Re: Any issues with packet updates?

On Monday 21 April 2003 15:04, Scott MacKay wrote:
> Question summary:  Are there any issues when mangling
> packets as they pass thru the bridge, changing TCP/UDP
> payload content and size?  The symptoms are very, very
> slow thruput (sometimes higher volume bursts) but
> traffic eventually completing.
> I have a userspace (iptables) QUEUE target on my dual
> ether machine, loaded in PREROUTING (marked for when
> incoming to the physical interface) and POSTROUTING
> (marked for when outgoing on the physical interface)
> on eth1.  The jist is basically all outgoing packets
> (POSTROUTING) between the hosts will be marked on the
> outdev_name field in the userspace module and all
> incoming packets (PREROUTING) will be marked on the
> indev_name field in the userpace module.
> Overall, the intent of the userspace module is to
> mangle  TCP/UDP packets on the 'internet'.  Each side
> mangles on output, demangles on input, changing both
> the tcp/udp payload and it's size.  My configuration,
> when the mangling is turned off, works perfectly fine
> with great thruput.  As soon as I activate the
> mangling, it slows to a crawl, but does get there and
> is received correctly.  In router mode, everything
> looks like it works perfectly fine.

The PREROUTING chain is traversed before the bridge has decided if the frame 
has to be bridged. Perhaps you are also mangling packets that will never be 
bridged?

-- 
cheers,
Bart



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