WireGuard in the mainline Linux kernel

Linux kernel 5.6, released on March 29, 2020, was the first to carry WireGuard directly in-tree – after years of it running as an out-of-tree module that distributions (or an administrator) had to build and maintain separately from the kernel.

The small amount of code compared to older VPN solutions (IPsec, OpenVPN) was not a consequence of the kernel merge but a design goal from the start. The merge itself was not smooth, though: it was delayed by roughly two years by a dispute over WireGuard's own Zinc crypto library. WireGuard entered the kernel only after it was ported to the kernel's existing crypto API.