From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [RFC] ipv4: add link_filter sysctl Date: Wed, 18 Mar 2009 19:42:39 -0700 Message-ID: <20090318194239.1adc47d2@nehalam> References: <20090313161253.0f02da26@nehalam> <20090318.182115.43965264.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: David Miller Return-path: Received: from mail.vyatta.com ([76.74.103.46]:57770 "EHLO mail.vyatta.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753889AbZCSCms (ORCPT ); Wed, 18 Mar 2009 22:42:48 -0400 In-Reply-To: <20090318.182115.43965264.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 18 Mar 2009 18:21:15 -0700 (PDT) David Miller wrote: > From: Stephen Hemminger > Date: Fri, 13 Mar 2009 16:12:53 -0700 > > > Add a new parameter that controls how kernel responds to packets > > when interface is down. This is done to solve the problem of: > > > > Assume topology of: > > A <-----------> Router X--- down link > > 10.1.1.2/24 10.1.1.1/24 10.2.1.1/24 > > eth0 eth1 > > > > If A pings 10.2.1.1 then with normal Linux semantics Router would > > respond even if eth1 link on 10.2.1.1 was down. This causes some network > > management tools (that work with other router OS's) to falsely > > report that link is okay. > > > > The problem is that a Linux router does not respond the way > > other systems do. This is the router equivalent of "Strong ES" > > model, it is not the same as "Strong ES" as defined in Host > > Requirements. > > > > The new parameter adds an additional check on slow input packet > > path, and causes route cache flush if enabled and carrier is > > lost. > > > > Signed-off-by: Stephen Hemminger > > There is nothing "router" about this situation. > > When 10.2.1.1 is being pinged, it is in the role of an end-system in > that transaction. > > The "router" is reachable by "A", and as a consequence so is that IP > address 10.2.1.1, and therefore the ping should succeed. Unfortunately, network management tools expect routers to behave this way: WWCD