OpenVPN reconnect Bash script

openvpn-reconnect.sh

#!/bin/bash

# configuration
DEVICE="tap0"
USERNAME="twitter"
PASSWORD="twitter"

# check configuration and environment
if [ -z $DEVICE ]; then
  echo You must specific DEVICE first.
  exit 1
fi

if [ -z $USERNAME ]; then
  echo You must specific USERNAME first.
  exit 1
fi

if [ -z $PASSWORD ]; then
  echo You must specific PASSWORD first.
  exit 1
fi

which expect > /dev/null
if [ $? -gt 0 ]; then
  echo You must install "expect" package first.
  exit 1
fi

# check availability of url, if number of successful ping is larger than half, stop.
PING_NUM=`ping -n -c 10 twitter.com|grep received|awk '{ print $4 }'`
if [ $PING_NUM -gt 5 ]; then
  exit 0
fi

# delete related rule from iptables
RULENUM=`iptables -t nat -L POSTROUTING -n --line-numbers|grep '199.59.148.0'|awk '{ print $1;exit }'`
if [ -n "$RULENUM" ]; then
  iptables -t nat -D POSTROUTING $RULENUM
fi

# stop openvpn service if any
service openvpn stop

# start openvpn service
expect -c "
set send_human {.1 .3 1 .05 2}
spawn service openvpn start
expect {
  \"sername\" {
    send -h \"$USERNAME\\n\"
    exp_continue
  }
  \"assword\" {
    send -h \"$PASSWORD\\n\"
    exp_continue
  }
  eof {
    wait
  }
}
exit
"

# get openvpn ip
for i in `seq 5`; do
  sleep 3
  # check if openvpn is running
  ifconfig $DEVICE > /dev/null 2>&1
  if [ $? -eq 0 ]; then
    OPENVPN_IP=`ifconfig $DEVICE | grep inet | sed '2d'| awk '{ print $2}'| awk -F: '{ print $2 }'`
    break
  fi
done

# add rule to iptables
if [ -n "$OPENVPN_IP" ]; then
  iptables -t nat -A POSTROUTING -d 199.59.148.0/255.255.252.0 -j SNAT --to-source $OPENVPN_IP
else
  exit 1
fi