netdev - Re: Bridge stays down until a port is added

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Date:	Tue, 27 Sep 2011 02:28:42 +0200 (CEST)
From:	Sven-Haegar Koch <haegar@...net.de>
To:	Nicolas de Pesloüan 
	<nicolas.2p.debian@...il.com>
cc:	Stephen Hemminger <shemminger@...tta.com>,
	Marc Haber <mh+netdev@...schlus.de>, netdev@...r.kernel.org
Subject: Re: Bridge stays down until a port is added

On Tue, 27 Sep 2011, Nicolas de Pesloüan wrote:

> Le 26/09/2011 22:05, Stephen Hemminger a écrit :
> > On Mon, 26 Sep 2011 22:02:21 +0200
> > Nicolas de Pesloüan<nicolas.2p.debian@...il.com>  wrote:
> [...]
> > > 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.
> 
> Yes, and this is by design. Setting the option would state "I want to allow
> early bind(), prior to DAD and I assume the fact that a possible duplicate
> address will cause the corresponding socket to be dead and so the using
> application."

How about a setting just completely disabling this 
duplicate-address-detection crap?

I do not want my servers to ever give up servicing a configured IP no 
matter what else on the network tries to interfere.

If there are two machines using the same IP at a moment, then it may not 
work so great, but both should have all their services up and running, 
and once the invalid one got disconnected ("switch port down") 
everything works - not needing to reboot the real one because some 
daemons were not able to bind their service IPs.

c'ya
sven-haegar

-- 
Three may keep a secret, if two of them are dead.
- Ben F.