The following return values can currently occur for
SSL_want():SSL_NOTHING
There is no data to be written or to be read.
SSL_WRITING
There are data in the SSL buffer that must be written to the underlying BIO layer in order to complete the actual SSL_*() operation. A call to SSL_get_error(3) should return SSL_ERROR_WANT_WRITE.
SSL_READING
More data must be read from the underlying BIO layer in order to complete the actual SSL_*() operation. A call to SSL_get_error(3) should return SSL_ERROR_WANT_READ.
SSL_X509_LOOKUP
The operation did not complete because an application callback set by SSL_CTX_set_client_cert_cb() has asked to be called again. A call to SSL_get_error(3) should return SSL_ERROR_WANT_X509_LOOKUP.
SSL_want_nothing(), SSL_want_read(), SSL_want_write(), SSL_want_x509_lookup() return 1, when the corresponding condition is true or 0 otherwise.