This fix does not working and the bug still exists. There is a race condition between the `ip route show` check and the `/bin/ip route add` command, and systemd will launch multiple `ifup` concurrently.
Maybe the failure of `/etc/network/if-up.d/avahi-autoipd` should be ignored to avoid causing problem to ifup/ifdown.
FYI, one can recover from this problem by executing `ip addr flush dev xxx`
This fix does not working and the bug still exists. There is a race condition between the `ip route show` check and the `/bin/ip route add` command, and systemd will launch multiple `ifup` concurrently. if-up.d/ avahi-autoipd` should be ignored to avoid causing problem to ifup/ifdown.
Maybe the failure of `/etc/network/
FYI, one can recover from this problem by executing `ip addr flush dev xxx`