@deftypefun {int} {gnutls_x509_ext_export_tlsfeatures} (gnutls_x509_tlsfeatures_t @var{f}, gnutls_datum_t * @var{ext}) @var{f}: The features structure @var{ext}: The DER-encoded extension data; must be freed using @code{gnutls_free()} . This function will convert the provided TLS features structure structure to a DER-encoded TLS features PKIX extension. The output data in @code{ext} will be allocated using @code{gnutls_malloc()} . @strong{Returns:} On success, @code{GNUTLS_E_SUCCESS} (0) is returned, otherwise a negative error value. @strong{Since:} 3.5.1 @end deftypefun