[Xen-users] TX tcp checksum errors with Xen GPLPV 0.9.9 Drivers (xen 3.2.1 and windows Server x86 2003 R2)

[Arjan Filius <iafilius@xxxxxxxxx>]

Hello,

My first post on Xen-Users, so ..

i've discovered a strange problem.

Setup:
-A Windows server 2003R2 (x86) with GPL PV driver 0.9.9
 ipferf 1.7.0 (from 2003)
-dom0 a opensuse 11.0 xen:
 # rpm -q -a |grep -i xen
 kqemu-kmp-xen-1.3.0pre11_2.6.25.5_1.1-7.1
 kiwi-desc-xenboot-2.38-67.1
 xen-3.2.1_16881_04-4.2
 xen-tools-3.2.1_16881_04-4.2
 xen-libs-3.2.1_16881_04-4.2
 kernel-xen-2.6.25.9-0.2
 iperf 2.0.4
-1 interface as trunk on dom0, with some vlans's and xen bridges

-1 test machine in same subnet as the domU windows 2003 server.
 iperf 2.0.4

test:
1)
 on testmachachine: iperf -c <domU-IP> -p 2000
 on domU iperf.exe -s -p 2000
gives great performance, about 850Mbit/s

2)
 The other way around:
 on domU iperf -c <test-machine-IP> -p 2000
 on test machine; iperf -s -p 2000
gives dramatically low results like 50KBit/s (no typo!)

3)
 same tests as above but instead of a remote test machine using to dom0 
gives values beyound our physical limit (1.5GBit/s) in both ways.
(That may lead to a conclusion the something is wrong with the physical 
network, but it's not, see point  4 )
4) iperf tests in both directions from dom0 to the remote machine are just
 excellent. So nothing seems wrong with the physical network.


After some research i found exceptional many transmit tcp checksum 
errors. for that i:
-disabled all NIC offloading on the test machine (ethtool -K ethx ... off)
-disables all NIC offloading on dom0 (ethtool -K ethx .... off)
-and finally disabled offloading  in gplpv driver settings (gui)
-just to be sure also created a registry setting to disable NIC offloading

And still, after all this , while sniffing (tcpdump) on the virtual 
interface at the dom0 (vifx.0) the first syn packet seems to have a 
correct checksum, but the next packet (ACK 3th packet in tcp 3-way 
handshake) has an incorrect checksum.
All folowing packets that are transmitted have all tcp checksum errors
So exept for the first outgoing SYN no other correct TCP checksum packets 
seems to leave the system.
An other test met simple ftp results in terrible slow uploads (from domU 
to test machine)
I did't investigate this ftp further, however it intreges me why from my 
findings _any_ data gets transferred
just created a tcpdump on the vif of the ftp session, and found by the eye 
no packet without checksum error. the relative acknowledge numer is in all 
transmitted packets '0'.
While using the regular realtek NIC driver in xen i got a TX and RX 
performance from about 85Mbit/s witch is acceptable for a 100MBit/s NIC 
emulation, but not for the perpose i want to use (Gbit)

I also tried to sniff in the domU itself, but the M$ monitor tool seems 
just not to see the NIC. didn't try winpcap/wireshark yet.
Any thoughts, experiences solutions?

Many thanks in advance

please while reply-ing, reply directly to my email adres too please

Regards,

--
Arjan Filius
mailto:iafilius@xxxxxxxxx

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users