Find solution for receiving post handshake messages with blocking IO

[goatgoose]

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Problem:

s2n-tls handles post handshake messages in s2n_recv. After parsing the record, s2n_post_handshake_recv is called to process the message. If any application data is received as well as the post handshake message, it is returned from the s2n_recv call. If no application data is received, s2n_recv returns and sets the blocked status to S2N_BLOCKED_ON_READ.

However, in blocking IO mode, s2n_recv does not return if there is no application data. In this case, select/epoll will signal that data is available, the application will call s2n_recv, the post handshake message will be processed, and s2n_recv will hang, because there's no application data to return.

Solution:

A solution needs to be determined. A possible option would be to set a new blocked status in blocking mode to tell the application there's no application data to receive.