em network issues

[Jack Vogel]

I think there may be a few different problems going on with the em driver
on 6.2 that are being lumped under the general description of network
hangs. In order to solve these I need a reproducible failure, either on a
system here at Intel, or someone who is willing to be a remote guinea
pig :)

I need detailed reports, meaning EXACT system data, if its an OEM
box, what model, what addons, a pciconf list, description of the
network, and anything special that is connected with the problem
occurence.  OH, and if you have a 'before and after' situation, then
please give driver deltas that worked, and which failed.

I know that there are systems out there that have management
hardware that can interfere on the network, it grabs certain packets
as being 'management' and doesnt pass them on to the OS.
Specifically packets for port 623 and 664 get 'eaten' by this
hardware. There is a fix for this, you tell the portmapper to
not use ports below 665, in particular:

          sysctl net.inet.ip.portrange.lowlast 665 (default is 600)

So, if you have IPMI or AMT hardware, you should try this
change and see if it fixes hangs.

There is also a hardware eeprom issue on systems with an 82573
type NIC on SOME systems. There is a utility to fix that, if you
have a problem, and have that NIC email me and I can send that
out to you.

Lastly, our Linux crew have long believed that there are lurking
issues on some AMD based systems, we have problems with
these because we dont have easy access to this hardware (as
you can imagine :). But we now have evidence that SOMETIMES
completion on transmit descriptors is not being written back, and
this causes hangs. They (the linux team) have a modified transmit
cleanup algorithm that does not use the DONE bit, instead it just
using the head and tail pointers. If I can get a case where someone
has this kind of hardware and has hangs AND is willing to test
then perhaps I can try coding something similar up.

Also, remember to let everyone know if something gets fixed :)

Cheers,

Jack