On Wednesday 04 January 2012 10:03:49 Jozsef Kadlecsik wrote:
> On Wed, 4 Jan 2012, Hans Schillstrom wrote:
>
> > On Wednesday 04 January 2012 09:28:05 Jozsef Kadlecsik wrote:
> > >
> > > On Wed, 4 Jan 2012, Hans Schillstrom wrote:
> > >
> > > > In some cases it not desirable to have auto defrag.
> > > > Ex. in a cluster where packets can arrive on different blades.
> > > > In that case it is possible to use containers (LXC) and send
> > > > all fragments to one place where defrag is enabled.
> > > >
> > > > This patch makes it possible to turn off the defrag per network name space,
> > > > by setting net.netfilter.nf_conntrack_nodefrag to 1.
> > > > Both IPv4 and IPv6 is effected by this sysctl.
> > > > Default is 0 which is defrag.
> > >
> > > Conntrack assumes that the packets are defragmented and will drop any
> > > unfragmented one. So your patch results packet drops.
> >
> > Hmmm, more work...
> > >
> > > Also, if you want to disable defragmentation then why don't you simply
> > > "mark" the packets with the NOTRACK target?
> >
> > I don't think that will work since NF_IP_PRI_CONNTRACK_DEFRAG is -400
>
> Then change NF_IP_PRI_RAW so that it precedes NF_IP_PRI_CONNTRACK_DEFRAG.
> The raw table should be made possible to completely override conntack and
> defrag is implicit part of the latter.
>
An other idea, turn off both conntrack and defrag
i.e. do like NOTRAC and rename the flag ?
Quick example for IPv4:
--- 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;
+ }
...
--
Regards
Hans Schillstrom <hans.schillstrom@xxxxxxxxxxxx>
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