netdev - Re: Does IPv6 support Jumbograms ?

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Date:	Wed, 09 Apr 2014 17:36:10 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc:	Francois WELLENREITER <f.wellenreiter@...il.com>,
	netdev@...r.kernel.org
Subject: Re: Does IPv6 support Jumbograms ?

On Thu, 2014-04-10 at 00:35 +0200, Hannes Frederic Sowa wrote:
> On Wed, Apr 09, 2014 at 02:41:05PM -0700, Eric Dumazet wrote:
> > What do you mean by blocked ?
> > 
> > Please give more details (kernel version, exact mtu...), because it
> > should not happen !
> > 
> > # ifconfig lo mtu 100000
> > # scp -6 vmlinux edumazet@...-localhost:/tmp
> > Password: 
> > vmlinux
> > 100%   24MB  23.5MB/s   00:00    
> > # ls -l /tmp/vmlinux
> > -rwxr-xr-x 1 edumazet eng 24668915 Apr  9 14:37 /tmp/vmlinux
> 
> I couldn't test it on my development system with a recent net-next kernel
> yet, but on my laptop with a distribution 3.13.9 kernel this happened too.

Oh well, it seems ip6_mtu() needs to cap mtu to max mtu for non
jumbograms...

-	return mtu;
+	return min_t(unsigned int, mtu, IP6_MAX_MTU);

#define IP6_MAX_MTU (65535 + 40)



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