kern/185660: lagg(4) IPv6-related problem with interface creation

[Michael Moll]

>Number:         185660
>Category:       kern
>Synopsis:       lagg(4) IPv6-related problem with interface creation
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Jan 11 16:50:00 UTC 2014
>Closed-Date:
>Last-Modified:
>Originator:     Michael Moll
>Release:        10-STABLE
>Organization:
>Environment:
FreeBSD emperor.kvedulv.de 10.0-PRERELEASE FreeBSD 10.0-PRERELEASE #0 r260387: Tue Jan  7 04:39:10 CET 2014     mmoll at emperor.kvedulv.de:/usr/obj/svn/base/stable/10/sys/EMPEROR  amd64
>Description:
With the following in /etc/rc.conf:
cloned_interfaces="lagg0"
ifconfig_em0="up"
ifconfig_em1="up"
ifconfig_lagg0="up laggproto lacp laggport em0 laggport em1 192.168.200.8/24"
ifconfig_lagg0_ipv6="inet6 2001:x:x:x::8/64"
ipv6_defaultrouter="2001:x:x:x::1"
defaultrouter="192.168.200.1"
ipv6_activate_all_interfaces="YES"
ip6addrctl_policy="ipv6_prefer"

a successful startup looks like this:
Created clone interfaces: lagg0.
lagg0: IPv6 addresses on em0 have been removed before adding it as a member to prevent IPv6 address scope violation.
lagg0: link state changed to DOWN
lagg0: IPv6 addresses on em1 have been removed before adding it as a member to prevent IPv6 address scope violation.
Starting Network: lo0 em0 em1 lagg0.

However, about 70% of boots result in this:
Created clone interfaces: lagg0.
em0: link state changed to UP
em1: link state changed to UP
[hang]

When doing Ctrl-T at this point I get:
load: 1.51  cmd: ifconfig 606 [*in6_multi_mtx] 17.80r 0.00u 0.72s 0% 1940k
>How-To-Repeat:
I have a second box (different board, also with em-Interfaces) with the same behaviour.
>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted: