--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/openvpn-install.sh	Sun Sep 01 16:38:41 2024 +0800
@@ -0,0 +1,1101 @@
+#!/bin/bash
+#
+# https://github.com/hwdsl2/openvpn-install
+#
+# Based on the work of Nyr and contributors at:
+# https://github.com/Nyr/openvpn-install
+#
+# Copyright (c) 2022-2024 Lin Song <linsongui@gmail.com>
+# Copyright (c) 2013-2023 Nyr
+#
+# Released under the MIT License, see the accompanying file LICENSE.txt
+# or https://opensource.org/licenses/MIT
+
+exiterr()  { echo "Error: $1" >&2; exit 1; }
+exiterr2() { exiterr "'apt-get install' failed."; }
+exiterr3() { exiterr "'yum install' failed."; }
+exiterr4() { exiterr "'zypper install' failed."; }
+
+check_ip() {
+	IP_REGEX='^(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])$'
+	printf '%s' "$1" | tr -d '\n' | grep -Eq "$IP_REGEX"
+}
+
+check_os() {
+	if grep -qs "ubuntu" /etc/os-release; then
+		os="ubuntu"
+		os_version=$(grep 'VERSION_ID' /etc/os-release | cut -d '"' -f 2 | tr -d '.')
+		group_name="nogroup"
+	elif [[ -e /etc/debian_version ]]; then
+		os="debian"
+		os_version=$(grep -oE '[0-9]+' /etc/debian_version | head -1)
+		group_name="nogroup"
+	elif [[ -e /etc/almalinux-release || -e /etc/rocky-release || -e /etc/centos-release ]]; then
+		os="centos"
+		os_version=$(grep -shoE '[0-9]+' /etc/almalinux-release /etc/rocky-release /etc/centos-release | head -1)
+		group_name="nobody"
+	elif grep -qs "Amazon Linux release 2 " /etc/system-release; then
+		os="centos"
+		os_version="7"
+		group_name="nobody"
+	elif grep -qs "Amazon Linux release 2023" /etc/system-release; then
+		exiterr "Amazon Linux 2023 is not supported."
+	elif [[ -e /etc/fedora-release ]]; then
+		os="fedora"
+		os_version=$(grep -oE '[0-9]+' /etc/fedora-release | head -1)
+		group_name="nobody"
+	elif [[ -e /etc/SUSE-brand && "$(head -1 /etc/SUSE-brand)" == "openSUSE" ]]; then
+		os="openSUSE"
+		os_version=$(tail -1 /etc/SUSE-brand | grep -oE '[0-9\\.]+')
+		group_name="nogroup"
+	else
+		exiterr "This installer seems to be running on an unsupported distribution.
+Supported distros are Ubuntu, Debian, AlmaLinux, Rocky Linux, CentOS, Fedora, openSUSE and Amazon Linux 2."
+	fi
+}
+
+check_os_ver() {
+	if [[ "$os" == "ubuntu" && "$os_version" -lt 1804 ]]; then
+		exiterr "Ubuntu 18.04 or higher is required to use this installer.
+This version of Ubuntu is too old and unsupported."
+	fi
+
+	if [[ "$os" == "debian" && "$os_version" -lt 9 ]]; then
+		exiterr "Debian 9 or higher is required to use this installer.
+This version of Debian is too old and unsupported."
+	fi
+
+	if [[ "$os" == "centos" && "$os_version" -lt 7 ]]; then
+		exiterr "CentOS 7 or higher is required to use this installer.
+This version of CentOS is too old and unsupported."
+	fi
+}
+
+check_nftables() {
+	if [ "$os" = "centos" ]; then
+		if grep -qs "hwdsl2 VPN script" /etc/sysconfig/nftables.conf \
+			|| systemctl is-active --quiet nftables 2>/dev/null; then
+			exiterr "This system has nftables enabled, which is not supported by this installer."
+		fi
+	fi
+}
+
+check_dns_name() {
+	FQDN_REGEX='^([a-zA-Z0-9]([a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?\.)+[a-zA-Z]{2,}$'
+	printf '%s' "$1" | tr -d '\n' | grep -Eq "$FQDN_REGEX"
+}
+
+install_wget() {
+	# Detect some Debian minimal setups where neither wget nor curl are installed
+	if ! hash wget 2>/dev/null && ! hash curl 2>/dev/null; then
+		if [ "$auto" = 0 ]; then
+			echo "Wget is required to use this installer."
+			read -n1 -r -p "Press any key to install Wget and continue..."
+		fi
+		export DEBIAN_FRONTEND=noninteractive
+		(
+			set -x
+			apt-get -yqq update || apt-get -yqq update
+			apt-get -yqq install wget >/dev/null
+		) || exiterr2
+	fi
+}
+
+install_iproute() {
+	if ! hash ip 2>/dev/null; then
+		if [ "$auto" = 0 ]; then
+			echo "iproute is required to use this installer."
+			read -n1 -r -p "Press any key to install iproute and continue..."
+		fi
+		if [ "$os" = "debian" ] || [ "$os" = "ubuntu" ]; then
+			export DEBIAN_FRONTEND=noninteractive
+			(
+				set -x
+				apt-get -yqq update || apt-get -yqq update
+				apt-get -yqq install iproute2 >/dev/null
+			) || exiterr2
+		elif [ "$os" = "openSUSE" ]; then
+			(
+				set -x
+				zypper install iproute2 >/dev/null
+			) || exiterr4
+		else
+			(
+				set -x
+				yum -y -q install iproute >/dev/null
+			) || exiterr3
+		fi
+	fi
+}
+
+show_start_setup() {
+	if [ "$auto" = 0 ]; then
+		echo
+		echo 'Welcome to this OpenVPN server installer!'
+		echo 'GitHub: https://github.com/hwdsl2/openvpn-install'
+		echo
+		echo 'I need to ask you a few questions before starting setup.'
+		echo 'You can use the default options and just press enter if you are OK with them.'
+	else
+		show_header
+		echo
+		echo 'Starting OpenVPN setup using default options.'
