Open Source C VPN Software for OpenBSD

DSVPN is a Dead Simple VPN, designed to address the most common use case for using a VPN. Runs on TCP. Works pretty much everywhere, including on public WiFi where only TCP/443 is open or reliable. Uses only modern cryptography, with formally verified implementations. Small and constant memory footprint. Doesn't perform any heap memory allocations. Small (~25 KB), with an equally small and readable code base. No external dependencies. Works out of the box. No lousy documentation to read. No configuration file. No post-configuration. Run a single-line command on the server, a similar one on the client and you're done. No firewall and routing rules to manually mess with. Doesn't leak between reconnects if the network doesn't change. Blocks IPv6 on the client to prevent IPv6 leaks. Works on Linux (kernel >= 3.17), macOS and OpenBSD, as well as DragonFly BSD, FreeBSD and NetBSD in client and point-to-point modes. Adding support for other operating systems is trivial.

Campagnol is a decentralized VPN over UDP tunneling. It uses UDP hole punching to open connections through NAT/firewall and OpenSSL's DTLSv1 implementation for mutual authentication and encryption.

OpenVPN is a robust and highly flexible tunneling application that uses all of the encryption, authentication, and certification features of the OpenSSL library to securely tunnel IP networks over a single TCP/UDP port. Discussion forums and project wiki can be found here: https://forums.openvpn.net/ http://community.openvpn.net/openvpn