[dnstap] Adding support for DoT and DoH

[Chris Mikkelson]

On Mon, Dec 07, 2020 at 09:31:10AM +0100, Vladimír Čunát wrote:
>    Hello.
> 
>    We'd like dnstap to represent the new-ish standardized transports.  In
>    our use case it will be sufficient to trivially extend the
>    corresponding enum, so we suggest to do that step now and we can think
>    of additional related extensions later.  Any comments?

My main concern here is with extending SocketProtocol.
While DoT implies TCP, DoH may also be UDP (QUIC) if
used with HTTP/3. In that case, mixing DoH in with the
SocketProtocol values would conflate an HTTP/2 and HTTP/3
DoH service on a single host.

Thus, I would suggest moving DoT and DoH to a separate
field, say "tunnel_protocol" with a corresponding enum.
Better name suggestions are very welcome.

Does this sound workable and worthwhile?

Do we want to include other extant protocols (e.g.
dnscrypt) in this enum?

Thanks,
-- 
Chris Mikkelson
Farsight Security, Inc.
cmikk at fsi.io