From: YOSHIFUJI Hideaki <hideaki.yoshifuji@miraclelinux•com>
To: Hannes Frederic Sowa <hannes@redhat•com>,
Stephen Hemminger <stephen@networkplumber•org>
Cc: hideaki.yoshifuji@miraclelinux•com,
David Ahern <dsahern@gmail•com>,
"netdev@vger•kernel.org" <netdev@vger•kernel.org>
Subject: Re: why are IPv6 addresses removed on link down
Date: Tue, 13 Jan 2015 21:15:45 +0900 [thread overview]
Message-ID: <54B50C71.7090007@miraclelinux.com> (raw)
In-Reply-To: <54B50873.4090907@miraclelinux.com>
YOSHIFUJI Hideaki wrote:
> Hi,
>
> Hannes Frederic Sowa wrote:
>> On Mo, 2015-01-12 at 23:10 -0800, Stephen Hemminger wrote:
>>> On Mon, 12 Jan 2015 22:06:44 -0700
>>> David Ahern <dsahern@gmail•com> wrote:
>>>
>>>> We noticed that IPv6 addresses are removed on a link down. e.g.,
>>>> ip link set dev eth1
>>>>
>>>>
>>>> Looking at the code it appears to be this code path in addrconf.c:
>>>>
>>>> case NETDEV_DOWN:
>>>> case NETDEV_UNREGISTER:
>>>> /*
>>>> * Remove all addresses from this interface.
>>>> */
>>>> addrconf_ifdown(dev, event != NETDEV_DOWN);
>>>> break;
>>>>
>>>> IPv4 addresses are NOT removed on a link down. Is there a particular
>>>> reason IPv6 addresses are?
>>>>
>>>> Thanks,
>>>> David
>>>
>>> See RFC's which describes how IPv6 does Duplicate Address Detection.
>>> Address is not valid when link is down, since DAD is not possible.
>>
>> It should be no problem if the kernel would reacquire them on ifup and
>> do proper DAD. We simply must not use them while the interface is dead
>> (also making sure they don't get used for loopback routing).
>>
>> The problem the IPv6 addresses get removed is much more a historical
>> artifact nowadays, I think. It is part of user space API and scripts
>> deal with that already.
>
> We might have another "detached" state which essintially drops
> outgoing packets while link is down. Just after recovering link,
> we could start receiving packet from the link and perform optimistic
> DAD. And then, after it succeeds, we may start sending packets.
>
> Since "detached" state is like the state just before completing
> Optimistic DAD, it is not so difficult to implement this extended
> behavior, I guess.
>
Note that node is allowed to send packets to neighbours or default
routers if the node knows their link-layer addresses during Optimistic
DAD.
--
Hideaki Yoshifuji <hideaki.yoshifuji@miraclelinux•com>
Technical Division, MIRACLE LINUX CORPORATION
next prev parent reply other threads:[~2015-01-13 12:15 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-13 5:06 why are IPv6 addresses removed on link down David Ahern
2015-01-13 7:10 ` Stephen Hemminger
2015-01-13 10:35 ` Hannes Frederic Sowa
2015-01-13 11:58 ` YOSHIFUJI Hideaki
2015-01-13 12:15 ` YOSHIFUJI Hideaki [this message]
2015-01-13 12:36 ` Hannes Frederic Sowa
2015-01-13 14:53 ` David Ahern
2015-01-13 15:00 ` Hannes Frederic Sowa
2015-01-13 17:05 ` Nicolas Dichtel
2015-01-13 15:00 ` Sowmini Varadhan
2015-01-13 15:09 ` Hannes Frederic Sowa
2015-01-13 15:13 ` Sowmini Varadhan
2015-01-13 17:25 ` David Miller
2015-01-13 17:34 ` Hannes Frederic Sowa
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=54B50C71.7090007@miraclelinux.com \
--to=hideaki.yoshifuji@miraclelinux$(echo .)com \
--cc=dsahern@gmail$(echo .)com \
--cc=hannes@redhat$(echo .)com \
--cc=netdev@vger$(echo .)kernel.org \
--cc=stephen@networkplumber$(echo .)org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox