Re: [RFC net-next] ipv6: Use destination address determined by IPVS

To: Julian Anastasov <ja@xxxxxx>
Subject: Re: [RFC net-next] ipv6: Use destination address determined by IPVS
Cc: Simon Horman <horms@xxxxxxxxxxxx>, YOSHIFUJI Hideaki / 吉藤英明 <yoshfuji@xxxxxxxxxxxxxx>, lvs-devel@xxxxxxxxxxxxxxx, netdev@xxxxxxxxxxxxxxx, Mark Brooks <mark@xxxxxxxxxxxxxxxx>, Phil Oester <kernel@xxxxxxxxxxxx>
From: Hannes Frederic Sowa <hannes@xxxxxxxxxxxxxxxxxxx>
Date: Sat, 19 Oct 2013 20:34:33 +0200
On Sat, Oct 19, 2013 at 07:37:10PM +0300, Julian Anastasov wrote:
>       Hello,
> On Fri, 18 Oct 2013, Hannes Frederic Sowa wrote:
> > I played around with your patch and tested xt_TEE. I added a TEE rule to
> > mangle/OUTPUT and pinged. This happend, I have not yet analyzed it:
> > 
> > [  101.126649] ------------[ cut here ]------------
> > [  101.128436] BUG: unable to handle kernel paging request at 
> > fffffffb8a2fda88
> > [  101.129421] IP: [<ffffffff810c9737>] cpuacct_charge+0x97/0x200
> > [  101.129421] PGD 1c0f067 PUD 0
> > [  101.129421] Thread overran stack, or stack corrupted
>       Problem with process stack? May be some packet loop
> happens? Because I can not reproduce such problem in my
> virtual setup, I tested TEE too, with careful packet
> matching and 1 CPU. Should I assume that you don't have such
> oops when the patch is not applied, with the same TEE rule?

Oh, sorry, you are right. It happens with an unpatched net-next  kernel, too.

I inserted the TEE rule in mangel/OUTGOING and had only one route, ip -6 r a
default via fe80::1 dev eth0 which at the time of the panic was actually not

> > [  101.129421] Oops: 0000 [#1] SMP
>       You don't appear to have PREEMPT in above line.
> I'm not sure when preemption is enabled if tee_tg6() does
> not have a problem with its anti-loop measures (tee_active).
> Is preemption possible in OUTPUT hook, i.e. can we change
> the CPU while playing with tee_active and as result change
> different flag?

Hm, maybe. I don't have too much insight into netfilter stack and
what are the differences between OUTPUT and FORWARD path but plan to
investigate. ;)

Anyways just wanted to let you know that unpatched kernels are affected, too.
Will have a closer look later.



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