zt0: Invalid MTU 2800 requested, hw max 68

[paulfurley]

Hi,

I'm on a fresh install of Ubuntu 16.04: Linux xps 4.8.0-49-generic #52~16.04.1-Ubuntu SMP Thu Apr 20 10:55:59 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux and I'm getting the above error when starting ZeroTier One version 1.2.4 build 0 (platform 1 arch 2):

/var/log/syslog:

Apr 28 16:14:50 xps systemd[1]: Stopping ZeroTier One...
Apr 28 16:14:50 xps systemd[1]: Stopped ZeroTier One.
Apr 28 16:14:50 xps systemd[1]: Started ZeroTier One.
Apr 28 16:14:50 xps kernel: [22574.980808] zt0: Invalid MTU 2800 requested, hw max 68
Apr 28 16:14:50 xps NetworkManager[1033]: <info>  [1493392490.6062] devices added (path: /sys/devices/virtual/net/zt0, iface: zt0)
Apr 28 16:14:50 xps NetworkManager[1033]: <info>  [1493392490.6062] device added (path: /sys/devices/virtual/net/zt0, iface: zt0): no ifupdown configuration found.
Apr 28 16:14:50 xps NetworkManager[1033]: <info>  [1493392490.6091] devices removed (path: /sys/devices/virtual/net/zt0, iface: zt0)
Apr 28 16:14:50 xps zerotier-one[24011]: ERROR: unable to configure virtual network port: unable to configure TAP MTU

var/log/kern.log:

Apr 28 16:14:50 xps kernel: [22574.980808] zt0: Invalid MTU 2800 requested, hw max 68
Apr 28 16:14:50 xps NetworkManager[1033]: <info>  [1493392490.6062] devices added (path: /sys/devices/virtual/net/zt0, iface: zt0)
Apr 28 16:14:50 xps NetworkManager[1033]: <info>  [1493392490.6062] device added (path: /sys/devices/virtual/net/zt0, iface: zt0): no ifupdown configuration found.
Apr 28 16:14:50 xps NetworkManager[1033]: <info>  [1493392490.6091] devices removed (path: /sys/devices/virtual/net/zt0, iface: zt0)

Done a fair bit of Googling but haven't seen this elsewhere.

/dev/net/tun exists (altho doing cat /dev/net/tun results in cat: /dev/net/tun: File descriptor in bad state - not sure what that's about?

[kees-j-bot]

I had this problem under Ubuntu 16.10 running kernel 4.8.0-49-generic. After rebooting to 4.8.0-46-generic ZeroTier 1.2.4 would once again work.

[paulfurley]

Thanks @kees-j-bot, that's helpful. Possibly this bug? https://bugs.launchpad.net/ubuntu/+source/linux-hwe-edge/+bug/1679823

…

[adamierymenko]

Kernel bug. Not ours. Won't fix. :)

[carsontang]

Ran into the same issue with the symptom of PORT_ERROR after updating to 4.8.0-49-generic. Rebooting with 4.8.0-46-generic fixed the problem. Commenting here to help others connect PORT_ERRORs to the kernel bug.

[rtucker]

The kernel linked from https://bugs.launchpad.net/ubuntu/+source/linux-hwe-edge/+bug/1679823/comments/38 fixes this for me.

[rkrzr]

I ran into this same bug on a new 16.04 box on GCE. It was running kernel 4.8.0-52-generic.
After upgrading to the latest kernel (4.8.0-54-generic) and rebooting the zt0 network interface was created correctly.