From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Frederic Sowa Subject: Re: [patch net-next] ipv6: allow userspace to create address with IFLA_F_TEMPORARY flag Date: Wed, 6 Nov 2013 13:03:39 +0100 Message-ID: <20131106120339.GA8144@order.stressinduktion.org> References: <20131028.204306.2213130677400093266.davem@davemloft.net> <20131029124010.GA15762@order.stressinduktion.org> <52792499.3030201@6wind.com> <20131105211158.GL8832@order.stressinduktion.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Cc: nicolas.dichtel@6wind.com, David Miller , jiri@resnulli.us, vyasevich@gmail.com, netdev@vger.kernel.org, kuznet@ms2.inr.ac.ru, jmorris@namei.org, yoshfuji@linux-ipv6.org, kaber@trash.net, thaller@redhat.com, stephen@networkplumber.org To: David Laight Return-path: Received: from order.stressinduktion.org ([87.106.68.36]:53055 "EHLO order.stressinduktion.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756335Ab3KFMDk (ORCPT ); Wed, 6 Nov 2013 07:03:40 -0500 Content-Disposition: inline In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Wed, Nov 06, 2013 at 09:23:05AM -0000, David Laight wrote: > > By the way: > > Although dhclient uses an AF_PACKET socket, it never does request > > additional multicast addresses or promisc mode. So the only overhead is > > that we have to run the socket filter on each incoming packet. > > Just creating the AF_PACKET socket requires that every receive > frame be duplicated. > On Linux this is a reference counted but the cost is still non-zero. > On some other OS (I first saw this with VxWorks) it is a full data copy. Yes, I saw that, so my guess was that running the filter on every incoming UDP packet would be the highes cost factor (it still does get filtered by protocol number early in the stack).