extmod/modussl: Fix ussl read/recv/send/write errors when non-blocking.

Also fix related problems with socket on esp32, improve docs for
wrap_socket, and add more tests.

1 files changed, 17 insertions, 5 deletions

diff --git a/docs/library/ussl.rst b/docs/library/ussl.rst
index ffe146331..14e3f3ad1 100644
--- a/docs/library/ussl.rst
+++ b/docs/library/ussl.rst
@@ -13,16 +13,23 @@ facilities for network sockets, both client-side and server-side.
 Functions
 ---------
 
-.. function:: ussl.wrap_socket(sock, server_side=False, keyfile=None, certfile=None, cert_reqs=CERT_NONE, ca_certs=None)
-
+.. function:: ussl.wrap_socket(sock, server_side=False, keyfile=None, certfile=None, cert_reqs=CERT_NONE, ca_certs=None, do_handshake=True) 
    Takes a `stream` *sock* (usually usocket.socket instance of ``SOCK_STREAM`` type),
    and returns an instance of ssl.SSLSocket, which wraps the underlying stream in
    an SSL context. Returned object has the usual `stream` interface methods like
-   ``read()``, ``write()``, etc. In MicroPython, the returned object does not expose
-   socket interface and methods like ``recv()``, ``send()``. In particular, a
-   server-side SSL socket should be created from a normal socket returned from
+   ``read()``, ``write()``, etc.
+   A server-side SSL socket should be created from a normal socket returned from
    :meth:`~usocket.socket.accept()` on a non-SSL listening server socket.
 
+   - *do_handshake* determines whether the handshake is done as part of the ``wrap_socket``
+     or whether it is deferred to be done as part of the initial reads or writes
+     (there is no ``do_handshake`` method as in CPython).
+     For blocking sockets doing the handshake immediately is standard. For non-blocking
+     sockets (i.e. when the *sock* passed into ``wrap_socket`` is in non-blocking mode)
+     the handshake should generally be deferred because otherwise ``wrap_socket`` blocks
+     until it completes. Note that in AXTLS the handshake can be deferred until the first
+     read or write but it then blocks until completion.
+
    Depending on the underlying module implementation in a particular
    :term:`MicroPython port`, some or all keyword arguments above may be not supported.
 
@@ -31,6 +38,11 @@ Functions
    Some implementations of ``ussl`` module do NOT validate server certificates,
    which makes an SSL connection established prone to man-in-the-middle attacks.
 
+   CPython's ``wrap_socket`` returns an ``SSLSocket`` object which has methods typical
+   for sockets, such as ``send``, ``recv``, etc. MicroPython's ``wrap_socket``
+   returns an object more similar to CPython's ``SSLObject`` which does not have
+   these socket methods.
+
 Exceptions
 ----------