From: Stephen Hemminger <shemminger@vyatta.com>
To: "Nicolas de Pesloüan" <nicolas.2p.debian@gmail.com>
Cc: Marc Haber <mh+netdev@zugschlus.de>, netdev@vger.kernel.org
Subject: Re: Bridge stays down until a port is added
Date: Mon, 26 Sep 2011 13:05:07 -0700 [thread overview]
Message-ID: <20110926130507.1435d76b@nehalam.linuxnetplumber.net> (raw)
In-Reply-To: <4E80DA4D.3090404@gmail.com>
On Mon, 26 Sep 2011 22:02:21 +0200
Nicolas de Pesloüan <nicolas.2p.debian@gmail.com> wrote:
> Le 26/09/2011 17:47, Stephen Hemminger a écrit :
> > The root of this whole problem is really that IPv6 reports addresses
> > in a tentative state to applications that can not be passed to the bind() system call.
> > For most cases, this problem never happens because the tentative addresses are
> > resolved by Duplicate Address Detection before the application starts. But
> > I have seen (and fixed) this happen before this whole discussion started.
> >
> > 1. The problem is not unique to bridges. It happens with bridge, macvtap,
> > even on wireless networks where the device is available but carrier is
> > not asserted.
> >
> > 2. Any change to what the kernel does (like not reporting tentative addresses)
> > would break applications even worse.
> >
> > 3. When the bridge was always reporting carrier, it was in effect breaking
> > IPv6 Duplicate Address Detection. And that is bad.
>
> Stephen,
>
> What do you think about a generic per-interface option that would cause bind() to accept tentative
> address hold by a particular interface? This of course violate IPv6 principle, but we are talking
> about interfaces that are unable to do DAD, either permanently or until something happens on the
> underlying device.
>
> echo 1 > /sys/class/net/br0/allow_bind_on_tentative_address
> echo 1 > /sys/class/net/dummy0/allow_bind_on_tentative_address
> echo 1 > /sys/class/net/wlan0/allow_bind_on_tentative_address
> and so on...
>
> And we may possibly automatically reset this option to 0 if DAD eventually causes the address to be
> considered duplicate.
The issue is that if DAD rejects a duplicate, the socket is dead and application is
out of luck.
Has anyone looked at this issue in relation to systemd which does early
opportunistic binding of services?
next prev parent reply other threads:[~2011-09-26 20:05 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-11 7:06 Bridge stays down until a port is added Marc Haber
2011-08-11 15:17 ` Stephen Hemminger
2011-08-11 20:54 ` Marc Haber
2011-08-11 22:41 ` Stephen Hemminger
2011-08-12 12:22 ` Sven-Haegar Koch
2011-08-20 9:47 ` Marc Haber
2011-08-20 16:30 ` Stephen Hemminger
2011-08-21 12:13 ` Marc Haber
2011-08-22 15:57 ` Stephen Hemminger
2011-09-17 20:42 ` Marc Haber
2011-09-20 20:20 ` Dan Williams
2011-09-25 8:25 ` Marc Haber
2011-09-26 15:47 ` Stephen Hemminger
2011-09-26 20:02 ` Nicolas de Pesloüan
2011-09-26 20:05 ` Stephen Hemminger [this message]
2011-09-26 20:56 ` Ben Hutchings
2011-09-26 22:12 ` Nicolas de Pesloüan
2011-09-26 22:42 ` Stephen Hemminger
2011-09-27 0:28 ` Sven-Haegar Koch
2011-09-27 0:43 ` Stephen Hemminger
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=20110926130507.1435d76b@nehalam.linuxnetplumber.net \
--to=shemminger@vyatta.com \
--cc=mh+netdev@zugschlus.de \
--cc=netdev@vger.kernel.org \
--cc=nicolas.2p.debian@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
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;
as well as URLs for NNTP newsgroup(s).