More options

--tls-auth file direction
Add an additional layer of HMAC authentication on top of the TLS control channel to protect against DoS attacks.
--replay-persist
Persist replay-protection state across sessions using file to save and reload the state.
--port-share
New in 2.1: share the OpenVPN port with another application, such as an HTTPS server
--ns-cert-type client|server
Require that peer certificate was signed with an explicit nsCertType designation of "client" or "server".