Windows error 10022 kills threads

[AdamaTheHutt]

❓ I'm submitting a ...

• 🐞 bug report
• 🐣 feature request
• ❓ question about the decisions made in the repository

🐞 Describe the bug. What is the current behavior?
Sometimes when closing a connection, we get an error, probably because it's already closed or similar. This is addressed in 384e6d0 , the problem is that in windows the error might instead be WSAEINVAL (10022), and that is not caught.

❓ What is the motivation / use case for changing the behavior?
Because of this, in combination with, I think, the error seen in #358 , we are eventually running out of threads, and the server stops responding completely.

💡 To Reproduce
Don't know how to reproduce, we get this error sporadically in production. All threads are typically gone in a few days or sometimes weeks.

💡 Expected behavior
I expect this error to be ignored, so that the thread keeps on running.

📋 Details
Also tried switching to pyopenssl, but the same error happened there too.

📋 Environment

• Cheroot version: 8.5.2
• CherryPy version: -
• Python version: 3.8.9
• OS: Microsoft Windows Server 2016 Datacenter, 10.0.14393
• Browser: [?]

📋 Additional context
A typical error:

 Exception in thread CP Server Thread-18: 
Traceback (most recent call last): 
  File "c:\py\lib\threading.py", line 917, in _bootstrap_inner 
    self.run() 
  File "c:\py\lib\site-packages\cheroot\workers\threadpool.py", line 130, in run 
    conn.close() 
  File "c:\py\lib\site-packages\cheroot\server.py", line 1360, in close 
    self._close_kernel_socket() 
  File "c:\py\lib\site-packages\cheroot\server.py", line 1483, in _close_kernel_socket 
    shutdown(socket.SHUT_RDWR)  # actually send a TCP FIN 
  File "c:\py\lib\ssl.py", line 1090, in shutdown 
    super().shutdown(how) 
OSError: [WinError 10022] An invalid argument was supplied

Then similar exceptions for thread after thread, until none are left.

In the references added in 9f9de65 there are several examples of dealing with error 10022 also, for example python/cpython@83a2c28 .

[webknjaz]

Looks like this error code is sometimes exposed as EINVAL or WSAEINVAL:

• https://github.com/python/cpython/blob/19ca114/Modules/errnomodule.c#L146-L152
• https://github.com/python/cpython/blob/19ca114/Modules/errnomodule.c#L791-L793

So it seems like maybe it should be covered already. At least in some envs. But somebody needs to check a reproducer under a relevant env. One way to do this is to connect to a GHA worker using https://github.com/marketplace/actions/debugging-with-tmate.

[AzureIP]

Hi,
I experienced this error, too. What is the current state?