#!/bin/sh
# Ensure that NTP servers obtained from DHCP are made available to chronyd and
# that they are removed when releasing the DHCP lease.

set -e

added_servers="/run/chrony-helper/added_servers"

prepare_iface() {
    modprobe dummy
    ip link add name dummy0 type dummy
    ip address add 192.168.1.1/24 dev dummy0
    ip link set dev dummy0 up
}

dhcpd_config() {
cat <<EOF > /etc/dhcp/dhcpd.conf
default-lease-time 600;
max-lease-time 7200;
authorative;

subnet 192.168.1.0 netmask 255.255.255.0 {
    option subnet-mask              255.255.255.0;
    option broadcast-address        192.168.1.255;
    option ntp-servers              192.168.1.50;
    range 192.168.1.42 192.168.1.100;
}
EOF

sed -i 's/INTERFACESv4=""/INTERFACESv4="dummy0"/' /etc/default/isc-dhcp-server
}

printf "Preparing the dummy network interface and dhcpd configuration…\n"
if prepare_iface && dhcpd_config; then
    systemctl restart isc-dhcp-server && dhclient dummy0 && printf "Done!\n\n"
fi

printf "Check if the NTP server is made available to chronyd…\n"
grep -q 192.168.1.50 $added_servers && printf "SUCCESS!\n\n"

printf "Release the current lease and check if the NTP server has been correctly removed…\n"
dhclient -r dummy0 > /dev/null 2>&1 && [ ! -d "$added_servers" ] && printf "SUCCESS!\n\n"