linux-kernel - Re: [PATCH 0/2] ppp: mppe: fixes MPPE desync on links which don't guarantee packet ordering

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Message-Id: <20150426.232616.353503560380309931.davem@davemloft.net>
Date:	Sun, 26 Apr 2015 23:26:16 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	sylvain.rochet@...secur.com
Cc:	paulus@...ba.org, linux-ppp@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] ppp: mppe: fixes MPPE desync on links which don't
 guarantee packet ordering

From: Sylvain Rochet <sylvain.rochet@...secur.com>
Date: Sun, 26 Apr 2015 20:40:51 +0200

> I am currently having an issue with PPP over L2TP (UDP) and MPPE in
> stateless mode (default mode), UDP does not guarantee packet ordering so
> we might get out of order packet. MPPE needs to be continuously synched
> so we should drop late UDP packet.
> 
> I added a printk on the number of time we rekeyed in MPPE decompressor,
> this is what we currently have if we receive a slightly out of order UDP
> packet:
 ...
> This is obviously wrong, we missed packet 1561 and we already rekeyed 2
> times for 1562 we previously received, we can't recover the decryption
> key we need for 1561, we should drop it instead of rekeying 4095 times.
> 
> This patch series drop any packet with are not within the 4096/2 forward
> window.

Series applied, thanks Sylvain.
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