check for IPv6 connectivity

ipv6.sh

#!/bin/bash
# Check for IPv6 Connectivity by looking for a IPv6 address


function check_ipv6() {
        # Lets see if we got an IPv6, which in return means that we're live
        IPv6=`curl -6 -s https://wtfismyip.com/text`
        if [ $IPv6 ]
        then
                # OK IPv6 was found, return code 0 - OK
                echo "OK - IPv6 connection ESTABLISHED. IP: $IPv6"
                exit 0
        else
                # Error: IPv6 was not found, return code 2 - critical
                echo "CRITICAL - no IPv6 connection ESTABLISHED. Output: $IPv6"
                exit 1
        fi
}
check_ipv6
eof

ipv6check.service

[Unit]
Description=IPv6 connectivity check
After=network-online.target

[Service]
ExecStart=/usr/local/bin/ipv6.sh

RestartSec=5
Restart=always

[Install]
WantedBy=multi-user.target