[Fwd: SUMMARY: KVM+nf_conntrack_htable_size]

[Jon Masters]

On Mon, 2010-02-01 at 10:17 -0500, Kyle McMartin wrote:
> On Sun, Jan 31, 2010 at 04:12:07AM -0500, Jon Masters wrote:
> > The disabling of netfilter on bridges is not really "solving" this
> > problem. The problem is that the hashing code needs fixing. Until that
> > changes, whenever libvirtd plays with namespaces (as it does), we run
> > the risk of falling over as we play with the size of the hashtables.
> > 
> 
> Thanks for the heads up, Jon. I'll watch this and the internal thread
> for a fix.

Well, I sent a summary for why it happens. It happens because an IPv6
error (set via icmpv6_error) causes us to set the conntrack (ct) for an
incoming skb to nf_conntrack_untracked (a catchall struct). We then try
to free that like any other conntrack, back into the (now per-namespace)
cache, but it's not a SL[U]B allocated struct, it's a static...boom.

The conntrack code should catch this and error it, it should also do
per-namespace cache allocation, and per-namespace hashtable metadata.
I'm *very* surprised if this isn't biting a lot more Fedora users.

Jon.