From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 25D4DC3F2D7 for ; Tue, 3 Mar 2020 22:59:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 047C7206E6 for ; Tue, 3 Mar 2020 22:59:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728177AbgCCW7R (ORCPT ); Tue, 3 Mar 2020 17:59:17 -0500 Received: from shards.monkeyblade.net ([23.128.96.9]:36990 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726766AbgCCW7R (ORCPT ); Tue, 3 Mar 2020 17:59:17 -0500 Received: from localhost (unknown [IPv6:2601:601:9f00:477::3d5]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: davem-davemloft) by shards.monkeyblade.net (Postfix) with ESMTPSA id E1EC215A0FF4F; Tue, 3 Mar 2020 14:59:16 -0800 (PST) Date: Tue, 03 Mar 2020 14:59:16 -0800 (PST) Message-Id: <20200303.145916.1506066510928020193.davem@davemloft.net> To: mkubecek@suse.cz Cc: kuba@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net] tun: fix ethtool_ops get_msglvl and set_msglvl handlers From: David Miller In-Reply-To: <20200303082252.81F7FE1F46@unicorn.suse.cz> References: <20200303082252.81F7FE1F46@unicorn.suse.cz> X-Mailer: Mew version 6.8 on Emacs 26.1 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Tue, 03 Mar 2020 14:59:17 -0800 (PST) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Michal Kubecek Date: Tue, 3 Mar 2020 09:22:52 +0100 (CET) > The get_msglvl and setmsglvl handlers only work as expected if TUN_DEBUG > is defined (which required editing the source). Otherwise tun_get_msglvl() > returns -EOPNOTSUPP but as this handler is not supposed to return error > code, it is not recognized as one and passed to userspace as is, resulting > in bogus output of ethtool command. The set_msglvl handler ignores its > argument and does nothing if TUN_DEBUG is left undefined. > > The way to return EOPNOTSUPP to userspace for both requests is not to > provide these ethtool_ops callbacks at all if TUN_DEBUG is left undefined. > > Signed-off-by: Michal Kubecek I agree with your analysis. But this TUN_DEBUG thing stands outside of what we let drivers do. Either this tracing is not so useful and can be deleted, or the tracing should be available unconditionally so that it can be turned on by the vast majority of users who do not edit the source. I suspect making the TUN_DEBUG code unconditional is that way to go here.