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=-3.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham 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 84F0BC10F0E for ; Wed, 10 Apr 2019 02:17:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4CED72082E for ; Wed, 10 Apr 2019 02:17:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="n8kN77/0" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727261AbfDJCRT (ORCPT ); Tue, 9 Apr 2019 22:17:19 -0400 Received: from mail-pl1-f195.google.com ([209.85.214.195]:45673 "EHLO mail-pl1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726532AbfDJCRS (ORCPT ); Tue, 9 Apr 2019 22:17:18 -0400 Received: by mail-pl1-f195.google.com with SMTP id bf11so365881plb.12; Tue, 09 Apr 2019 19:17:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:openpgp:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=N6CLuPA/AJhfGD4Iu0YQ5LK2CB0ty+XzJLOlx2nNx34=; b=n8kN77/0SMaU8oWAbWVkX7bejuEg4CTGtLuXPuMhYxoWL9O4ocUe+d93DD4wwROm0n UGOw6lRcEvz/rHTl9hGnzZWf7lZQ4zv6wYIB6wx8ThfR96w/h9dzeiPCWuCrcCBhX50y ZF8t2yw35dBrNa6lUmGTyk7uaKi9SqiIsgjyFy0VwKoMCUTksXk37UPb2/DtuWmsh4dF lsjNrXota9UgoyIet2yCvm6Elui350dbrv5k08oU5Ff+E4q1hSUYJwdymS3R7JWAPHrg yzRXdr2Uo8mnNiPHo49H3gkrmg9aCD79mBiLitYsynpzYfZVYknN29vohcNX77yfOMnf efQQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:openpgp:message-id :date:user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=N6CLuPA/AJhfGD4Iu0YQ5LK2CB0ty+XzJLOlx2nNx34=; b=EahY2Jc1QINef+YDgFfCBlFu667fBqLY9U3WbEKiGllzBnnPp4Nm4QURCtZn3fONxn OiAJKPjqG8I8+neXXM/WsyMc8A4ef+3huPi3BpmUK1bMfo5hed1yQokADPTAeR4pdsiq ccuSPw/hOzDmu3pQEBvOYfajPVCeQzyzgwYBZKicjdrfxsweBsJxjhdyvgm1JEO6VtmO wFFFLYHRJQ5U1lLs790+PA0ob4MLGgtp/BmrShcD7ouEoQxHzQYYXxM7HvZvQDMBD+hU cQJ7wZW7XxuBj9ZfR77VoQsFQC3ZsiIdko7+gPey2jfOt2Oc+gyJOwN16ba2858TT+PF 0/3g== X-Gm-Message-State: APjAAAXDKgSuLcKcmNIIfUK3ljHMR2yE569UYUNP6AWBDOu+lKmcORYb EK7nu+eXY+A+L6VkN9kRlTOZqsma X-Google-Smtp-Source: APXvYqxahvER3l3RWHaJDgYOoEty7DE5Royj2KsXzmqAy3GsHSn1AzB3Fg5d+n5YS2JdswahOE3fvw== X-Received: by 2002:a17:902:5ac4:: with SMTP id g4mr39056294plm.261.1554862637923; Tue, 09 Apr 2019 19:17:17 -0700 (PDT) Received: from [10.230.28.107] ([192.19.223.250]) by smtp.gmail.com with ESMTPSA id y1sm44932398pgc.29.2019.04.09.19.17.16 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 09 Apr 2019 19:17:17 -0700 (PDT) Subject: Re: [PATCH v2 net-next 11/22] net: dsa: Allow drivers to modulate between presence and absence of tagging To: Vladimir Oltean , vivien.didelot@gmail.com, andrew@lunn.ch, davem@davemloft.net Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, georg.waibel@sensor-technik.de References: <20190410005700.31582-1-olteanv@gmail.com> <20190410005700.31582-12-olteanv@gmail.com> From: Florian Fainelli Openpgp: preference=signencrypt Message-ID: Date: Tue, 9 Apr 2019 19:17:15 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190410005700.31582-12-olteanv@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/9/2019 5:56 PM, Vladimir Oltean wrote: > Frames get processed by DSA and redirected to switch port net devices > based on the ETH_P_XDSA multiplexed packet_type handler found by the > network stack when calling eth_type_trans(). > > The running assumption is that once the DSA .rcv function is called, DSA > is always able to decode the switch tag in order to change the skb->dev > from its master. > > However there are tagging protocols (such as the new > DSA_TAG_PROTO_SJA1105) where this assumption is not completely true, > since switch tagging piggybacks on the absence of a vlan_filtering > bridge. > > Having DSA receive untagged traffic would put it in an impossible > situation: the eth_type_trans() function would invoke the DSA .rcv(), > which could not change skb->dev, then eth_type_trans() would be invoked > again, which again would call the DSA .rcv, and the packet would never > be able to exit the DSA filter and would spiral in a loop until the > whole system dies. > > This happens because eth_type_trans() doesn't actually look at the skb > (so as to identify a potential tag) when it deems it as being > ETH_P_XDSA. It just checks whether skb->dev has a DSA private pointer > installed (therefore it's a DSA master) and that there exists a .rcv > callback (everybody except DSA_TAG_PROTO_NONE has that). This is > understandable as there are many switch tags out there, and exhaustively > checking for all of them is far from ideal. > > The solution lies in the observation that a more nuanced check can be > made when eth_type_trans() determines that switch tagging is used or > not. In a way, this reverts patch "717ffbfb28ac net: dsa: remove > dsa_uses_tagged_protocol", but instead of adding it back as a DSA > function, it is now a boolean property. This is because the driver might > actually know better when it can and can't support switch tagging. > > With this patch, all tagging protocols can morph at runtime into the > DSA_TAG_PROTO_NONE on receive, by setting cpu_dp->uses_tag_protocol = 0. > This permits them to at least terminate traffic through the master net > device. Their .rcv callback no longer even gets called in this mode. > > Signed-off-by: Vladimir Oltean > --- [snip] > + /* Property used to allow traffic at runtime to bypass the DSA > + * filter in eth_type_trans and be processed as regular on the > + * master net device. > + */ > + bool uses_tag_protocol; This gets used in the hot path can you make sure this is part of the first cache line of a dsa_port? pahole is a good tool for determining where a member is in a given structure. With that: Reviewed-by: Florian Fainelli -- Florian