Network metadata fails to state correct mtu

[Dr. Jens Harbott]

Scenario:

Instance is booted on Neutron tenant network with ML2 OVS driver and encapsulation. The MTU for that network is automatically calculated as 1450. Instance has --config-drive=true set.

Result:

In <config_drive>/openstack/latest/network_data.json we get:

 "links": [{"ethernet_mac_address": "fa:16:3e:36:96:c8", "mtu": null, "type": "ovs", "id": "tapb989c3aa-5c", "vif_id": "b989c3aa-5c1f-4d2b-8711-b96c66604902"}]

Expected:

Have "mtu": "1450" instead.

Environment:

OpenStack Mitaka on Ubuntu 16.04

[Matt Riedemann (mriedem)]

Can you confirm that you have this fix in your environment?

https://github.com/openstack/nova/commit/69ec718b62db5766e43552cadfc7b659c7025ba4

And can you confirm that the 'mtu' value on the network resource in Neutron is set to 1450 since that's where Nova is getting the information when building the network info that goes into the config drive.

[Dr. Jens Harbott (j-harbott)]

Yes to both. After looking at the above commit, I also checked that the veth pair gets created with the correct mtu. So I dug into the code some more and I think I found the bad code, patch forthcoming.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/316395

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/316395
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=37f26ad82f6fef8c6fc21903b8c8183424bfd3fe
Submitter: Jenkins
Branch: master

commit 37f26ad82f6fef8c6fc21903b8c8183424bfd3fe
Author: Jens Rosenboom <email address hidden>
Date: Sat May 14 21:52:14 2016 +0200

    Fix network mtu in network_metadata

    The mtu field is hidden inside the "meta" section, so we have to get
    it from there.

    Change-Id: Ic44dcdb04cbaf8a007338258d74eec136a580289
    Closes-Bug: 1576713

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/mitaka
Review: https://review.openstack.org/322400

[Davanum Srinivas (DIMS) (dims-v)]

This issue was fixed in the openstack/nova 14.0.0.0b1 development milestone.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/322400
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=6ff048b0aed6e2f780bcc6bce265d8e3f8887cec
Submitter: Jenkins
Branch: stable/mitaka

commit 6ff048b0aed6e2f780bcc6bce265d8e3f8887cec
Author: Jens Rosenboom <email address hidden>
Date: Sat May 14 21:52:14 2016 +0200

    Fix network mtu in network_metadata

    The mtu field is hidden inside the "meta" section, so we have to get
    it from there.

    Change-Id: Ic44dcdb04cbaf8a007338258d74eec136a580289
    Closes-Bug: 1576713
    (cherry picked from commit 37f26ad82f6fef8c6fc21903b8c8183424bfd3fe)

[Doug Hellmann (doug-hellmann)]

This issue was fixed in the openstack/nova 13.1.0 release.