Handle multiple incoming connection at the beginning of Http3LoopbackConnection use

[rzikm]

Fixes #69387.

This PR makes sure the Http3LoopbackConnection used in tests does not choke on multiple simultaneous requests from a client, when two or more request streams are accepted before the control stream.

The Http functional tests were run in a tight loop and the original test failure was not observed.

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Issue Details

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Fixes #69387.

This PR makes sure the Http3LoopbackConnection used in tests does not choke on multiple simultaneous requests from a client, when two or more request streams are accepted before the control stream.

The Http functional tests were run in a tight loop and the original test failure was not observed.

Author:	rzikm
Assignees:	-
Labels:	area-System.Net.Http
Milestone:	-

[rzikm]

cc: @ManickaP

[ManickaP]

Was the problem that not all unidirectional streams were the one and only control stream?

[CarnaViire]

In general LGTM, but the only question is whether any synchronization needed over _delayedStreams access... can AcceptRequestStreamAsync ever be called concurrently? it feels like it might be...

[rzikm]

Was the problem that not all unidirectional streams were the one and only control stream?

No, the problem was that client started multiple requests and it happened that two (or more) request streams arrived before the control stream.

[rzikm]

In general LGTM, but the only question is whether any synchronization needed over _delayedStreams access... can AcceptRequestStreamAsync ever be called concurrently? it feels like it might be...

It does not seem that we are accepting multiple requests concurrently in any test. There are other parts of the simple loopback server that were not thread safe before (such as setting the _currentStream and _currentStreamId). Making it all threadsafe would require bigger changes and likely redesign of the class/tests.

[CarnaViire]

Ok. If Http3LoopbackConnection is not thread-safe in general, I'm fine with this.
LGTM. Thanks!