+	fi
+}
+
+enter_server_address() {
+	echo
+	echo "Do you want OpenVPN clients to connect to this server using a DNS name,"
+	printf "e.g. vpn.example.com, instead of its IP address? [y/N] "
+	read -r response
+	case $response in
+		[yY][eE][sS]|[yY])
+			use_dns_name=1
+			echo
+			;;
+		*)
+			use_dns_name=0
+			;;
+	esac
+	if [ "$use_dns_name" = 1 ]; then
+		read -rp "Enter the DNS name of this VPN server: " server_addr
+		until check_dns_name "$server_addr"; do
+			echo "Invalid DNS name. You must enter a fully qualified domain name (FQDN)."
+			read -rp "Enter the DNS name of this VPN server: " server_addr
+		done
+		ip="$server_addr"
+		echo
+		echo "Note: Make sure this DNS name resolves to the IPv4 address"
+		echo "      of this server. If you add or update the DNS record"
+		echo "      at a later time, reboot this server to take effect."
+	else
+		detect_ip
+		check_nat_ip
+	fi
+}
+
+find_public_ip() {
+	ip_url1="http://ipv4.icanhazip.com"
+	ip_url2="http://ip1.dynupdate.no-ip.com"
+	# Get public IP and sanitize with grep
+	get_public_ip=$(grep -m 1 -oE '^[0-9]{1,3}(\.[0-9]{1,3}){3}$' <<< "$(wget -T 10 -t 1 -4qO- "$ip_url1" || curl -m 10 -4Ls "$ip_url1")")
+	if ! check_ip "$get_public_ip"; then
+		get_public_ip=$(grep -m 1 -oE '^[0-9]{1,3}(\.[0-9]{1,3}){3}$' <<< "$(wget -T 10 -t 1 -4qO- "$ip_url2" || curl -m 10 -4Ls "$ip_url2")")
+	fi
+}
+
+detect_ip() {
+	# If system has a single IPv4, it is selected automatically.
+	if [[ $(ip -4 addr | grep inet | grep -vEc '127(\.[0-9]{1,3}){3}') -eq 1 ]]; then
+		ip=$(ip -4 addr | grep inet | grep -vE '127(\.[0-9]{1,3}){3}' | cut -d '/' -f 1 | grep -oE '[0-9]{1,3}(\.[0-9]{1,3}){3}')
+	else
+		# Use the IP address on the default route
+		ip=$(ip -4 route get 1 | sed 's/ uid .*//' | awk '{print $NF;exit}' 2>/dev/null)
+		if ! check_ip "$ip"; then
+			find_public_ip
+			ip_match=0
+			if [ -n "$get_public_ip" ]; then
+				ip_list=$(ip -4 addr | grep inet | grep -vE '127(\.[0-9]{1,3}){3}' | cut -d '/' -f 1 | grep -oE '[0-9]{1,3}(\.[0-9]{1,3}){3}')
+				while IFS= read -r line; do
+					if [ "$line" = "$get_public_ip" ]; then
+						ip_match=1
+						ip="$line"
+					fi
+				done <<< "$ip_list"
+			fi
+			if [ "$ip_match" = 0 ]; then
+				if [ "$auto" = 0 ]; then
+					echo
+					echo "Which IPv4 address should be used?"
+					num_of_ip=$(ip -4 addr | grep inet | grep -vEc '127(\.[0-9]{1,3}){3}')
+					ip -4 addr | grep inet | grep -vE '127(\.[0-9]{1,3}){3}' | cut -d '/' -f 1 | grep -oE '[0-9]{1,3}(\.[0-9]{1,3}){3}' | nl -s ') '
+					read -rp "IPv4 address [1]: " ip_num
+					until [[ -z "$ip_num" || "$ip_num" =~ ^[0-9]+$ && "$ip_num" -le "$num_of_ip" ]]; do
+						echo "$ip_num: invalid selection."
+						read -rp "IPv4 address [1]: " ip_num
+					done
+					[[ -z "$ip_num" ]] && ip_num=1
+				else
+					ip_num=1
+				fi
+				ip=$(ip -4 addr | grep inet | grep -vE '127(\.[0-9]{1,3}){3}' | cut -d '/' -f 1 | grep -oE '[0-9]{1,3}(\.[0-9]{1,3}){3}' | sed -n "$ip_num"p)
+			fi
+		fi
+	fi
+	if ! check_ip "$ip"; then
+		echo "Error: Could not detect this server's IP address." >&2
+		echo "Abort. No changes were made." >&2
+		exit 1
+	fi
+}
+
+check_nat_ip() {
+	# If $ip is a private IP address, the server must be behind NAT
+	if printf '%s' "$ip" | grep -qE '^(10|127|172\.(1[6-9]|2[0-9]|3[0-1])|192\.168|169\.254)\.'; then
+		find_public_ip
+		if ! check_ip "$get_public_ip"; then
+			if [ "$auto" = 0 ]; then
+				echo
+				echo "This server is behind NAT. What is the public IPv4 address?"
+				read -rp "Public IPv4 address: " public_ip
+				until check_ip "$public_ip"; do
+					echo "Invalid input."
+					read -rp "Public IPv4 address: " public_ip
+				done
+			else
+				echo "Error: Could not detect this server's public IP." >&2
+				echo "Abort. No changes were made." >&2
+				exit 1
+			fi
+		else
+			public_ip="$get_public_ip"
+		fi
+	fi
+}
+
+show_config() {
+	if [ "$auto" != 0 ]; then
+		echo
+		printf '%s' "Server IP: "
+		[ -n "$public_ip" ] && printf '%s\n' "$public_ip" || printf '%s\n' "$ip"
+		echo "Port: UDP/1194"
+		echo "Client name: client"
+		echo "Client DNS: Google Public DNS"
+	fi
+}
+
+detect_ipv6() {
+	ip6=""
+	if [[ $(ip -6 addr | grep -c 'inet6 [23]') -ne 0 ]]; then
+		ip6=$(ip -6 addr | grep 'inet6 [23]' | cut -d '/' -f 1 | grep -oE '([0-9a-fA-F]{0,4}:){1,7}[0-9a-fA-F]{0,4}' | sed -n 1p)
+	fi
+}
+
+select_protocol() {
+	if [ "$auto" = 0 ]; then
+		echo
+		echo "Which protocol should OpenVPN use?"
