From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: ipv4 regression in 2.6.31 ? Date: Wed, 16 Sep 2009 10:00:28 -0700 Message-ID: <20090916100028.654f7893@nehalam> References: <20090914093128.4d709ff6@nehalam> <20090915081354.GA10037@ff.dom.local> <20090915155719.22bae41e@nehalam> <20090916052304.GA4894@ff.dom.local> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: David Miller , Stephan von Krawczynski , Eric Dumazet , linux-kernel@vger.kernel.org, Linux Netdev List To: Jarek Poplawski Return-path: Received: from mail.vyatta.com ([76.74.103.46]:49443 "EHLO mail.vyatta.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753283AbZIPRAb (ORCPT ); Wed, 16 Sep 2009 13:00:31 -0400 In-Reply-To: <20090916052304.GA4894@ff.dom.local> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 16 Sep 2009 05:23:04 +0000 Jarek Poplawski wrote: > On Tue, Sep 15, 2009 at 03:57:19PM -0700, Stephen Hemminger wrote: > > 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). > > This additional value is not necessary (it'd give as superpowers). > Max seems logical to me only when values are sorted (especially if > max is the strictest). The values had to be unsorted because of the requirement to retain interface compatibility with older releases. --