Red Hat Bugzilla – Bug 443452
TCP traffic is dropped if TX checksum flag is enabled in guest
Last modified: 2008-05-13 05:09:59 EDT
Description of problem:
Booting up a F8 guest, the eth0 device has following settings by default:
# ethtool -k eth0
Offload parameters for eth0:
tcp segmentation offload: off
udp fragmentation offload: off
generic segmentation offload: off
If I try to 'wget http://google.com' the connections all fail - some, but not
all, packets are not replied to.
If I turn off checksum offload with
ethtool -K eth0 tx off
then, everything works fine. This blocks install of new guests becasue they have
TX checksum enabled by default.
Version-Release number of selected component (if applicable):
Guest kernel: 2.6.21-2950.fc8xen
Steps to Reproduce:
1. Setup guest config to use libvirt 'default' network, ie connect the TAP
device to 'virbr0', which is connected to outside world with NAT.
1. Boot the guest
2. Run wget http://google.com
Created attachment 303167 [details]
Created attachment 303168 [details]
netbackd log file
Created attachment 303169 [details]
tcpdump log when tx is enabled (and traffic fails)
Created attachment 303170 [details]
tcpdump log when tx is disabled (and traffic succeeds)
Ok, can reproduce it, investigating ...
(scratch build, seems cvs isn't fully up'n'running yet).
Confirm this works now - although on i386 Xenner fails with a exception about
missing instruction emulation. Xenner 0.33 works though, so be good to get that
pushed to F9 updates
Thanks for testing.
F10 has 0.33 already. F9 update is planned but I think I'll address the libvirt
integration issues first ...