+		echo "   1) UDP (recommended)"
+		echo "   2) TCP"
+		read -rp "Protocol [1]: " protocol
+		until [[ -z "$protocol" || "$protocol" =~ ^[12]$ ]]; do
+			echo "$protocol: invalid selection."
+			read -rp "Protocol [1]: " protocol
+		done
+	else
+		protocol=1
+	fi
+	case "$protocol" in
+		1|"")
+		protocol=udp
+		;;
+		2)
+		protocol=tcp
+		;;
+	esac
+}
+
+select_port() {
+	if [ "$auto" = 0 ]; then
+		echo
+		echo "Which port should OpenVPN listen to?"
+		read -rp "Port [1194]: " port
+		until [[ -z "$port" || "$port" =~ ^[0-9]+$ && "$port" -le 65535 ]]; do
+			echo "$port: invalid port."
+			read -rp "Port [1194]: " port
+		done
+		[[ -z "$port" ]] && port=1194
+	else
+		port=1194
+	fi
+}
+
+enter_custom_dns() {
+	read -rp "Enter primary DNS server: " dns1
+	until check_ip "$dns1"; do
+		echo "Invalid DNS server."
+		read -rp "Enter primary DNS server: " dns1
+	done
+	read -rp "Enter secondary DNS server (Enter to skip): " dns2
+	until [ -z "$dns2" ] || check_ip "$dns2"; do
+		echo "Invalid DNS server."
+		read -rp "Enter secondary DNS server (Enter to skip): " dns2
+	done
+}
+
+select_dns() {
+	if [ "$auto" = 0 ]; then
+		echo
+		echo "Select a DNS server for the clients:"
+		echo "   1) Current system resolvers"
+		echo "   2) Google Public DNS"
+		echo "   3) Cloudflare DNS"
+		echo "   4) OpenDNS"
+		echo "   5) Quad9"
+		echo "   6) AdGuard DNS"
+		echo "   7) Custom"
+		read -rp "DNS server [2]: " dns
+		until [[ -z "$dns" || "$dns" =~ ^[1-7]$ ]]; do
+			echo "$dns: invalid selection."
+			read -rp "DNS server [2]: " dns
+		done
+	else
+		dns=2
+	fi
+	if [ "$dns" = 7 ]; then
+		enter_custom_dns
+	fi
+}
+
+set_client_name() {
+	# Allow a limited set of characters to avoid conflicts
+	client=$(sed 's/[^0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-]/_/g' <<< "$unsanitized_client")
+}
+
+enter_client_name() {
+	if [ "$auto" = 0 ]; then
+		echo
+		echo "Enter a name for the first client:"
+		read -rp "Name [client]: " unsanitized_client
+		set_client_name
+		[[ -z "$client" ]] && client=client
+	else
+		client=client
+	fi
+}
+
+check_firewall() {
+	# Install a firewall if firewalld or iptables are not already available
+	if ! systemctl is-active --quiet firewalld.service && ! hash iptables 2>/dev/null; then
+		if [[ "$os" == "centos" || "$os" == "fedora" ]]; then
+			firewall="firewalld"
+		elif [[ "$os" == "openSUSE" ]]; then
+			firewall="firewalld"
+		elif [[ "$os" == "debian" || "$os" == "ubuntu" ]]; then
+			firewall="iptables"
+		fi
+		if [[ "$firewall" == "firewalld" ]]; then
+			# We don't want to silently enable firewalld, so we give a subtle warning
+			# If the user continues, firewalld will be installed and enabled during setup
+			echo
+			echo "Note: firewalld, which is required to manage routing tables, will also be installed."
+		fi
+	fi
+}
+
+abort_and_exit() {
+	echo "Abort. No changes were made." >&2
+	exit 1
+}
+
+confirm_setup() {
+	if [ "$auto" = 0 ]; then
+		printf "Do you want to continue? [Y/n] "
+		read -r response
+		case $response in
+			[yY][eE][sS]|[yY]|'')
+				:
+				;;
+			*)
+				abort_and_exit
+				;;
+		esac
+	fi
+}
+
+get_export_dir() {
+	export_to_home_dir=0
+	export_dir=~/
+	if [ -n "$SUDO_USER" ] && getent group "$SUDO_USER" >/dev/null 2>&1; then
+		user_home_dir=$(getent passwd "$SUDO_USER" 2>/dev/null | cut -d: -f6)
+		if [ -d "$user_home_dir" ] && [ "$user_home_dir" != "/" ]; then
+			export_dir="$user_home_dir/"
+			export_to_home_dir=1
+		fi
+	fi
+}
+
+new_client() {
+	get_export_dir
+	# Generates the custom client.ovpn
+	{
+	cat /etc/openvpn/server/client-common.txt
+	echo "<ca>"
+	cat /etc/openvpn/server/easy-rsa/pki/ca.crt
+	echo "</ca>"
+	echo "<cert>"
+	sed -ne '/BEGIN CERTIFICATE/,$ p' /etc/openvpn/server/easy-rsa/pki/issued/"$client".crt
+	echo "</cert>"
+	echo "<key>"
+	cat /etc/openvpn/server/easy-rsa/pki/private/"$client".key
+	echo "</key>"
+	echo "<tls-crypt>"
+	sed -ne '/BEGIN OpenVPN Static key/,$ p' /etc/openvpn/server/tc.key
+	echo "</tls-crypt>"
+	} > "$export_dir$client".ovpn
+	if [ "$export_to_home_dir" = 1 ]; then
+		chown "$SUDO_USER:$SUDO_USER" "$export_dir$client".ovpn
+	fi
+	chmod 600 "$export_dir$client".ovpn
+}
+
+update_sysctl() {
+	mkdir -p /etc/sysctl.d
+	conf_fwd="/etc/sysctl.d/99-openvpn-forward.conf"
+	conf_opt="/etc/sysctl.d/99-openvpn-optimize.conf"
+	# Enable net.ipv4.ip_forward for the system
+	echo 'net.ipv4.ip_forward=1' > "$conf_fwd"
+	if [[ -n "$ip6" ]]; then
+		# Enable net.ipv6.conf.all.forwarding for the system
+		echo "net.ipv6.conf.all.forwarding=1" >> "$conf_fwd"
+	fi
