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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, 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 29613C433E1 for ; Thu, 27 Aug 2020 01:04:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 05CF92073A for ; Thu, 27 Aug 2020 01:04:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=aixah.de header.i=@aixah.de header.b="yFyF8kop" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726839AbgH0BET (ORCPT ); Wed, 26 Aug 2020 21:04:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44538 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726148AbgH0BES (ORCPT ); Wed, 26 Aug 2020 21:04:18 -0400 Received: from mout-p-202.mailbox.org (mout-p-202.mailbox.org [IPv6:2001:67c:2050::465:202]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F08F0C061796; Wed, 26 Aug 2020 18:04:17 -0700 (PDT) Received: from smtp1.mailbox.org (smtp1.mailbox.org [IPv6:2001:67c:2050:105:465:1:1:0]) (using TLSv1.2 with cipher ECDHE-RSA-CHACHA20-POLY1305 (256/256 bits)) (No client certificate requested) by mout-p-202.mailbox.org (Postfix) with ESMTPS id 4BcPd82w4DzQkjS; Thu, 27 Aug 2020 03:04:12 +0200 (CEST) X-Virus-Scanned: amavisd-new at heinlein-support.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=aixah.de; s=MBO0001; t=1598490246; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=q6j+hA2/dONqWHhiG0eN90dTxudsQeR1jOdQOyycNIg=; b=yFyF8kopQGa6vkjuFrLzQCFZfVTA39aKI3oQLg9f55qz3XJqOKPZYILZYhEQL0oJHFOnfL F/oOBsL5Dwf0tb/K/RfK/mFFBNqS9CoWuiW4+zg8X2fAkxZ4iqH1Mq/WV2BuYr2aViKDQR xIPhazIvb7VdraksOEtzi07nkrrXIpsJP/xF7BJjJjMHO8L7me6SHcM84wbUkItnh1e9/0 Svy7nyrOlEV/Ot49HkdlRhBX7PGRbA5/9BkUgpVMVulLRbogUKcRRSDKici0Wty/cc83kn ywGSoIqxBJ/HetDkO/hvw9HD7lTKaFtVCPcWfzFFgWPL1StrqOHcWEyn9XIvIQ== Received: from smtp1.mailbox.org ([80.241.60.240]) by spamfilter04.heinlein-hosting.de (spamfilter04.heinlein-hosting.de [80.241.56.122]) (amavisd-new, port 10030) with ESMTP id ppw00nlC4MBF; Thu, 27 Aug 2020 03:04:04 +0200 (CEST) Date: Thu, 27 Aug 2020 01:04:03 +0000 From: Mira Ressel To: David Miller Cc: kuba@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] veth: Initialize dev->perm_addr Message-ID: <20200827010403.r3zic7s66shcjcrb@vega> References: <20200826152000.ckxrcfyetdvuvqum@vega> <20200826.082857.584544823490249841.davem@davemloft.net> <20200826162901.4js4u5u2whusp4l4@vega> <20200826.093329.96316850316598868.davem@davemloft.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200826.093329.96316850316598868.davem@davemloft.net> X-MBO-SPAM-Probability: X-Rspamd-Score: -1.34 / 15.00 / 15.00 X-Rspamd-Queue-Id: F267068C X-Rspamd-UID: 510460 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 26, 2020 at 09:33:29AM -0700, David Miller wrote: > From: Mira Ressel > Date: Wed, 26 Aug 2020 16:29:01 +0000 > > > On Wed, Aug 26, 2020 at 08:28:57AM -0700, David Miller wrote: > >> From: Mira Ressel > >> Date: Wed, 26 Aug 2020 15:20:00 +0000 > >> > >> > I'm setting the peer->perm_addr, which would otherwise be zero, to its > >> > dev_addr, which has been either generated randomly by the kernel or > >> > provided by userland in a netlink attribute. > >> > >> Which by definition makes it not necessarily a "permanent address" and > >> therefore is subject to being different across boots, which is exactly > >> what you don't want to happen for automatic address generation. > > > > That's true, but since veth devices aren't backed by any hardware, I > > unfortunately don't have a good source for a permanent address. The only > > inherently permanent thing about them is their name. > > > > People who use the default eui64-based address generation don't get > > persistent link-local addresses for their veth devices out of the box > > either -- the EUI64 is derived from the device's dev_addr, which is > > randomized by default. > > > > If that presents a problem for anyone, they can configure their userland > > to set the dev_addr to a static value, which handily fixes this problem > > for both address generation algorithms. > > > > I'm admittedly glancing over one problem here -- I'm only setting the > > perm_addr during device creation, whereas userland can change the > > dev_addr at any time. I'm not sure if it'd make sense here to update the > > perm_addr if the dev_addr is changed later on? > > We are talking about which parent device address to inherit from, you > have choosen to use dev_addr and I am saying you should use perm_addr. > > Can you explain why this isn't clear? Which parent device? This is the veth patch, not the vlan patch. I'm setting the perm_addrs of both sides of the veth pair to their respective dev_addrs that they were assigned by userland or through random generation. If I were to give both of them the same perm_addr, we'd again have the problem that they'd get conflicting link-local addresses and trigger DAD. My apologies if I'm misunderstanding something here! Regards, Mira