Ubuntu kernel error: unregister_netdevice

I’ve got three of these messages repeating in the syslog for some of my rancher hosts, seemingly repeating 3 times every 10 seconds.

Message from syslogd@rancher05 at Nov  3 00:16:59 ...
 kernel:[17152.031039] unregister_netdevice: waiting for lo to become free. Usage count = 3

This seems to have showed up after the latest update which uses the following versions:

Component	Version
Rancher	v0.43.1
Cattle	v0.106.0
User Interface	v0.63.0
Rancher Compose	v0.5.0

It looks like the Ubuntu folks fixed this very recently (within 5 days), and just wanted to let it percolate up in case others happened to find themselves with the same situation.

The symptoms are that the server is useless, and Docker isn’t responding properly until the server is rebooted.

The relevant bug is at https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1403152

Yes, this is a well known Docker bug that’s been there for awhile.

Unfortunately, the only workaround that I know of has been to restart the host.

@denise are you certain it is a docker bug? I interpret the discussion to be a linux kernel bug that impacts both LXC and docker. I am seeing this problem on Centos 7.3 with Linux kernel 3.10. It might be fixed in kernel 4.4

While technically correct, she’s pointing a Docker issue and what specific level underneath that it’s broken in is not particularly relevant as an end-user. There’s over 3 years of “try this kernel” history for this issue so I wouldn’t get your hopes up.

As a follow up, we were hitting a known ipv6 driver bug when duplicate addresses are found on the network that caused the same problem. We do not need ipv6 and just disabled it to avoid this issue.