+	# Optimize sysctl settings such as TCP buffer sizes
+	base_url="https://github.com/hwdsl2/vpn-extras/releases/download/v1.0.0"
+	conf_url="$base_url/sysctl-ovpn-$os"
+	[ "$auto" != 0 ] && conf_url="${conf_url}-auto"
+	wget -t 3 -T 30 -q -O "$conf_opt" "$conf_url" 2>/dev/null \
+		|| curl -m 30 -fsL "$conf_url" -o "$conf_opt" 2>/dev/null \
+		|| { /bin/rm -f "$conf_opt"; touch "$conf_opt"; }
+	# Enable TCP BBR congestion control if kernel version >= 4.20
+	if modprobe -q tcp_bbr \
+		&& printf '%s\n%s' "4.20" "$(uname -r)" | sort -C -V \
+		&& [ -f /proc/sys/net/ipv4/tcp_congestion_control ]; then
+cat >> "$conf_opt" <<'EOF'
+net.core.default_qdisc = fq
+net.ipv4.tcp_congestion_control = bbr
+EOF
+	fi
+	# Apply sysctl settings
+	sysctl -e -q -p "$conf_fwd"
+	sysctl -e -q -p "$conf_opt"
+}
+
+update_rclocal() {
+	ipt_cmd="systemctl restart openvpn-iptables.service"
+	if ! grep -qs "$ipt_cmd" /etc/rc.local; then
+		if [ ! -f /etc/rc.local ]; then
+			echo '#!/bin/sh' > /etc/rc.local
+		else
+			if [ "$os" = "ubuntu" ] || [ "$os" = "debian" ]; then
+				sed --follow-symlinks -i '/^exit 0/d' /etc/rc.local
+			fi
+		fi
+cat >> /etc/rc.local <<EOF
+
+$ipt_cmd
+EOF
+		if [ "$os" = "ubuntu" ] || [ "$os" = "debian" ]; then
+			echo "exit 0" >> /etc/rc.local
+		fi
+		chmod +x /etc/rc.local
+	fi
+}
+
+show_header() {
+cat <<'EOF'
+
+OpenVPN Script
+https://github.com/hwdsl2/openvpn-install
+EOF
+}
+
+show_header2() {
+cat <<'EOF'
+
+Copyright (c) 2022-2024 Lin Song
+Copyright (c) 2013-2023 Nyr
+EOF
+}
+
+show_usage() {
+	if [ -n "$1" ]; then
+		echo "Error: $1" >&2
+	fi
+	show_header
+	show_header2
+cat 1>&2 <<EOF
+
+Usage: bash $0 [options]
+
+Options:
+  --auto      auto install OpenVPN using default options
+  -h, --help  show this help message and exit
+
+To customize install options, run this script without arguments.
+EOF
+	exit 1
+}
+
+ovpnsetup() {
+
+export PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
+
+if [ "$(id -u)" != 0 ]; then
+	exiterr "This installer must be run as root. Try 'sudo bash $0'"
+fi
+
+# Detect Debian users running the script with "sh" instead of bash
+if readlink /proc/$$/exe | grep -q "dash"; then
+	exiterr 'This installer needs to be run with "bash", not "sh".'
+fi
+
+# Detect OpenVZ 6
+if [[ $(uname -r | cut -d "." -f 1) -eq 2 ]]; then
+	exiterr "The system is running an old kernel, which is incompatible with this installer."
+fi
+
+check_os
+check_os_ver
+
+if [[ ! -e /dev/net/tun ]] || ! ( exec 7<>/dev/net/tun ) 2>/dev/null; then
+	exiterr "The system does not have the TUN device available.
+TUN needs to be enabled before running this installer."
+fi
+
+auto=0
+if [[ ! -e /etc/openvpn/server/server.conf ]]; then
+	check_nftables
+	while [ "$#" -gt 0 ]; do
+		case $1 in
+			--auto)
+				auto=1
+				shift
+				;;
+			-h|--help)
+				show_usage
+				;;
+			*)
+				show_usage "Unknown parameter: $1"
+				;;
+		esac
+	done
+	install_wget
+	install_iproute
+	show_start_setup
+	public_ip=""
+	if [ "$auto" = 0 ]; then
+		enter_server_address
+	else
+		detect_ip
+		check_nat_ip
+	fi
+	show_config
+	detect_ipv6
+	select_protocol
+	select_port
+	select_dns
+	enter_client_name
+	if [ "$auto" = 0 ]; then
+		echo
+		echo "OpenVPN installation is ready to begin."
+	fi
+	check_firewall
+	confirm_setup
+	echo
+	echo "Installing OpenVPN, please wait..."
+	# If running inside a container, disable LimitNPROC to prevent conflicts
+	if systemd-detect-virt -cq; then
+		mkdir /etc/systemd/system/openvpn-server@server.service.d/ 2>/dev/null
+		echo "[Service]
+LimitNPROC=infinity" > /etc/systemd/system/openvpn-server@server.service.d/disable-limitnproc.conf
+	fi
+	if [[ "$os" = "debian" || "$os" = "ubuntu" ]]; then
+		export DEBIAN_FRONTEND=noninteractive
+		(
+			set -x
+			apt-get -yqq update || apt-get -yqq update
+			apt-get -yqq --no-install-recommends install openvpn >/dev/null
+		) || exiterr2
+		(
+			set -x
+			apt-get -yqq install openssl ca-certificates $firewall >/dev/null
+		) || exiterr2
+	elif [[ "$os" = "centos" ]]; then
+		if grep -qs "Amazon Linux release 2 " /etc/system-release; then
+			(
+				set -x
+				amazon-linux-extras install epel -y >/dev/null
+			) || exit 1
+		else
+			(
+				set -x
+				yum -y -q install epel-release >/dev/null
+			) || exiterr3
+		fi
+		(
+			set -x
+			yum -y -q install openvpn openssl ca-certificates tar $firewall >/dev/null 2>&1
+		) || exiterr3
+	elif [[ "$os" = "fedora" ]]; then
+		(
+			set -x
+			dnf install -y openvpn openssl ca-certificates tar $firewall >/dev/null
+		) || exiterr "'dnf install' failed."
