#!/usr/bin/env ruby
# this script could be used as an up/down script for the openvpn client
# it parses the dhcp options provided by the openvpn server to update the
# resolv.conf file accordingly.
# The notify-send command shows a nice popup to notify connecting and
# disconnecting.
script_type = ENV['script_type']

def osd(message)
    `notify-send "#{message}"`
end

if 'up' == script_type
    puts '[UP] Backup Resolv.conf'
    `cp /etc/resolv.conf /etc/resolv.conf.ovpn_backup`
    puts '[UP] Parse dhcp_options:'
    num = 1; options = []
    while true
        option_key = 'foreign_option_%d' % num
        num += 1
        if ENV.has_key? option_key
            options << ENV[option_key] if not ENV[option_key].empty?
        else
            break
        end
    end
    puts '[UP] dhcp_options: %s' % (options.inspect)
    puts '[UP] trucate resolv.conf, write nameservers'
    file = File.open('/etc/resolv.conf', 'w')
    options.each do |option|
        if option.match /dhcp-option DNS (.*)$/
           file << "nameserver #{$1}\n"
        end
    end
    file.close()
    osd('OpenVPN connection established')
elsif 'down' == script_type
    puts '[DOWN] Revert Resolv.conf to backup'
    `cp /etc/resolv.conf.ovpn_backup /etc/resolv.conf`

    osd('OpenVPN disconnected')
end