linux-kernel - Re: [BUG] SNAT sometimes allows packets to pass through unchanged

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Message-ID: <4999434F.1050101@trash.net>
Date:	Mon, 16 Feb 2009 11:43:27 +0100
From:	Patrick McHardy <kaber@...sh.net>
To:	Alan Stern <stern@...land.harvard.edu>
CC:	netdev@...r.kernel.org,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] SNAT sometimes allows packets to pass through unchanged

Alan Stern wrote:
> On Thu, 12 Feb 2009, Patrick McHardy wrote:
> 
>> If the connection has already timed out (from conntracks perspective),
>> it has lost its state. Unless connection pickup is enabled, the packet 
>> will be marked as INVALID because it doesn't belong to a connection.
>> You can control dropping of these packets yourself by adding the
>> appropriate "-m state --state INVALID" rules.
> 
> I tried adding a rule to log these unaccounted-for packets.  Nothing 
> showed up, even when I could see the packets being sent.

Where (table/chain/position) did you add this rule?

>> That said, there were
>> some bugs in the past few releases that caused some bad interaction
>> between TCP and TCP conntrack (not sure anymore which one of both was
>> to blame). Its possible that this is the root cause for this, so
>> you might want to consider a kernel update.
> 
> It does sound like the result of a bug.  Do you have any pointers to 
> patches or locations to check in the source?

Sorry, there were quite a few patches and I don't remember which
ones exactly are related.
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