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=-6.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 5430FC433DF for ; Sat, 17 Oct 2020 18:54:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 19CF02073A for ; Sat, 17 Oct 2020 18:54:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2439107AbgJQSyN (ORCPT ); Sat, 17 Oct 2020 14:54:13 -0400 Received: from mailout08.rmx.de ([94.199.90.85]:58689 "EHLO mailout08.rmx.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2439068AbgJQSyM (ORCPT ); Sat, 17 Oct 2020 14:54:12 -0400 Received: from kdin01.retarus.com (kdin01.dmz1.retloc [172.19.17.48]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mailout08.rmx.de (Postfix) with ESMTPS id 4CDBy83CvqzMstg; Sat, 17 Oct 2020 20:54:08 +0200 (CEST) Received: from mta.arri.de (unknown [217.111.95.66]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by kdin01.retarus.com (Postfix) with ESMTPS id 4CDBxs3nTgz2xDh; Sat, 17 Oct 2020 20:53:53 +0200 (CEST) Received: from n95hx1g2.localnet (192.168.54.12) by mta.arri.de (192.168.100.104) with Microsoft SMTP Server (TLS) id 14.3.408.0; Sat, 17 Oct 2020 20:53:20 +0200 From: Christian Eggers To: Vladimir Oltean CC: Andrew Lunn , Vivien Didelot , Florian Fainelli , Jakub Kicinski , Kurt Kanzenbach , "David S . Miller" , Woojung Huh , "Microchip Linux Driver Support" , , Subject: Re: [PATCH net-next 1/3] net: dsa: don't pass cloned skb's to drivers xmit function Date: Sat, 17 Oct 2020 20:53:19 +0200 Message-ID: <2130539.dlFve3NVyK@n95hx1g2> Organization: Arnold & Richter Cine Technik GmbH & Co. Betriebs KG In-Reply-To: <20201017004816.q4l6cypw4fd4vu5f@skbuf> References: <20201016200226.23994-1-ceggers@arri.de> <20201016200226.23994-2-ceggers@arri.de> <20201017004816.q4l6cypw4fd4vu5f@skbuf> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Originating-IP: [192.168.54.12] X-RMX-ID: 20201017-205359-4CDBxs3nTgz2xDh-0@kdin01 X-RMX-SOURCE: 217.111.95.66 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Vladimir, On Saturday, 17 October 2020, 02:48:16 CEST, Vladimir Oltean wrote: > On Fri, Oct 16, 2020 at 10:02:24PM +0200, Christian Eggers wrote: > > Ensure that the skb is not cloned and has enough tail room for the tail > > tag. This code will be removed from the drivers in the next commits. > > > > Signed-off-by: Christian Eggers > > --- > > Does 1588 work for you using this change, or you haven't finished > implementing it yet? If you haven't, I would suggest finishing that > part first. Yes it does. Just after finishing this topic, I would to sent the patches for PTP. Maybe I'll do it in parallel, anything but the combination of L2/E2E/SLOB seems to work. > The post-reallocation skb looks nothing like the one before. > > Before: > skb len=68 headroom=2 headlen=68 tailroom=186 > mac=(2,14) net=(16,-1) trans=-1 > shinfo(txflags=1 nr_frags=0 gso(size=0 type=0 segs=0)) > csum(0x0 ip_summed=0 complete_sw=0 valid=0 level=0) > hash(0x9d6927ec sw=1 l4=0) proto=0x88f7 pkttype=0 iif=0 > dev name=swp2 feat=0x0x0002000000005020 > sk family=17 type=3 proto=0 > > After: > skb len=68 headroom=2 headlen=68 tailroom=186 > mac=(2,16) net=(18,-17) trans=1 > shinfo(txflags=0 nr_frags=0 gso(size=0 type=0 segs=0)) > csum(0x0 ip_summed=0 complete_sw=0 valid=0 level=0) > hash(0x0 sw=0 l4=0) proto=0x0000 pkttype=0 iif=0 > > Notice how you've changed shinfo(txflags), among other things. I get a similar output when placing the two skb_dump() calls in the current ksz_common_xmit() code: [ 5052.662168] old:skb len=58 headroom=2 headlen=58 tailroom=68 [ 5052.662168] mac=(2,14) net=(16,-1) trans=-1 [ 5052.662168] shinfo(txflags=1 nr_frags=0 gso(size=0 type=0 segs=0)) [ 5052.662168] csum(0x0 ip_summed=0 complete_sw=0 valid=0 level=0) [ 5052.662168] hash(0x0 sw=0 l4=0) proto=0x88f7 pkttype=0 iif=0 [ 5052.676360] old:dev name=lan0 feat=0x0x0002000000005220 [ 5052.679001] old:sk family=17 type=3 proto=0 [ 5052.681140] old:skb linear: 00000000: 01 1b 19 00 00 00 52 d9 a9 5d a1 40 88 f7 01 02 [ 5052.685236] old:skb linear: 00000010: 00 2c 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ 5052.689342] old:skb linear: 00000020: 00 00 52 d9 a9 ff fe 5d a1 40 00 01 00 00 01 7f [ 5052.693418] old:skb linear: 00000030: 00 00 00 00 00 00 00 00 00 00 [ 5052.696843] new:skb len=65 headroom=2 headlen=65 tailroom=61 [ 5052.696843] mac=(2,16) net=(18,-17) trans=1 [ 5052.696843] shinfo(txflags=0 nr_frags=0 gso(size=0 type=0 segs=0)) [ 5052.696843] csum(0x0 ip_summed=0 complete_sw=0 valid=0 level=0) [ 5052.696843] hash(0x0 sw=0 l4=0) proto=0x0000 pkttype=0 iif=0 [ 5052.711215] new:skb linear: 00000000: 01 1b 19 00 00 00 52 d9 a9 5d a1 40 88 f7 01 02 [ 5052.715305] new:skb linear: 00000010: 00 2c 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ 5052.719407] new:skb linear: 00000020: 00 00 52 d9 a9 ff fe 5d a1 40 00 01 00 00 01 7f [ 5052.723484] new:skb linear: 00000030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ 5052.727587] new:skb linear: 00000040: 00 Note that whilst some skb members differ, the two hexdumps look correct. > Which proves that you can't just copy&paste whatever you found in > tag_trailer.c. I did. tag_trailer and tag_ksz are quite similar here, so I took a combination of them. > I am not yet sure whether there is any helper that can be used instead > of this crazy open-coding. Right now, not having tested anything yet, my > candidates of choice would be pskb_expand_head or __pskb_pull_tail. You > should probably also try to cater here for the potential reallocation > done in the skb_cow_head() of non-tail taggers. Which would lean the > balance towards pskb_expand_head(), I believe. The "open coding" is from the existing code (which doesn't say that it is correct). I will investigate why the copied skb is different and whether psk_expand_head can do better. I don't like to touch the non-tail taggers, this is too much out of the scope of my current work. > Also, if the result is going to be longer than ~20 lines of code, I > strongly suggest moving the reallocation to a separate function so you > don't clutter dsa_slave_xmit. As Florian requested I'll likely put the code into a separate function in slave.c and call it from the individual tail-taggers in order not to put extra conditionals in dsa_slave_xmit. regards Christian