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=-4.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 7808EC433DF for ; Tue, 4 Aug 2020 06:53:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 821662076C for ; Tue, 4 Aug 2020 06:53:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726877AbgHDGxX (ORCPT ); Tue, 4 Aug 2020 02:53:23 -0400 Received: from host-88-217-225-28.customer.m-online.net ([88.217.225.28]:50164 "EHLO mail.dev.tdt.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725904AbgHDGxW (ORCPT ); Tue, 4 Aug 2020 02:53:22 -0400 Received: from mail.dev.tdt.de (localhost [IPv6:::1]) by mail.dev.tdt.de (Postfix) with ESMTP id 03F3620084; Tue, 4 Aug 2020 06:53:15 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Tue, 04 Aug 2020 08:53:15 +0200 From: Martin Schiller To: Xie He Cc: "David S. Miller" , Jakub Kicinski , Linux Kernel Network Developers , LKML , Linux X25 Subject: Re: [PATCH v2] drivers/net/wan/lapbether: Use needed_headroom instead of hard_header_len Organization: TDT AG In-Reply-To: References: <20200730073702.16887-1-xie.he.0141@gmail.com> Message-ID: X-Sender: ms@dev.tdt.de User-Agent: Roundcube Webmail/1.1.5 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-07-30 10:02, Xie He wrote: > Hi Martin, > > I'm currently working on a plan to make all X.25 drivers (lapbether.c, > x25_asy.c, hdlc_x25.c) to set dev->hard_header_len / > dev->needed_headroom correctly. So that upper layers no longer need to > guess how much headroom a X.25 device needs with a constant value (as > they currently do). > > After studying af_packet.c, I found that X.25 drivers needed to set > needed_headroom to reserve the headroom instead of using > hard_header_len. Because hard_header_len should be the length of the > header that would be created by dev_hard_header, and in this case it > should be 0, according to the logic of af_packet.c. > > So my first step is to fix the settings in lapbether.c. Could you > review this patch and extend your support via a "Reviewed-by" tag? If > this can be fixed, I'll go on and fix other X.25 drivers. Thanks! > > It's very hard to find reviewers for X.25 code because it is > relatively unmaintained by people. I hope I can do some of the > maintenance work. I greatly appreciate your support! I don't like the idea to get rid of the 1-byte header. This header is also used in userspace, for example when using a tun/tap interface for an XoT (X.25 over TCP) application. A change would therefore have very far-reaching consequences. BTW: The linux x25 mailing list does not seem to work anymore. I've been on it for some time now, but haven't received a single email from it. I've tried to contact owner-linux-x25@vger.kernel.org, but only got an "undeliverable" email back. It would be great if you could add me to CC list of all versions of your patches, so I don't need to "google" for any further related mails. So, what's the latest version of the patch now, which you want me to review?