From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jiri Benc Subject: Re: [PATCH 2/2] ipvlan: always allow the broadcast MAC address Date: Sat, 28 Mar 2015 19:32:54 +0100 Message-ID: <20150328193254.6c79784d@griffin> References: <1427409698.18540.11.camel@redhat.com> <1427409822.18540.13.camel@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Dan Williams , linux-netdev To: Mahesh Bandewar Return-path: Received: from mx1.redhat.com ([209.132.183.28]:52974 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751016AbbC1Sc6 (ORCPT ); Sat, 28 Mar 2015 14:32:58 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Fri, 27 Mar 2015 22:56:15 -0700, Mahesh Bandewar wrote: > The current logic disables broadcast by default and enables only when > an IPv4 address is added. If this is inverted and - > enables broadcast by default but disables it when only IPv6 > address(es) is / are added. These links can have multiple addresses > and hence have to be careful if any one of those is IPv4 then > broadcast bit has to be set. You'd have to be careful and ignore IPv6 link local addresses. Those are added automatically whenever IPv6 is enabled and their presence does not mean the network is not IPv4 only. But I don't like such magic behavior. It would lead to DHCP sometimes working and sometimes not in mixed v4/v6 environment depending on whether DHCPv4 or SLAAC was faster. Could we perhaps add a flag when creating ipvlan interface stating whether IPv4 broadcast should be always enabled? Or, rather, the other way round - whether it should be disabled by default. Call it "nodhcp" or so. Btw, speaking about IPv6 link local addresses, these actually do not work with ipvlan correctly. I'm getting DAD failures if I have more than one ipvlan interface, which is no wonder. This means that ipvlan cannot work with IPv6 reliably by default (unless you take care of ll address assignment and ensure all ipvlan interfaces get a different one). Jiri -- Jiri Benc