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, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 67DA8C433E3 for ; Wed, 26 Aug 2020 16:33:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4D07F206FA for ; Wed, 26 Aug 2020 16:33:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727107AbgHZQdi (ORCPT ); Wed, 26 Aug 2020 12:33:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49752 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726894AbgHZQdf (ORCPT ); Wed, 26 Aug 2020 12:33:35 -0400 Received: from shards.monkeyblade.net (shards.monkeyblade.net [IPv6:2620:137:e000::1:9]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4E96AC061574; Wed, 26 Aug 2020 09:33:35 -0700 (PDT) Received: from localhost (unknown [IPv6:2601:601:9f00:477::3d5]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: davem-davemloft) by shards.monkeyblade.net (Postfix) with ESMTPSA id 534181359D96A; Wed, 26 Aug 2020 09:16:46 -0700 (PDT) Date: Wed, 26 Aug 2020 09:33:29 -0700 (PDT) Message-Id: <20200826.093329.96316850316598868.davem@davemloft.net> To: aranea@aixah.de Cc: kuba@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] veth: Initialize dev->perm_addr From: David Miller In-Reply-To: <20200826162901.4js4u5u2whusp4l4@vega> References: <20200826152000.ckxrcfyetdvuvqum@vega> <20200826.082857.584544823490249841.davem@davemloft.net> <20200826162901.4js4u5u2whusp4l4@vega> X-Mailer: Mew version 6.8 on Emacs 26.3 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Wed, 26 Aug 2020 09:16:46 -0700 (PDT) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 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?