Basically, in the portability layer, it is checked if the socket is
NON-block, and if not, then even the EAGAIN and EWOULDBLOCK errors are
diverted to a RECV error. This causes a problem for sockets with
receive timeouts set. When such a timeout is set, the condition for
NON_BLOCK isn't met and hence a hard error is returned.
Searching for EAGAIN and EWOULDBLOCK in lwip returns only 3 results
(accept, recvfrom, close) and all of them look to be genuine cases for
EWOULDBLOCK. So removing this check to make receive timeout with TLS
work.
As per upgrade notes of lwIP v2.1.0:
socket API: according to the standard, SO_ERROR now only returns asynchronous errors.
All other/normal/synchronous errors are (and always were) available via 'errno'.
LWIP_SOCKET_SET_ERRNO has been removed - 'errno' is always set - and required!
Refer: https://www.nongnu.org/lwip/2_1_x/upgrading.html
Fixes https://github.com/espressif/esp-azure/issues/51