netdev - Re: [PATCH] tcp: more documentation for tcp_tw_reuse and tcp_tw

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Message-Id: <20140507.151637.562958118271192092.davem@davemloft.net>
Date:	Wed, 07 May 2014 15:16:37 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	vincent@...nat.im
Cc:	edumazet@...gle.com, linux-doc@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: [PATCH] tcp: more documentation for tcp_tw_reuse and
 tcp_tw_recycle

From: Vincent Bernat <vincent@...nat.im>
Date: Sun,  4 May 2014 11:41:39 +0200

> The documentation is not very helpful about what those settings
> affect. We find numerous tuning guides advising to set both these
> settings to 1 to reduce the number of entries in the TIME-WAIT
> state. However, enabling tcp_tw_recycle will cause massive problems when
> working with NAT.
> 
> The documentation is completed a bit to explain quickly what kind of
> connections both those settings will affect and to encourage the use of
> tcp_tw_reuse instead of tcp_tw_recycle for outgoing connections.

First of all your change locks a proper signoff.

Second of all, both options can cause problems in the presence of NAT
because both optimizations assume unique IP addresses identify unique
physical hosts.
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