+	else
+		# Else, OS must be openSUSE
+		(
+			set -x
+			zypper install -y openvpn openssl ca-certificates tar $firewall >/dev/null
+		) || exiterr4
+	fi
+	# If firewalld was just installed, enable it
+	if [[ "$firewall" == "firewalld" ]]; then
+		(
+			set -x
+			systemctl enable --now firewalld.service >/dev/null 2>&1
+		)
+	fi
+	# Get easy-rsa
+	easy_rsa_url='https://github.com/OpenVPN/easy-rsa/releases/download/v3.1.7/EasyRSA-3.1.7.tgz'
+	mkdir -p /etc/openvpn/server/easy-rsa/
+	{ wget -t 3 -T 30 -qO- "$easy_rsa_url" 2>/dev/null || curl -m 30 -sL "$easy_rsa_url" ; } | tar xz -C /etc/openvpn/server/easy-rsa/ --strip-components 1
+	if [ ! -f /etc/openvpn/server/easy-rsa/easyrsa ]; then
+		exiterr "Failed to download EasyRSA from $easy_rsa_url."
+	fi
+	chown -R root:root /etc/openvpn/server/easy-rsa/
+	cd /etc/openvpn/server/easy-rsa/ || exit 1
+	(
+		set -x
+		# Create the PKI, set up the CA and the server and client certificates
+		./easyrsa --batch init-pki >/dev/null
+		./easyrsa --batch build-ca nopass >/dev/null 2>&1
+		./easyrsa --batch --days=3650 build-server-full server nopass >/dev/null 2>&1
+		./easyrsa --batch --days=3650 build-client-full "$client" nopass >/dev/null 2>&1
+		./easyrsa --batch --days=3650 gen-crl >/dev/null 2>&1
+	)
+	# Move the stuff we need
+	cp pki/ca.crt pki/private/ca.key pki/issued/server.crt pki/private/server.key pki/crl.pem /etc/openvpn/server
+	# CRL is read with each client connection, while OpenVPN is dropped to nobody
+	chown nobody:"$group_name" /etc/openvpn/server/crl.pem
+	# Without +x in the directory, OpenVPN can't run a stat() on the CRL file
+	chmod o+x /etc/openvpn/server/
+	(
+		set -x
+		# Generate key for tls-crypt
+		openvpn --genkey --secret /etc/openvpn/server/tc.key >/dev/null
+	)
+	# Create the DH parameters file using the predefined ffdhe2048 group
+	echo '-----BEGIN DH PARAMETERS-----
+MIIBCAKCAQEA//////////+t+FRYortKmq/cViAnPTzx2LnFg84tNpWp4TZBFGQz
++8yTnc4kmz75fS/jY2MMddj2gbICrsRhetPfHtXV/WVhJDP1H18GbtCFY2VVPe0a
+87VXE15/V8k1mE8McODmi3fipona8+/och3xWKE2rec1MKzKT0g6eXq8CrGCsyT7
+YdEIqUuyyOP7uWrat2DX9GgdT0Kj3jlN9K5W7edjcrsZCwenyO4KbXCeAvzhzffi
+7MA0BM0oNC9hkXL+nOmFg/+OTxIy7vKBg8P+OxtMb61zO7X8vC7CIAXFjvGDfRaD
+ssbzSibBsu/6iGtCOGEoXJf//////////wIBAg==
+-----END DH PARAMETERS-----' > /etc/openvpn/server/dh.pem
+	# Generate server.conf
+	echo "local $ip
+port $port
+proto $protocol
+dev tun
+ca ca.crt
+cert server.crt
+key server.key
+dh dh.pem
+auth SHA256
+tls-crypt tc.key
+topology subnet
+server 10.8.0.0 255.255.255.0" > /etc/openvpn/server/server.conf
+	# IPv6
+	if [[ -z "$ip6" ]]; then
+		echo 'push "block-ipv6"' >> /etc/openvpn/server/server.conf
+		echo 'push "ifconfig-ipv6 fddd:1194:1194:1194::2/64 fddd:1194:1194:1194::1"' >> /etc/openvpn/server/server.conf
+	else
+		echo 'server-ipv6 fddd:1194:1194:1194::/64' >> /etc/openvpn/server/server.conf
+	fi
+	echo 'push "redirect-gateway def1 ipv6 bypass-dhcp"' >> /etc/openvpn/server/server.conf
+	echo 'ifconfig-pool-persist ipp.txt' >> /etc/openvpn/server/server.conf
+	# DNS
+	case "$dns" in
+		1)
+			# Locate the proper resolv.conf
+			# Needed for systems running systemd-resolved
+			if grep '^nameserver' "/etc/resolv.conf" | grep -qv '127.0.0.53' ; then
+				resolv_conf="/etc/resolv.conf"
+			else
+				resolv_conf="/run/systemd/resolve/resolv.conf"
+			fi
+			# Obtain the resolvers from resolv.conf and use them for OpenVPN
+			grep -v '^#\|^;' "$resolv_conf" | grep '^nameserver' | grep -v '127.0.0.53' | grep -oE '[0-9]{1,3}(\.[0-9]{1,3}){3}' | while read line; do
+				echo "push \"dhcp-option DNS $line\"" >> /etc/openvpn/server/server.conf
+			done
+		;;
+		2|"")
+			echo 'push "dhcp-option DNS 8.8.8.8"' >> /etc/openvpn/server/server.conf
+			echo 'push "dhcp-option DNS 8.8.4.4"' >> /etc/openvpn/server/server.conf
+		;;
+		3)
+			echo 'push "dhcp-option DNS 1.1.1.1"' >> /etc/openvpn/server/server.conf
+			echo 'push "dhcp-option DNS 1.0.0.1"' >> /etc/openvpn/server/server.conf
+		;;
+		4)
+			echo 'push "dhcp-option DNS 208.67.222.222"' >> /etc/openvpn/server/server.conf
+			echo 'push "dhcp-option DNS 208.67.220.220"' >> /etc/openvpn/server/server.conf
+		;;
+		5)
+			echo 'push "dhcp-option DNS 9.9.9.9"' >> /etc/openvpn/server/server.conf
+			echo 'push "dhcp-option DNS 149.112.112.112"' >> /etc/openvpn/server/server.conf
+		;;
+		6)
+			echo 'push "dhcp-option DNS 94.140.14.14"' >> /etc/openvpn/server/server.conf
+			echo 'push "dhcp-option DNS 94.140.15.15"' >> /etc/openvpn/server/server.conf
+		;;
+		7)
+			echo "push \"dhcp-option DNS $dns1\"" >> /etc/openvpn/server/server.conf
