tlsext_funcs
ext = tlsext_funcs(tlsext, is_server);
ext = tlsext_funcs(tlsext, is_server);
const struct tls_extension_funcs *tlsext_funcs(const struct tls_extension *,
if ((*client_funcs = tlsext_funcs(ext, 0)) == NULL)
if ((*server_funcs = tlsext_funcs(ext, 1)) == NULL)