BeginConnect_EndPoint_AddressFamily_Throws_NotSupported test fails deterministically on netfx on RS4

[stephentoub]

System.Net.Sockets.Tests.ArgumentValidation.BeginConnect_EndPoint_AddressFamily_Throws_NotSupported [FAIL]
        Assert.Throws() Failure
        Expected: typeof(System.NotSupportedException)
        Actual:   typeof(System.InvalidOperationException): BeginConnect cannot be called while another asynchronous operation is in progress on the same Socket.
        Stack Trace:
             at System.Net.Sockets.Socket.BeginConnect(EndPoint remoteEP, AsyncCallback callback, Object state)
             at System.Threading.Tasks.TaskFactory`1.FromAsyncImpl[TArg1](Func`4 beginMethod, Func`2 endFunction, Action`1 endAction, TArg1 arg1, Object state, TaskCreationOptions cr
  eationOptions)
             at System.Net.Sockets.SocketTaskExtensions.ConnectAsync(Socket socket, EndPoint remoteEndPoint)
             at System.Net.Sockets.Tests.ArgumentValidation.<>c.<BeginConnect_EndPoint_AddressFamily_Throws_NotSupported>b__106_1()

[davidsh]

RS4 (Windows 10 April 2018 Update) contains .NET Framework 4.7.2. There was an explicit bug fix for 4.7.2 that made this exception happen when concurrent I/O (a form of misuse) happens with those APIs.

[stephentoub]

There's no concurrent use in this test. Seems like the fix may have been broken.

[davidsh]

See internal bug: 188428

cc: @Caesar1995

[davidsh]

From: https://github.com/Microsoft/dotnet/blob/master/releases/net472/dotnet472-changes.md#networking

Socket.BeginConnect will now consistently throw InvalidOperationException when attempting multiple operations. [188428, System.dll, Bug]

[stephentoub]

From looking at the decompiled source, I see this:

if (Interlocked.Exchange(ref this.asyncConnectOperationLock, 1) != 0)
    throw new InvalidOperationException(SR.GetString("net_sockets_no_duplicate_async"));

and then after that it does things like:

if ((point.AddressFamily != AddressFamily.Unspecified) && !this.CanTryAddressFamily(point.AddressFamily))
    throw new NotSupportedException(SR.GetString("net_invalidversion"));

That means we're leaving asyncConnectOperationLock set to 1 when something fails after it, and the socket becomes unusable for any subsequent attempt at a connect. That seems wrong, and we should be resetting asyncConnectOperationLock in such cases.

[davidsh]

cc: @karelz

[stephentoub]

In any event, I'll fix up the test to not depend on this.