COMMAND=/usr/bin/chronyc
CHRONY_KEY=$(awk '/^1 / { print $2; }' /etc/chrony/chrony.keys)

chrony_control() {
$COMMAND << EOF
password $CHRONY_KEY
$1
EOF
}

[ "$ACTION" = "ifup" -a "$INTERFACE" = "wan" ] && {
        [ -x $COMMAND ] && [ -n "$CHRONY_KEY" ] &&{
            chrony_control online
        }
}

[ "$ACTION" = "ifdown" -a "$INTERFACE" = "wan" ] && {
        [ -x $COMMAND ] && [ -n "$CHRONY_KEY" ] &&{
            chrony_control offline
        }
}