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=-5.3 required=3.0 tests=BAYES_00, 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 80A95C4338F for ; Sun, 15 Aug 2021 13:49:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6346560EB5 for ; Sun, 15 Aug 2021 13:49:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232498AbhHONt5 (ORCPT ); Sun, 15 Aug 2021 09:49:57 -0400 Received: from mail.netfilter.org ([217.70.188.207]:53358 "EHLO mail.netfilter.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231881AbhHONt5 (ORCPT ); Sun, 15 Aug 2021 09:49:57 -0400 Received: from netfilter.org (unknown [78.30.35.141]) by mail.netfilter.org (Postfix) with ESMTPSA id 632F26005D; Sun, 15 Aug 2021 15:48:40 +0200 (CEST) Date: Sun, 15 Aug 2021 15:49:22 +0200 From: Pablo Neira Ayuso To: Florian Westphal Cc: Jan Engelhardt , netfilter-devel@vger.kernel.org Subject: Re: [PATCH iptabes-nft] iptables-nft: allow removal of empty builtin chains Message-ID: <20210815134922.GA10659@salvia> References: <20210814174643.130760-1-fw@strlen.de> <84q02320-o5pp-8q8q-q646-473ssq92n552@vanv.qr> <20210814205314.GF607@breakpoint.cc> <20210815131223.GA30503@salvia> <20210815132733.GI607@breakpoint.cc> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20210815132733.GI607@breakpoint.cc> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org On Sun, Aug 15, 2021 at 03:27:33PM +0200, Florian Westphal wrote: > Pablo Neira Ayuso wrote: > > On Sat, Aug 14, 2021 at 10:53:14PM +0200, Florian Westphal wrote: > > > Indeed. Since this removes the base chain, it implicitly reverts > > > a DROP policy too. > > > > User still has to iptables -F on that given chain before deleting, > > right? > > Yes, -X fails if the chain has rules. > > > If NLM_F_NONREC is used, the EBUSY is reported when trying to delete > > a chain with rules. > > Yes. But we really do not need NLM_F_NONREC for this new feature, right? I mean, a quick shortcut to remove the basechain and its content should be fine. > > My assumption is that the user will perform: > > > > iptables-nft -F -t filter > > iptables-nft -D -t filter > > Yes, assuminy you meant -X instead of -D. Oh well, embarrasing, yes. > This behaves just like before, it deletes all rules (-F) and all user-defined > chains (-X). > > > I mean, by when the user has an empty basechain with default policy to > > DROP, if they remove the chain, then they are really meaning to remove > > the chain and this default policy to DROP. > > ATM iptables -X $BUILTIN will always fail. > In -legecy there is no kernel API to allow for its removal, > for -nft there is an extra check that throws an error. > > > Or am I missing anything else? > > No, I don't think so. I would prefer if > iptables-nft -F -t filter > iptables-nft -X -t filter > > ... would result in an empty "filter" table. Your concern is that this would change the default behaviour? > I could also add a patch that requests removal > of the table as well for the -X case; but unlike base chain the > presence of the table alone has no impact on dataplane. Then, probably add a new command for this? iptables-nft -K INPUT -t filter => to remove the INPUT/filter basechain. Then: iptables-nft -N INPUT -t filter to bring it back (if it was removed).