From owner-freebsd-ipfw@freebsd.org Wed Jul 29 14:03:54 2015 Return-Path: Delivered-To: freebsd-ipfw@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 12D749AD6BB for ; Wed, 29 Jul 2015 14:03:54 +0000 (UTC) (envelope-from julian@freebsd.org) Received: from vps1.elischer.org (vps1.elischer.org [204.109.63.16]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "vps1.elischer.org", Issuer "CA Cert Signing Authority" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id E66C2E8C for ; Wed, 29 Jul 2015 14:03:53 +0000 (UTC) (envelope-from julian@freebsd.org) Received: from Julian-MBP3.local (ppp121-45-239-102.lns20.per1.internode.on.net [121.45.239.102]) (authenticated bits=0) by vps1.elischer.org (8.14.9/8.14.9) with ESMTP id t6TE3l5m060582 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO); Wed, 29 Jul 2015 07:03:51 -0700 (PDT) (envelope-from julian@freebsd.org) Subject: Re: keep-state and in-kernel NAT exposes local ip on external interface To: bycn82 References: <1435692039.18121.12.camel@yahoo.com> <5594395D.6050103@FreeBSD.org> <20150728150845.V17327@sola.nimnet.asn.au> <55B7DB52.7010504@FreeBSD.org> <55B8833B.3030205@freebsd.org> Cc: freebsd-ipfw From: Julian Elischer Message-ID: <55B8DD3D.1030900@freebsd.org> Date: Wed, 29 Jul 2015 22:03:41 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Content-Filtered-By: Mailman/MimeDel 2.1.20 X-BeenThere: freebsd-ipfw@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: IPFW Technical Discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 29 Jul 2015 14:03:54 -0000 On 7/29/15 5:26 PM, bycn82 wrote: > /Hi Julian,/ > / > / > /So below are the rules in your example/ > / > / > /5 skipto 10 from A to B > / > /6 skipto 11 from any to any/ > /10{action} from A to B keep-state/ > /11{action} from C to D/ > / > / > / > / > /If I remove the "skipto" rules they will become/ > // > /10 {action} from A to B keep-state/ > /11 {action} from C to D / > / > / > /Correct me if I was wrong, but in my opinion, the rule 5 and 10 > are almost the same, so I dont see the benefit by introducing the > "skipto" rulees. //IMHO, the "check-state" is to speed-up some > selected packets, it will slow-down all other unexpected packets at > the same time./ > / > / /so because C -D is already in the dynamic table it triggers on 10 and never reaches 11. see? you fell for it too. / > > /Regards,/ > /bycn82/ > > > > > On 29 July 2015 at 15:39, Julian Elischer > wrote: > > On 7/29/15 3:43 AM, Lev Serebryakov wrote: > > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA512 > > On 28.07.2015 08:30, Ian Smith wrote: > > I have global lack of any spare time (and all my FreeBSD > activity is > only a hobby) for last ~2 months. I see the end of this > unfortunate > state of affairs in near future and I remember about these > examples. > > > there are some simple examples of things this patch addresses.. > For example in the current code, the following (extemely > simplified) set of > rules will not do what you would think when you are working with > a tcp > session from A to B and another from C to D *which has > previously been** > **accepted with a keep-state at some other point in the ruleset* > > > 10 {any action} from A to B keep-state > 20 {any action} tcp from C to D > > because despite the fact that you are only triggering on a > 'setup' packet for A to B, any rule > that includes "keep-state" does a "check-state" implicitly. > so the packet from C to D never gets past rule 10. > the only way you can do this is to prefix rule 10 by something like > > 5 skipto 10 from A to B > 6 skipto 11 from any to any > > to make sure packets that are not A to B do not hit the hidden > 'check-state' . > > this is a very simple example and yes there are ways to get > around it, > but it complicates the ruleset and increases errors > > that reminds me I'd also like to be able to put a "not" at the > front of the rule matching to negate the whole test but it > doesn't seem to like that. > > > > > _______________________________________________ > freebsd-ipfw@freebsd.org > mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-ipfw > To unsubscribe, send any mail to > "freebsd-ipfw-unsubscribe@freebsd.org > " > >