From patchwork Mon Nov 10 16:09:33 2008 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Alex_Villac=C3=AD=C2=ADs_Lasso?= X-Patchwork-Id: 8019 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.176.167]) by ozlabs.org (Postfix) with ESMTP id 4E2F5DDDE3 for ; Tue, 11 Nov 2008 03:10:29 +1100 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752408AbYKJQKY (ORCPT ); Mon, 10 Nov 2008 11:10:24 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751564AbYKJQKY (ORCPT ); Mon, 10 Nov 2008 11:10:24 -0500 Received: from host-200-93-199-98.telconet.net ([200.93.199.98]:58354 "EHLO elastix.palosanto.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1751347AbYKJQKX (ORCPT ); Mon, 10 Nov 2008 11:10:23 -0500 Received: by elastix.palosanto.com (Postfix, from userid 501) id 1BEAD1B08C82; Mon, 10 Nov 2008 11:10:21 -0500 (ECT) X-Spam-Checker-Version: SpamAssassin 3.2.4 (2008-01-01) on elastix.palosanto.com X-Spam-Level: X-Spam-Status: No, score=-4.2 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 autolearn=ham version=3.2.4 Received: from srv64.palosanto.com (unknown [192.168.1.64]) by elastix.palosanto.com (Postfix) with ESMTP id A9CA61B08C82; Mon, 10 Nov 2008 11:10:19 -0500 (ECT) Message-ID: <49185CBD.2040601@ceibo.fiec.espol.edu.ec> Date: Mon, 10 Nov 2008 11:09:33 -0500 From: =?ISO-8859-1?Q?Alex_Villac=ED=ADs_Lasso?= User-Agent: Thunderbird 2.0.0.16 (X11/20080723) MIME-Version: 1.0 To: irda-users@lists.sourceforge.net, netdev@vger.kernel.org Subject: [1/3] IRDA: Create new field tx_extra in skbuff Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org For background, see regression report at http://bugzilla.kernel.org/show_bug.cgi?id=11795 This patchset attempts to fix a regression that broke the irda stack as a result of the qdisc patches merged in 2.6.27. The previous patchsets attempt to fix the clobbering of the irda information by storing it within the data payload itself, as an additional header. For this, space has been allocated via skb_pull (?!) and later, skb_reserve(). The problem with this approach is that we do not have a guarantee that all skbuffs that are processed in the irda stack are actually allocated with functions that reserve the required space for the irda metadata, especially in the tx route. In addition, this approach mixes the payload data with metadata that should not be transmitted at all, which is a bit disorganized. This is the first of 3 patches that try a different approach. Instead of allocating an additional "header" within the data buffer itself, it introduces a new field within the skbuff, named tx_extra. This field should be used for passing data from the higher layers that is required for the drivers to transmit the packet correctly, and formalizes the previous usage of the cb field by the irda stack. The only issue I see is that every single skbuff carries an additional 32 bytes which are not put to any use in other stacks (for now). I was thinking about a pointer field to on-the-fly allocated data, but that means messing around with the skbuff allocation functions, the cloning functions (involving deciding how to behave on cloning), etc. This way is simpler to understand. This patch and the other two that follow fix the issue for me under 2.6.28-rc3. Please comment on this, as I am messing around with the skbuff structure, which potentially affects all network stacks. Signed-off-by: Alex Villacís Lasso diff -ur linux-2.6.28-rc3-git-orig/include/linux/skbuff.h linux-2.6.28-rc3-git/include/linux/skbuff.h --- linux-2.6.28-rc3-git-orig/include/linux/skbuff.h 2008-11-06 19:44:23.000000000 -0500 +++ linux-2.6.28-rc3-git/include/linux/skbuff.h 2008-11-08 11:47:46.000000000 -0500 @@ -279,6 +279,14 @@ */ char cb[48]; + /* + * Additional space for layer-specific variables that need to + * survive past dev_queue_xmit(), which clobbers cb above. + * Intended for use by drivers that need additional layer-specific + * parameters in order to transmit a packet properly. + */ + char tx_extra[32]; + unsigned int len, data_len; __u16 mac_len, diff -ur linux-2.6.28-rc3-git-orig/include/net/irda/irda_device.h linux-2.6.28-rc3-git/include/net/irda/irda_device.h --- linux-2.6.28-rc3-git-orig/include/net/irda/irda_device.h 2008-11-06 19:44:23.000000000 -0500 +++ linux-2.6.28-rc3-git/include/net/irda/irda_device.h 2008-11-08 11:55:00.000000000 -0500 @@ -230,6 +230,12 @@ void irda_setup_dma(int channel, dma_addr_t buffer, int count, int mode); + +static inline struct irda_skb_cb *irda_get_skb_cb(struct sk_buff *skb) +{ + return (struct irda_skb_cb *)skb->tx_extra; +} + /* * Function irda_get_mtt (skb) *