the callback is successful it B<MUST> return 1 even if no certificates have
been set. A zero is returned on error which will abort the handshake with a
fatal internal error alert. A negative return value will suspend the handshake
-and the handshake function will return immediatly.
+and the handshake function will return immediately.
L<SSL_get_error(3)|SSL_get_error(3)> will return SSL_ERROR_WANT_X509_LOOKUP to
indicate, that the handshake was suspended. The next call to the handshake
function will again lead to the call of cert_cb(). It is the job of the