netdev - Re: [PATCH v2] tcp: tcp_replace_ts_recent() should not be called from tcp_validate

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Message-Id: <20121113.143544.503592471078426014.davem@davemloft.net>
Date:	Tue, 13 Nov 2012 14:35:44 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	romain@...bokech.com, netdev@...r.kernel.org, ncardwell@...gle.com,
	ycheng@...gle.com, nanditad@...gle.com, hkchu@...gle.com
Subject: Re: [PATCH v2] tcp: tcp_replace_ts_recent() should not be called
 from tcp_validate_incoming()

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Tue, 13 Nov 2012 07:37:18 -0800

> From: Eric Dumazet <edumazet@...gle.com>
> 
> We added support for RFC 5961 in latest kernels but TCP fails
> to perform exhaustive check of ACK sequence.
> 
> We can update our view of peer tsval from a frame that is
> later discarded by tcp_ack()
> 
> This makes timestamps enabled sessions vulnerable to injection of
> a high tsval : peers start an ACK storm, since the victim
> sends a dupack each time it receives an ACK from the other peer.
> 
> As tcp_validate_incoming() is called before tcp_ack(), we should
> not peform tcp_replace_ts_recent() from it, and let callers do it
> at the right time.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied, thanks a lot.

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