Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 16 Sep 2002 12:45:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 16 Sep 2002 12:45:35 -0400 Received: from 66.148.196.79.nw.nuvox.net ([66.148.196.79]:47503 "HELO greatwhite.teamics.com") by vger.kernel.org with SMTP id ; Mon, 16 Sep 2002 12:45:35 -0400 Subject: Problem: RFC1166 addressing To: linux-kernel@vger.kernel.org X-Mailer: Lotus Notes Release 5.0.6a January 17, 2001 Message-ID: From: tomc@teamics.com Date: Mon, 16 Sep 2002 11:50:36 -0500 X-MIMETrack: Serialize by Router on greatwhite/teamics(Release 5.0.8 |June 18, 2001) at 09/16/2002 11:50:37 AM MIME-Version: 1.0 Content-type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 989 Lines: 33 RFC 1166 states that: The class A network number 127 is assigned the "loopback" function, that is, a datagram sent by a higher level protocol to a network 127 address should loop back inside the host. No datagram "sent" to a network 127 address should ever appear on any network anywhere. Linux does not enforce this. I have uncovered some users using this function to attempt to circumvent the firewall. I am able to "create" 127 network traffic as follows: Machine 1: ifconfig eth0:1 127.1.2.3 [ running kernel 2.2.14 ] Machine 2: ifconfig eth0:1 127.1.2.4 [ running kernel 2.4.19 ] Machine 2: ping 127.1.2.3 Packets move between the hosts. Also seems to work on Macintosh. tc - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/