A killswitch script with autoconnecting function for OpenVPN

This script performs the following:

• It blocks all traffic through your default network interface, except the communication with the VPN, meaning that if the VPN goes down, your traffic will not go through your default interface.

• It allows full communication through the VPN tunnel interface.

• It reconnects to the VPN tunnel in case it gets disconnected.

Give the script execution permission:

chmod +x killswitch.sh

Run the script specifying the full path of your .ovpn file:

sudo ./killswitch.sh /tmp/vpn.ovpn

To stop the script and flush the firewall rules, press:

Ctrl + c

• NetworkManager and NetworkManager front-end(nmcli) - It is used to check whether the tunnel link is active or not. Note that Networkmanager is installed by default in Ubuntu and Ubuntu based distros.

• The script is using tun0 as the VPN tunnel interface, if your distro uses a different one, edit the following line

TUNNEL=tun0

• Make sure your authentication credentials are properly configured within your .ovpn file, so, when the VPN is reconnected, it will not ask you for credentials.