[openib-general] "arping" failing over ipoib

[Roland Dreier]

    Tom> # arping -c 2 -w 3 -D -I ib0 192.168.0.62
    Tom> ARPING 192.168.0.62 from 0.0.0.0 ib0
    Tom> Sent 2 probes (2 broadcast(s))
    Tom> Received -1 response(s)

What are the network startup scripts expecting?  How is arping getting
so confused that it reports -1 responses?  (Sorry, haven't had a
chance to look at the code).

    Tom> I have looked at the arping code, and it seems to be crafting
    Tom> the packet correctly, even using 32 in the type field, so I
    Tom> am a bit befuddled as to why this isn't working.

What packet does arping create?  Unfortunately, because a "normal"
IPoIB packet doesn't include any encapsulation beyond the 4 bytes of
ethertype/reserved, it's a little difficult for userspace to send
broadcast packets.  If arping tries to create an ethernet-like header,
then the IPoIB driver is going to get a little confused.

 - R.