OpenVPN integration with interfaces(5)

tun0

iface tun0 inet manual
	pre-up openvpn --mktun --dev tun0
	up openvpn --config /etc/openvpn/YOURVPN.ovpn \
		   --daemon \
		   --dev tun0 \
		   --route-noexec \
		   --script-security 2 \
		   --route-up /etc/openvpn/on-route-up \
		   --writepid /var/run/openvpn.tun0
	down /etc/openvpn/kill-service -w /var/run/openvpn.tun0
	post-down resolvconf -d tun0
	post-down openvpn --rmtun --dev tun0

kill-service

#!/bin/sh

usage() {
    echo "Usage: kill-service PID_FILE

Kill a service process given its PID file.

Options:

  -w — wait for the process to exit before returning"
}

main() {
    local kill_cmd=kill_now

    while getopts w opt; do
        case "$opt" in
            w) kill_cmd=kill_wait ;;
        esac
    done
    shift $(( OPTIND - 1 ))
    OPTIND=1

    if [ $# -eq 1 ]; then
        kill_service "$1"
    else
        usage
    fi

}

kill_service() {
    local pid="$(cat "$1")"

    if [ -n "$pid" ]; then
        "$kill_cmd" "$pid"
        rm -f -- "$1"
    fi
}

kill_now() {
    kill -- "$1"
}

kill_wait() {
    kill_now "$1" &&
    while ps -p "$1" >/dev/null; do
        sleep 1
    done
}

main "$@"

on-route-up

#!/bin/sh

usage() {
    echo "Usage: on-route-up INTERFACE

Add routes and DNS servers that are pushed from the OpenVPN server.  This
script is intended to be run by OpenVPN's \`--route-up\` feature."
}

main() {
    if [ "$1" = '-h' ] || [ -z "$dev" ]; then
        usage
    else
        add_routes
        configure_dns "$dev"
    fi
}

add_routes() {
    local n=1
    while has_route "$n"; do
        add_route "$n"
        n=$(( n + 1 ))
    done
}

has_route() {
    [ -n "$(get_var "route_network_$1")" ]
}

add_route() {
    local network="$(get_var "route_network_$n")"
    local gateway="$(get_var "route_gateway_$n")"
    local netmask="$(get_var "route_netmask_$n")"

    ip route add "$network"/"$(mask_to_cidr "$netmask")" via "$gateway"
}

configure_dns() {
    get_dns_options | create_resolv_entries | resolvconf -a "$1"
}

get_dns_options() {
    local n=1 server
    while has_foreign_option "$n"; do
        get_var "foreign_option_$n" |
            sed -nE 's/^dhcp-option DNS ([0-9.]+)$/\1\n/ p'
        n=$(( n + 1 ))
    done
}

create_resolv_entries() {
    local server
    while read -r server; do
        echo "nameserver $server"
    done
}

has_foreign_option() {
    [ -n "$(get_var "foreign_option_$1")" ]
}

get_var() {
    eval printf '%s' \"\$"$1"\"
}

mask_to_cidr() {
    local IFS=.
    set -- $*
    echo $(( $(count_bits "$1") + $(count_bits "$2") + $(count_bits "$3") + $(count_bits "$4") ))
}

count_bits() {
    case "$1" in
        255) echo 8 ;;
        254) echo 7 ;;
        252) echo 6 ;;
        248) echo 5 ;;
        240) echo 4 ;;
        224) echo 3 ;;
        192) echo 2 ;;
        128) echo 1 ;;
          *) echo 0 ;;
    esac
}

main "$@"

zzz-LICENSE.txt

The MIT License (MIT)

Copyright (c) 2014 Michael Kropat

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.