On Thu, 5 Jan 2012, Hans Schillstrom wrote:
> On Wednesday 04 January 2012 22:40:09 Jozsef Kadlecsik wrote:
> > On Wed, 4 Jan 2012, Hans Schillstrom wrote:
> >
> > > On Wednesday, January 04, 2012 19:05:10 Jozsef Kadlecsik wrote:
> > > > On Wed, 4 Jan 2012, Pablo Neira Ayuso wrote:
> > > >
> > > > > On Wed, Jan 04, 2012 at 12:48:35PM +0100, Hans Schillstrom wrote:
> > > > > > I like that idea, an "early" table at prio -500 with PREROUTING.
> > > > > > There is also a need for a new flag "--allfrags"
> > > > > > i.e. all fragments needs to be sorted out and sent to same dest for defrag.
> > > > > >
> > > > > > ex.
> > > > > > iptables -t early -A PREROUTING -i eth0 --allfrags -j NOTRACK
> > > > >
> > > > > New tables add too much overhead. We have discussed this before with
> > > > > Patrick.
> > > > >
> > > > > Since this still remains specific to your needs, I think you can
> > > > > remove nf_conntrack module in your setup.
> > > > >
> > > > > I don't come with one sane setup that may want selectively defragment
> > > > > some traffic yes and other not.
> > > > >
> > > > > Am I missing anything else?
> > > >
> > > > I agree. If you don't want defragmentation at all, then make sure you
> > > > don't load the nf_conntrack module directly/indirectly. Conntrack doesn't
> > > > work without defragmentation anyway.
> > >
> > > We are using LXC and it's only in the container that holds the external
> > > interface that can't have defragmentation.
> > > The problem is if it's loaded you have it in all namespaces :-(
> >
> > Conntrack is per net namespaces. You may have one container with conntrack
> > enabled and another one without conntrack.
>
> How do you disable conntrack per netns ?
> I can't see how to do it except for NOTRACK
> Then the nf_defrag issue is still there...
OK, I see. Conntrack is per net namespace but it's enabled globally.
So at the moment I think the best solution is something like your patch
variant (but the condition is wrong, it should be "&& !skb->nfct"):
--- a/net/ipv4/netfilter/nf_defrag_ipv4.c
+++ b/net/ipv4/netfilter/nf_defrag_ipv4.c
@@ -74,6 +74,14 @@ static unsigned int ipv4_conntrack_defrag(unsigned int
hooknum,
...
+ const struct net_device *dev = (hooknum == NF_INET_LOCAL_OUT ?
+ out : in);
+
+ /* No defrag and not Previously seen (loopback)? */
+ if (dev_net(dev)->ct.sysctl_notrac_defrag && skb->nfct) {
+ /* Attach fake conntrack entry. as in NOTRACK */
+ skb->nfct = &nf_ct_untracked_get()->ct_general;
+ skb->nfctinfo = IP_CT_NEW;
+ nf_conntrack_get(skb->nfct);
+ return NF_ACCEPT;
+ }
...
Best regards,
Jozsef
-
E-mail : kadlec@xxxxxxxxxxxxxxxxx, kadlecsik.jozsef@xxxxxxxxxxxxx
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Address : Wigner Research Centre for Physics, Hungarian Academy of Sciences
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