netdev - Re: IPv6 path MTU discovery broken

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Date:	Sun, 13 Oct 2013 09:51:03 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	"Steinar H. Gunderson" <sgunderson@...foot.com>
Cc:	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	netdev@...r.kernel.org, edumazet@...gle.com, fan.du@...driver.com
Subject: Re: IPv6 path MTU discovery broken

On Sun, 2013-10-13 at 12:40 +0200, Steinar H. Gunderson wrote:
> [resending with proper quoting and cc]
> 
> On Mon, Oct 07, 2013 at 05:09:10AM +0200, Hannes Frederic Sowa wrote:
> > Could you try to check (with e.g. nstat) if any of the following counters
> > change if the icmp messages hit the host?
> > 
> > TcpExtOutOfWindowIcmps
> > Icmp6InErrors
> > TcpExtTCPMinTTLDrop
> > TcpExtListenDrops
> 
> Hi,
> 
> I am now seeing the same problem against a 3.9.0 machine (that I've never had
> problems with before). I looked through the four nstat counters, and none of
> them are increasing. Here's /proc/net/ipv6_route from the server while it's
> going on; the client is 2001:67c:a4:1:71f9:c84b:8b2a:c65b (second line) and
> the server is 2001:67c:29f4::2007.

I am not sure, but the skb_is_gso() checks seem too lazy.

Why don't we check that gso_size+headers is below mtu, I dont know.



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