From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Emelyanov Subject: Re: [PATCH 1/2] net: Allow to create links with given ifindex Date: Tue, 31 Jul 2012 17:30:17 +0400 Message-ID: <5017DDE9.4020008@parallels.com> References: <50160EEF.6050406@parallels.com> <87pq7dh6b2.fsf@xmission.com> <87fw89h5zk.fsf@xmission.com> <50179F66.1000604@parallels.com> <878ve0dtw3.fsf@xmission.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Linux Netdev List , David Miller To: "Eric W. Biederman" Return-path: Received: from mailhub.sw.ru ([195.214.232.25]:23240 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752101Ab2GaNa0 (ORCPT ); Tue, 31 Jul 2012 09:30:26 -0400 In-Reply-To: <878ve0dtw3.fsf@xmission.com> Sender: netdev-owner@vger.kernel.org List-ID: >> First, let's imagine that on host A the loopback device got registered as >> first device, but on host B for some reason some other device got registered >> first. In that case after migration from A to B the lo on B will have index >> equals 2. And there's no any strict requirement that lo's per net operations >> are registered first. Please, correct me if I'm wrong. > > Actually there is a hard requirement that the loopback device be the > last device in a network namespace to be unregistered. We meet that > requirement by registering the loopback device first > "net/core/dev.c:net_dev_init()". Hm... Indeed, and this is good news! >> Next. In fact, lo is not the only problem. Look at the e.g. sit versus ipgre >> fallback devices. Both gets created on netns creation and obtain whatever >> ifindices are generated for them. Even if we make ifidex per netns chances >> that sit gets registered _strictly_ before ipgre equal zero, since they are >> both modules. > > True. However those fallback devices should no longer be needed, > and even if they are I think you can delete and recreate them. Good idea! I will look at that direction. > Making lo the particularly interesting case. Yup, provided we can manually recreate those auto-created devices this solves the issue. >> Just an idea -- is it worth moving the possibility to have ifindidces intersect >> under CONFIG_ (EXPERT/CHECKPOINT_RESTORE) to let wider audience check >> the code in real-life? > > I think the best testing we are going to get diversity wise is to create > a per netns counter into dev_new_index when net-next opens up. > > Having an ifindex that we can only set at netdevice creation time seems > reasonable. OK, thank you, Eric. > Eric > . > Thanks, Pavel