Normally when a SSL connection is finished, the parties must send out "close notify" alert messages using
SSL_shutdown(3) for a clean shutdown.When setting the "quiet shutdown" flag to 1, SSL_shutdown(3) will set the internal flags to SSL_SENT_SHUTDOWN|SSL_RECEIVED_SHUTDOWN. ( SSL_shutdown(3) then behaves like SSL_set_shutdown(3) called with SSL_SENT_SHUTDOWN|SSL_RECEIVED_SHUTDOWN.) The session is thus considered to be shutdown, but no "close notify" alert is sent to the peer. This behaviour violates the TLS standard.
The default is normal shutdown behaviour as described by the TLS standard.