netdev - Re: DNAT sporadically doesn't replace destination IP address

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Date:	Mon, 26 May 2008 14:11:04 +0200
From:	"Ulrik De Bie" <ulrik.debie@...tec.eu>
To:	"Kris Op de Beeck" <kris.op.de.beeck@...tec.eu>, <kaber@...sh.net>
Cc:	<netdev@...r.kernel.org>, <netfilter-devel@...r.kernel.org>
Subject: Re: DNAT sporadically doesn't replace destination IP address

> Kris Op de Beeck wrote:
>> 
>>>>> On 22/05/2008 at 17:28, in message <4835913A.4020909@...sh.net>, Patrick McHardy <kaber@...sh.net> wrote:
>>>> [  927.204000] nf_ct_tcp: invalid SYNIN= OUT= SRC=192.168.1.30 DST=10.9.9.29 
>>> LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=25745 DF PROTO=TCP SPT=52775 DPT=80 
>>> SEQ=2154890499 ACK=0 WINDOW=5840 RES=0x00 SYN URGP=0 OPT 
>>> (020405B40402080A000264810000000001030307) UID=1000
>>>> For those DST ip addresses I've got failures
>>> Which kernel is this test running on? That message
>>> is gone since 2.6.22.
>> 
>> s3p@...nin:~$ uname -a
>> Linux burnin 2.6.22-14-generic #1 SMP Sun Oct 14 23:05:12 GMT 2007 i686 GNU/Linux
>> 
>> This was the config where I detected the problem. (Ubuntu 7.10)

>I didn't find the reason why your kernel even has that message
>(didn't try to hard though). Could you rerun the test with a
>more current kernel, like 2.6.24 or 2.6.25 please?
Kris already provided you with the results for 2.6.24, behaviour there seems to have become even worse. 

But about your first remark:
The ubuntu 2.6.22-14 kernel has that message still, it's based on kernel version 2.6.22.9 and I downloaded the original from kernel.org, and that still contains the message:
linux-2.6.22.9/net/netfilter/nf_conntrack_proto_tcp.c at line 909 in function tcp_packet.

I also compared with the 2.6.17.1 (which is definitely older than the ubuntu 2.6.17), and the function tcp_packet has not changed between these versions. In 2.6.25 this function did have some changes though. So the relevant change causing the behaviour must be outside function tcp_packet.

Best regards,
Ulrik De Bie
Newtec will be present at the following exhibitions :

CommunicAsia, 17-20 June, Singapore, Booth 6B2-01

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