#!/bin/bash

#
# Quick info:
#  - script that is running OpenVPN client in a loop, breaking out of it when
#	the "Network is unreachable" message comes up
#  - after each client termination it wipes out left tunnel interfaces (tap0, tap1, .., tapN)
#  - also it kills all of the running OpenVPN clients, preventing consecutive logons.
#
# Some Background:
#  Simple script made when I had been suffering from unstable link/connection
#  because of my ISP which made my running in the background daemons and scanners become
#  unstable after dealing with continuous connection closing.
#  I figured out that a simple re-running of the OpenVPN client from a pristine environment
#  will be sort of a solution. And it actually worked.
#

VPN_CONFIGURATION=/etc/openvpn/default.conf
VPN_USERNAME=<username>
VPN_PASSWORD=<password>

cat << EOF > /tmp/expect
#!/usr/bin/expect -f
match_max 1000000
set timeout -1

spawn openvpn $VPN_CONFIGURATION
expect "*?sername:*"
send -- "$VPN_USERNAME"
send -- "\r"

expect "*?assword:*"
send -- "$VPN_PASSWORD"
send -- "\r"

# Awaiting for link to be become closed.
expect "*Network is unreachable*"
close
EOF

i=0
while true; do
	i=$((i+1))
	echo -ne "\n[+] Starting another instance of OpenVPN client ($i)\n"

	# This is needed to prevent concurrent VPN connections in the background.
	killall -9 openvpn @> /dev/null
	sleep 2

	B=$IFS
	IFS=$'\n'

	# Removing other tunnel interfaces to make the OpenVPN client stick to the "tap0".
	# We want this in order to make daemons (and programs) running in the background which
	# already sticked to the "tap0" interface not become unstable.
	for iface in $(find /sys/class/net -name "tap*" -exec basename {} \;); do
		sudo ip link delete $iface
	done

	IFS=$B
	sleep 2

	# Spawning the client.
	/usr/bin/expect -f /tmp/expect

	# Awaiting for user interruption (Ctrl+C), which will break out of the loop
	test $? -gt 128 && break
done

echo "Script has fininshed."
killall -9 openvpn @> /dev/null