pyopenssl
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Retry on `WANT_WRITE` & `WANT_READ` in `sendall()`
This change introduces retries in OpenSSL.SSL.Connection.sendall()
when WANT_WRITE_ERROR
or WANT_READ_ERROR
happen.
It relies on SSL_MODE_ENABLE_PARTIAL_WRITE
being set on the context,
that changes the mode of SSL_write()
to return errors only if zero
bytes has been sent making it safe to retry in these cases.
Ideally, the calling code is supposed to poll()
/select()
the
socket to know when it's okay to attempt the next retry (hence it is
readable or writable) but it's not available in the sendall()
method
and just retrying the operation is good enough.
Fixes #176
Refs:
- http://openssl.6102.n7.nabble.com/SSL-MODE-ACCEPT-MOVING-WRITE-BUFFER-td6421.html
- https://stackoverflow.com/a/28992313/595220
- https://www.openssl.org/docs/manmaster/man3/SSL_write.html
- https://stackoverflow.com/a/20817394/595220
Is there a way we can cover this with a test? And is SSL_MODE_ENABLE_PARTIAL_WRITE
being set anywhere?
And is
SSL_MODE_ENABLE_PARTIAL_WRITE
being set anywhere?
It's set in the context initializer: https://github.com/pyca/pyopenssl/blob/124a013/src/OpenSSL/SSL.py#L660. Also, the docstring of send()
seems to imply the same: https://github.com/pyca/pyopenssl/blob/124a013/src/OpenSSL/SSL.py#L1623-L1625 — I did not understand why is that at first but now it makes sense.
Is there a way we can cover this with a test?
I'm not sure how to properly trigger this in a stable manner at the moment. Although, the suspicion is that maybe if we could limit the buffer size of the test socket and feed a sufficiently big chunk of data into it, it should work. https://github.com/pyca/pyopenssl/blob/124a0134fdb7decb0136b4b6f7892b87b919e74e/tests/test_ssl.py#L2659-L2690 seems to be doing this exactly.
I'm trying to come up with with a reproducer @ https://github.com/pyca/pyopenssl/pull/955 but it still needs polishing.