#!/bin/bash
#
# <https://forge.univention.org/bugzilla/show_bug.cgi?id=49837>
# <https://hutten.knut.univention.de/mediawiki/index.php/Philipp_memo/DHCP>
#
# shellcheck disable=SC2034

#set -e -u # -o pipefail
export LANG=C LC_ALL=C

main () {
	setup_ucs
	setup_interface 1
	main1="$main" guest1="$guest"
	setup_interface 2
	main2="$main" guest2="$guest"
	setup_dhcp 1
	subnet1="$subnet" gw1="$gw" host1="$host"
	setup_dhcp 2
	subnet2="$subnet" gw2="$gw" host2="$host"
	wait_dhcp_restart
	test_guest 1
	test_guest 2
	# bash -i
	teardown_dhcp 1
	teardown_dhcp 2
	teardown_interface 1
	teardown_interface 2
}


setup_ucs () {
	apt-get -qq install univention-dhcp ethtool

	if [ -z "${tmp:-}" ]
	then
		tmp=$(mktemp -d)
		# shellcheck disable=SC2064
		trap "rm -rf '$tmp'" EXIT
		lease="${tmp}/dhclient.lease"
		pid="${tmp}/pid"
	fi

	NET1='192.0.2'  # .0/24 # "TEST-NET-1"
	NET2='198.51.100'  # .0/24 # "TEST-NET-2"
}

setup_interface () {
	[ -e "/sys/class/net/veth${1}-main" ] && return
	ip link add name "veth${1}-main" type veth peer name "veth${1}-guest"
	main=$(<"/sys/class/net/veth${1}-main/address")
	[ -n "$main" ]
	guest=$(<"/sys/class/net/veth${1}-guest/address")
	[ -n "$guest" ]
	local NET="NET${1}"
	ip addr add "${!NET}.1/24" dev "veth${1}-main"
	ip link set "veth${1}-main" up

	ethtool -K "veth${1}-main" tx off >/dev/null
	ethtool -K "veth${1}-guest" tx off >/dev/null

	ip netns add "my-env${1}"
	ip link set dev "veth${1}-guest" netns "my-env${1}" name eth0
	ip netns exec "my-env${1}" ip addr flush eth0
	ip netns exec "my-env${1}" ip link set eth0 up
}

setup_dhcp () {
	service=$(udm dhcp/service list|DN1)
	[ -n "$service" ] || die service

	local NET="NET${1}"
	udm policies/dhcp_routing create --ignore_exists --set name="gw${1}" --set routers="${!NET}.0"
	gw=$(udm policies/dhcp_routing list --filter name="gw${1}"|DN1)

	udm dhcp/subnet create --ignore_exists --superordinate="$service" --set subnet="${!NET}.0" --set subnetmask="24" --policy-reference "$gw"
	subnet=$(udm dhcp/subnet list --superordinate="$service" --filter subnet="${!NET}.0"|DN1)
	[ -n "$subnet" ] || die subnet

	local guest="guest${1}"
	udm dhcp/host create --superordinate="$service" --set hwaddress="ethernet ${!guest}" --set host="${!guest}" --set fixedaddress="${!NET}.50"
	host=$(udm dhcp/host list --superordinate="$service" --filter host="${!guest}"|DN1)
	[ -n "$host" ] || die host
}

wait_dhcp_restart () {
	local i oldpid
	oldpid=$(</var/run/dhcpd.pid)
	for ((i=20;i>0;i+=-1))
	do
		sleep 1
		[ "$oldpid" -eq "$(</var/run/dhcpd.pid)" ] || break
		printf '%d ' "$i"
	done
	echo "dhcpd.pid: $oldpid -> $(</var/run/dhcpd.pid)"
}

test_guest () {
	local NET="NET${1}" host="host${1}"
	: >"$lease" 2>"$pid"
	ip netns exec "my-env${1}" dhclient -1 -pf "$pid" -sf /bin/true -lf "$lease" -q -4 eth0
	grep --color -F -e "  fixed-address ${!NET}.50" "$lease"
	grep --color -F -e "  option dhcp-server-identifier ${!NET}.1;" "$lease"
	grep --color -F -e "  option routers ${!NET}.0;" "$lease"
	ip netns exec "my-env${1}" dhclient -1 -pf "$pid" -sf /bin/true -lf "$lease" -q -r -4 eth0
	udm dhcp/host list --policies 0 --position "${!host}"
	echo
}


teardown_dhcp () {
	local subnet="subnet${1}"
	udm dhcp/subnet remove --superordinate "$service" --dn "${!subnet}"
	local host="host${1}"
	udm dhcp/host remove --superordinate "$service" --dn "${!host}"
	local gw="gw${1}"
	udm policies/dhcp_routing remove --dn "${!gw}"
}


teardown_interface () {
	ip link del dev "veth${1}-main"
	ip netns del "my-env${1}"
}


die () {
	echo "${0##*/}: $*" >&2
	exit 1
}
DN1 () {
	sed -ne 's/^DN: //p;T;q'
}
udm () {
	local module="$1" action="$2"
	shift 2
	/usr/sbin/udm "$module" "$action" "$@"
}

main "$@"