Xen and network issues.

[Mike McGrath]

We've got issues.  Many of our xen guests are experiencing tcp checksum 
corruption.  Research on the net suggests ethtool -K eth0 tx off will 
fix the issue but it hasn't in our case.  I've tried the koji guest on 
many physical hosts, same issue.  It's been on two FC6 dom0 hosts and a 
RHEL5 dom0 host. 

For now I'm going to stick koji on app1 as a physical host.  Just 
because that box has gotten to the point where it becomes unusable and 
we cannot have that happening right now.

I've contacted some internal xen developers, some guys in ##xen on 
freenode and the Fedora-xen list.  Anyone who is able I'd encourage you 
to take a look as well.  Simple test:

"tcpdump -vvv | grep incomplete"

You'll see:
 06:34:20.135530 IP (tos 0x0, ttl  64, id 39370, offset 0, flags [DF], 
proto: TCP (6), length: 40) nat-pool.fedora.phx.redhat.com.49457 > 
publictest8.fedora.phx.redhat.com.http: P, cksum 0x76af (incorrect (-> 
0x6100), 601:601(0) ack 6801 win 597

    -Mike