[Xen-devel] Yet another tx checksum problem

[Alexander Wilms <alex.wilms@xxxxxxxxxxxxx>]

Hello all,

seems that I found another bug regarding tx checksum.

Had a problem with DNAT'ing ftp. Found out that the ip_nat_ftp module didn't 
rewrite the pasv source address correctly. With wireshark I could see that 
this happened because of excessive TCP retransmissions due to wrong checksum.

My Xen/network setup looks like this:

ftpserver --- firewall ---internet

While the ftp server runs in dom0. Dom0 is bridged. Firewall is a domU with 
delegated nics.

Xen is the version released with openSUSE 10.2:
xm info
host                   : xen0
release                : 2.6.18.2-34-xen
version                : #1 SMP Mon Nov 27 11:46:27 UTC 2006
machine                : i686
nr_cpus                : 2
nr_nodes               : 1
sockets_per_node       : 2
cores_per_socket       : 1
threads_per_core       : 1
cpu_mhz                : 498
hw_caps                : 0383fbff:00000000:00000000:00000040
total_memory           : 1023
free_memory            : 1
max_free_memory        : 139
max_para_memory        : 135
max_hvm_memory         : 126
xen_major              : 3
xen_minor              : 0
xen_extra              : .3_11774-20
xen_caps               : xen-3.0-x86_32
xen_pagesize           : 4096
platform_params        : virt_start=0xfc000000
xen_changeset          : 11774
cc_compiler            : gcc version 4.1.2 20061115 (prerelease) (SUSE Linux)
cc_compile_by          : abuild
cc_compile_domain      : suse.de
cc_compile_date        : Tue Nov 28 09:28:29 UTC 2006
xend_config_format     : 2

Workaround/Solution:
Execute ethtool -K tx off eth0 in dom0 and the problem disappears.

If needed network dumps are available upon request.

Alex

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