Improved version of ECHCheck test

[hellais]

This issue is to track the work @johnhess is doing on expanding our echcheck test to fully support the ECH handshake, see: johnhess/probe-cli#1.

What we should ensure happens as part of this new iteration is:

• Add support for truly speaking ECH (as opposed to just greased ECH), using the tls client implementation in golang stdlib
• Get rid of the utls dependency
• Add support for setting the queries, tcp_connect and network_events keys

xref: #1453

[johnhess]

The first and second should be done already :-)

Re: the third item, is the intention that the probe would also populate results for the other dataformats e.g. queries? If so, I can add those. Which network events do you want to see captured?

[hellais]

is the intention that the probe would also populate results for the other dataformats e.g. queries

Yes that's correct. These should already be emitted by the measurement library functions you are using.

Which network events do you want to see captured?

Similarly also network_events are automatically collected and you just have to add them to your test_keys.

Here are some examples of how this is done in other tests

network_events: https://github.com/ooni/probe-cli/blob/ef139c525f1b1e751f21cccf842982b4a2720dbd/internal/experiment/simplequicping/simplequicping.go#L190

queries, tcp_connect: https://github.com/ooni/probe-cli/blob/ef139c525f1b1e751f21cccf842982b4a2720dbd/internal/experiment/urlgetter/getter.go#L62

[johnhess]

Working on that. Ran into a semantics question.

When we attempt to do a GREASE connection, we get an error. We expect that error; it's an EchRejectionError! We can & do use the retry_configs that come with it to attempt a real ECH connection.

Question: Do we want to log 2 ArchivalTLSOrQUICHandshakeResults with the GREASE'd one as having a Failure? A SoError? My guess is "no, that's not a failure" since it's doing what we expect (even if golang is returning a conspicuous error to the caller so they know they didn't get the ECH they wanted).

[johnhess]

For net_events: do we want to capture all net events for the DNS queries, then again for each TCP+TLS attempt? Or just a subset?