Re: Bridge stays down until a port is added

On Tue, 27 Sep 2011 02:28:42 +0200 (CEST)
Sven-Haegar Koch [off-list ref] wrote:

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

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Le 26/09/2011 22:05, Stephen Hemminger a écrit :

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On Mon, 26 Sep 2011 22:02:21 +0200
Nicolas de Pesloüan[off-list ref]  wrote:

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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?

Already multiple ways to disable it:
  1. Set /proc/sys/net/ipv6/XXX/accept_dad to 0
  2. Set flag when assigning address with 'ip add add ... nodad' 
  3. Set IFF_NOARP on the interface (done by drivers)