From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rick Jones Subject: DF, IP ID always 0 and the reassembly protections Date: Tue, 20 Jun 2006 16:44:55 -0700 Message-ID: <44988877.2030205@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from palrel13.hp.com ([156.153.255.238]:28378 "EHLO palrel13.hp.com") by vger.kernel.org with ESMTP id S1751865AbWFTXo4 (ORCPT ); Tue, 20 Jun 2006 19:44:56 -0400 Received: from tardy.cup.hp.com (tardy.cup.hp.com [15.244.56.217]) by palrel13.hp.com (Postfix) with ESMTP id 37D6B3521C for ; Tue, 20 Jun 2006 16:44:56 -0700 (PDT) Received: from hp.com (localhost [127.0.0.1]) by tardy.cup.hp.com (8.9.3 (PHNE_28810)/8.9.3 SMKit7.02) with ESMTP id QAA14213 for ; Tue, 20 Jun 2006 16:44:55 -0700 (PDT) To: Linux Network Development list Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org A while back (I cannot recall exactly when) the issue of always setting the IP datagram ID to zero when the DF bit was set was brought-up. I suggested it might not be a good idea because there are admittedly broken devices out there that "helpfully" and silently clear DF and the start to fragment. The counter point was that coding around such broken hardware was silly. I was just writing a missive to one of my co-workers on IP fragmentation. It got me to thinking about the stuff (I think it went-in?) to try to protect against "Frankengrams" during IP fragment reassembly. Doesn't that mechanism rely on watching the IP ID's between the pair of IPs? For both fragmented and non-fragmented datagrams? If so, does always setting the IP ID to zero when DF is set affect that mechanism? rick jones