netdev - Re: [RFC] net/bridge: port based vlan filtering for bridges

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Message-ID: <20120411083835.39fed750@nehalam.linuxnetplumber.net>
Date:	Wed, 11 Apr 2012 08:38:35 -0700
From:	Stephen Hemminger <shemminger@...tta.com>
To:	Benjamin LaHaise <bcrl@...ck.org>
Cc:	netdev@...r.kernel.org
Subject: Re: [RFC] net/bridge: port based vlan filtering for bridges

On Wed, 11 Apr 2012 11:36:29 -0400
Benjamin LaHaise <bcrl@...ck.org> wrote:

> On Wed, Apr 11, 2012 at 08:30:52AM -0700, Stephen Hemminger wrote:
> > On Wed, 11 Apr 2012 11:10:02 -0400
> > Benjamin LaHaise <bcrl@...ck.org> wrote:
> > 
> > > Hello folks,
> > > 
> > > Attached is the first stab at a patch to make it possible to filter packets 
> > > received from other bridge ports based on the port number.  This can be used 
> > > to emulate port based VLANs that some switches support.
> > > 
> > > The justification for this is a bit interesting.  Initially, I had been 
> > > filtering packets using firewall rules.  Unfortunately, the number of 
> > > filter rules becomes impossible to manage when trying to filter traffic 
> > > between 100 different ports.  CPU overhead of the filters is also a major 
> > > problem.
> > > 
> > > The particular use-case I'm dealing with is simulating wireless networks 
> > > on a system using LXC containers.  Each guest has a veth device that is a 
> > > member of the bridge, but the topology of which nodes can "hear" each other 
> > > changes at runtime.
> > > 
> > > Comments/thoughts?
> > > 
> > 
> > Nak. If firewall doesn't work then implement a better netfilter
> > module.
> 
> That still results in the CPU overhead of packet duplication for each and 
> every bridge port regardless of the port receiving the packet or not.  
> Hmmmm, would a NF_HOOK in should_deliver be okay?

Sure. Having better way to do policy would be great. Just don't want
to have implementations of specific policies in generic code.
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