Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754593AbZIOW7b (ORCPT ); Tue, 15 Sep 2009 18:59:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752771AbZIOW7Z (ORCPT ); Tue, 15 Sep 2009 18:59:25 -0400 Received: from mail.vyatta.com ([76.74.103.46]:60956 "EHLO mail.vyatta.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751163AbZIOW7Y (ORCPT ); Tue, 15 Sep 2009 18:59:24 -0400 Date: Tue, 15 Sep 2009 15:57:19 -0700 From: Stephen Hemminger To: Jarek Poplawski , David Miller Cc: Stephan von Krawczynski , Eric Dumazet , linux-kernel@vger.kernel.org, davem@davemloft.net, Linux Netdev List Subject: Re: ipv4 regression in 2.6.31 ? Message-ID: <20090915155719.22bae41e@nehalam> In-Reply-To: <20090915081354.GA10037@ff.dom.local> References: <20090914093128.4d709ff6@nehalam> <20090915081354.GA10037@ff.dom.local> Organization: Vyatta X-Mailer: Claws Mail 3.6.1 (GTK+ 2.16.1; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3259 Lines: 84 On Tue, 15 Sep 2009 08:13:55 +0000 Jarek Poplawski wrote: > On 14-09-2009 18:31, Stephen Hemminger wrote: > > On Mon, 14 Sep 2009 17:55:05 +0200 > > Stephan von Krawczynski wrote: > > > >> On Mon, 14 Sep 2009 15:57:03 +0200 > >> Eric Dumazet wrote: > >> > >>> Stephan von Krawczynski a A~(c)crit : > >>>> Hello all, > ... > >>> rp_filter - INTEGER > >>> 0 - No source validation. > >>> 1 - Strict mode as defined in RFC3704 Strict Reverse Path > >>> Each incoming packet is tested against the FIB and if the interface > >>> is not the best reverse path the packet check will fail. > >>> By default failed packets are discarded. > >>> 2 - Loose mode as defined in RFC3704 Loose Reverse Path > >>> Each incoming packet's source address is also tested against the FIB > >>> and if the source address is not reachable via any interface > >>> the packet check will fail. > ... > > RP filter did not work correctly in 2.6.30. The code added to to the loose > > mode caused a bug; the rp_filter value was being computed as: > > rp_filter = interface_value & all_value; > > So in order to get reverse path filter both would have to be set. > > > > In 2.6.31 this was change to: > > rp_filter = max(interface_value, all_value); > > > > This was the intended behaviour, if user asks all interfaces to have rp > > filtering turned on, then set /proc/sys/net/ipv4/conf/all/rp_filter = 1 > > or to turn on just one interface, set it for just that interface. > > Alas this max() formula handles also cases where both values are set > and it doesn't look very natural/"user friendly" to me. Especially > with something like this: all_value = 2; interface_value = 1 > Why would anybody care to bother with interface_value in such a case? > > "All" suggests "default" in this context, so I'd rather expect > something like: > rp_filter = interface_value ? : all_value; > which gives "the inteded behaviour" too, plus more... > > We'd only need to add e.g.: > 0 - Default ("all") validation. (No source validation if "all" is 0). > 3 - No source validation on this interface. More values == more confusion. I chose the maxconf() method to make rp_filter consistent with other multi valued variables (arp_announce and arp_ignore). -------- Subject: [PATCH] Document rp_filter behaviour Signed-off-by: Stephen Hemminger --- a/Documentation/networking/ip-sysctl.txt 2009-09-15 15:54:25.844934373 -0700 +++ b/Documentation/networking/ip-sysctl.txt 2009-09-15 15:55:40.709205883 -0700 @@ -744,6 +744,8 @@ rp_filter - INTEGER Default value is 0. Note that some distributions enable it in startup scripts. + The max value from conf/{all,interface}/rp_filter is used. + arp_filter - BOOLEAN 1 - Allows you to have multiple network interfaces on the same subnet, and have the ARPs for each interface be answered -- -- 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/