[openib-general] "arping" failing over ipoib

[Hal Rosenstock]

On Wed, 2005-03-02 at 23:40, Roland Dreier wrote:
> What packet does arping create?  

I think it creates an ARP first. It does everything "directly".

> 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.  

For ARP specifically (ethertype 0x0806), there is no way without
additional information for the IPoIB driver to know whether it is
intended to be broadcast or unicast. I'm also not sure how responses
would make it back to user space either as I would expect arping to be
looking for the response or lack thereof.

> If arping tries to create an ethernet-like header,
> then the IPoIB driver is going to get a little confused.

That's what is currently going on and is why the group gets confused.
The driver is likely looking into this different packet incorrectly.
It does recognize that it is not a unicast packet.

-- Hal