BusyBox ash (OpenWRT) script for checking connection to VPN host over VPN interface. Restarts OpenVPN if needed.

vpn-check.sh

#!/bin/ash
set -x #debugging

VPN_CHECK_LOG="/var/log/vpncheck.log"
VPN_SERVER="nl.privateinternetaccess.com"
VPN_INTERFACE="tun0"
INTERNET_INTERFACE="eth0"

# Check to see if the VPN server is ping-able
ping_success () {
  PING_TEST=`ping -I $1 -c 4 -q $2 | grep "100% packet loss"`
  if [ "$PING_TEST" ]; then
#   print_to_log "NO ping from $2 over interface $1"
    return 1 #Returning above 0 means error
  else
#   print_to_log "Ping test OK, $2 reacable over interface $1"
    return 0
  fi
}

# Check to see if the VPN interface is still there.
interface_available () {
  RESULT=`ifconfig | grep -o "$1"`
  if [ "$RESULT" == "$1" ]; then
#    print_to_log "$1 interface available"
      return 0
  else
#    print_to_log "Interface $1 NOT found"
    return 1 #Returning above 0 means error
  fi
}

# Function uses ./opevpn start if no other instance running, otherwise restart.
restart_vpn () {
  if [ `pgrep openvpn` ]; then
#   echo "using restart"
    `/etc/init.d/openvpn restart`
  else
#   echo "using start"
    `/etc/init.d/openvpn start`
  fi
}

# Print $1 to logfile prepended with a timestamp
print_to_log () {
  local DATE_TIME=`date "+%Y-%m-%d %H:%M:%S"`
  echo "$DATE_TIME - $1" >> $VPN_CHECK_LOG&
}

if interface_available $VPN_INTERFACE; then
  if ping_success $VPN_INTERFACE $VPN_SERVER; then
    print_to_log "$VPN_INTERFACE found, $VPN_SERVER reachable over $VPN_INTERFACE, all OK"
  else
    if ping_success $INTERNET_INTERFACE $VPN_SERVER; then
      print_to_log "$VPN_SERVER NOT ping-able over $VPN_INTERFACE but reachable over $INTERNET_INTERFACE, restarting VPN..."
      restart_vpn
    else
      print_to_log "$VPN_SERVER NOT reachable over $VPN_INTERFACE or $INTERNET_INTERFACE. Internet and/or VPN Server NOT available."
    fi
  fi
 else
  if ping_success $INTERNET_INTERFACE $VPN_SERVER; then
    print_to_log "$VPN_INTERFACE down, $VPN_SERVER reachable over $INTERNET_INTERFACE, restarting VPN..."
    restart_vpn
  else
    print_to_log "$VPN_INTERFACE down, $VPN_SERVER NOT reachable over $INTERNET_INTERFACE. Internet and/or VPN Server NOT available."
  fi
fi