netdev - Re: PMTU discovery is broken on kernel 3.7.1 for UDP sockets

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Message-ID: <50FD2708.6060906@oktetlabs.ru>
Date:	Mon, 21 Jan 2013 15:31:20 +0400
From:	"Yurij M. Plotnikov" <Yurij.Plotnikov@...etlabs.ru>
To:	Steffen Klassert <steffen.klassert@...unet.com>
CC:	Ben Hutchings <bhutchings@...arflare.com>, netdev@...r.kernel.org,
	"Alexandra N. Kossovsky" <Alexandra.Kossovsky@...etlabs.ru>
Subject: Re: PMTU discovery is broken on kernel 3.7.1 for UDP sockets

On 01/18/13 12:11, Steffen Klassert wrote:
> On Mon, Jan 14, 2013 at 12:26:59PM +0400, Yurij M. Plotnikov wrote:
>    
>> Could you, please, tell me is there any news about this bug?
>>
>>      
> Ok, I tried to reconstruct your testcase and I can confirm this bug.
> It happens only on the first pmtu event on a given route. It works
> if I run this test again. Actually it works sometimes even on the
> first pmtu event, so it took me quite a while to understand what's ging on.
>
> This is because standart routes (no pmtu or redirect events happened on
> that route) are per cpu, so each cpu has it's own struct rtable. This means
> that we do not invalidate the socket cached route if the NET_RX_SOFTIRQ
> (which handles the pmtu event) is not served by the same cpu that the
> sending socket uses. Exceptional routes (routes where a pmtu or redirect
> event occured) are not per cpu, so there is no problem.
>
> I'll send three patches in reply to this mail. Applying patch one and two
> should fix the bug you reported. If you use IPsec you need patch three too.
> The patches are marked as RFC, I'll do proper patch submission if you can
> confirm that they fix this bug.
>    
Sorry for long delay. I've just checked patches 1+2 and they fix the bug 
for me.

Yurij.
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