From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755650AbZBWXqx (ORCPT ); Mon, 23 Feb 2009 18:46:53 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751910AbZBWXql (ORCPT ); Mon, 23 Feb 2009 18:46:41 -0500 Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:41530 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751828AbZBWXqk convert rfc822-to-8bit (ORCPT ); Mon, 23 Feb 2009 18:46:40 -0500 Date: Mon, 23 Feb 2009 15:46:21 -0800 (PST) Message-Id: <20090223.154621.08279126.davem@davemloft.net> To: linux@kolla.no Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org Subject: Re: PROBLEM: IPv6 autoconf/accept_ra default values From: David Miller In-Reply-To: References: X-Mailer: Mew version 6.1 on Emacs 22.1 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=iso-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Kolbjørn Barmen Date: Mon, 23 Feb 2009 15:42:41 +0100 (CET) > > Hello > > 1. Summary of problem You'll get more replies if you contact the networking developers at netdev@vger.kernel.org > autoconfig and accept_ra is by default on (by the way of forwarning) - > this is very problematic in many ways. > > 2. Full description of the problem/report: > > * if you want staticly only configured addresses/gateway (which is > something you just might want for server machines for example) you need > to change the sysctl parameters before the interface is brought up. > (yes, I want staticly, and only staticly configured addresses, dont get > me started on why - keywords: source address, dns, ssl, access control) > > * to change the default values, ipv6 module needs to be loaded, in many > distros this leads to race conditions, especially in these "autodetect > hardware and bring up everything magically" days :) > > * if you netboot with ipv6 enabled kernel, interface will pick up ipv6 > autoconf no matter, so you need to remove addresses and routes manually > after boot. As far as I know there is now kernel parameters to tell > kernel to not autoconf ipv6. I admit I have not tested out whether it's > possible to use ipv6-addresses as kernel parameters at all. > > * ipv6 kernel module has no load paramters as far as I can tell? > > * changing net.ipv6.conf.all.* and net.ipv6.conf.default.* dont work as > intended? I'm really not sure how this is meant to work, but intuitively > I would think that "...all.*" would affect all interfaces present, and > "...*.default.*" would set the default values for "future" interfaces. > Maybe I'm wrong? Look further down... > > 3. Keywords > ipv6, forwarding, autoconf, accept_ra > > 4. Kernel version (from /proc/version): > This goes accross all 2.6 kernels as far as I can tell, no matter what > distro. > > 5. Output of Oops.. message > No oops so far :) > > 6. A small shell script or example program which triggers the problem > > root:~# sysctl net.ipv6.conf.all.accept_ra > net.ipv6.conf.all.accept_ra = 1 > root:~# sysctl -w net.ipv6.conf.all.accept_ra=0 > net.ipv6.conf.all.accept_ra = 0 > root:~# sysctl net.ipv6.conf.eth0.accept_ra > net.ipv6.conf.all.accept_ra = 1 > > I suppose the above is fals behaviour? I'm really not sure, but if this is > not a bug, then I fail to see the purpose of the "...all.*" and > "...default.*" sysctl parameters. From the documentation > (networking/ip-sysctl.txt) I get the impression that the above behaviour > is wrong: > > --- > conf/default/*: > Change the interface-specific default settings. > > conf/all/*: > Change all the interface-specific settings. > > [XXX: Other special features than forwarding?] > --- > > Looks like this is unclear for more than just me :) > > > My personal oppinion is that anything ipv6 autoconfig/accept_ra should be > default _off_, since this simplifies all the above mentioned issues, and > it is incredibly easy to turn on again with systcl if people want it. > It is much easier to enable ipv6 automagic than to disable it. > At least there should be kernel/module parameter to set default behaviour. > > Part of the problem with deploying IPv6 is due to "magic" like this, all > the autoconfig/router announcement magic looks very well on paper and in > theory, but out in the field it quickly leads to loads of totally > unnecessary extra work, work that could easily be avoided if default > behaviour was to have it off. It should be in the interest of IPv6 > advocates to support a "soft" transition from IPv4-only to dual-stack, > fencing off unwanted "magic" only adds to the frustration for those who > actually try to deploy it. > > What do you think? > > If there already is a simple stright forward solution, then I apologize > for this rant - please enlighten me :) > > -- kolla > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/