netdev - Re: [PATCH net] tcp: don't allow syn packets without timestamps to pass tcp_tw

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Message-ID: <1408030715.6804.21.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Thu, 14 Aug 2014 08:38:35 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	fw@...len.de
Subject: Re: [PATCH net] tcp: don't allow syn packets without timestamps to
 pass tcp_tw_recycle logic

On Thu, 2014-08-14 at 11:37 +0200, Hannes Frederic Sowa wrote:

> did you have a chance to look at this patch again?
> 
> I found this during code review. Non time stamped SYN packets could
> eventually trigger the completion of a 3WHS even though we had
> tw_recycle enabled and the SYN arrived in a TCP_PAWS_MSL of this host
> period.


> 
> I don't want to make this feature more general usable (without time
> stamps), they are absolutely required. It just adds protection against
> accidental 3WHS completion of 3WHS if a packet without time stamps
> arrived.
> 
> I don't have a strong opinion on that but it just seems to be natural,
> as we also conditional schedule the timeout for the tw buckets depending
> on if we saw time stamps on the prior connection.

I believe this patch gives a wrong sense of comfort, and honestly this
is caused by its changelog.

Sane people should not use tw_recycle, and eventually we should remove
its support.

Your changelog is misleading because it could give bad incentive about
_using_ tw_recycle.

Please rephrase it so that no doubt is possible.

Thanks

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