Don't call immediatly self._process_write_backlog() but schedule the call using
call_soon(). _on_handshake_complete() can be called indirectly from
_process_write_backlog(), and _process_write_backlog() is not reentrant.
The new SSL implementation is based on the new ssl.MemoryBIO which is only
available on Python 3.5. On Python 3.4 and older, the legacy SSL implementation
(using SSL_write, SSL_read, etc.) is used. The proactor event loop only
supports the new implementation.
The new asyncio.sslproto module adds _SSLPipe, SSLProtocol and
_SSLProtocolTransport classes. _SSLPipe allows to "wrap" or "unwrap" a socket
(switch between cleartext and SSL/TLS).
Patch written by Antoine Pitrou. sslproto.py is based on gruvi/ssl.py of the
gruvi project written by Geert Jansen.
This change adds SSL support to ProactorEventLoop on Python 3.5 and newer!
It becomes also possible to implement STARTTTLS: switch a cleartext socket to
SSL.
Victor Stinner