Ubuntu PCをルータ代わりに, OpenVPN,DNS,routing
http://d.hatena.ne.jp/chibatching/20130428/1367154401
http://www.clear-code.com/blog/2010/11/19.html
http://blog.kazu634.com/2013/09/20/how_to_install_openvpn_under_ubuntu_1204/
http://www.openvpn.jp/document/how-to/
http://www.slsmk.com/getting-started-with-openvpn/installing-openvpn-on-ubuntu-server-12-04-or-14-04-using-tap/
http://www.eva-shin.com/openvpn_server/
http://server-setting.info/centos/openvpn-setting.html
https://www.linode.com/docs/networking/vpn/secure-communications-with-openvpn-on-ubuntu-12-04-precise-and-debian-7