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 C94A4C7618B for ; Tue, 23 Jul 2019 15:06:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A29152239F for ; Tue, 23 Jul 2019 15:06:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388497AbfGWPGs (ORCPT ); Tue, 23 Jul 2019 11:06:48 -0400 Received: from orbyte.nwl.cc ([151.80.46.58]:48646 "EHLO orbyte.nwl.cc" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731767AbfGWPGs (ORCPT ); Tue, 23 Jul 2019 11:06:48 -0400 Received: from n0-1 by orbyte.nwl.cc with local (Exim 4.91) (envelope-from ) id 1hpwNI-0001Ba-EF; Tue, 23 Jul 2019 17:06:44 +0200 Date: Tue, 23 Jul 2019 17:06:44 +0200 From: Phil Sutter To: Pablo Neira Ayuso Cc: Florian Westphal , netfilter-devel@vger.kernel.org Subject: Re: [nf PATCH v2 1/2] net: nf_tables: Make nft_meta expression more robust Message-ID: <20190723150644.GO22661@orbyte.nwl.cc> Mail-Followup-To: Phil Sutter , Pablo Neira Ayuso , Florian Westphal , netfilter-devel@vger.kernel.org References: <20190719123921.1249-1-phil@nwl.cc> <20190719163521.oozthobj33ejswrx@salvia> <20190720151502.GD32501@orbyte.nwl.cc> <20190722195321.uf2r5lp46bvslvtd@salvia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190722195321.uf2r5lp46bvslvtd@salvia> 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 Hi Pablo, On Mon, Jul 22, 2019 at 09:53:21PM +0200, Pablo Neira Ayuso wrote: > On Sat, Jul 20, 2019 at 05:15:02PM +0200, Phil Sutter wrote: > > Hi, > > > > On Fri, Jul 19, 2019 at 06:35:21PM +0200, Pablo Neira Ayuso wrote: > > > On Fri, Jul 19, 2019 at 02:39:20PM +0200, Phil Sutter wrote: > > > > nft_meta_get_eval()'s tendency to bail out setting NFT_BREAK verdict in > > > > situations where required data is missing breaks inverted checks > > > > like e.g.: > > > > > > > > | meta iifname != eth0 accept > > > > > > > > This rule will never match if there is no input interface (or it is not > > > > known) which is not intuitive and, what's worse, breaks consistency of > > > > iptables-nft with iptables-legacy. > > > > > > > > Fix this by falling back to placing a value in dreg which never matches > > > > (avoiding accidental matches): > > > > > > > > {I,O}IF: > > > > Use invalid ifindex value zero. > > > > > > > > {BRI_,}{I,O}IFNAME, {I,O}IFKIND: > > > > Use an empty string which is neither a valid interface name nor > > > > kind. > > > > > > > > {I,O}IFTYPE: > > > > Use ARPHRD_VOID (0xFFFF). > > > > > > What could it be done with? > > > > > > NFT_META_BRI_IIFPVID > > > NFT_META_BRI_IIFPVPROTO > > > > > > Those will still not work for > > > > > > meta ibrpvid != 40 > > > > > > if interface is not available. > > > > > > For VPROTO probably it's possible. I don't have a solution for > > > IIFPVID. > > > > VLAN IDs 0 and 4095 are reserved, we could use those. I refrained from > > changing bridge VLAN matches because of IIFPVPROTO, no idea if there's > > an illegal value we could use for that. If you have an idea, I'm all for > > it. :) > > I think we can add something like: > > NFT_META_BRI_IIFVLAN > > just to check for br_vlan_enabled(), from userspace we can check for > exists/missing as a boolean, so we don't have to worry on assuming an > unused value for things like this. This can be added in the next > release cycle. Adding existence checks where missing is indeed a good idea, but doesn't quite solve the problem we're facing here. :) [...] > These ones are missing: > > NFT_META_IIFGROUP > NFT_META_OIFGROUP > > For these two, the default group (0) should be fine since every > interface is falling under this category by default. > > I can squash this small patch to this one and push it one. My problem with these "sane defaults" is that we may cause inconsistent behaviour in rulesets: In prerouting, 'meta oifgroup 0' will match no matter which interface the packet will be routed to. Yes, prerouting implies there is no output interface (yet), but I consider this an implementation detail and there will likely be cases where it is not as easy to spot why something can't work. Cheers, Phil