FreeBSD bridge + filtering, BIG problem

[Josh Kayse]

On Thu, 2 Dec 2004 12:39:20 +0900, Pyun YongHyeon <yongari at kt-is.co.kr> wrote:
> On Wed, Dec 01, 2004 at 08:23:39AM -0500, Josh Kayse wrote:
> 
> [...]
> >
> > I know it's been touched on in the past, but can you explain why
> > stateful inspection does not work in a bridged mode?  And why it only
> > filters for inbound traffic?  Does ipfw suffer from the same feature?
> > Thanks.
> >
> 
> Both pf/ipf should see inbound/outbound traffic in order to
> create states. But in bridge(4), pfil(9) hook for outbound packet
> is absent. ipfw can create states without seeing outbound packet.
> Maybe it would be authors intention to reduce overhead by not
> checking packets in both directions.
> 
> I guess ipfw can't filter outbound packet in bridged setup too.
> 
> Long time ago, I wrote a patch to add pfil(9) outbound hook
> in bridge setup. The patch makes pf's scrub rule work too.
> It wouldn't apply to 5.3R but you can see the point.
> 
> http://www.kr.freebsd.org/~yongari/patches/bridge.patch
> 
> > -josh
> >
> > --
> > Joshua Kayse
> > Computer Engineering
> 
> --
> 
> 
> Regards,
> Pyun YongHyeon
> http://www.kr.freebsd.org/~yongari      |       yongari at freebsd.org
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> 

I managed to get your patch to apply to FreeBSD RELENG_5.

I have a question about the bridge_fragment function though.  Would
this prevent packets from linux NFS clients from working, the
fragmented ones with the DF flag set?  Thanks for any information.

I'll post the patch later if anyone wants it.  It hasn't been
thoroughly tested but is currently running on a bridge setup in my
test lab with my work machine behind it.

-josh

-- 
Joshua Kayse
Computer Engineering