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=-8.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 38AB5C433DF for ; Fri, 31 Jul 2020 11:25:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 100C5208E4 for ; Fri, 31 Jul 2020 11:25:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732508AbgGaLZn (ORCPT ); Fri, 31 Jul 2020 07:25:43 -0400 Received: from correo.us.es ([193.147.175.20]:53112 "EHLO mail.us.es" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732303AbgGaLZm (ORCPT ); Fri, 31 Jul 2020 07:25:42 -0400 Received: from antivirus1-rhel7.int (unknown [192.168.2.11]) by mail.us.es (Postfix) with ESMTP id 366C74A7060 for ; Fri, 31 Jul 2020 13:25:40 +0200 (CEST) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id 23DD9DA78C for ; Fri, 31 Jul 2020 13:25:40 +0200 (CEST) Received: by antivirus1-rhel7.int (Postfix, from userid 99) id 23119DA78B; Fri, 31 Jul 2020 13:25:40 +0200 (CEST) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id E2128DA793; Fri, 31 Jul 2020 13:25:37 +0200 (CEST) Received: from 192.168.1.97 (192.168.1.97) by antivirus1-rhel7.int (F-Secure/fsigk_smtp/550/antivirus1-rhel7.int); Fri, 31 Jul 2020 13:25:37 +0200 (CEST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/antivirus1-rhel7.int) Received: from us.es (unknown [90.77.255.23]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: 1984lsi) by entrada.int (Postfix) with ESMTPSA id C379F4265A2F; Fri, 31 Jul 2020 13:25:37 +0200 (CEST) Date: Fri, 31 Jul 2020 13:25:37 +0200 X-SMTPAUTHUS: auth mail.us.es From: Pablo Neira Ayuso To: Phil Sutter , netfilter-devel@vger.kernel.org Subject: Re: [iptables PATCH] nft: Eliminate table list from cache Message-ID: <20200731112537.GA10915@salvia> References: <20200730135710.23076-1-phil@nwl.cc> <20200730192554.GA5322@salvia> <20200731112134.GA13697@orbyte.nwl.cc> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200731112134.GA13697@orbyte.nwl.cc> User-Agent: Mutt/1.10.1 (2018-07-13) X-Virus-Scanned: ClamAV using ClamSMTP Sender: netfilter-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org On Fri, Jul 31, 2020 at 01:21:34PM +0200, Phil Sutter wrote: > Hi Pablo, > > On Thu, Jul 30, 2020 at 09:25:54PM +0200, Pablo Neira Ayuso wrote: > > On Thu, Jul 30, 2020 at 03:57:10PM +0200, Phil Sutter wrote: > > > The full list of tables in kernel is not relevant, only those used by > > > iptables-nft and for those, knowing if they exist or not is sufficient. > > > For holding that information, the already existing 'table' array in > > > nft_cache suits well. > > > > > > Consequently, nft_table_find() merely checks if the new 'exists' boolean > > > is true or not and nft_for_each_table() iterates over the builtin_table > > > array in nft_handle, additionally checking the boolean in cache for > > > whether to skip the entry or not. > > > > > > Signed-off-by: Phil Sutter > > > --- > > > iptables/nft-cache.c | 73 +++++++++++--------------------------------- > > > iptables/nft-cache.h | 9 ------ > > > iptables/nft.c | 55 +++++++++------------------------ > > > iptables/nft.h | 2 +- > > > 4 files changed, 34 insertions(+), 105 deletions(-) > > > > This diffstat looks interesting :-) > > As promised, I wanted to leverage your change for further optimization, > but ended up optimizing your code out along with the old one. :D > > > One question: > > > > c->table[i].exists = true; > > > > then we assume this table is still in the kernel and we don't recheck? > > Upon each COMMIT line, nft_action() calls nft_release_cache(). This will > also reset the 'exists' value to false. Thanks for explaining. I think the chain cache can also be converted to use linux list, right? > > I mean, if you pipe command to an open process running > > iptables-restore (which has been the recommended interface for years > > to avoid of the overhead of system() invocation and to ensure atomic > > updates), is there any cache this new approach might get out of sync? > > This is not just a problem of iptables-restore running in a pipe - > restoring a large ruleset (or just pure coincidence) could lead to the > same result. > > Playing with 'iptables-nft-restore --noflush' reading from stdin and > calling 'nft flush ruleset' in a second shell right before entering > 'COMMIT' leads to funny errors. This is not related to the table list > elimination though. I'll investigate. There is a generation number that the userspace sends to the kernel to validate that it's working with a stale cache to retry. This should help catch the interference scenario to basically (transparently) restart from scratch.