From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [RFC PATCH] net: ipv6: Make address flushing on ifdown optional Date: Thu, 22 Jan 2015 22:40:33 -0800 Message-ID: <20150122224033.6e2db5ce@urahara> References: <1421263039-96198-1-git-send-email-dsahern@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, hannes@redhat.com To: David Ahern Return-path: Received: from mail-pd0-f174.google.com ([209.85.192.174]:59758 "EHLO mail-pd0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751125AbbAWGkp (ORCPT ); Fri, 23 Jan 2015 01:40:45 -0500 Received: by mail-pd0-f174.google.com with SMTP id ft15so6737958pdb.5 for ; Thu, 22 Jan 2015 22:40:44 -0800 (PST) In-Reply-To: <1421263039-96198-1-git-send-email-dsahern@gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 14 Jan 2015 12:17:19 -0700 David Ahern wrote: > Currently, ipv6 addresses are flushed when the interface is configured down: > > [root@f20 ~]# ip -6 addr add dev eth1 2000:11:1:1::1/64 > [root@f20 ~]# ip addr show dev eth1 > 3: eth1: mtu 1500 qdisc noop state DOWN group default qlen 1000 > link/ether 02:04:11:22:33:01 brd ff:ff:ff:ff:ff:ff > inet6 2000:11:1:1::1/64 scope global tentative > valid_lft forever preferred_lft forever > [root@f20 ~]# ip link set dev eth1 up > [root@f20 ~]# ip link set dev eth1 down > [root@f20 ~]# ip addr show dev eth1 > 3: eth1: mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000 > link/ether 02:04:11:22:33:01 brd ff:ff:ff:ff:ff:ff > > Add a new sysctl to make this behavior optional. Setting defaults to flush > addresses to maintain backwards compatibility. When reset flushing is bypassed: > > [root@f20 ~]# echo 0 > /proc/sys/net/ipv6/conf/eth1/flush_addr_on_down > [root@f20 ~]# ip -6 addr add dev eth1 2000:11:1:1::1/64 > [root@f20 ~]# ip addr show dev eth1 > 3: eth1: mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000 > link/ether 02:04:11:22:33:01 brd ff:ff:ff:ff:ff:ff > inet6 2000:11:1:1::1/64 scope global tentative > valid_lft forever preferred_lft forever > [root@f20 ~]# ip link set dev eth1 up > [root@f20 ~]# ip link set dev eth1 down > [root@f20 ~]# ip addr show dev eth1 > 3: eth1: mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000 > link/ether 02:04:11:22:33:01 brd ff:ff:ff:ff:ff:ff > inet6 2000:11:1:1::1/64 scope global > valid_lft forever preferred_lft forever > inet6 fe80::4:11ff:fe22:3301/64 scope link > valid_lft forever preferred_lft forever > > Suggested-by: Hannes Frederic Sowa > Signed-off-by: David Ahern > Cc: Hannes Frederic Sowa Would this break existing application expecting a particular semantic by listening to netlink? What happens to packets received with the static address when interface is down? With IPv4 Linux is mostly a weak host model, and IPv6 somewhere in between. For vendors that control the application stack or have limited number of services this would work fine, but what about RHEL?