kern/48450: ath (and athn) seem to loop back some packets

[martin%NetBSD.org@localhost]

>Number:         48450
>Category:       kern
>Synopsis:       ath (and athn) seem to loop back some packets
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Dec 15 18:45:00 +0000 2013
>Originator:     Martin Husemann
>Release:        NetBSD 6.99.28
>Organization:
The NetBSD Foundation, Inc.
>Environment:
System: NetBSD night-owl.duskware.de 6.99.28 NetBSD 6.99.28 (NIGHT-OWL) #209: 
Fri Dec 13 10:01:22 CET 2013 
martin%night-owl.duskware.de@localhost:/usr/src/sys/arch/amd64/compile/NIGHT-OWL
 amd64
Architecture: x86_64
Machine: amd64
>Description:

Sometimes IPv6 DAD fails for me:
athn0: DAD detected duplicate IPv6 address 
2001:4dd0:ff00:9258:c617:feff:fece:3734: NS in/out=1/1, NA in=0

Most of the time it works fine, I have never seen it happen on any
other interface. Packettraces from other machines on the network and the
affected machine itself seem to indicate that noone else is sending answers
to the NS.

The athn0 interface is marked IFF_SIMPLEX, but it looks like the NS is looped
back "sometimes".

>How-To-Repeat:

run a machine with ath or athn network interface on an ipv6 enabled network.

>Fix:
n/a