From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jakub Sitnicki Subject: Re: [PATCH net-next v2] net: ipv4: add support for ECMP hash policy choice Date: Wed, 08 Mar 2017 13:05:36 +0100 Message-ID: <878togdldb.fsf@redhat.com> References: <1488884508-14016-1-git-send-email-nikolay@cumulusnetworks.com> Mime-Version: 1.0 Content-Type: text/plain Cc: netdev@vger.kernel.org, edumazet@google.com, davem@davemloft.net, roopa@cumulusnetworks.com, dsa@cumulusnetworks.com To: Nikolay Aleksandrov Return-path: Received: from mail-wr0-f172.google.com ([209.85.128.172]:34520 "EHLO mail-wr0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750745AbdCHMHa (ORCPT ); Wed, 8 Mar 2017 07:07:30 -0500 Received: by mail-wr0-f172.google.com with SMTP id l37so21798208wrc.1 for ; Wed, 08 Mar 2017 04:05:39 -0800 (PST) In-reply-to: <1488884508-14016-1-git-send-email-nikolay@cumulusnetworks.com> Sender: netdev-owner@vger.kernel.org List-ID: Hi Nikolay, On Tue, Mar 07, 2017 at 11:01 AM GMT, Nikolay Aleksandrov wrote: > This patch adds support for ECMP hash policy choice via a new sysctl > called fib_multipath_hash_policy and also adds support for L4 hashes. > The current values for fib_multipath_hash_policy are: > 0 - layer 3 (default) > 1 - layer 4 > If there's an skb hash already set and it matches the chosen policy then it > will be used instead of being calculated. The ICMP inner IP addresses use > is removed. > > Signed-off-by: Nikolay Aleksandrov > --- > v2: > - removed the output_key_hash as it's not needed anymore > - reverted to my original/internal patch with L3 as default hash What about ICMP PTB (Fragmentation Needed) forwarding that makes PMTUD work with ECMP in setups like described in RFC7690 [1]? ptb -> router ecmp -> next hop L4/L7 load balancer -> destination router --> load balancer 1 ---> \\--> load balancer 2 ---> load-balanced service \--> load balancer N ---> Removing special treatment of ICMP errors will break it, won't it? FWIW, I gave a run to your patch (default settings, L3 hash) with a test script [2] that simulates such a setup and it confirmed my worries - PTB errors don't travel back to the source host any more. -Jakub [1] https://tools.ietf.org/html/rfc7690#section-2 [2] https://github.com/jsitnicki/tools/commit/ccb85e68421df4ffd8b7abf00f6f5fe1c6a5af76