kern/52319: [Change request] Don't mark addresses as DETACHED when the interface is still a part of a bridge

[dmb%yenn.ulegend.net@localhost]

>Number:         52319
>Category:       kern
>Synopsis:       When the link goes down, and the interface is part of a bridge, the interface's IP should still be active
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          change-request
>Submitter-Id:   net
>Arrival-Date:   Tue Jun 20 13:05:00 +0000 2017
>Originator:     Dominik Bialy
>Release:        NetBSD 8.0_BETA
>Organization:
Underlegend Networks
>Environment:
System: NetBSD yenn 8.0_BETA NetBSD 8.0_BETA (YENN) #3: Mon Jun 19 14:52:28 UTC 2017 builds@yenn:/var/obj/sys/arch/amd64/compile/YENN amd64
Architecture: x86_64
Machine: amd64
>Description:
Example:

ex1 is an ethenernet inteface

on ex1 there's a local IP being a gateway address for a local ethernet network

ex1 is bridged with tap0, which has OpenVPN on it

the VPN shares the gateway IP with the local ethernet

when the link goes down on ex1, the VPN also stops working

I think it should still keep the IP active, until the bridge is destroyed, or the other member(s)
of a bridge are also down or removed.  It should mark addresses as TENTATIVE when at least one
member of the bridge has link up again.

>How-To-Repeat:
See above.

>Fix:
None known to me.