#!/bin/sh
set -eu

USE_LXC_BRIDGE="true"
LXC_BRIDGE="lxcbr0"
LXC_ADDR="10.0.3.1"
LXC_NETMASK="255.255.255.0"
LXC_NETWORK="10.0.3.0/24"
LXC_DHCP_RANGE="10.0.3.2,10.0.3.254"
LXC_DHCP_MAX="253"
LXC_DHCP_CONFILE=""
varrun="/run/lxc"
LXC_DOMAIN=""

start() {
	[ -f /etc/default/lxc ] && . /etc/default/lxc

	[ "x$USE_LXC_BRIDGE" = "xtrue" ] || { stop; exit 0; }

	use_iptables_lock="-w"
	iptables -w -L -n > /dev/null 2>&1 || use_iptables_lock=""
	cleanup() {
		# dnsmasq failed to start, clean up the bridge
		iptables $use_iptables_lock -D INPUT -i ${LXC_BRIDGE} -p udp --dport 67 -j ACCEPT
		iptables $use_iptables_lock -D INPUT -i ${LXC_BRIDGE} -p tcp --dport 67 -j ACCEPT
		iptables $use_iptables_lock -D INPUT -i ${LXC_BRIDGE} -p udp --dport 53 -j ACCEPT
		iptables $use_iptables_lock -D INPUT -i ${LXC_BRIDGE} -p tcp --dport 53 -j ACCEPT
		iptables $use_iptables_lock -D FORWARD -i ${LXC_BRIDGE} -j ACCEPT
		iptables $use_iptables_lock -D FORWARD -o ${LXC_BRIDGE} -j ACCEPT
		iptables $use_iptables_lock -t nat -D POSTROUTING -s ${LXC_NETWORK} ! -d ${LXC_NETWORK} -j MASQUERADE || true
		iptables $use_iptables_lock -t mangle -D POSTROUTING -o ${LXC_BRIDGE} -p udp -m udp --dport 68 -j CHECKSUM --checksum-fill
		ifconfig ${LXC_BRIDGE} down || true
		brctl delbr ${LXC_BRIDGE} || true
	}

	if [ -d /sys/class/net/${LXC_BRIDGE} ]; then
		if [ ! -f ${varrun}/network_up ]; then
			# bridge exists, but we didn't start it
			stop;
		fi
		exit 0;
	fi

	# set up the lxc network
	brctl addbr ${LXC_BRIDGE} || { echo "Missing bridge support in kernel"; stop; exit 0; }
	echo 1 > /proc/sys/net/ipv4/ip_forward
	mkdir -p ${varrun}
	ifconfig ${LXC_BRIDGE} ${LXC_ADDR} netmask ${LXC_NETMASK} up
	iptables $use_iptables_lock -I INPUT -i ${LXC_BRIDGE} -p udp --dport 67 -j ACCEPT
	iptables $use_iptables_lock -I INPUT -i ${LXC_BRIDGE} -p tcp --dport 67 -j ACCEPT
	iptables $use_iptables_lock -I INPUT -i ${LXC_BRIDGE} -p udp --dport 53 -j ACCEPT
	iptables $use_iptables_lock -I INPUT -i ${LXC_BRIDGE} -p tcp --dport 53 -j ACCEPT
	iptables $use_iptables_lock -I FORWARD -i ${LXC_BRIDGE} -j ACCEPT
	iptables $use_iptables_lock -I FORWARD -o ${LXC_BRIDGE} -j ACCEPT
	iptables $use_iptables_lock -t nat -A POSTROUTING -s ${LXC_NETWORK} ! -d ${LXC_NETWORK} -j MASQUERADE
	iptables $use_iptables_lock -t mangle -A POSTROUTING -o ${LXC_BRIDGE} -p udp -m udp --dport 68 -j CHECKSUM --checksum-fill

	LXC_DOMAIN_ARG=""
	if [ -n "$LXC_DOMAIN" ]; then
		LXC_DOMAIN_ARG="-s $LXC_DOMAIN -S /$LXC_DOMAIN/"
	fi
	dnsmasq $LXC_DOMAIN_ARG -u lxc-dnsmasq --strict-order --bind-interfaces --pid-file=${varrun}/dnsmasq.pid --conf-file=${LXC_DHCP_CONFILE} --listen-address ${LXC_ADDR} --dhcp-range ${LXC_DHCP_RANGE} --dhcp-lease-max=${LXC_DHCP_MAX} --dhcp-no-override --except-interface=lo --interface=${LXC_BRIDGE} --dhcp-leasefile=/var/lib/misc/dnsmasq.${LXC_BRIDGE}.leases --dhcp-authoritative || cleanup
	touch ${varrun}/network_up
}

stop() {
	[ -f /etc/default/lxc ] && . /etc/default/lxc
	[ -f "${varrun}/network_up" ] || exit 0;
	# if $LXC_BRIDGE has attached interfaces, don't shut it down
	ls /sys/class/net/${LXC_BRIDGE}/brif/* > /dev/null 2>&1 && exit 0;

	if [ -d /sys/class/net/${LXC_BRIDGE} ]; then
		use_iptables_lock="-w"
		iptables -w -L -n > /dev/null 2>&1 || use_iptables_lock=""
		ifconfig ${LXC_BRIDGE} down
		iptables $use_iptables_lock -D INPUT -i ${LXC_BRIDGE} -p udp --dport 67 -j ACCEPT
		iptables $use_iptables_lock -D INPUT -i ${LXC_BRIDGE} -p tcp --dport 67 -j ACCEPT
		iptables $use_iptables_lock -D INPUT -i ${LXC_BRIDGE} -p udp --dport 53 -j ACCEPT
		iptables $use_iptables_lock -D INPUT -i ${LXC_BRIDGE} -p tcp --dport 53 -j ACCEPT
		iptables $use_iptables_lock -D FORWARD -i ${LXC_BRIDGE} -j ACCEPT
		iptables $use_iptables_lock -D FORWARD -o ${LXC_BRIDGE} -j ACCEPT
		iptables $use_iptables_lock -t nat -D POSTROUTING -s ${LXC_NETWORK} ! -d ${LXC_NETWORK} -j MASQUERADE || true
		iptables $use_iptables_lock -t mangle -D POSTROUTING -o ${LXC_BRIDGE} -p udp -m udp --dport 68 -j CHECKSUM --checksum-fill
		pid=`cat ${varrun}/dnsmasq.pid 2>/dev/null` && kill -9 $pid || true
		rm -f ${varrun}/dnsmasq.pid
		brctl delbr ${LXC_BRIDGE}
	fi
	rm -f ${varrun}/network_up
}

if [ "$1" = start ]; then
    start
elif [ "$1" = stop ]; then
    stop
else
    echo "Usage: $0 start|stop" >&2
    exit 1
fi