Workaround for Raspberry Pi automatic WiFi/WLAN reconnect

My old Raspberry Pi Zero W sometimes had problems restoring the WiFi connection when the AP was rebooted or reprovisioned. I don't know why Rasbian can't do this, but this workaround is my solution: I created a script that continuously tests the connection to the local gateway. If the gateway cannot be reached, the WiFi interface is restarted.

• Add the following line to /etc/crontab:

*/1    *    * * *    root    /usr/local/bin/wifi_reconnect.sh
#

• Create bash script /usr/local/bin/wifi_reconnect.sh with this content:

!/bin/bash

#echo "Script runned @ $(date)" >>/var/log/wifi_reconnect 

# The IP for the server you wish to ping (get default getway)
SERVER=$(/sbin/ip route | awk '/default/ { print $3 }')

#echo "> Server: ${SERVER}" >>/var/log/wifi_reconnect 

# Specify wlan interface
WLANINTERFACE=wlan0

#echo "> WLAN Interface: ${WLANINTERFACE}" >>/var/log/wifi_reconnect

# Only send two pings, sending output to /dev/null
ping -I ${WLANINTERFACE} -c2 ${SERVER} >/dev/null 

# If the return code from ping ($?) is not 0 (meaning there was an error)
if [ $? != 0 ]
then
echo "> WiFi doenst work. Restart!" >>/var/log/wifi_reconnect 
# Restart the wireless interface
ip link set wlan0 down
ip link set wlan0 up
#else
#echo "> WiFi works. No restart" >>/var/log/wifi_reconnect
fi 

I added some "echo to file" lines. Remove the # to log what the script does.