kern/172683: Duplicate IPv6 Link Local Addresses
>Number: 172683
>Category: kern
>Synopsis: Duplicate IPv6 Link Local Addresses
>Confidential: no
>Severity: critical
>Priority: high
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Sun Oct 14 06:40:00 UTC 2012
>Closed-Date:
>Last-Modified:
>Originator: Doug Hardie <bc979@lafn.org>
>Release: FreeBSD 9.1-RC2 i386
>Organization:
>Environment:
System: FreeBSD master.lafn.org 9.1-RC2 FreeBSD 9.1-RC2 #0 r241133: Tue Oct 2 17:11:45 UTC 2012 root@obrian.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC i386
>Description:
You can assign identical link local addresses to two different 9.1-RC2
systems on the same LAN and the problem is not detected. When the
second machine becomes alive it properly sends a Neighbor Solication
with the proper address, but the first machine does not respond to it
with a Neighbor Advertisement which would alert the second machine to
the duplication and permit it to select a different address. As a
result both machines have the same link local address and nothing works.
>How-To-Repeat:
Determine the link local address the second machine will use and shut it down. On the first machine assign manually that link local address to
the appropriate port. Run a tcpdump -ixxx -vx ip6 on the first machine
and power up the second. The second machine will send a Neighbor
Solication with the duplicated address, but the first machine will not
respond to that packet.
I have one machine that never sends the original Neighbor Solication
for the link local address. It does send for its global addresses.
It just starts using the link local address. I can't find any
significant differences between those two systems other that the
first was a direct install from the CD and the second was a
freebsd-update from 9.1-RC1.
>Fix:
>Release-Note:
>Audit-Trail:
>Unformatted:
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