[openib-general] Unicast ARP

[Dror Goldenberg]

> -----Original Message-----
> From: Roland Dreier [mailto:roland at topspin.com] 
> Sent: Monday, November 29, 2004 9:04 PM
> 
> 
>     Michael> Currently it also seems that by just bringing the
>     Michael> interface up and down the hw address will change.  Unless
>     Michael> I am doing something wrong, this inconvenience seems to
>     Michael> be caused by a different QP number being assigned.  Cant
>     Michael> this be solved e.g. by assigning a fixed QP number for IP
>     Michael> over IB?
> 
> It seems you are doing something wrong.  The QP is allocated 
> when the interface is created and remains the same when the 
> interface is brought up and down:
> 
>     # ip addr show dev ib0
>     7: ib0: <BROADCAST,MULTICAST,UP> mtu 2044 qdisc 
> pfifo_fast qlen 128
>         link/[32] 
> 00:02:04:04:fe:80:00:00:00:00:00:00:00:05:ad:00:00:01:82:06 
> brd 00:ff:ff:ff:ff:12:40:1b:ff:ff:00:00:00:00:00:00:ff:ff:ff:ff
>     # ifconfig ib0 down
>     # ifconfig ib0 up
>     # ip addr show dev ib0
>     7: ib0: <BROADCAST,MULTICAST,UP> mtu 2044 qdisc 
> pfifo_fast qlen 128
>         link/[32] 
> 00:02:04:04:fe:80:00:00:00:00:00:00:00:05:ad:00:00:01:82:06 
> brd 00:ff:ff:ff:ff:12:40:1b:ff:ff:00:00:00:00:00:00:ff:ff:ff:ff
> 
Roland, 
You're right, it takes more than "ifconfig down" for the  QPN to change.
If you take the module down after doing ifconfig down, then the QPN
may change.
Assigning specific QPN for ipoib requires allocation of QPN space which
is beyond IB spec verbs. Current verbs do not allow it. I don't have any
objection for that, except that you have to hold a set of preallocated QPs
with specific numbers and hand them over to privileged consumer when
requested to.  I wouldn't commit that it will work on any HCA architecture.

-Dror
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