fix(qns): always use Version1 on server

[mxinden]

The Quic Interop Runner expects the server to use Version::Version1 in all testcases but versionnegotiation and v2.

See discussion in Quic Interop Runner issue and corresponding code in the Quic Interop Runner.

While Neqo's default Version is Version1, the default VersionConfig includes all versions (Version::all()) and thus the server will currently upgrade the connection to the compatible Version::Version2.

With this commit, the server will always choose Version1 when running a qns testcase. Given that Neqo's qns implementation does not support the versionnegotiation and v2 testcases, this fix is applicable for all supported testcases.

@larseggert I opted for a fix in neqo-server/src/main.rs instead of, as you suggested, in qns/interop.sh. I find it much easier to maintain this logic in Rust rather than a shell script. I don't feel strongly about it. Let me know whether you prefer the -V 1 fix in interop.sh.

---

While this does not fix all interop test failures, it does get us much closer.

Before:

After:

I will take a look at the remaining failures next.

[codecov-commenter]

Codecov Report

Attention: 7 lines in your changes are missing coverage. Please review.

Comparison is base (64fb41f) 87.63% compared to head (7742df5) 87.60%.

Files	Patch %	Lines
neqo-server/src/main.rs	0.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1563      +/-   ##
==========================================
- Coverage   87.63%   87.60%   -0.03%     
==========================================
  Files         117      117              
  Lines       38323    38330       +7     
==========================================
- Hits        33584    33580       -4     
- Misses       4739     4750      +11     

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[martinthomson]

I'd rather leave the footgun in place (that what these tools are for) and only set the version if it is unset.

[mxinden]

@martinthomson can you take another look? Let me know if you want me to remove the qwarn!.

[larseggert]

Neqo does support v2?

[mxinden]

As far as I can tell, it does not implement the v2 Quic Interop Runner testcase:

neqo/neqo-client/src/main.rs

Lines 989 to 1017 in 64fb41f

	match testcase.as_str() {
	"http3" => {}
	"handshake" | "transfer" | "retry" => {
	args.use_old_http = true;
	}
	"zerortt" | "resumption" => {
	if args.urls.len() < 2 {
	eprintln!("Warning: resumption tests won't work without >1 URL");
	exit(127);
	}
	args.use_old_http = true;
	args.resume = true;
	}
	"multiconnect" => {
	args.use_old_http = true;
	args.download_in_series = true;
	}
	"chacha20" => {
	args.use_old_http = true;
	args.ciphers.clear();
	args.ciphers
	.extend_from_slice(&[String::from("TLS_CHACHA20_POLY1305_SHA256")]);
	}
	"keyupdate" => {
	args.use_old_http = true;
	args.key_update = true;
	}
	_ => exit(127),
	}

Am I missing something @larseggert?

[mxinden]

Happy to work on it once the current test failures (quic-interop/quic-interop-runner#344) are resolved.

[larseggert]

I'd prefer to lock the version in the shell script, but don't care strongly.

[martinthomson]

This is fine, though if Lars would prefer a simple version override in the interop runner script, that's also fine.

[mxinden]

@larseggert note that once we implement the versionnegotiation and v2 testcase, this logic will have to live in neqo-server/src/main.rs. We will then have to use Version::Version1 in all but those two cases. In other words, a simpel -V 1 override in interop.sh won't do.

Let me know if that changes your mind. If not, given that neither of us feels strongly about it, let's go with your approach, namely to override in interop.sh.

[larseggert]

That's a good point. Let's do it this way.