docs: reverse_proxy: Add guide for Caddy

[Rijul-A]

Now that mholt/caddy-l4#33 has been merged, Caddy can be used as a reverse proxy for Snikket with all the features of sslh, and forwarding port 80 to Snikket's 5080.

[mwild1]

Thanks for this! And your contribution to Caddy :)

I note that your changes don't appear to be in a release yet. It might be worth noting that, or holding off on merging this until they are (but even then it should probably clarify what Caddy version is required).

Would love for someone to test this (@turguenev? 🙂 ) and report how they get on.

[Rijul-A]

I note that your changes don't appear to be in a release yet. It might be worth noting that, or holding off on merging this until they are (but even then it should probably clarify what Caddy version is required).

Caddy's plugins do not need a release; they are simply based on the master branch. A build made right now includes the modules layer4.matchers.xmpp and tls.handshake_match.alpn

$ wget https://github.com/caddyserver/xcaddy/releases/download/v0.2.0/xcaddy_0.2.0_linux_amd64.tar.gz
$ tar -xvzf xcaddy_0.2.0_linux_amd64.tar.gz
$ ./xcaddy build --with github.com/mholt/caddy-l4
$ ./caddy version
v2.4.6 h1:HGkGICFGvyrodcqOOclHKfvJC0qTU7vny/7FhYp9hNw=
$ ./caddy list-modules | grep -E '(xmpp|alpn)'
layer4.matchers.xmpp
tls.handshake_match.alpn

Would love for someone to test this (@turguenev? slightly_smiling_face ) and report how they get on.

Let me know if you get stuck somewhere; the JSON / YAML syntax takes a bit of getting used to, as opposed to the Caddyfile.

[Rijul-A]

I will incorporate changes from this discussion on Caddy forums to the PR soon. Hopefully, we should have a testing report to go along.

[mwild1]

Thanks Rijul!