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=-4.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 C6942C433E0 for ; Sun, 2 Aug 2020 00:58:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9599A20738 for ; Sun, 2 Aug 2020 00:58:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="cDFC28TN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727937AbgHBA6m (ORCPT ); Sat, 1 Aug 2020 20:58:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56022 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725883AbgHBA6l (ORCPT ); Sat, 1 Aug 2020 20:58:41 -0400 Received: from mail-pj1-x1042.google.com (mail-pj1-x1042.google.com [IPv6:2607:f8b0:4864:20::1042]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BB65DC06174A; Sat, 1 Aug 2020 17:58:41 -0700 (PDT) Received: by mail-pj1-x1042.google.com with SMTP id f9so9523128pju.4; Sat, 01 Aug 2020 17:58:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=Wtd1dTqkIQZNG0/L93HORXN7DmmIz2UILlkYQcDT6aM=; b=cDFC28TNCnBL9i2dwpdgSVKxiqUVFYdv7Is61GyKTALJ4OkNnKxhn7wQw0NdfUPgNT h659nPgUZhPC5HqFoFN+Hw250ELXr6du7JHOpzb4B5Oz+bC/xDfRUTqcV+9twoL4SDf0 4mpXQpLJDoGZt1MG6A1bsyi8jIRbqmeUoau0G3Hq8XM9JHLtMsYGNOCaDsWyoCZk/ePd ukBM4BcNquw1FBowrXsJIJX+0Y2O7kpuq/1WdnKLyN/R/c4poi8YCRt4Cy+h4C9QNT8C /J9GROMbyEeZjsySqm4LoZe2owKJ0gLpoVRYOmwN2ittIlmtobeKMWi5AYTSNFb3owkd sEQQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Wtd1dTqkIQZNG0/L93HORXN7DmmIz2UILlkYQcDT6aM=; b=k3rLcVBRPpruqowVoObdEAs+qdXbBKSOnlxm/vBofk3NbuenSIEg1j+bAgIILGsko5 x5K9R8h3Ik8pC9z+UdhdUJdckXzBwQYGrUgGSc9FjePZr5u9awDHsCfzGOoiNpMFzZFy hcyAdYYDnercKpEcEUxPLH3rW1sXdBuTSRO0Y4ygBUZi4Cyj3HfVjrG87udy2AaD+mwS O5uKbtDc3zzyL/Nin8NZGwv3lu3hqsAvxEJwRhi+1pfo5MQzFyq2vSx/0f5x2mCabeEH uoXMWCUoAEdFX4vqVBIXWJcUHwxxSeDWQUQEKUZ7yAHtkGjADgt1rbBUSBjlpPt/ZdXm 5Hvw== X-Gm-Message-State: AOAM530nYxOEDnDKWI8CklejcXN0sJd7rhQsdNdgEQcMnqiHeyxnjVKY 5IPCOGYSR10TEhP+7hnTxDvCTVYWjI62oAaOq7E= X-Google-Smtp-Source: ABdhPJzPBLsWF2rZygMeBjB8RfVFHbGp7efQqNHqgIP4lm9QeoY43S6Ay+IW2SbZNYx1HkPMGzhRhuvBpvLvZzvBdz8= X-Received: by 2002:a17:90b:128e:: with SMTP id fw14mr10858638pjb.66.1596329921179; Sat, 01 Aug 2020 17:58:41 -0700 (PDT) MIME-Version: 1.0 References: <20200730073702.16887-1-xie.he.0141@gmail.com> In-Reply-To: From: Xie He Date: Sat, 1 Aug 2020 17:58:30 -0700 Message-ID: Subject: Re: [PATCH v2] drivers/net/wan/lapbether: Use needed_headroom instead of hard_header_len To: Willem de Bruijn Cc: "David S. Miller" , Jakub Kicinski , Linux Kernel Network Developers , LKML , Linux X25 , Brian Norris Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Aug 1, 2020 at 6:31 AM Willem de Bruijn wrote: > > The kernel interface cannot be changed. If packet sockets used to pass > the first byte up to userspace, they have to continue to do so. > > So I think you can limit the header_ops to only dev_hard_header. Actually if we want to keep the kernel interface unchanged, we shouldn't implement header_ops for dev_hard_header either, because this changes the way the user space program sends DGRAM packets, too. Before the change the userspace program needs to add the 1-byte header before sending, and after the change the userspace program will let the kernel add the header via dev_hard_header. > Fixes should be small and targeted. Any larger refactoring is > best addressed in a separate net-next patch. I guess the best way for this fix patch would be just add a 0-byte packet check before the driver reads skb->data[0]. Thanks! I'll add the check and re-send the patch.