#!/bin/ash

set -e

default_route_ip=$(ip route | grep default | awk '{print $3}')
if [[ -z "$default_route_ip" ]]; then
	echo "No default route configured" >&2
	exit 1
fi

configs=`find /etc/wireguard -type f -printf "%f\n"`
if [[ -z "$configs" ]]; then
	echo "No configuration file found in /etc/wireguard" >&2
	exit 1
fi

config=`echo $configs | head -n 1`
interface="${config%.*}"

if [[ "$(cat /proc/sys/net/ipv4/conf/all/src_valid_mark)" != "1" ]]; then
	echo "sysctl net.ipv4.conf.all.src_valid_mark=1 is not set" >&2
	exit 1
fi

# The net.ipv4.conf.all.src_valid_mark sysctl is set when running the container, so don't have WireGuard also set it
sed -i "s:sysctl -q net.ipv4.conf.all.src_valid_mark=1:echo Skipping setting net.ipv4.conf.all.src_valid_mark:" /usr/bin/wg-quick

# Start WireGuard
wg-quick up $interface

# IPv4 kill switch: traffic must be either (1) to the WireGuard interface, (2) marked as a WireGuard packet, (3) to a local address, or (4) to the container network
container_ipv4_network="$(ip -o addr show dev eth0 | awk '$3 == "inet" {print $4}')"
container_ipv4_network_rule=$([ ! -z "$container_ipv4_network" ] && echo "! -d $container_ipv4_network" || echo "")
iptables -I OUTPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
iptables -I OUTPUT ! -o $interface -m mark ! --mark $(wg show $interface fwmark) -m conntrack ! --ctstate ESTABLISHED,RELATED -m addrtype ! --dst-type LOCAL $container_ipv4_network_rule -j REJECT

# Get the default gateway for eth0
DEFAULT_GATEWAY=$(ip route show default | grep -o 'via [0-9.]*' | awk '{print $2}')

TABLE="custom"

mkdir -p /etc/iproute2
# Add to rt_tables
echo "200 $TABLE" | tee -a /etc/iproute2/rt_tables

# Add routing rule
ip rule add from $container_ipv4_network table $TABLE

# Add default route for this table
ip route add default via $DEFAULT_GATEWAY dev eth0 table $TABLE

echo "Routing rule and route added for $IP_ADDR with gateway $DEFAULT_GATEWAY"


# IPv6 kill switch: traffic must be either (1) to the WireGuard interface, (2) marked as a WireGuard packet, (3) to a local address, or (4) to the container network
container_ipv6_network="$(ip -o addr show dev eth0 | awk '$3 == "inet6" && $6 == "global" {print $4}')"
if [[ "$container_ipv6_network" ]]; then
	container_ipv6_network_rule=$([ ! -z "$container_ipv6_network" ] && echo "! -d $container_ipv6_network" || echo "")
	ip6tables -I OUTPUT ! -o $interface -m mark ! --mark $(wg show $interface fwmark) -m addrtype ! --dst-type LOCAL $container_ipv6_network_rule -j REJECT
else
	echo "IPv6 interface not found, skipping IPv6 kill switch" >&2
fi

# Allow traffic to local subnets
for local_subnet in ${LOCAL_SUBNETS//,/$IFS}
do
	echo "Allowing traffic to local subnet ${local_subnet}" >&2
	ip route add $local_subnet via $default_route_ip
	iptables -I OUTPUT -d $local_subnet -j ACCEPT
done

shutdown () {
	wg-quick down $interface
	exit 0
}

trap shutdown SIGTERM SIGINT SIGQUIT

sleep infinity &
wait $!