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=-13.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 C39A9C433DF for ; Thu, 30 Jul 2020 07:37:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A565322BEF for ; Thu, 30 Jul 2020 07:37:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="gcQTdkUw" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728934AbgG3HhK (ORCPT ); Thu, 30 Jul 2020 03:37:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48082 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728645AbgG3HhJ (ORCPT ); Thu, 30 Jul 2020 03:37:09 -0400 Received: from mail-pl1-x644.google.com (mail-pl1-x644.google.com [IPv6:2607:f8b0:4864:20::644]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A9A66C061794; Thu, 30 Jul 2020 00:37:09 -0700 (PDT) Received: by mail-pl1-x644.google.com with SMTP id t10so7969181plz.10; Thu, 30 Jul 2020 00:37:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=K+Oo0bHEpODF7XLQBQ6GDyIq38DUDAb0nnpXubPm0uI=; b=gcQTdkUwMvU1FPhnUFLPP+UPLAy2jxmTogTN2emcrLTfrpzcy5xxre8T4B4/PeTPEJ /Mz40YKCWv+F52Z6VI00Fcf+4FmiJBl4341OILo+enlqoGli0586/XSBRTjL6//WiKwP vKPo3NFq1H1Or6BHlxSLKDq/odvYSy39q+pTv6ZY/3p1D/RnFpPm0exZGMgVTUO3AWmm IpYo5g1xmDgnp4nPd+y0n7W/3HY7rCx8MW5Ac65Xl3gUOsq/mD2nLfPhJfxahNzeBgFS lZ5uTeDWusdNq07HOOiqipYsL1aL/A6NsaThNpZkivIqJfZp/sCT7q1zWe0NQ6CTry2K 8kjA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=K+Oo0bHEpODF7XLQBQ6GDyIq38DUDAb0nnpXubPm0uI=; b=TV2NuetAAFOQ/MSaPdKa3NHFH4VHTllkPy2kePIsW1AfO13xcVpi/6IF5ZFdm7fhLH fq0G65nejx4NZ6dIrHFUqWFO0LfXt6G54XdHiL3O7lM/sbvAz80/2YFBu4ds4e7PkNIS QNLgmjYQUOUBr5/6+vBbKcYkJUYDr5JRxsflkXu1gCNcPj3m4CFXJ8I/v64o1+fkMXkE Aei/SGB4S8NrhakirtAq55UV7u/qEdRDVrHtS2X6URL3opt5UVZrufeBh49aUqY++B1m HPit+LsdyoN+fo+ysQhB7VQyCIKq3jfyPWWcDuX6Ux+Ac3kg2udBJpJCIuFXTaDOF+Ek JMnA== X-Gm-Message-State: AOAM533RJ3pXo+TasrC1qYzEDOQjInFAyfaac7NDEXOwWDVXU+L5PTfl NvKiNUfKSDNJXWZsqKhN4MYiRSVY X-Google-Smtp-Source: ABdhPJxPHZwDLjW/Q8zuk2uuWdoo43CpqfYLo+tFfec3HcKfuVt0EK9EZSKqNEI/8lIatQ3t+2rpZw== X-Received: by 2002:a17:902:c405:: with SMTP id k5mr30209769plk.202.1596094629206; Thu, 30 Jul 2020 00:37:09 -0700 (PDT) Received: from shane-XPS-13-9380.hsd1.ca.comcast.net ([2601:646:8880:9ae0:e460:1d84:b10c:de38]) by smtp.gmail.com with ESMTPSA id o19sm287113pjs.8.2020.07.30.00.37.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Jul 2020 00:37:08 -0700 (PDT) From: Xie He To: "David S. Miller" , Jakub Kicinski , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-x25@vger.kernel.org Cc: Xie He Subject: [PATCH v2] drivers/net/wan/lapbether: Use needed_headroom instead of hard_header_len Date: Thu, 30 Jul 2020 00:37:02 -0700 Message-Id: <20200730073702.16887-1-xie.he.0141@gmail.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org In net/packet/af_packet.c, the function packet_snd first reserves a headroom of length (dev->hard_header_len + dev->needed_headroom). Then if the socket is a SOCK_DGRAM socket, it calls dev_hard_header, which calls dev->header_ops->create, to create the link layer header. If the socket is a SOCK_RAW socket, it "un-reserves" a headroom of length (dev->hard_header_len), and assumes the user to provide the appropriate link layer header. So according to the logic of af_packet.c, dev->hard_header_len should be the length of the header that would be created by dev->header_ops->create. However, this driver doesn't provide dev->header_ops, so logically dev->hard_header_len should be 0. So we should use dev->needed_headroom instead of dev->hard_header_len to request necessary headroom to be allocated. Signed-off-by: Xie He --- Patch v2 has no difference from v1. I re-submitted it because I want to find new reviewers, and I want to free new reviewers from the burden of reading the lengthy discussion and explanations in the v1 email threads. Summary of v1 discussion: Cong Wang referred me to Brian Norris, who did a similar change before. Brian Norris agreed with me on "hard_header_len vs needed_headroom", but was unfamiliar with X.25 drivers. --- drivers/net/wan/lapbether.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/net/wan/lapbether.c b/drivers/net/wan/lapbether.c index b2868433718f..34cf6db89912 100644 --- a/drivers/net/wan/lapbether.c +++ b/drivers/net/wan/lapbether.c @@ -305,6 +305,7 @@ static void lapbeth_setup(struct net_device *dev) dev->netdev_ops = &lapbeth_netdev_ops; dev->needs_free_netdev = true; dev->type = ARPHRD_X25; + dev->hard_header_len = 0; dev->mtu = 1000; dev->addr_len = 0; } @@ -331,7 +332,8 @@ static int lapbeth_new_device(struct net_device *dev) * then this driver prepends a length field of 2 bytes, * then the underlying Ethernet device prepends its own header. */ - ndev->hard_header_len = -1 + 3 + 2 + dev->hard_header_len; + ndev->needed_headroom = -1 + 3 + 2 + dev->hard_header_len + + dev->needed_headroom; lapbeth = netdev_priv(ndev); lapbeth->axdev = ndev; -- 2.25.1