+			if [ -n "$dns2" ]; then
+				echo "push \"dhcp-option DNS $dns2\"" >> /etc/openvpn/server/server.conf
+			fi
+		;;
+	esac
+	echo 'push "block-outside-dns"' >> /etc/openvpn/server/server.conf
+	echo "keepalive 10 120
+cipher AES-128-GCM
+user nobody
+group $group_name
+persist-key
+persist-tun
+verb 3
+crl-verify crl.pem" >> /etc/openvpn/server/server.conf
+	if [[ "$protocol" = "udp" ]]; then
+		echo "explicit-exit-notify" >> /etc/openvpn/server/server.conf
+	fi
+	update_sysctl
+	if systemctl is-active --quiet firewalld.service; then
+		# Using both permanent and not permanent rules to avoid a firewalld
+		# reload.
+		# We don't use --add-service=openvpn because that would only work with
+		# the default port and protocol.
+		firewall-cmd -q --add-port="$port"/"$protocol"
+		firewall-cmd -q --zone=trusted --add-source=10.8.0.0/24
+		firewall-cmd -q --permanent --add-port="$port"/"$protocol"
+		firewall-cmd -q --permanent --zone=trusted --add-source=10.8.0.0/24
+		# Set NAT for the VPN subnet
+		firewall-cmd -q --direct --add-rule ipv4 nat POSTROUTING 0 -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j MASQUERADE
+		firewall-cmd -q --permanent --direct --add-rule ipv4 nat POSTROUTING 0 -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j MASQUERADE
+		if [[ -n "$ip6" ]]; then
+			firewall-cmd -q --zone=trusted --add-source=fddd:1194:1194:1194::/64
+			firewall-cmd -q --permanent --zone=trusted --add-source=fddd:1194:1194:1194::/64
+			firewall-cmd -q --direct --add-rule ipv6 nat POSTROUTING 0 -s fddd:1194:1194:1194::/64 ! -d fddd:1194:1194:1194::/64 -j MASQUERADE
+			firewall-cmd -q --permanent --direct --add-rule ipv6 nat POSTROUTING 0 -s fddd:1194:1194:1194::/64 ! -d fddd:1194:1194:1194::/64 -j MASQUERADE
+		fi
+	else
+		# Create a service to set up persistent iptables rules
+		iptables_path=$(command -v iptables)
+		ip6tables_path=$(command -v ip6tables)
+		# nf_tables is not available as standard in OVZ kernels. So use iptables-legacy
+		# if we are in OVZ, with a nf_tables backend and iptables-legacy is available.
+		if [[ $(systemd-detect-virt) == "openvz" ]] && readlink -f "$(command -v iptables)" | grep -q "nft" && hash iptables-legacy 2>/dev/null; then
+			iptables_path=$(command -v iptables-legacy)
+			ip6tables_path=$(command -v ip6tables-legacy)
+		fi
+		echo "[Unit]
+Before=network.target
+[Service]
+Type=oneshot
+ExecStart=$iptables_path -t nat -A POSTROUTING -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j MASQUERADE
+ExecStart=$iptables_path -I INPUT -p $protocol --dport $port -j ACCEPT
+ExecStart=$iptables_path -I FORWARD -s 10.8.0.0/24 -j ACCEPT
+ExecStart=$iptables_path -I FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
+ExecStop=$iptables_path -t nat -D POSTROUTING -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j MASQUERADE
+ExecStop=$iptables_path -D INPUT -p $protocol --dport $port -j ACCEPT
+ExecStop=$iptables_path -D FORWARD -s 10.8.0.0/24 -j ACCEPT
+ExecStop=$iptables_path -D FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT" > /etc/systemd/system/openvpn-iptables.service
+		if [[ -n "$ip6" ]]; then
+			echo "ExecStart=$ip6tables_path -t nat -A POSTROUTING -s fddd:1194:1194:1194::/64 ! -d fddd:1194:1194:1194::/64 -j MASQUERADE
+ExecStart=$ip6tables_path -I FORWARD -s fddd:1194:1194:1194::/64 -j ACCEPT
+ExecStart=$ip6tables_path -I FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
+ExecStop=$ip6tables_path -t nat -D POSTROUTING -s fddd:1194:1194:1194::/64 ! -d fddd:1194:1194:1194::/64 -j MASQUERADE
+ExecStop=$ip6tables_path -D FORWARD -s fddd:1194:1194:1194::/64 -j ACCEPT
+ExecStop=$ip6tables_path -D FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT" >> /etc/systemd/system/openvpn-iptables.service
+		fi
+		echo "RemainAfterExit=yes
+[Install]
+WantedBy=multi-user.target" >> /etc/systemd/system/openvpn-iptables.service
+		(
+			set -x
+			systemctl enable --now openvpn-iptables.service >/dev/null 2>&1
+		)
+	fi
+	if [ "$os" != "openSUSE" ]; then
+		update_rclocal
+	fi
+	# If SELinux is enabled and a custom port was selected, we need this
+	if sestatus 2>/dev/null | grep "Current mode" | grep -q "enforcing" && [[ "$port" != 1194 ]]; then
+		# Install semanage if not already present
+		if ! hash semanage 2>/dev/null; then
+			if [[ "$os_version" -eq 7 ]]; then
+				# Centos 7
+				(
+					set -x
+					yum -y -q install policycoreutils-python >/dev/null
+				) || exiterr3
+			else
+				# CentOS 8/9 or Fedora
+				(
+					set -x
+					dnf install -y policycoreutils-python-utils >/dev/null
+				) || exiterr "'dnf install' failed."
