netdev - Re: Regression caused by commit "netfilter: iptables: lock free counters"

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Date:	Sun, 05 Apr 2009 12:30:17 +0200
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Graham Murray <graham@...rray.org.uk>
CC:	linux-kernel@...r.kernel.org,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: Regression caused by commit "netfilter: iptables: lock free counters"

Graham Murray a écrit :
> Eric Dumazet <dada1@...mosbay.com> writes:
> 
>>>>> 784544739a25c30637397ace5489eeb6e15d7d49 is first bad commit
>>>>> commit 784544739a25c30637397ace5489eeb6e15d7d49             
>>>> I am seeing a different problem which also bisects to this commit. There are
>>>> no kernel messages but ip6tables fails to run.
>>>>
>>>> newton ~ # ip6tables -L -v
>>>> FATAL: Module ip6_tables not found.
>>>> ip6tables v1.4.3.1: can't initialize ip6tables table `filter': Memory allocation problem
>>>> Perhaps ip6tables or your kernel needs to be upgraded.
>>>>
>>>> I get this error no matter which ip6tables sub-command I run. Ip6tables
>>>> is built into the kernel, not as modules.
>>>>
>>>> An strace shows the failure to be 
>>>> socket(PF_INET6, SOCK_RAW, IPPROTO_RAW) = 3
>>>> getsockopt(3, SOL_IPV6, 0x40 /* IPV6_??? */, "filter\0\305\0w~\300\0wb\305P\24\312\t\0009b\305\216\23\0\0\310\341/g\16"..., [84]) = 0
>>>> brk(0)                                  = 0x8273000
>>>> brk(0x8294000)                          = 0x8294000
>> so ip6tables allocates about 128 Kbytes of ram in order to get rules from kernel.
>>
>>>> getsockopt(3, SOL_IPV6, 0x41 /* IPV6_??? */, 0x8273090, 0xbfd23628) = -1 ENOMEM (Cannot allocate memory)
>>>> close(3)                                = 0
>>>>
>>
>> This is a big problem yes, since "iptables|ip6tables" -L needs to allocate kernel memory
>> to perform the momentary swap.
>>
>> On x86, this is potentially a problem if vmalloc space is exhausted or fragmented,
>> (or lowmem exhausted) and/or many cpus are online/possible.
> 
> iptables gives me no problems at all, it is just ip6tables that
> fails. The first indication of this is during the init scripts when
> ip6tables-restore fails.

I see, its a plain bug in net/ipv6/netfilter/ip6_tables.c
function alloc_counters() always returns -ENOMEM

Unfortunatly , its Sunday here and I have to run for lunch time with family :)

If nobody beats me, I will do the fix in a couple of hours...

Thank you

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