[Wien] ipv6 with olsrd2?

[Erich N. Pekarek]

Hi!
Am 2017-08-15 um 11:43 schrieb Matthias Šubik:
> let me have a guess ...
Let me guess a bit further...
>> On 11 Aug 2017, at 15:37, Gui Iribarren <(spam-protected)> wrote:
>>
>> On 11/08/17 13:43, Christian Pock wrote:
> ...
>>>
>>> For some reason, not all routers running olsr2 are reachable via IPv6. As far as we found out, this is related to the  setting "WDS bridge" on Ubiquiti-Antennas running AirOS 6 or earlier (with must be enabled). So in case there's a node listed in the "olsr2 cloud", a missing WDS-bridge-enabled setting could cause that the node is not available (highlighted blue in the listing and map).
>> yeah, "WDS" must always be enabled on all bridges (in some AirOs
>> versions is called "Transparent bridge mode") or funny things happen in
>> IPv6 world
> I don’t know AirOS, but I guess if disabled, it filters ethernet multicast, this kills neighbour discovery, which is essential for normal IPv6 operation.
> If you debug IPv6, please take into account the subtile differences between IPv4 and IPv6 on layer two.
Multicast is not the only problem. Since AirOS is used in bridged mode, 
you'd then have 'foreign' MAC addresses leaving the Wireless Interface.
This is, what WDS is usually for: it resembles 4-address mode, that 
rewrites packets.

The effect of using a non-WDS-bridge would be, that ip neigh show would 
list the neighbours correctly, but all of them will be STALE in the 
first place.
If you try to ping them, you will fail, which will be represented by a 
FAILED link in die neighbour table.
The funny thing is, that you could still ping6 the link local address 
from a direct 1 hop neighbour.

So you may be lead to believe it's a mere multicast problem. But 
debugging that, you will see, that proxying the multicast won't help.
The problem resides in NDP failing to resolve devices behind the bridge, 
since it will only discover the wrong originator MAC - that is the one 
of the AP on non-WDS-enabled devices.

>
> TL;DR: ARP reachability is not v6 reachability.
Full Ack.
>
> just a little reminder,
> Matthias
>
>
> --
> Wien mailing list
> (spam-protected)
> https://lists.funkfeuer.at/mailman/listinfo/wien
> Best regards
Erich