From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH net-next] Revert "net/ipv6: add sysctl option accept_ra_min_hop_limit" Date: Wed, 02 Sep 2015 16:11:10 -0700 (PDT) Message-ID: <20150902.161110.223512323094619164.davem@davemloft.net> References: <20150902094301.GA6434@via.ecp.fr> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, liuhangbin@gmail.com, hideaki.yoshifuji@miraclelinux.com To: sd@queasysnail.net Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:39939 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752666AbbIBXLL (ORCPT ); Wed, 2 Sep 2015 19:11:11 -0400 In-Reply-To: <20150902094301.GA6434@via.ecp.fr> Sender: netdev-owner@vger.kernel.org List-ID: From: Sabrina Dubroca Date: Wed, 2 Sep 2015 11:43:01 +0200 > This reverts commit 8013d1d7eafb0589ca766db6b74026f76b7f5cb4. > > There are several issues with this patch. > It completely cancels the security changes introduced by 6fd99094de2b > ("ipv6: Don't reduce hop limit for an interface"). > The current default value (min hop limit = 1) can result in the same > denial of service that 6fd99094de2b prevents, but it is hard to define > a correct and sane default value. > More generally, it is yet another IPv6 sysctl, and we already have too > many. > > This was introduced to satisfy a TAHI test case which, in my opinion, is > too strict, turning the RFC's "SHOULD" into a "MUST": > > If the received Cur Hop Limit value is non-zero, the host > SHOULD set its CurHopLimit variable to the received value. > > The behavior of this sysctl is wrong in multiple ways. Some are > fixable, but let's not rush this commit into mainline, and revert this > while we still can, then we can come up with a better solution. > > Signed-off-by: Sabrina Dubroca I don't agree with this revert. If you look at the original commit, the quoted RFC recommends adding a configurable method to protect against this. And that's exactly what the commit you are trying to revert is doing. The only thing I would entertain is potentially an adjustment of the default, working in concert with the TAHI folks to make sure their tests still pass with any new default. Thanks.