vpnmanager/device-config/2/bin/heartbeat

# Get IP address on VPN bridge interface through some arcane magic
ipaddr(){
 if="${1:-br-VPN360}"
 result=$(/sbin/ip -o -4 addr show dev "${if}" 2&>/dev/null | /bin/sed 's/^.*inet // ; s/\/...*$//')
 /usr/bin/printf %s "${result}"
}

# Disable (broadcast) WiFi device
stopwifi(){
  /sbin/uci set wireless.radio0.disabled=1
  /sbin/uci commit
}

# Enable (broadcast) WiFi device
startwifi(){
  /sbin/uci set wireless.radio0.disabled=0
  /sbin/uci commit
  /sbin/wifi
}

# Disable and re-enable (broadcast) WiFi device
restartwifi(){
  stopwifi
  startwifi
}

# Set power LED brightness
powerled(){
  echo $1 > /sys/devices/platform/leds-gpio/leds/gl-ar750:white:power/brightness
}

# Set second LED brightness
led2g(){
  echo $1 > /sys/devices/platform/leds-gpio/leds/gl-ar750:white:wlan2g/brightness
}

# Set third LED brightness
led5g(){
  echo $1 > /sys/devices/platform/leds-gpio/leds/gl-ar750:white:wlan5g/brightness
}

. /etc/vpnsecret # Source the server authentication secret

# Prepare for default VPN-WiFi bridge
/sbin/uci set wireless.@wifi-iface[0].network="VPN360"
/sbin/uci commit

# Disable WiFi for as long as there is no bridge providing IP addresses
stopwifi

# Turn off all LEDs
powerled 0
led2g 0
led5g 0

# Launch VPN client
/usr/sbin/openvpn /etc/openvpn/client.conf >/var/log/openvpn &

# Try for approx. 1 minute to get an IP from the VPN before falling back to DHCP
counter=0

while [ $counter -lt 60 ]
 do
   # Retrieve hosts file from server
   if /usr/bin/wget -O/etc/hosts https://$HOSTNAME/hosts --timeout=2 --post-data "secret=$SECRET" --no-check-certificate >/var/log/wget 2>&1
    then

     if pgrep "openvpn" >/dev/null
      then
       if [ $(ipaddr) ] # = If connection to the server is working
        then
         # Turn on LEDs indicating boot completion and connection success
         powerled 1
         led5g 1

         # Enable WiFi as the VPN bridge is now functional
         startwifi

         # Send a heartbeat to the server every 10 seconds
         # This is also used to transfer commands from the server to the device
         while [ True ]
          do
           /bin/sleep 10

           # Let's hope there is an IP address on the VPN interface
           # If not, this might be a temporary issue (lost network connection or lease expiration)
           # We assume that users will reboot the device if it doesn't work for extended periods of time
           if [ $(ipaddr) ]
            then
             /usr/bin/wget -O- https://$HOSTNAME/heartbeat --post-data "secret=$SECRET&ip=$(ipaddr)" --no-check-certificate 2>/var/log/wget | /bin/ash
           fi
          done

       fi
      else
       # Launch VPN client if not running
       /usr/sbin/openvpn /etc/openvpn/client.conf >/var/log/openvpn &
     fi
   fi
   counter=$(( counter + 1 ))
   powerled $(( counter % 2 ))
   /bin/sleep 1 # Wait for a second before re-trying
  done

# We should only ever get to this point if no VPN connection was established within a minute

# Switch WiFi device to the DHCP bridge
/sbin/uci set wireless.@wifi-iface[0].network="DHCP"
/sbin/uci commit

# Turn on LEDs indicating connection failure and DHCP fallback
powerled 1
led2g 1

# Start WiFi device now bridged to the DHCP and assign server IP
startwifi
/sbin/ip a add 192.168.36.1/24 dev br-DHCP
/sbin/ifconfig br-DHCP down
/sbin/ifconfig br-DHCP up

# Send a heartbeat to the server every 10 seconds
# This is also used to transfer commands from the server to the device
while [ True ]
 do
  sleep 10
  /usr/bin/wget -O- https://$HOSTNAME/heartbeat --post-data "secret=$SECRET" --no-check-certificate 2>/var/log/wget | /bin/ash
 done