From owner-freebsd-net@freebsd.org Tue May 1 19:00:56 2018 Return-Path: Delivered-To: freebsd-net@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 4B3F6FB464B for ; Tue, 1 May 2018 19:00:56 +0000 (UTC) (envelope-from "."@babolo.ru) Received: from smtp.babolo.ru (smtp.babolo.ru [194.58.246.31]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "smtp.babolo.ru", Issuer "babolo" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 4D78971422; Tue, 1 May 2018 19:00:54 +0000 (UTC) (envelope-from "."@babolo.ru) Received: from citycat.babolo.ru (cicuta.babolo [127.0.2.61]) by smtp.babolo.ru (8.15.2/8.15.2) with SMTP id w41JKuqx047574; Tue, 1 May 2018 22:20:56 +0300 (MSK) (envelope-from "."@babolo.ru) Received: (nullmailer pid 79577 invoked by uid 136); Tue, 01 May 2018 18:52:25 -0000 Date: Tue, 1 May 2018 21:52:25 +0300 From: Aleksandr A Babaylov <"."@babolo.ru> To: Julian Elischer Cc: Eugene Grosbein , Jeff Kletsky , freebsd-net@freebsd.org Subject: Re: ipfw -- selecting locally generated packets Message-ID: <20180501185224.GA79544@babolo.ru> References: <979d3478-4bec-e6a1-41cd-bb26beb93123@wagsky.com> <5AE75A4E.6020907@grosbein.net> <600886b2-f78d-0af7-224e-a2711f7e1106@freebsd.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <600886b2-f78d-0af7-224e-a2711f7e1106@freebsd.org> X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 01 May 2018 19:00:56 -0000 On Tue, May 01, 2018 at 09:04:36PM +0800, Julian Elischer wrote: > On 1/5/18 2:02 am, Eugene Grosbein wrote: > >01.05.2018 0:48, Jeff Kletsky wrote: > > > >> From time to time, I rewrite my firewall rules to take advantages of the > >> ever-improving set of features that ipfw provides. One of the challenges > >> I have faced in the past was selecting packets that are generated on the > >> firewall host itself, as opposed to those that it received through an > >> interface. > >> > >>While I find most of the Linux firewall implementations untenable for a > >>variety of reasons, it does provide differentiation between what they > >>call "OUTPUT" and "FORWARD". I'm looking to see if there is a "better" > >>way to implement this kind of selection with the 11.1 version of ipfw. > >> > >>"out and not in" may years ago seemed an obvious selector, and it's good > >>to see that it is now clearly documented that it doesn't work in "man > >>ipfw" with "(in fact, out is implemented as not in)". > >> > >>"not recv any" doesn't seem to be helpful either > >> > >> $ sudo ipfw add 64000 count ip from any to any out xmit any not recv > >> any > >> 64000 count ip from any to any out > >> > >>In the past, I've tagged all incoming packets and used that tag to > >>differentiate between the two. > >> > >>Is there something "cleaner" (or perhaps clearer) that using a tag in > >>that way? > >I have been using "from me" for years and it works. > >If you have NAT, process "from me" packets before translating outgoing > >packets > >and process "to me" after translating incoming packet > On a host with two interfaces you can use subtraction.. > i.e in the outgoing part of the rules you can test on recv xxx0 and if > it doesn't match it must be locally generated. > I've also used the uid rule, which can only match on local packets > ut it only works if you only have a single 'user' on an appliance. Why recv * not used for this task?