OCSP stapling: loading OCSP responses. This includes the ssl_stapling_responder directive (defaults to OCSP responder set in certificate's AIA extension). OCSP response for a given certificate is requested once we get at least one connection with certificate_status extension in ClientHello, and certificate status won't be sent in the connection in question. This due to limitations in the OpenSSL API (certificate status callback is blocking). Note: SSL_CTX_use_certificate_chain_file() was reimplemented as it doesn't allow to access the certificate loaded via SSL_CTX.