CUSTOM_EXT_TYPE_0
if (!SSL_CTX_add_client_custom_ext(c_ctx, CUSTOM_EXT_TYPE_0,
|| !SSL_CTX_add_server_custom_ext(s_ctx, CUSTOM_EXT_TYPE_0,
|| !SSL_CTX_add_server_custom_ext(s_ctx2, CUSTOM_EXT_TYPE_0,
if (ext_type != CUSTOM_EXT_TYPE_0)