OpenVPN 是一个基于 OpenSSL 库的应用层 VPN 实现。和传统 VPN 相比，它的优点是简单易用。
OpenVPN允许参与建立VPN的单点使用共享金钥，电子证书，或者用户名/密码来进行身份验证。它大量使用了OpenSSL加密库中的SSLv3/TLSv1 协议函式库。目前OpenVPN能在Solaris、Linux、OpenBSD、FreeBSD、NetBSD、Mac OS X与Windows 2000/XP/Vista上运行，并包含了许多安全性的功能。它并不是一个基于Web的VPN软件，也不与IPsec及其他VPN软件包兼容。
OpenVPN使用OpenSSL库加密数据与控制信息：它使用了OpenSSL的加密以及验证功能，意味着，它能够使用任何OpenSSL支持的算法。它提供了可选的数据包HMAC功能以提高连接的安全性。此外，OpenSSL的硬件加速也能提高它的性能。
2.3.0新特性包括：§ Full IPv6 support
§ SSL layer modularised, enabling easier implementation for other SSL libraries
§ PolarSSL support as a drop-in replacement for OpenSSL
§ New plug-in API providing direct certificate access, improved logging API and easier to extend in the future
§ Added 'dev_type' environment variable to scripts and plug-ins - which is set to 'TUN' or 'TAP'
§ New feature: --management-external-key - to provide access to the encryption keys via the management interface
§ New feature: --x509-track option, more fine grained access to X.509 fields in scripts and plug-ins
§ New feature: --client-nat support
§ New feature: --mark which can mark encrypted packets from the tunnel, suitable for more advanced routing and firewalling
§ New feature: --management-query-proxy - manage proxy settings via the management interface (supercedes --http-proxy-fallback)
§ New feature: --stale-routes-check, which cleans up the internal routing table
§ New feature: --x509-username-field, where other X.509v3 fields can be used for the authentication instead of Common Name
§ Improved client-kill management interface command
§ Improved UTF-8 support - and added --compat-names to provide backwards compatibility with older scripts/plug-ins
§ Improved auth-pam with COMMONNAME support, passing the certificate's common name in the PAM conversation
§ More options can now be used inside
§ Completely new build system, enabling easier cross-compilation and Windows builds
§ Much of the code has been better documented
§ Many documentation updates
§ Plenty of bug fixes and other code clean-ups
下载：ftp://61.135.158.199/pub/openvpn-2.3.0.tar.gz （主站因为众所周知的原因被墙了）
来自:开源中国社区