+			fi
+		fi
+		semanage port -a -t openvpn_port_t -p "$protocol" "$port"
+	fi
+	# If the server is behind NAT, use the correct IP address
+	[[ -n "$public_ip" ]] && ip="$public_ip"
+	# client-common.txt is created so we have a template to add further users later
+	echo "client
+dev tun
+proto $protocol
+remote $ip $port
+resolv-retry infinite
+nobind
+persist-key
+persist-tun
+remote-cert-tls server
+auth SHA256
+cipher AES-128-GCM
+ignore-unknown-option block-outside-dns block-ipv6
+verb 3" > /etc/openvpn/server/client-common.txt
+	# Enable and start the OpenVPN service
+	if [ "$os" != "openSUSE" ]; then
+		(
+			set -x
+			systemctl enable --now openvpn-server@server.service >/dev/null 2>&1
+		)
+	else
+		ln -s /etc/openvpn/server/* /etc/openvpn >/dev/null 2>&1
+		(
+			set -x
+			systemctl enable --now openvpn@server.service >/dev/null 2>&1
+		)
+	fi
+	# Generates the custom client.ovpn
+	new_client
+	echo
+	echo "Finished!"
+	echo
+	echo "The client configuration is available in: $export_dir$client.ovpn"
+	echo "New clients can be added by running this script again."
+else
+	show_header
+	echo
+	echo "OpenVPN is already installed."
+	echo
+	echo "Select an option:"
+	echo "   1) Add a new client"
+	echo "   2) Export config for an existing client"
+	echo "   3) List existing clients"
+	echo "   4) Revoke an existing client"
+	echo "   5) Remove OpenVPN"
+	echo "   6) Exit"
+	read -rp "Option: " option
+	until [[ "$option" =~ ^[1-6]$ ]]; do
+		echo "$option: invalid selection."
+		read -rp "Option: " option
+	done
+	case "$option" in
+		1)
+			echo
+			echo "Provide a name for the client:"
+			read -rp "Name: " unsanitized_client
+			[ -z "$unsanitized_client" ] && abort_and_exit
+			set_client_name
+			while [[ -z "$client" || -e /etc/openvpn/server/easy-rsa/pki/issued/"$client".crt ]]; do
+				echo "$client: invalid name."
+				read -rp "Name: " unsanitized_client
+				[ -z "$unsanitized_client" ] && abort_and_exit
+				set_client_name
+			done
+			cd /etc/openvpn/server/easy-rsa/ || exit 1
+			(
+				set -x
+				./easyrsa --batch --days=3650 build-client-full "$client" nopass >/dev/null 2>&1
+			)
+			# Generates the custom client.ovpn
+			new_client
+			echo
+			echo "$client added. Configuration available in: $export_dir$client.ovpn"
+			exit
+		;;
+		2)
+			num_of_clients=$(tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep -c "^V")
+			if [[ "$num_of_clients" = 0 ]]; then
+				echo
+				echo "There are no existing clients!"
+				exit
+			fi
+			echo
+			echo "Select the client to export:"
+			tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep "^V" | cut -d '=' -f 2 | nl -s ') '
+			read -rp "Client: " client_num
+			[ -z "$client_num" ] && abort_and_exit
+			until [[ "$client_num" =~ ^[0-9]+$ && "$client_num" -le "$num_of_clients" ]]; do
+				echo "$client_num: invalid selection."
+				read -rp "Client: " client_num
+				[ -z "$client_num" ] && abort_and_exit
+			done
+			client=$(tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep "^V" | cut -d '=' -f 2 | sed -n "$client_num"p)
+			new_client
+			echo
+			echo "$client exported. Configuration available in: $export_dir$client.ovpn"
+			exit
+		;;
+		3)
+			echo
+			echo "Checking for existing client(s)..."
+			num_of_clients=$(tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep -c "^V")
+			if [[ "$num_of_clients" = 0 ]]; then
+				echo
+				echo "There are no existing clients!"
+				exit
+			fi
+			echo
+			tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep "^V" | cut -d '=' -f 2 | nl -s ') '
+			if [ "$num_of_clients" = 1 ]; then
+				printf '\n%s\n' "Total: 1 client"
+			elif [ -n "$num_of_clients" ]; then
+				printf '\n%s\n' "Total: $num_of_clients clients"
+			fi
+			exit
+		;;
+		4)
+			num_of_clients=$(tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep -c "^V")
+			if [[ "$num_of_clients" = 0 ]]; then
+				echo
+				echo "There are no existing clients!"
+				exit
+			fi
+			echo
+			echo "Select the client to revoke:"
+			tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep "^V" | cut -d '=' -f 2 | nl -s ') '
+			read -rp "Client: " client_num
+			[ -z "$client_num" ] && abort_and_exit
+			until [[ "$client_num" =~ ^[0-9]+$ && "$client_num" -le "$num_of_clients" ]]; do
+				echo "$client_num: invalid selection."
+				read -rp "Client: " client_num
+				[ -z "$client_num" ] && abort_and_exit
+			done
+			client=$(tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep "^V" | cut -d '=' -f 2 | sed -n "$client_num"p)
+			echo
+			read -rp "Confirm $client revocation? [y/N]: " revoke
+			until [[ "$revoke" =~ ^[yYnN]*$ ]]; do
+				echo "$revoke: invalid selection."
