fastd is a very small VPN daemon which tunnels IP packets and Ethernet frames over UDP. It supports various modern encryption and authentication schemes and can be used in many different network topologies (1:1, 1:n, meshed).
fastd runs on Linux, FreeBSD, OpenBSD and macOS. Android support exists in the code, but is currently unmaintained. Binary packages are provided by many major Linux distributions.
For more information, see the documentation and the project wiki.