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 15:10:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 6 Sep 2001 15:10:35 -0400 Received: from clavin.efn.org ([206.163.176.10]:54224 "EHLO clavin.efn.org") by vger.kernel.org with ESMTP id ; Thu, 6 Sep 2001 15:10:28 -0400 From: Steve VanDevender MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <15255.51738.928064.590637@tzadkiel.efn.org> Date: Thu, 6 Sep 2001 12:10:18 -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: <20010906182518.3C907BC06C@spike.porcupine.org> In-Reply-To: <15255.48233.706962.451093@tzadkiel.efn.org> <20010906182518.3C907BC06C@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: > Steve VanDevender: > > 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: > > You are making unjustified assumptions: > > If the kernel knows about subnets, then an application should be > able to find out about them. Whether or not you agree with the > application's reasons does not matter. The only justification I've seen you offer so far for wanting this netmask information is apparently to use to decide whether your MTA should allow relaying to another host or not. As a sysadmin who manages several large MTA installations I'd say that allowing relaying to or from other hosts on "local" subnets as determined by available interfaces and netmasks should at best be an option, and that option should be off by default -- there are too many common situations where that would open an MTA to abuse, or circumvent other controls one would want to put on an MTA's relaying permissions. If you were just talking about the problem of determining which IP addresses are bound to the host, I wouldn't disagree with you, but you keep saying things that make it look like you really want to have your MTA permit relaying by default to all hosts in "local" networks based on available interfaces and netmasks. So if the only reason your application wants this information is to apply it in a useless or even awful way, I'd have to question why you feel the need to obtain the information at all. In a pure sense maybe an application should be able to obtain this information, but in a practical sense if there's no good use for the information in this specific situation then why make a big fuss about not being able to obtain it?