RE: Buffer problems

["Mark Rivers" <rivers@cars.uchicago.edu>]

Jeff,

> The particular type of PPC SBC used at the SNS as been 
> observed to go into an ENOBUF error producing state when there is
shortage of 
> driver buffer pool. Dave Thompson has observed that an IOC can get
into 
> this state by sending large ping messages. CA routinely sends UDP
messages 
> with a 1472 byte payload. Here is an excerpt from his message on the
subject.

Thanks very much, that seems to be the problem.  If I do the following
on a Unix system (must be root to do it):
> ping -s 1500 -l 2000 x26a-vmecpu

pinging my PPC vxWorks system with 2000 1500-byte packets as fast as
possible then it immediately crashes the network on vxWorks.  This is
MVME2700 and Tornado 2.0.2. I start to get the messages:
iocx26a> CAC: error = "S_errno_ENOBUFS" sending UDP msg to
130.199.193.255:5064
CAC: error = "S_errno_ENOBUFS" sending UDP msg to 130.199.193.255:5064
..../online_notify.c: CA beacon (send to "130.199.193.255:5065") error was
"S_errno_ENOBUFS"
CAC: error = "S_errno_ENOBUFS" sending UDP msg to 130.199.193.255:5064

NFS no longer works, and I have to reboot.

These are exactly the symptoms the VME crates at Brookhaven were seeing
this afternoon.  I suspect someone or some virus is pounding on machines
on their subnet, and this is crashing the vxWorks network stack.

Mark