From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julian Anastasov Subject: Re: net/ipv4/route.c: Routing anomaly introduced by 89aef89 (ipv4: Delete routing cache.) Date: Tue, 9 Jul 2013 08:43:14 +0300 (EEST) Message-ID: References: <20130708113457.4a0d6023@pluto> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: "David S. Miller" , Alexey Kuznetsov , netdev@vger.kernel.org, eyal.birger@gmail.com To: Shmulik Ladkani Return-path: Received: from ja.ssi.bg ([178.16.129.10]:44235 "EHLO ja.ssi.bg" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1751500Ab3GIFhh (ORCPT ); Tue, 9 Jul 2013 01:37:37 -0400 In-Reply-To: <20130708113457.4a0d6023@pluto> Sender: netdev-owner@vger.kernel.org List-ID: Hello, On Mon, 8 Jul 2013, Shmulik Ladkani wrote: > Hi, > > In 89aef89 (ipv4: Delete routing cache) the following was removed from > ip_route_input_common (nowadays named ip_route_input_noref): > > - tos &= IPTOS_RT_MASK; > > As a side effect, the 'tos' argument passed to 'ip_route_input_slow' is > the "raw" u8, as present in iph->tos (opposed to the formerly "masked" > value). > > This may affect the route calculation, as this value is later placed in > fl4.flowi4_tos for matching purposes (using equality to the tos stored > in the FIB Rule and/or Route). > > (BTW, the question whether applying the historical IPTOS_RT_MASK > prior route lookup is interesting on its own...) > > However, 89aef89 created an anomaly - since in the output path, routing > *still* uses the IPTOS_RT_MASK (see __ip_route_output_key for example). > > It seems the omission of 'tos &= IPTOS_RT_MASK' from > 'ip_route_input_noref' was accidental. Agreed > We should align input/output behavior by reverting the omission, or > alternatively we may reconsider the entire IPTOS_RT_MASK thing. The right thing should be to use tos &= IPTOS_RT_MASK at beginning of ip_route_input_noref. Regards -- Julian Anastasov