From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 6 Sep 2001 14:12:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 6 Sep 2001 14:12:18 -0400 Received: from clavin.efn.org ([206.163.176.10]:32961 "EHLO clavin.efn.org") by vger.kernel.org with ESMTP id ; Thu, 6 Sep 2001 14:12:04 -0400 From: Steve VanDevender MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <15255.48233.706962.451093@tzadkiel.efn.org> Date: Thu, 6 Sep 2001 11:11:53 -0700 To: wietse@porcupine.org (Wietse Venema) Cc: linux-kernel@vger.kernel.org Subject: Re: notion of a local address [was: Re: ioctl SIOCGIFNETMASK: ip alias In-Reply-To: <20010906172316.E0B74BC06C@spike.porcupine.org> In-Reply-To: <20010906172316.E0B74BC06C@spike.porcupine.org> X-Mailer: VM 6.95 under 21.1 (patch 14) "Cuyahoga Valley" XEmacs Lucid Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Wietse Venema writes: > If an MTA receives a mail relaying request for user@domain.name > then it would be very useful if Linux could provide the MTA with > the necessary information to distinguish between local subnetworks > and the rest of the world. Requiring the local sysadmin to enumerate > all local subnetwork blocks by hand is not practical. I think you're making a couple of unjustified assumptions here: First, you shouldn't assume that all the other hosts on a local subnet are under the same administrative control as the host with the MTA in question (think of a host in a colocation facility), and therefore you also shouldn't assume that you should allow mail relaying to or from other hosts on the same subnet by default. Second, you can't assume that an administrator can or will put all hosts he wants to allow relaying to or from on the same subnet as the MTA. It's not only practical to require the sysadmin to enumerate which hosts or networks he wants to permit relaying from, it's the only solution that gives the sysadmin the required level of control over relaying based on client IP addresses.