[LARTC] Re: IMQ device problems with iptables: dead looping?

[Patrick McHardy <kaber@trash.net>]

Andrew Hall wrote:

>Hello,
>
>I am using the IMQ with iptables (latest versions) and asking all packets to
>be enqueued to IMQ0 from both prerouting and postrouting (using different
>iptables rules to mark different streams). When I do this I get the kernel
>saying:
>
>"Dead loop on netdevice imq0, fix it urgently!" and communications stop
>intermittently. If I remove the jump from either preroute or postroute it
>works fine but won't work together.
>
>Is this what is mean't to happen, because as far as I can see there is no
>loop happening here?
>

You probably forward packets. The loop happening ist
input-device -> prerouting -> imq (xmit_lock locked) -> reinject -> ... 
-> postrouting -> imq (LOCKED!!)

To avoid this one has to drop xmit_lock in imq_xmit function before 
reinjecteing and grab it back afterwards.
unfortunately this allows for endless recursion which is not possible in 
the kernel due to limited stack space.
I've completed a version which should hopefully fix this as many people 
requested such a feature.
I haven't released it yet because i have to do alot for my university 
atm and haven't got the time for testing
although i promised the new version to some people for january ;(
In about two weeks my semester-vacation start, i hope to release the new 
version very quickly afterwards.

Thanks for your patience,
Patrick

_______________________________________________
LARTC mailing list / LARTC@mailman.ds9a.nl
http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/