It builds a kernel module, which may hinder adoption somewhat. Especially when thinking about supporting other platforms like Windows or Android/iOS.
It seems to work over UDP. One of the nice features that e.g. OpenVPN and OpenConnect have is that it is possible to route all traffic over TCP/443 (with a performance penalty, but at least it works…).
There’s a lot of comments over at HN with details by the authors, but they’ve also said they’ll be releasing a userspace version that’s cross-platform and in Rust.
HN link: https://news.ycombinator.com/item?id=11994265
I think their design is well justified and I really appreciate the focus on keeping the code small (4000 lines!). I think this is the VPN I’ve been waiting for. The cross-platform Rust version sounds promising too.