How to report IPv6 bug to Microsoft - Vista and 7 won't "undeprecate" a prefix

[Mark Smith]

Hi Tore,

On 12/04/2011 5:15 PM, Tore Anderson wrote:
> Hi Mark,
>
> * Mark Smith
>
>> No it isn't one of yours.
>
> AVM FRITZ!Box?
>

Yes it is, it's a 7390 running firmware 84.04.88, which according to the 
device web gui is the latest available production firmware.

> http://getipv6.info/index.php/Customer_problems_that_could_occur#AVM
>
>> I've just had a closer look at what it is doing on it's LAN interface -
>>
>> 1. While the ADSL link is up, it advertises both it's global prefix and
>> a "ULA" prefix in it's LAN interface RAs. The global prefix preferred
>> lifetime is 3600, while the valid lifetime is 7200, regardless of what
>> we are setting on the delegated prefix. The "ULA" prefix is announced
>> with a 0 second preferred and valid lifetimes.
>
> What happens if you connect the WAN port to an IPv4-only network; ULA
> PIO with normal lifetimes? What about the RA lifetime in this case?
>

In this situation, with the IPv6 recommended defaults ("IPv6 
Connectivity - Detect settings automatically (recommended)", "Assign 
unique local addresses (ULA) as long as no IPv6 connection exists 
(recommended)"), the 7390 brings up a 6to4 tunnel, and then announces 
the 2002:..XX../64 prefix onto the LAN in the same manner as before, 
swapping the ULA for the 6to4 prefix when the ADSL interface goes down 
and vice versa. The router lifetime stays at 1800 seconds. With the ADSL 
link down, a ULA and end-nodes with a default gateway, the 7390 should 
be generating ICMPv6 destination unreachables, but it doesn't. When I've 
had a router that does generate destination unreachables in this 
situation, my linux end-node immediately switches to trying to use IPv4 
and then successfully accesses the IPv4 version of the website.


>> 2. When the ADSL link fails, the prefix lifetime values are reversed -
>> the global gets all zeros, while the "ULA"'s become 3600/7200.
>
> I'm curious to hear if something happens with the lifetime of the RA
> itself in this case. Does it get set to 0 so that the hosts on the LAN
> remove the default route?
>

No the default route doesn't get withdrawn by the router.

> What happens if only the IPv6 part of the WAN connection fails (e.g. if
> a DHCPv6 lease expires)?
>

We're using SLAAC on the WAN side. I'll have a think to see if I can 
work out a way to simulate an IPv6 WAN failure to see what happens.

> The reason I'm asking is that this device might cause end-user
> brokenness if it can be made to announce a ULA prefix with a router
> lifetime of>0 that is *not* accompanied by a global prefix. This would
> cause end-user hosts to attempt to use the ULA addresses when connecting
> to dual-stacked destinations, as ULAs have global scope and are not
> assigned a distinct label in the RFC3484 policy table in any recent
> operating system. If that is the case I would very much like to document
> this device as a source of brokenness in the ARIN Wiki.
>

Regards,
Mark.