OpenSSL 3.0.0 state machine handles unexpected EOFs more strict and requires peers to properly shut down connections. The old OpenSSL 1.1.1 behavior can be get back with SSL_OP_IGNORE_UNEXPECTED_EOF.

I propose to add the option by default until Python's ssl module has better ways to perform one-way shutdown of connections.

https://www.openssl.org/docs/manmaster/man3/SSL_CTX_set_options.html

> Some TLS implementations do not send the mandatory close_notify alert on shutdown. If the application tries to wait for the close_notify alert but the peer closes the connection without sending it, an error is generated. When this option is enabled the peer does not need to send the close_notify alert and a closed connection will be treated as if the close_notify alert was received.

> You should only enable this option if the protocol running over TLS can detect a truncation attack itself, and that the application is checking for that truncation attack.