netdev - Re: [PATCH net-next] ipv6: RTAX_FEATURE_ALLFRAG causes inefficient TCP segment sizing

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Message-ID: <1335350667.3274.53.camel@edumazet-glaptop>
Date:	Wed, 25 Apr 2012 12:44:27 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Maciej Żenczykowski <maze@...gle.com>
Cc:	Tore Anderson <tore@....no>, David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Tom Herbert <therbert@...gle.com>
Subject: Re: [PATCH net-next] ipv6: RTAX_FEATURE_ALLFRAG causes inefficient
 TCP segment sizing

On Wed, 2012-04-25 at 03:30 -0700, Maciej Żenczykowski wrote:

> Hmm, it may be best to honour PMTUs below 1280 to some small but not
> too small value (512?), and below that give up, say mtu remains 1280
> but still add the frag header.
> 

Thats a good idea.


> (re: Eric's patch, I think it should protect itself against malicious
> PMTU messages with too small MTUs, like 0 or 1 or 68 [not enough for
> timestamped ipv6/tcp)

Yes, in fact we are going to keep the allfrag feature, and arm it if we
receive an mtu < 512.

I'll send a v3 patch soon.

Thanks


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