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: Tue, 5 Nov 2013 21:57:44 +0100 Message-ID: <20131105205744.GK8832@order.stressinduktion.org> References: <20131028.204306.2213130677400093266.davem@davemloft.net> <20131029124010.GA15762@order.stressinduktion.org> <52792499.3030201@6wind.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: 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 To: Nicolas Dichtel Return-path: Received: from order.stressinduktion.org ([87.106.68.36]:51642 "EHLO order.stressinduktion.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754726Ab3KEU5q (ORCPT ); Tue, 5 Nov 2013 15:57:46 -0500 Content-Disposition: inline In-Reply-To: <52792499.3030201@6wind.com> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, Nov 05, 2013 at 06:02:17PM +0100, Nicolas Dichtel wrote: > 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 t= he > >>>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 = not=20 > >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 packe= ts with > 0.0.0.0 when another IP address is available on the system: >=20 > RFC2131 > 4.1 Constructing and sending DHCP messages > ... > 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. >=20 > We made a patch (never proposed upstream) to add a socket option to k= eep > this 0.0.0.0 address. > If people are interested, I can try to port it on net-next. Yes, this indeed is a problem for a socket only dhcp client. I would ma= ke the appropriate changes to isc-dhcp if you submit such a patch. Thanks, Hannes