From mboxrd@z Thu Jan 1 00:00:00 1970 From: "David Shwatrz" Subject: [PATCH net-2.6][NEIGH] Updating affected neighbours about MAC address change Date: Sun, 23 Dec 2007 12:55:16 +0200 Message-ID: <31436f4a0712230255w48e19a12ia686f326e87a21db@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit To: davem@davemloft.net, netdev@vger.kernel.org Return-path: Received: from wa-out-1112.google.com ([209.85.146.178]:22833 "EHLO wa-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752309AbXLWKzR (ORCPT ); Sun, 23 Dec 2007 05:55:17 -0500 Received: by wa-out-1112.google.com with SMTP id v27so1871087wah.23 for ; Sun, 23 Dec 2007 02:55:16 -0800 (PST) Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: Hello, We know that changes in MAC addresses are not frequent but we are working on a special, highly advanced networking Linux based project in our LABs, where we do change MAC addresses of an interface quite frequently. (We do not go totally wild; the MAC addresses we are changing into are from a set of given MAC addresses). Normally, when we change a MAC address of some interface, the relevant neighbours in the LAN which have entries with the previous MAC address are not sent any update notification; instead, it is there regular timers mechanisms which update the MAC address to the new one in their ARP tables. I had written a small patch to neigh_changeaddr() in net/core/neighbour.c against the 2.6 git net tree, which sends a gratuitous ARP to update the list of all the involved neighbours with the change of MAC address. The patch is for neigh_changeaddr() only. This patch was tested and it does work in my LAB; if such a patch is not needed, I wonder why ? It seems to me that it could not cause any troubles. BTW, I had noticed that in irlan driver, there is such a mechanism of sending a gratuitous ARP to update all the neighbours when a MAC address is changed. Signed-off-by: David Shwatrz