GRE Tunnel mit dynamischer IP-Adresse

"/etc/network/interfaces"

auto tun1
iface tun1 inet6 static
       address 2001:67c:75c::1
       netmask 48

       pre-up ip tunnel add tun1 mode gre remote 123.123.123.123 local 185.37.145.80 ttl 255
       post-up /root/gre-updater.sh tun1 example.dyndns.org 185.37.145.80

"/root/gre-updater.sh"

#!/bin/bash
 
tunnel_if="$1"
tunnel_ext_host="$2"
tunnel_int_host="$3"

if (( $# == 3 ))
then
       tunnel_home_old=`ip tunnel show | grep $tunnel_if | awk '/remote/ {split ($4,A," "); print A[1]}'`
       tunnel_home_new=`nslookup $tunnel_ext_host | awk -F ': ' 'NR==6 { print $2 } '`

       if [ ! "$tunnel_home_old" = "$tunnel_home_new" ] ; then
               ip tunnel change $tunnel_if mode gre remote $tunnel_home_new local $tunnel_int_host ttl 255
               echo "Remote IP updated"
       else
               echo "Remote IP is correct"
       fi
else
       echo usage:  gre-updater.sh tun1 example.dyndns.org 123.123.123.123
fi

"/etc/crontab"

Prüft alle 5 Minuten, ob die IP-Adresse noch stimmt und passt diese ggf. an.

*/5 *   * * *   root    /root/gre-updater.sh tun1 example.dyndns.org 185.37.145.80 > /dev/null