On Sat, Oct 19, 2013 at 08:34:33PM +0200, Hannes Frederic Sowa wrote: > 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 > reachable. > > > > [ 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. ;) It seems tables are processed with bh disabled, so no preemption while recursing. So I guess the use of tee_active is safe for breaking the tie here. The reason I exhaust stack space is that we can actually send out packets while looking up routes (rt6_probe). The nonreachability of the default gateway and the to-teed-to box does the rest. We need to change the route lookup of the duplicated packet in xt_tee to not cause ndisc probes to be generated. The more I review the patch the more I think it is ok. But we could actually try to just always return rt6i_gateway, as we should always be handed a cloned rt6_info where the gateway is already filled in, no? Greetings, Hannes -- To unsubscribe from this list: send the line "unsubscribe lvs-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
