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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 8AAB1C3A59F for ; Thu, 29 Aug 2019 20:58:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 577C12173E for ; Thu, 29 Aug 2019 20:58:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728248AbfH2U6h (ORCPT ); Thu, 29 Aug 2019 16:58:37 -0400 Received: from Chamillionaire.breakpoint.cc ([193.142.43.52]:53624 "EHLO Chamillionaire.breakpoint.cc" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726935AbfH2U6h (ORCPT ); Thu, 29 Aug 2019 16:58:37 -0400 Received: from fw by Chamillionaire.breakpoint.cc with local (Exim 4.92) (envelope-from ) id 1i3RV2-0007J3-97; Thu, 29 Aug 2019 22:58:32 +0200 Date: Thu, 29 Aug 2019 22:58:32 +0200 From: Florian Westphal To: Leonardo Bras Cc: Pablo Neira Ayuso , Florian Westphal , "David S. Miller" , netfilter-devel@vger.kernel.org, coreteam@netfilter.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Jozsef Kadlecsik , Alexey Kuznetsov , Hideaki YOSHIFUJI Subject: Re: [PATCH v2 1/1] netfilter: nf_tables: fib: Drop IPV6 packages if IPv6 is disabled on boot Message-ID: <20190829205832.GM20113@breakpoint.cc> References: <20190821141505.2394-1-leonardo@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: netfilter-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org Leonardo Bras wrote: > On Thu, 2019-08-29 at 17:04 -0300, Leonardo Bras wrote: > > > Thats a good point -- Leonardo, is the > > > "net.bridge.bridge-nf-call-ip6tables" sysctl on? > > > > Running > > # sudo sysctl -a > > I can see: > > net.bridge.bridge-nf-call-ip6tables = 1 > > Also, doing > # echo 0 > /proc/sys/net/bridge/bridge-nf-call-ip6tables > And then trying to boot the guest will not crash the host. > > Which would make sense, since host iptables is not dealing with guest > IPv6 packets. Yes. > So, the real cause of this bug is the bridge making host ip6tables deal > with guest IPv6 packets ? > If so, would it be ok if write a patch testing ipv6_mod_enabled() > before passing guest ipv6 packets to host ip6tables? I'm not sure. This switch is very old, it was added 10 years ago in v2.6.31-rc1. Even if we disable call-ip6tables in br_netfilter we will at least in addition need a patch for nft_fib_netdev.c. >From a "avoid calls to ipv6 stack when its disabled" standpoint, the safest fix is to disable call-ip6tables functionality if ipv6 module is off *and* fix nft_fib_netdev.c to BREAK in ipv6 is off case. I started to place a list of suspicous modules here, but that got out of hand quickly. So, given I don't want to plaster ipv6_mod_enabled() everywhere, I would suggest this course of action: 1. add a patch to BREAK in nft_fib_netdev.c for !ipv6_mod_enabled() 2. change net/bridge/br_netfilter_hooks.c, br_nf_pre_routing() to make sure ipv6_mod_enabled() is true before doing the ipv6 stack "emulation". Makes sense? Thanks, Florian