networkd-dispatcher bash script to set all IPv6 addresses to preferred_lft 0

50-set-preferred-lft

#!/bin/bash

# bash v4 required because of associative array below.

# networkd-dispatcher hook script that sets every IPv6 address on the system to
# have preferred_lft 0. Put it in for example in
# /etc/networkd-dispatcher/routable.d/50-set-preferred-lft and make sure it's
# executable and owned by root:root.
#
# There's an associative array below where you can list addresses NOT to
# interfere with.

logname="set-preferred-lft"

declare -A exceptions

# Associative array with keys for each address that you DON'T want to have
# a preferred_lft of 0. Every other v6 address on the system will have
# preferred_lft 0 set.
exceptions["2001:ba8:1f1:f1d7::2"]="1"

logger -t $logname \
        "$IFACE/$STATE: Looking for IPv6 addresses to set preferred_lft 0…"

for ip6 in $IP6_ADDRS
do
        if [[ -n "${exceptions[$ip6]}" ]]
        then
                logger -t $logname \
                "Not setting preferred_lft for $ip6 as it's in exception list"
        else
                logger -t $logname \
                "Setting preferred_lft 0 for $ip6"
                ip address change ${ip6} dev ${IFACE} preferred_lft 0
        fi
done

logger -t $logname \
        "$IFACE/$STATE: Done."