MTU 9000 not possible on openvswitch bridge

[Endre Vaade]

After clean installation of Ubuntu 17.04 (standard tools + openssh server)

running commands:

>apt-get install openvswitch-switch

>ip link set eno1 mtu 9000

>ovs-vsctl add-br br-eno1

>ovs-vsctl add-port br-eno1 eno1

>ip link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eno3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000
    link/ether 24:6e:96:4c:2e:3c brd ff:ff:ff:ff:ff:ff
3: eno4: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether 24:6e:96:4c:2e:3d brd ff:ff:ff:ff:ff:ff
4: eno1: <BROADCAST,MULTICAST> mtu 9000 qdisc noop master ovs-system state DOWN mode DEFAULT group default qlen 1000
    link/ether 24:6e:96:4c:2e:38 brd ff:ff:ff:ff:ff:ff
5: eno2: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether 24:6e:96:4c:2e:3a brd ff:ff:ff:ff:ff:ff
6: ovs-system: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether 26:80:9b:af:36:44 brd ff:ff:ff:ff:ff:ff
7: br-eno1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether 24:6e:96:4c:2e:38 brd ff:ff:ff:ff:ff:ff

>ip link set br-eno1 mtu 9000
RTNETLINK answers: Invalid argument

#from dmesg
[ 163.884229] nf_conntrack version 0.5.0 (65536 buckets, 262144 max)
[ 163.909923] openvswitch: Open vSwitch switching datapath
[ 178.560656] ixgbe 0000:01:00.0 eno1: changing MTU from 1500 to 9000
[ 195.748455] device ovs-system entered promiscuous mode
[ 196.002269] device br-eno1 entered promiscuous mode
[ 206.564564] device eno1 entered promiscuous mode
[ 206.564732] br-eno1: Invalid MTU 9000 requested, hw max 1500
[ 222.901294] br-eno1: Invalid MTU 9000 requested, hw max 1500

>dpkg -l |grep openvswitch
ii openvswitch-common 2.6.1-0ubuntu5 amd64 Open vSwitch common components
ii openvswitch-switch 2.6.1-0ubuntu5 amd64 Open vSwitch switch implementations

>uname -a
Linux xen35 4.10.0-19-generic #21-Ubuntu SMP Thu Apr 6 17:04:57 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

This was working as expected in Ubuntu 16.10 (kernel 4.8.0-39-generic openvswitch-switch 2.6.0-0ubuntu2).

Br
Endre Vaade

[Launchpad Janitor (janitor)]

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

[Ralf Trezeciak (r-uone)]

see also https://bugs.launchpad.net/ubuntu/zesty/+source/linux-hwe/+bug/1679823

not fixed for ovs in 4.10.0-20 (and 4.8.0-49)

[Endre Vaade (vaaend)]

Thank you Ralf.

The kernel from https://people.canonical.com/~jesse/lp1679823v2/ did work (linux-image-4.8.0-52-generic_4.8.0-52.55~16.04.1.lp1679823v2_amd64.deb) and as you said not fixed in 4.10.0-20

[Ralf Trezeciak (r-uone)]

I have been testing self build vanilla kernels on 17.04:

* 4.10.13 - ovs mtu setting higher than 1500 *fails*
* 4.11 - works for ovs - also for the nics (intel i219 and usb3 r8152)

[Ralf Trezeciak (r-uone)]

This might be necessary?

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/openvswitch/vport-internal_dev.c?id=425df17ce3a26d98f76e2b6b0af2acf4aeb0b026

[Thiago Martins (martinx)]

Ralf, that might be also needed!

I'm trying to run jumbo frames on top of Neutron with Networking OVN and it is not working.

I just saw that the commit you posted, comes from someone from @ovn.org! So, go figure... lol

Hope to see this fixed ASAP!

[Endre Vaade (vaaend)]

After building vanilla kernel 4.10.13 with the patch #5 jumbo frames is possible on ovs.

[Thiago Martins (martinx)]

Any chance to include patch #5 on Xenial?

[Jesse Sung (wenchien)]

As far as I can tell this is the same issue as lp:1679823. Please try https://people.canonical.com/~jesse/lp1679823v2/ and see if it fixes this issue, thanks.

[Endre Vaade (vaaend)]

Jesse, I can confirm that your build 4.8.0-52-generic #55~16.04.1.lp1679823v2 did fix this issue (#3). Still can not find a fix for this at kernel.org on 4.10 kernel (fixed in 4.11). Have reported this to kernel.org https://bugzilla.kernel.org/show_bug.cgi?id=195695

I downloaded kernel 4.10.13 from kernel.org and had the same issue. I built it with this patch

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/openvswitch/vport-internal_dev.c?id=425df17ce3a26d98f76e2b6b0af2acf4aeb0b026

and this issue was fixed. Hoping for a fix on this in Zesty Zapus soon.