OpenConnect server (ocserv) is an SSL VPN server. Its purpose is
to be a secure, small, fast and configurable VPN server. It implements
the OpenConnect SSL VPN protocol, and has also (currently experimental)
compatibility with clients using the AnyConnect SSL VPN protocol.
The OpenConnect protocol provides a dual TCP/UDP VPN channel, and
uses the standard IETF security protocols to secure it. Both IPv4
and IPv6 are supported.

Ocserv's main features are security through provilege separation
and sandboxing, accounting, and resilience due to a combined use
of TCP and UDP.  Authentication occurs in an isolated security
module process, and each user is assigned an unprivileged worker
process, and a networking (tun) device. That not only eases the
control of the resources of each user or group of users, but also
prevents data leak (e.g., heartbleed-style attacks), and privilege
escalation due to any bug on the VPN handling (worker) process. A
management interface allows for viewing and querying logged-in
users.

WWW: http://www.infradead.org/ocserv/