 10 décembre 2011 à 13:16 -0500, John A. Sullivan III a écrit :
> > Hello, all.  Given that there are several ways to direct packets into
> > the appropriate queue, I was wondering which ways are generally more
> > efficient.  There seem to be a number of email discussions but nothing
> > authoritative.  From those discussions, it would seem that for most
> > corporate usage (as in more traffic than a home user) we would have from
> > most efficient to least efficient:
> > 
> > 1) Mark the connection with CONNMARK and us --restore-mark to mark all
> > packets in the connection for classification via an fw filter
> > 
> > 2) Use the iptables CLASSIFY target
> > 
> > 3) u32 filter
> > 
> > 4) Mark individual packets and use an fw filter - one email thread says
> > this is more efficient than #3
> > 
> > Is this correct?
> 
> Unfortunately CONNTRACK is a bit expensive...
> 
> If you control applications, you also can use SO_MARK from them.
> 
> 
> 
OK.  Does that mean that #1 is actually #4?

If we are using connection tracking in general to produce a "stateful"
firewall (let's just say we are - I certainly don't want to set off a
debate :) ), does that put #1 back on top as the most efficient since we
are incurring the conntrack overhead anyway or does the CONNMARK target
itself add considerable overhead? Thanks - John

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