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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5114AC433EF for ; Tue, 30 Nov 2021 14:34:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242235AbhK3OiM (ORCPT ); Tue, 30 Nov 2021 09:38:12 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:52506 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242222AbhK3OiM (ORCPT ); Tue, 30 Nov 2021 09:38:12 -0500 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-186-5jPsumc4Oumeh-9dNTjcig-1; Tue, 30 Nov 2021 09:34:46 -0500 X-MC-Unique: 5jPsumc4Oumeh-9dNTjcig-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A3933190D35B; Tue, 30 Nov 2021 14:34:42 +0000 (UTC) Received: from localhost (unknown [10.22.33.169]) by smtp.corp.redhat.com (Postfix) with ESMTP id 07CE279452; Tue, 30 Nov 2021 14:34:41 +0000 (UTC) Date: Tue, 30 Nov 2021 09:34:41 -0500 From: Eric Garver To: Florian Westphal Cc: netfilter-devel@vger.kernel.org, Phil Sutter Subject: Re: [PATCH nf] netfilter: nat: force port remap to prevent shadowing well-known ports Message-ID: Mail-Followup-To: Eric Garver , Florian Westphal , netfilter-devel@vger.kernel.org, Phil Sutter References: <20211129144218.2677-1-fw@strlen.de> <20211129220254.GA17540@breakpoint.cc> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211129220254.GA17540@breakpoint.cc> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org On Mon, Nov 29, 2021 at 11:02:54PM +0100, Florian Westphal wrote: > Eric Garver wrote: > > On Mon, Nov 29, 2021 at 03:42:18PM +0100, Florian Westphal wrote: > > > If destination port is above 32k and source port below 16k > > > assume this might cause 'port shadowing' where a 'new' inbound > > > connection matches an existing one, e.g. > > > > How did you arrive at 16k? > > I had to pick some number. 1k is too low since some administrative > portals (or openvpn for that matter) are on ports above that. > > I wanted to pick something that would not kick in for most cases. > 16k just seemed like a good compromise, thats all. Understood. I don't have a real reason to choose anything else. That being said, there are more things registered in the > 16k range than I realized.