OpenVPN/openvpn ? reverse-engineered prompt

Build me an open source VPN daemon like OpenVPN. I want a secure command line program that can run as either a VPN server or client, create an encrypted tunnel between machines, and use config files so people can start it without changing code.

It should support certificate based authentication, safe defaults, logging, clear error messages, and sample config files for testing. Include sample keys only for local testing and make it very clear they are not safe for real use. Add basic scripts or examples that show how someone would verify a client certificate field during login.

Please make it buildable from source on Linux with the normal configure, make, make install flow, and include notes for Windows builds too. Add docs that explain installation, basic usage, where to find examples, and how to report issues. Keep it focused on being a reliable secure tunneling service, not a fancy app.