TCP does not work properly with virtio-net and tx/rx offloading is on

[Peter Kieser]

Description: Ubuntu 14.04 LTS
Release: 14.04

linux-image-generic:
  Installed: 3.13.0.30.36
  Candidate: 3.13.0.30.36
  Version table:
 *** 3.13.0.30.36 0
        500 http://ca.archive.ubuntu.com/ubuntu/ trusty-updates/main amd64 Packages
        500 http://security.ubuntu.com/ubuntu/ trusty-security/main amd64 Packages
        100 /var/lib/dpkg/status
     3.13.0.24.28 0
        500 http://ca.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages

Please see Debian Bug Report, this issue exists in the latest kernel. You cannot pass traffic between virtio enabled guests:

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=738863

Thank you.

[Brad Figg (brad-figg)]

This bug is missing log files that will aid in diagnosing the problem. From a terminal window please run:

apport-collect 1335292

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Peter Kieser (pfak)]

I had to hand build Linux 3.10 kernel due to this bug, and this system is now in production.

"Package openvswitch not installed and no hook available, ignoring"

root@kvm:~# dpkg -l | grep -i openvswitch
ii openvswitch-common 2.0.1+git20140120-0ubuntu2 amd64 Open vSwitch common components
ii openvswitch-switch 2.0.1+git20140120-0ubuntu2 amd64 Open vSwitch switch implementations

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[YAMAMOTO Hirotaka (ymmt2005)]

Same but without openvswitch.

In our case, source NAT virtual machine cannot property forward TCP traffics.
Disabling physical NIC rx-checksumming helps resolving the problem, i.e.,

ethtool -K em1 rx off