[vortex-bug] transfer errors with 3C905C-TX-M

Donald Becker becker@scyld.com
Mon, 4 Sep 2000 21:18:28 -0400 (EDT)

On Mon, 4 Sep 2000, Michael Marxmeier wrote:

> Data corruption using FTP has happened to me to me when using
> the older 3x900 and 3c905 cards with the 2.0 and 2.2 kernel.
> NFS and ssh always worked without a problem. AFAIR this effect was
> reproducable. After changing to a 3x905-C card this no longer happens.
> I don't think this is a protocol problem. I would guess its HW
> problem or some exceptional condition that the driver did not
> handle properly. SMP could be another reason.

The TCP stack includes software checksums for the incoming data.  This
software checksum is in addition to the Ethernet CRC, and acts as a
last-chance filter for packets corrupted by routers and bridges, where the
CRC might have be recalculated on the corrupted data.  It also covers any
data corruption from the Ethernet adapter to main memory (except on the
3c905C, when the hardware checksum feature is used).

In general, if you are seeing corrupted files from network transfers, it's
very unlikely to be a bug in the device driver.  It's most likely to be
simple memory data corruption, perhaps made more obvious when the machine is
busy e.g. doing something with the network.

Donald Becker				becker@scyld.com
Scyld Computing Corporation		http://www.scyld.com
410 Severn Ave. Suite 210		Beowulf-II Cluster Distribution
Annapolis MD 21403