generate_stateless_cookie_callback
int generate_stateless_cookie_callback(SSL *ssl, unsigned char *cookie,
&& generate_stateless_cookie_callback(ssl, result, &resultlength)
int res = generate_stateless_cookie_callback(ssl, cookie, &temp);
SSL_CTX_set_stateless_cookie_generate_cb(ctx, generate_stateless_cookie_callback);
SSL_CTX_set_stateless_cookie_generate_cb(sctx, generate_stateless_cookie_callback);