[openib-general] "arping" failing over ipoib

[Tom Duffy]

On Wed, 2005-03-02 at 20:40 -0800, Roland Dreier wrote:
>     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).

That is a good question.  I think the code is b0rked.  -1 is coming from
the "received" variable.  This is never initialized.  Initializing it to
0 at least causes arping to fail gracefully, letting ifup continue. I
have opened fedora bug 150156 regarding this and emailed the arping
maintainer.

>     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.

OK, well I thought it was right according to the ARP IPoIB encapsulation
IETF draft.  I will look at it a bit more in depth tomorrow.  In any
event, what is the right format of the packet for userspace to craft?

Thanks,

-tduffy
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