[ANNOUNCE] WireGuardNT, a high-performance WireGuard implementation for the Windows kernel

[Jason A. Donenfeld]

Hi everyone,

As described in the original announcement:

> There will be three phases of the 0.4.z series:
>
>   Phase 1) WireGuardNT is hidden behind the "ExperimentalKernelDriver"
>            registry knob. If you don't manually tinker around to enable it,
>            the client will continue to use wireguard-go/Wintun like before.
>
>   Phase 2) WireGuardNT is enabled by default and is no longer hidden.
>            However, in case there are late-stage problems that cause
>            downtime for existing infrastructure, there'll be a new hidden
>            knob called "UseUserspaceImplementation" that goes back to
>            using wireguard-go/Wintun like before.
>
>   Phase 3) WireGuardNT is enabled, and wireguard-go/Wintun is removed from
>            the client.

After quite a bit of testing, the bug reports have dried up. We've
gone through several subphases of phase 1, from being masked behind a
registry knob, to introducing a checkbox, to opting in users part of
the Windows Insider program. There's been a pretty heavy amount of
testing, from what I can gather, and I think things have shaped up
nicely.

Finally, tomorrow with the release of v0.4.8, we will move onto phase
2. That means that WireGuardNT will be on by default. If something
goes wrong, you will still be able to disable it and revert to the
older wireguard-go/Wintun using the "UseUserspaceImplementation"
switch described on this page (as of September 2021; will be removed
in the future):

    https://git.zx2c4.com/wireguard-windows/about/docs/adminregistry.md

But note that if you /do/ revert to using wireguard-go/Wintun, you
*must* absolutely email team at wireguard.com with details as to why
you've done so, so that if there is a bug, we can fix it. If you do
not do this, it is possible that your bug will never be fixed, and in
a month or so, we'll move onto phase 3, and you will lose the ability
to revert to using wireguard-go/Wintun. Do not rely on other people to
report your bug for you; Windows is weird and diverse and there are no
guarantees that somebody else will run into your same problem. So
please: if you enable "UseUserspaceImplementation", send an email
saying why.

Depending on how Monday morning goes, this should be released in
around 12 hours from now. Enjoy!

Regards,
Jason