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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 E5819C3F2D1 for ; Fri, 28 Feb 2020 11:40:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B0E4A246A0 for ; Fri, 28 Feb 2020 11:40:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="TEBJk+jH" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725861AbgB1Lkv (ORCPT ); Fri, 28 Feb 2020 06:40:51 -0500 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:20368 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725536AbgB1Lkv (ORCPT ); Fri, 28 Feb 2020 06:40:51 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1582890049; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=51b9CHD9jN6AHDokVTrETHRd1wKpWwLJIuf3FThjMPY=; b=TEBJk+jHnjHVfvOQjoBJ5qTDyXQ7v+rh0PoSvWKxclnm9/JGr/nPfQ1IG3gyddLW1oc/gJ Nr5FNUt7zjnUAgvzaoJ5VyZ6ikzP9PAEICuOtNF7JpnsczaiqRIIvuZYMSPB0jHeTx6EDA SklF1twQOYQ78ZZ0ae0yXCDZwU51PU0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-74-27AVyINNO5yNOA5jKL4HAw-1; Fri, 28 Feb 2020 06:40:47 -0500 X-MC-Unique: 27AVyINNO5yNOA5jKL4HAw-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C7146107ACC7; Fri, 28 Feb 2020 11:40:46 +0000 (UTC) Received: from localhost (ovpn-200-16.brq.redhat.com [10.40.200.16]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 90A9392972; Fri, 28 Feb 2020 11:40:45 +0000 (UTC) Date: Fri, 28 Feb 2020 12:40:39 +0100 From: Stefano Brivio To: Jozsef Kadlecsik Cc: netfilter-devel@vger.kernel.org, Mithil Mhatre Subject: Re: [PATCH] ipset: Update byte and packet counters regardless of whether they match Message-ID: <20200228124039.00e5a343@redhat.com> In-Reply-To: References: <20200225094043.5a78337e@redhat.com> <20200225132235.5204639d@redhat.com> <20200225215322.6fb5ecb0@redhat.com> Organization: Red Hat MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Sender: netfilter-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org Hi Jozsef, On Thu, 27 Feb 2020 21:37:10 +0100 (CET) Jozsef Kadlecsik wrote: > Hi Stefano, > > On Tue, 25 Feb 2020, Stefano Brivio wrote: > > > On Tue, 25 Feb 2020 21:37:45 +0100 (CET) > > Jozsef Kadlecsik wrote: > > > > > On Tue, 25 Feb 2020, Stefano Brivio wrote: > > > > > > > > The logic could be changed in the user rules from > > > > > > > > > > iptables -I INPUT -m set --match-set c src --bytes-gt 800 -j DROP > > > > > > > > > > to > > > > > > > > > > iptables -I INPUT -m set --match-set c src --bytes-lt 800 -j ACCEPT > > > > > [ otherwise DROP ] > > > > > > > > > > but of course it might be not so simple, depending on how the rules are > > > > > built up. > > > > > > > > Yes, it would work, unless the user actually wants to check with the > > > > same counter how many bytes are sent "in excess". > > > > > > You mean the counters are still updated whenever the element is matched in > > > the set and then one could check how many bytes were sent over the > > > threshold just by listing the set elements. > > > > Yes, exactly -- note that it was possible (and, I think, used) before. > > I'm still not really convinced about such a feature. Why is it useful to > know how many bytes would be sent over the "limit"? This is useful in case one wants different treatments for packets according to a number of thresholds in different rules. For example, iptables -I INPUT -m set --match-set c src --bytes-lt 100 -j noise iptables -I noise -m set --match-set c src --bytes-lt 20000 -j download and you want to log packets from chains 'noise' and 'download' with different prefixes. > Also, there's no protection against overflow in the counters. I know > firewalls with ipset, 10gb interfaces and long uptimes, so it's not > completely a theoretical issue. With 10GbE, 64-bit counters can cover more than: 2 ^ 64 / (10 * 1000 * 1000 * 1000 / 8) = 14757395259 seconds that is, 14757395259 / (60 * 60 * 24) = 170803 days that is, 170803 / 365 = 468 years ...is that a real issue? > > > > > I almost added to my previous mail that the 'ge' and 'gt' matches > > > > > are not really useful at the moment... > > > > > > > > ...yes, I can't think of any other use for those either. > > > > > > Those could really be useful if the counters could be decremented. > > > Otherwise I think the counter matching in the sets is not as useful as > > > it seems to be. > > > > Still, if counters are updated with just matching element, but not > > necessarily matching rule, they should be as useful as in the hypothesis > > of introducing a "decrementing" feature -- one just needs to adjust the > > rule logic to that. > > That's true. > > > > > > The other possibility is to force counter update. I.e. instead of > > > > > > > > > > iptables -I INPUT -m set --match-set c src --bytes-gt 800 -j DROP > > > > > > > > > > something like > > > > > > > > > > iptables -I INPUT -m set --match-set c src --update-counters \ > > > > > --bytes-gt 800 -j DROP > > > > > > > > > > but that also requires some internal changes to store a new flag, because > > > > > at the moment only "! --update-counters" is supported. So there'd be then > > > > > a fine-grained control over how the counters are updated: > > > > > > > > > > - no --update-counters flag: update counters only if the whole rule > > > > > matches, including the counter matches > > > > > - --update-counters flag: update counters if counter matching is false > > > > > > > > ...this should probably be "in any case", also if it's true. > > > > > > Yes, but now I don't really like the name itself: --force-update-counters > > > or something like that would be more clear. > > > > > > > > - ! --update-counters flag: don't update counters > > > > > > > > I think that would fix the issue as well, I'm just struggling to find a > > > > sensible use case for the "no --update-counters" case -- especially one > > > > where there would be a substantial issue with the change I proposed. > > > > > > The no update counter flag was introduced to handle when one needs to > > > match in the same set multiple times, i.e. there are multiple rules with > > > the same set. Like you need to match in the raw/mangle/filter tables as > > > well. Unfortunately I can't recall the usercase. > > > > Okay, but what you're describing is the "! --update-counters" option. > > That works, didn't work before 4750005a85f7, but would still work with > > this change. > > > > What I meant is really the case where "--update-counters" (or > > "--force-update-counters") and "! --update-counters" are both absent: I > > don't see any particular advantage in the current behaviour for that > > case. > > The counters are used just for statistical purposes: reflect the > packets/bytes which were let through, i.e. matched the whole "rule". > In that case updating the counters before the counter value matching is > evaluated gives false results. Well, but for that, iptables/x_tables counters are available and (as far as I know) typically used. -- Stefano