From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [PATCH net-next-2.6] ipv4: sysctl to block responding on down interface Date: Wed, 30 Jun 2010 13:55:35 -0700 Message-ID: <20100630135535.0e3a5ea1@nehalam> References: <20100611084854.0680c014@nehalam> <20100622.101537.245382806.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: joakim.tjernlund@transmode.se, netdev@vger.kernel.org To: David Miller Return-path: Received: from mail.vyatta.com ([76.74.103.46]:59718 "EHLO mail.vyatta.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751211Ab0F3Uzh (ORCPT ); Wed, 30 Jun 2010 16:55:37 -0400 In-Reply-To: <20100622.101537.245382806.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, 22 Jun 2010 10:15:37 -0700 (PDT) David Miller wrote: > From: Stephen Hemminger > Date: Fri, 11 Jun 2010 08:48:54 -0700 > > > The initial problem report was for a management application that used ICMP > > to check link availability. > > That application is buggy, and even if we apply this patch it will > only properly function when speaking to systems in a non-default > configuration. And, it would be a non-default setting which, by your > own admission below, cannot function properly in valid interface > configurations. It is a remote management system not a local application. The management system is stupid, but it is hard to argue with customers that other system is broken. > It's easier to fix the app to work in all cases than to add another > sysctl knob hack for a segment of the world that can't seem to wrap > their head around the fact that our behavior is valid, specified, and > an explicit design decision meant to increase the chances of > successful communication between two systems. > > > The default is disabled to maintain compatibility with previous behavior. > > This is not recommended for server systems because it makes fail over more > > difficult, and does not account for configurations where multiple interfaces > > have the same IP address. > > The fact that the syctl knob, when enabled, can't even function properly > in this "multiple interfaces with same address" case is another reason I > have decided to not apply this. We already have sysctl knobs that exist to work around broken printer TCP, middleboxes and other broken stacks; my opinion this is just another one of those types of workarounds.