From mboxrd@z Thu Jan 1 00:00:00 1970 From: Timo Teras Subject: Re: [PATCH net-next 2/2] arp: flush arp cache on IFF_NOARP change Date: Thu, 23 May 2013 15:01:02 +0300 Message-ID: <20130523150102.43010d84@vostro> References: <1369303109-12003-1-git-send-email-timo.teras@iki.fi> <1369303109-12003-2-git-send-email-timo.teras@iki.fi> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: To: "David Laight" Return-path: Received: from mail-ea0-f176.google.com ([209.85.215.176]:48081 "EHLO mail-ea0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758514Ab3EWL70 (ORCPT ); Thu, 23 May 2013 07:59:26 -0400 Received: by mail-ea0-f176.google.com with SMTP id k11so1803545eaj.21 for ; Thu, 23 May 2013 04:59:25 -0700 (PDT) In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Thu, 23 May 2013 11:23:28 +0100 "David Laight" wrote: > > IFF_NOARP affects what kind of neighbor entries are created > > (nud NOARP or nud INCOMPLETE). If the flag changes, flush the arp > > cache to refresh all entries. > > Might someone want to use this to stop further arp table > entries being created? > In which case you don't want anything flushed. I don't think that would make any sense. The entries we have would expire soon, and the other hosts would not be able to get arp replies for our host. Normally this flag is not changed. My use case is with ip gre tunnels, and starting opennhrp daemon. Opennhrp enables address resolution via netlink for gre tunnels - it turns off NOARP flag and configures real ARP off and enables netlink ARPD requests. If before startup there was traffic to gre tunnel, there will be stale NOARP entries preventing traffic after daemon is started. - Timo