Re: [Openvpn-users] CPU 100% when waiting for ping-restart

[James Yonan <jim@xxxxxxxxx>]

On Fri, 3 Jun 2005, Markku Leinio wrote:

> openvpn.exe (in the client-side) starts spending 100% CPU time when ping
> has failed and it is waiting for ping-restart to happen. Is this a known
> fact, and can it be avoided somehow?

This can occur if you get a routing loop -- in such a case the CPU goes to 
100% because OpenVPN is receiving a flood of packets to push through the 
tunnel, and so is spending a lot of cycles to encrypt/decrypt them.

> CPU load is near zero, but when the network connection fails, my laptop
> starts spinning the fans as CPU load goes to 100%, until OpenVPN notices
> that the connection has failed.
> 
> Server is Linux 2.4.x, client is Windows XP Pro SP2, both running
> OpenVPN 2.0.
> 
> server.conf:
> dev tun
> port 1194
> server 192.168.88.0 255.255.255.0
> push "route <vpn-server-ip> 255.255.255.255 net_gateway"
> push "route <first-network> 255.255.255.0 default 100"
> push "route <second-network> 255.255.255.0 default 100"
> push "route <third-network> 255.255.0.0 default 100"
> push "explicit-exit-notify 2"
> keepalive 10 60
> ca dcroot.crt
> dh dh1024.pem
> cert vpn-server.crt
> key vpn-server.key
> crl-verify crl.pem
> user nobody
> group nogroup
> persist-key
> persist-tun
> comp-lzo
> verb 3
> 
> client.conf:
> remote <vpn-server-ip>
> dev tun
> port 1194
> client
> ca   "C:\\Program Files\\OpenVPN\\config\\dcroot.crt"
> cert "C:\\Program Files\\OpenVPN\\config\\mleinio.crt"
> key  "C:\\Program Files\\OpenVPN\\config\\mleinio.key"
> comp-lzo
> nobind
> tls-remote "<x509-of-the-server>"
> verb 3

I checked your config without the route pushes, and I can't reproduce the
behavior you describe on the Windows side, where CPU utilization of the
OpenVPN process goes to 100%.  I would guess that there is a routing loop
issue which you could confirm by using a packet sniffer like Ethereal to
see what's going over the TAP interface when the CPU is at 100%.

James


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