+				read -rp "Confirm $client revocation? [y/N]: " revoke
+			done
+			if [[ "$revoke" =~ ^[yY]$ ]]; then
+				echo
+				echo "Revoking $client..."
+				cd /etc/openvpn/server/easy-rsa/ || exit 1
+				(
+					set -x
+					./easyrsa --batch revoke "$client" >/dev/null 2>&1
+					./easyrsa --batch --days=3650 gen-crl >/dev/null 2>&1
+				)
+				rm -f /etc/openvpn/server/crl.pem
+				cp /etc/openvpn/server/easy-rsa/pki/crl.pem /etc/openvpn/server/crl.pem
+				# CRL is read with each client connection, when OpenVPN is dropped to nobody
+				chown nobody:"$group_name" /etc/openvpn/server/crl.pem
+				get_export_dir
+				ovpn_file="$export_dir$client.ovpn"
+				if [ -f "$ovpn_file" ]; then
+					echo "Removing $ovpn_file..."
+					rm -f "$ovpn_file"
+				fi
+				echo
+				echo "$client revoked!"
+			else
+				echo
+				echo "$client revocation aborted!"
+			fi
+			exit
+		;;
+		5)
+			echo
+			read -rp "Confirm OpenVPN removal? [y/N]: " remove
+			until [[ "$remove" =~ ^[yYnN]*$ ]]; do
+				echo "$remove: invalid selection."
+				read -rp "Confirm OpenVPN removal? [y/N]: " remove
+			done
+			if [[ "$remove" =~ ^[yY]$ ]]; then
+				echo
+				echo "Removing OpenVPN, please wait..."
+				port=$(grep '^port ' /etc/openvpn/server/server.conf | cut -d " " -f 2)
+				protocol=$(grep '^proto ' /etc/openvpn/server/server.conf | cut -d " " -f 2)
+				if systemctl is-active --quiet firewalld.service; then
+					ip=$(firewall-cmd --direct --get-rules ipv4 nat POSTROUTING | grep '\-s 10.8.0.0/24 '"'"'!'"'"' -d 10.8.0.0/24' | grep -oE '[^ ]+$')
+					# Using both permanent and not permanent rules to avoid a firewalld reload.
+					firewall-cmd -q --remove-port="$port"/"$protocol"
+					firewall-cmd -q --zone=trusted --remove-source=10.8.0.0/24
+					firewall-cmd -q --permanent --remove-port="$port"/"$protocol"
+					firewall-cmd -q --permanent --zone=trusted --remove-source=10.8.0.0/24
+					firewall-cmd -q --direct --remove-rule ipv4 nat POSTROUTING 0 -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j MASQUERADE
+					firewall-cmd -q --permanent --direct --remove-rule ipv4 nat POSTROUTING 0 -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j MASQUERADE
+					if grep -qs "server-ipv6" /etc/openvpn/server/server.conf; then
+						ip6=$(firewall-cmd --direct --get-rules ipv6 nat POSTROUTING | grep '\-s fddd:1194:1194:1194::/64 '"'"'!'"'"' -d fddd:1194:1194:1194::/64' | grep -oE '[^ ]+$')
+						firewall-cmd -q --zone=trusted --remove-source=fddd:1194:1194:1194::/64
+						firewall-cmd -q --permanent --zone=trusted --remove-source=fddd:1194:1194:1194::/64
+						firewall-cmd -q --direct --remove-rule ipv6 nat POSTROUTING 0 -s fddd:1194:1194:1194::/64 ! -d fddd:1194:1194:1194::/64 -j MASQUERADE
+						firewall-cmd -q --permanent --direct --remove-rule ipv6 nat POSTROUTING 0 -s fddd:1194:1194:1194::/64 ! -d fddd:1194:1194:1194::/64 -j MASQUERADE
+					fi
+				else
+					systemctl disable --now openvpn-iptables.service
+					rm -f /etc/systemd/system/openvpn-iptables.service
+				fi
+				if sestatus 2>/dev/null | grep "Current mode" | grep -q "enforcing" && [[ "$port" != 1194 ]]; then
+					semanage port -d -t openvpn_port_t -p "$protocol" "$port"
+				fi
+				if [ "$os" != "openSUSE" ]; then
+					systemctl disable --now openvpn-server@server.service
+				else
+					systemctl disable --now openvpn@server.service
+				fi
+				rm -f /etc/systemd/system/openvpn-server@server.service.d/disable-limitnproc.conf
+				rm -f /etc/sysctl.d/99-openvpn-forward.conf /etc/sysctl.d/99-openvpn-optimize.conf
+				if [ ! -f /usr/bin/wg-quick ] && [ ! -f /usr/sbin/ipsec ] \
+					&& [ ! -f /usr/local/sbin/ipsec ]; then
+					echo 0 > /proc/sys/net/ipv4/ip_forward
+					echo 0 > /proc/sys/net/ipv6/conf/all/forwarding
+				fi
+				ipt_cmd="systemctl restart openvpn-iptables.service"
+				if grep -qs "$ipt_cmd" /etc/rc.local; then
+					sed --follow-symlinks -i "/^$ipt_cmd/d" /etc/rc.local
+				fi
+				if [[ "$os" = "debian" || "$os" = "ubuntu" ]]; then
+					(
+						set -x
+						rm -rf /etc/openvpn/server
+						apt-get remove --purge -y openvpn >/dev/null
+					)
+				elif [[ "$os" = "openSUSE" ]]; then
+					(
+						set -x
+						zypper remove -y openvpn >/dev/null
+						rm -rf /etc/openvpn/server
+					)
+					rm -f /etc/openvpn/ipp.txt
+				else
+					# Else, OS must be CentOS or Fedora
+					(
+						set -x
+						yum -y -q remove openvpn >/dev/null
+						rm -rf /etc/openvpn/server
+					)
+				fi
+				echo
+				echo "OpenVPN removed!"
+			else
+				echo
+				echo "OpenVPN removal aborted!"
+			fi
+			exit
+		;;
+		6)
+			exit
+		;;
+	esac
+fi
+}
+
+## Defer setup until we have the complete script
+ovpnsetup "$@"
+
+exit 0