[casper] Problem with tap?

[Gary, Dale]

Hi All,

I am setting up a ROACH at the observatory that worked fine in the lab.  
However, here I am not getting 10Gbe packets, although the internal counters 
show that the design is creating them.  I looked around and believe I have a 
problem with the tap creation.  The Python script does this:

    print 'Configuring transmitter core...',
    sys.stdout.flush()
    fpga.tap_start('tap3',tx_core_name,mac_base+source_ip,source_ip,fabric_port)
    print 'done'

where

    source_ip=10*(2**24) + 20 #10.0.0.20
    mac_base=(2<<40) + (2<<32)

I therefore expect a hardware address 00 02 02 10 00 00 20.  When I do an 
ifconfig, I see 

tap3      Link encap:UNSPEC  HWaddr 
00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  
          inet addr:10.0.0.20  P-t-P:10.0.0.20  Mask:255.255.255.0
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:500 
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

That is a lot of zeros in the hardware address!  Am I right that this anomalous 
hardware MAC address is the cause of the problem?  I could have some setup 
wrong somewhere.  Any ideas what could cause this?  All other register settings 
seem to work okay.

Thanks,
Dale