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

["Yurij M. Plotnikov" <Yurij.Plotnikov@oktetlabs.ru>]

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.