From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: linux kernel's IPV6_MULTICAST_HOPS default is 64; should be 1? Date: Thu, 06 May 2010 00:10:32 -0700 (PDT) Message-ID: <20100506.001032.245396059.davem@davemloft.net> References: <4BE1907F.40903@hp.com> <20100505.150008.102542618.davem@davemloft.net> <4BE2205A.3050900@hp.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: dlstevens@us.ibm.com, enh@google.com, netdev@vger.kernel.org, netdev-owner@vger.kernel.org To: brian.haley@hp.com Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:39204 "EHLO sunset.davemloft.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751191Ab0EFHK0 (ORCPT ); Thu, 6 May 2010 03:10:26 -0400 In-Reply-To: <4BE2205A.3050900@hp.com> Sender: netdev-owner@vger.kernel.org List-ID: From: Brian Haley Date: Wed, 05 May 2010 21:50:18 -0400 > David Miller wrote: >> From: Brian Haley >> Date: Wed, 05 May 2010 11:36:31 -0400 >> >>> I now see that in Elliot's email, but I think it's incorrect. The RFC >>> says that setting it to -1 should get you the kernel default, which is >>> now 1. Without this change, setting it to -1 will get you 64, the >>> old behavior. If the user wants to, they can always just set it to >>> 64 themselves, that's better than assuming when you set it to -1 >>> you're going to get 64. >> >> It's not 64, it's whatever the per-route metric is. > > Not unless that metric's been set via RTAX_HOPLIMIT (and I believe > this is the unicast hop limit value anyways), and that metric > defaults to -1. Right, if it is, and anyone who does set it and expects the default multicast hop limit to follow along have no portable way to code their application in a way that works before and after fixing the RFC issues. I gave them a way, by making explicit setting of "-1" do what it's always done. > At this point in time I'll gladly implement a per-interface sysctl > to end this discussion. The game is over, the result decided, and this is just post-game discussion as far as I'm concerned. :-)