[WireGuard] continuous integration/testing across multiple kernels

[Jason A. Donenfeld]

As unit tests are a development building block, insecure hacks like
client.sh should not be used. You could easily repurpose client.sh to
invoke openssl-s_client or some similarly disgusting TLS hack, I
guess. In any case, though, it's not even needed. Check out what I did
with contrib/external-tests and src/debug.mk. There are just hard
coded public/private keys in there, which are more than sufficient for
unit testing. If you'd like, you can experiment with using those same
public/private keys and test.wireguard.io (NOT demo.wireguard.io), for
constructing an automated testing framework.

However, perhaps a better and more robust way of doing this would be
to use network namespaces. See src/netns.sh for an example of how this
works. This way there can be several wireguard instances and different
networking configurations all within the same machine, enabling
offline reliable unit tests.