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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 47FFBC10F13 for ; Mon, 15 Apr 2019 03:07:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 134D02077C for ; Mon, 15 Apr 2019 03:07:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=lunn.ch header.i=@lunn.ch header.b="M6e+n60g" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727011AbfDODHS (ORCPT ); Sun, 14 Apr 2019 23:07:18 -0400 Received: from vps0.lunn.ch ([185.16.172.187]:32810 "EHLO vps0.lunn.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725789AbfDODHR (ORCPT ); Sun, 14 Apr 2019 23:07:17 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lunn.ch; s=20171124; h=In-Reply-To:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=oKpgIhBVpDdsPi4+lN5iHvcrVeFVVmNwfzgBgdJt0VY=; b=M6e+n60gBT5jacB71pxCFeYkll DCcM1PM75WDyJvfwavaySVuzEZSJG5etfpL1IgbjB9H0G++TFW+NwGVvTueHEz3NNOc5kHueJvu0D b7UHakcXGdRpNn+ItdeSocmhnzy7jD4/O/5sFS5Ej2wpcNZEe3XW27XKZxgZtOp25/JM=; Received: from andrew by vps0.lunn.ch with local (Exim 4.89) (envelope-from ) id 1hFrxe-0006e3-DJ; Mon, 15 Apr 2019 05:07:10 +0200 Date: Mon, 15 Apr 2019 05:07:10 +0200 From: Andrew Lunn To: Vladimir Oltean Cc: Florian Fainelli , vivien.didelot@gmail.com, davem@davemloft.net, netdev , linux-kernel@vger.kernel.org, Georg Waibel Subject: Re: [PATCH v3 net-next 18/24] net: dsa: sja1105: Add support for traffic through standalone ports Message-ID: <20190415030710.GC24455@lunn.ch> References: <20190413012822.30931-1-olteanv@gmail.com> <20190413012822.30931-19-olteanv@gmail.com> <20190413163754.GG17901@lunn.ch> <20190414161757.GB10323@lunn.ch> <20190414191318.GE10323@lunn.ch> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > It fails to decode the frames, obviously. But so does any other EtherType. > Florian was hinting > (https://lwn.net/ml/netdev/b52f4cdf-edcf-0757-1d6e-d4a831ec7943@gmail.com/) > at the recent pull requests submitted to tcpdump and libpcap that make > it possible to decode based on the string in > /sys/class/net/${master}/dsa/tagging. I admit I haven't actually > tested or studied those closely yet (there are more important things > to focus on ATM), but since my driver returns "8021q" in sysfs and > yours returns "edsa", I would presume tcpdump could use that > information. No it does not. It is a valid EtherType, that is what is used to trigger the decoding, it takes no notice of what is in /sys/class/net/${master}/dsa/tagging, nor the extra meta-data added to the pcap file. There is no need. you can identify it is a Marvell EDSA header from the EtherType. In fact, this tcpdump code for decoding EDSA pre-dated Florians patches by a few years. You only need the code which Florian added when you cannot identify the header directly from the packet. And that is true for most of the tagging protocols. But EDSA you can. > Anyway, since you obviously know more on this topic than I do, > please make me understand what are the real problems in spoofing the > Ethertype as a Marvell one. Despite there being an EDSA EtherType in the frame, what follows is not an ESDA header. It is like having the IPv4 EtherType but what following is not an IP header. Broken. Andrew