From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nicolas Dichtel Subject: Re: [patch net-next] ipv6: allow userspace to create address with IFLA_F_TEMPORARY flag Date: Tue, 05 Nov 2013 18:02:17 +0100 Message-ID: <52792499.3030201@6wind.com> References: <20131028.204306.2213130677400093266.davem@davemloft.net> <20131029124010.GA15762@order.stressinduktion.org> Reply-To: nicolas.dichtel@6wind.com Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE To: David Laight , 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 Return-path: Received: from mail-bk0-f49.google.com ([209.85.214.49]:41258 "EHLO mail-bk0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755342Ab3KERCV (ORCPT ); Tue, 5 Nov 2013 12:02:21 -0500 Received: by mail-bk0-f49.google.com with SMTP id w14so3629809bkz.8 for ; Tue, 05 Nov 2013 09:02:19 -0800 (PST) In-Reply-To: <20131029124010.GA15762@order.stressinduktion.org> Sender: netdev-owner@vger.kernel.org List-ID: Le 29/10/2013 13:40, Hannes Frederic Sowa a =C3=A9crit : > On Tue, Oct 29, 2013 at 09:37:06AM -0000, David Laight wrote: >>> Note that you don't even need to put the DHCP protocol core into th= e >>> kernel to fix the promiscuous problem. You just have to use the >>> current kernel interfaces correctly. >>> >>> It used to be the case a very long time ago that you couldn't even >>> receive broadcast UDP datagrams on a socket until an address was >>> configured on it. >>> >>> So everyone turns on promiscuous mode and uses RAW sockets or >>> AF_PACKET. >>> >>> Stupid? yes. >> >> Not only that, but the dhcp client could use a normal UDP socket >> to keep the lease renewed - I suspect it has only ever needed >> to use the BPF interface (I didn't think it set promiscuous) >> when acquiring the initial lease. > > Yes, this is a very unfortunate situation. From my experience it is n= ot that > easy to get a patch merged into isc-dhcp. > > It seems not that invasive to switch from af_packet to an udp socket = with > SO_BROADCAST set. If I remember well, another problem is to be able to send these packets= with 0.0.0.0 when another IP address is available on the system: RFC2131 4.1 Constructing and sending DHCP messages =2E.. DHCP messages broadcast by a client prior to that client obtaining its IP address must have the source address field in the IP header set to 0. We made a patch (never proposed upstream) to add a socket option to kee= p this 0.0.0.0 address. If people are interested, I can try to port it on net-next. Nicolas