gre_sys set to default 1472 when using path_mtu > 1500 with ovs 2.8.x
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
Ubuntu Cloud Archive |
Fix Released
|
High
|
James Page | ||
Pike |
Fix Released
|
Critical
|
James Page | ||
Queens |
Fix Released
|
High
|
James Page | ||
neutron |
Invalid
|
Undecided
|
Unassigned | ||
linux (Ubuntu) |
Confirmed
|
Undecided
|
Unassigned | ||
Artful |
Won't Fix
|
Undecided
|
Unassigned | ||
Bionic |
Confirmed
|
Undecided
|
Unassigned | ||
openvswitch (Ubuntu) |
Fix Released
|
High
|
James Page | ||
Artful |
Fix Released
|
Critical
|
James Page | ||
Bionic |
Fix Released
|
High
|
James Page |
Bug Description
[Impact]
OpenStack Clouds using GRE overlay tunnels with > 1500 MTU's will observe packet fragmentation/
[Test Case]
Deploy OpenStack Pike (xenial + pike UCA or artful)
Create tenant networks using GRE segmentation
Boot instances
Instance networking will be broken/slow
gre_sys devices will be set to mtu=1472 on hypervisor hosts.
[Regression Potential]
Minimal; the fix to OVS works around an issue for GRE tunnel port setup via rtnetlink by performing a second request once the gre device is setup to set the MTU to a high value (65000).
[Original Bug Report]
Setup:
Pike neutron 11.0.2-
OVS 2.8.0
Jumbo frames setttings per: https:/
global_physnet_mtu = 9000
path_mtu = 9000
Symptoms:
gre_sys MTU is 1472
Instances with MTUs > 1500 fail to communicate across GRE
Temporary Workaround:
ifconfig gre_sys MTU 9000
Note: When ovs rebuilds tunnels, such as on a restart, gre_sys MTU is set back to default 1472.
Note: downgrading from OVS 2.8.0 to 2.6.1 resolves the issue.
Previous behavior:
With Ocata or Pike and OVS 2.6.x
gre_sys MTU defaults to 65490
It remains at 65490 through restarts.
This may be related to some combination of the following changes in OVS which seem to imply MTUs must be set in the ovs database for tunnel interfaces and patches:
https:/
https:/
https:/
tags: | added: serverstack uosci upgrade |
description: | updated |
tags: | added: ovs |
Changed in openvswitch (Ubuntu Artful): | |
assignee: | nobody → James Page (james-page) |
Changed in openvswitch (Ubuntu Bionic): | |
assignee: | nobody → James Page (james-page) |
Changed in openvswitch (Ubuntu Artful): | |
importance: | Undecided → Critical |
status: | New → In Progress |
Changed in openvswitch (Ubuntu Bionic): | |
status: | Confirmed → In Progress |
importance: | Critical → High |
Pinged upstream dev mailing list for openvswitch for feedback