[Enhancement] Support for OpenVPN 3 Linux

[dsommers]

OpenVPN 3 Linux provides a simpler way to start and manage VPN configurations and sessions out-of-the-box, including setting up DNS resolver settings and on supported Linux distributions also provides DCO (kernel based Data Channel Offload)

OpenVPN 3 Linux also ships with a Python 3 module, to more easily integrate. There are several examples here: https://github.com/OpenVPN/openvpn3-linux/tree/master/src/tests/python Other resources can be the openvpn3-autoload utility, which is also Python based.

Enabling DCO on a session is as easy as calling the SetDCO() method before calling Connect() on the openvpn3.Session object.

[dsommers]

Just a quick comment on DNS resolver settings; the next release will enable systemd-resolved integration on Fedora and Ubuntu 20.04 and newer. Otherwise it will modify /etc/resolv.conf directly.