From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4FCCCC433E1 for ; Thu, 13 Aug 2020 21:36:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 38C1420768 for ; Thu, 13 Aug 2020 21:36:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726947AbgHMVgQ (ORCPT ); Thu, 13 Aug 2020 17:36:16 -0400 Received: from mx2.suse.de ([195.135.220.15]:57660 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726522AbgHMVgP (ORCPT ); Thu, 13 Aug 2020 17:36:15 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 4A2C7AD89; Thu, 13 Aug 2020 21:36:36 +0000 (UTC) Received: by localhost (Postfix, from userid 1000) id 703E57F447; Thu, 13 Aug 2020 23:36:13 +0200 (CEST) Date: Thu, 13 Aug 2020 23:36:13 +0200 From: Michal Kubecek To: Jay Vosburgh Cc: Jarod Wilson , linux-kernel@vger.kernel.org, Veaceslav Falico , Andy Gospodarek , "David S. Miller" , netdev@vger.kernel.org Subject: Re: [PATCH net] bonding: show saner speed for broadcast mode Message-ID: <20200813213613.qvem7gv4ri2trfvv@carpenter> References: <20200813035509.739-1-jarod@redhat.com> <27389.1597296596@famine> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <27389.1597296596@famine> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 12, 2020 at 10:29:56PM -0700, Jay Vosburgh wrote: > Did you notice this by inspection, or did it come up in use > somewhere? I can't recall ever hearing of anyone using broadcast mode, > so I'm curious if there is a use for it, but this change seems > reasonable enough regardless. I did actually encountered our customers using broadcast mode twice. But I have to disappoint you, their "use for it" was rather an abuse. One of them had a number of hosts, each having two NICs in broadcast mode bond, one connected to one switch and one connected to another switch (with no direct connection between the switches). Having each packet duplicated when everything worked triggered some corner cases in networking stack (IIRC one issue in fragment reassembly and one in TCP lockless listener). Thankfully I was eventually able to convince them that this kind of redundancy does not really work if one host loses connection to one switch and another host to the other. I don't remember the other use case from the top of my head but I'm quite sure it made even less sense. Michal