From mboxrd@z Thu Jan  1 00:00:00 1970
From: Patrick McHardy <kaber@trash.net>
Subject: Re: Checksum problem in tcp-window-tracking
Date: Tue, 15 Jun 2004 20:32:19 +0200
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Cc: Martin Josefsson <gandalf@wlug.westbo.se>,
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To: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
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Hi Jozsef,

Jozsef Kadlecsik wrote:
> I committed the fixed version of the patch in cvs. Besides the fix the
> talkative log messages were trimmed in order to fit (better) into the
> ULOG buffer.

I think there is still a problem.

+       if (csum_tcpudp_magic(iph->saddr, iph->daddr,
+                             tcplen, IPPROTO_TCP,
+                             skb->ip_summed == CHECKSUM_HW
+                             && hooknum == NF_IP_PRE_ROUTING
+                               ? skb->csum
+                               : skb_checksum(skb, iph->ihl*4, tcplen, 
0))) {

On the outgoing path, the NIC is supposed to checksum the packet when
CHECKSUM_HW is set, so it hasn't got a valid checksum when the check is
performed. Do we need to check the checksum in LOCAL_OUT at all ?
Other than from raw-sockets, invalid packets can not occur.

Regards
Patrick

PS: Martin, how did you trigger these errors ?