Hannes Frederic Sowa [off-list ref] writes:

IFF_NOARP seems to be a bit messed up in ipv6. Your patch seems fine to
me but I would add protection to the ndisc_rcv and sending routines to
do nothing if IFF_NOARP is set for that interface.

That's what I thought.  So for my problem, this will not really change
much.

So it would be possible that you could resolve this issue by just issuing
an "ip link set arp on dev <interface>" and won't have hassle with racing
interface initialization.

Yes, but that would also make the IP layer try to resolve IP to link
layer addressess both for IPv4 and IPv6, which just won't work. At least
not for IPv4, where there just is no way to transport an ARP to the
modem.  And I assume it may fail for IPv6 too on any sane device.

Is this a specific bug of the modem you are using or are all devices
powered by this driver like this?

Unfortunately I have no IPv6 enabled SIM myself, so I have no
information about other devices.  This report was based on user
feedback.

I assume the bug is specific to this firmware implementation, probably
extending to all similar devices from the same vendor.  But it could be
more common than that.  The fact that the bug is there indicates that
this works just fine in Windows.

Yes, I realize that I am in ugly-hack-to-workaround-firmware-issues land
again... But it sure would be nice to have some way for a driver to
indicate that L2 neighbour tables are meaningless, but that any incoming
requests should still be answered.


Bjørn