netdev - Change in IPv4 TCP reset behavior after kernel upgrade

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Date:	Wed, 4 Dec 2013 10:09:01 +0000
From:	Fiedler Roman <Roman.Fiedler@....ac.at>
To:	"davem@...emloft.net" <davem@...emloft.net>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Change in IPv4 TCP reset behavior after kernel upgrade

Hello,

After upgrading from linux-image-3.10.17 to linux-image-3.10.21 I noticed, that afterwards reset packets started to be transmitted with ID != 0. For testing:

tcpdump -i eth0 -nn -s0 -X -vvv 'tcp[tcpflags] & tcp-rst != 0'

I did a short search to find out when and why this was changed (PATCH), but did not get any wiser.

Was this an intended change, e.g. to increase resilience against RST-packet injection/DOS scenarios? Is it just accidentally?

The ID seems to be in sequence, so it is not uninitialized memory content.

Roman

PS: The kernel was patched with the vserver-patch, this might have an influence. I did not have time yet to build a kernel without that modification.
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