HttpSys HTTP_SEND_RESPONSE_FLAG_GOAWAY detection side effects

[Tratcher]

Background

#14522 added 3.1 support for HttpSys GoAway via a new flag HTTP_SEND_RESPONSE_FLAG_GOAWAY. OS support for the new flag is detected by checking for an Invalid Parameter error on first use and trying again without it.

Describe the bug

The invalid parameter error is working as expected on the server, but it has an unexpected side-effect on the client. The client receives a RST_STREAM (Cancel) error rather than the expected headers for the response that included the HTTP_SEND_RESPONSE_FLAG_GOAWAY flag. This only happens for the first response with the new flag because the flag is disabled for the remainder of the application.

Reproed on Win10 19H1 1903 (18362.418).

I'm following up with Http.Sys but we may have to find an alternate detection mechanic here. Skipping the new negative test for now. Edit: Confirmed, Http.Sys cancels requests when it encounters invalid parameters. We need a different detection mechanism.

Depending on the solution, we might want to patch 3.1.

[analogrelay]

Let's get a fix ready for 5.0 and then open a PR to backport and discuss with Tactics.

[Tratcher]

We've confirmed this behavior with the Http.Sys team. Unfortunately there isn't an alternate light-up mechanism available. The next best option is to check the OS version, but Windows reports the wrong version unless you add an app manifest. Requiring manifests would be a breaking change. Trying to read the version from the registry would require complex p-invokes.

@anurse, @shirhatti and I recommend backlogging this issue until we see a customer impact. All available fixes are higher impact than the original issue.