Re: [PATCH v2] net: preserve IP control block during GSO segmentation

[Hannes Frederic Sowa]

On 14.01.2016 00:36, Florian Westphal wrote:
> David Miller <davem@xxxxxxxxxxxxx> wrote:
> > From: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
> > Date: Fri, 08 Jan 2016 15:21:46 +0300
> >
> > > Skb_gso_segment() uses skb control block during segmentation.
> > > This patch adds 32-bytes room for previous control block which
> > > will be copied into all resulting segments.
> > >
> > > This patch fixes kernel crash during fragmenting forwarded packets.
> > > Fragmentation requires valid IP CB in skb for clearing ip options.
> > > Also patch removes custom save/restore in ovs code, now it's redundant.
> > >
> > > Signed-off-by: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
> > > Link: http://lkml.kernel.org/r/CALYGNiP-0MZ-FExV2HutTvE9U-QQtkKSoE--KN=JQE5STYsjAA@xxxxxxxxxxxxxx
> >
> > If this works I definitely prefer this approach to the other patch
> > where the CB is copied back and forth.
>
> I quite frankly don't care and just like you to apply one or the other;
> use coin toss if needed :-}
>
> I would prefer to use a on-stack state since there is no need to
> use skb->cb (no queueing) but when I gave it a try it got out of hand
> rather quick :-/

Be careful with the encap counter within SKB_GSO_CB when trying to put 
it on the stack.

Bye,
Hannes