Re: Routing loops & TTL tracking with tunnel devices

From: Jason A. Donenfeld
Date: Mon Nov 16 2015 - 21:57:34 EST

On Mon, Nov 16, 2015 at 11:25 PM, Hannes Frederic Sowa
<hannes@xxxxxxxxxxxxxxxxxxx> wrote:
> Have a look at __dev_queue_xmit and the per_cpu recursion limits
> implemented there:
> if (__this_cpu_read(xmit_recursion) >
> goto recursion_alert;

Ahh, thanks for pointing that out. So this works with virtual devices
with no queue. As of some recent changes, that now applies to what I'm

Unfortunately, I get a complete hard crash, with the blinking
keyboard. The only thing written to serial before it dies is:
[ 171.347446] Dead loop on virtual device wg0, fix it urgently!
This means it did hit that recursion condition, which is good.
I assume the recursion limit is just too high, and this has something
to do with me overflowing the stack. I'll test this hypothesis and see
if I can add a similar check inside my driver to make it lower. If
this works, I'm satisfied.

Thanks a lot for the pointer here.
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