As soon as somebody ports it and sends me a patch. I receive about 3-5 mails per week asking for this feature... but apparently nobody is willing to contribute some time back to the netfilter project.
It appears Mandrake have ported the patch to 2.6. See http://lists.netfilter.org/pipermail/netfilter-devel/2004-August/016550.html It still needs at least some testing, but should be close.
-- Philip Craig - SnapGear, A CyberGuard Company - http://www.SnapGear.com