Openvpn tap uses 99% cpu time

[Emile Coetzee]

Emile Coetzee wrote:
> Okay I finally have a ktrace of the offending process. You can view it
here:
> http://www.clarotech.co.za/dump/openvpn2.txt
>   
>>Thanks for this. If this is the correct trace, of the correct process, 
then it looks like OpenVPN is hanging immediately on opening the tap
device.<<

>>One thing that does jump out at me is the use of the persist-tun 
keyword. Can you try removing the use of this keyword? It is something 
I've never had to use with OpenVPN.<<

I did try it without the persist settings and it seemed to work but then I
put it back again and that worked too (i.e. no 100% CPU usage). However
after restarting the box and repeating the tests, both produced the 100% CPU
usage issue. 

What I suspect happened is that somehow the tap device was already present
and thus openvpn did not need to create one. I then tried to use the
cloned_interfaces="tap0" to see if that would create a tap device for me at
boot time. But the server hung similarly to when openvpn uses 100% CPU time
more or less where I would expect it to initialize the NICs. Unfortunately I
did not think to check if the tap device was present before testing it
without the persist setting. So it's a bit of mystery.

I have lost the box I was testing on (off to a client) and will only be able
to setup a new one to do testing on next week. So I will feed back with any
new findings.

Cheers
Emile