Bug 2035199 - IPv6 support in mtu-migration-dispatcher.yaml
Summary: IPv6 support in mtu-migration-dispatcher.yaml
Alias: None
Product: OpenShift Container Platform
Classification: Red Hat
Component: Machine Config Operator
Version: 4.10
Hardware: Unspecified
OS: Unspecified
Target Milestone: ---
: 4.10.0
Assignee: Riccardo Ravaioli
QA Contact: Dan Brahaney
Depends On:
TreeView+ depends on / blocked
Reported: 2021-12-23 09:20 UTC by Riccardo Ravaioli
Modified: 2022-03-10 16:36 UTC (History)
3 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Last Closed: 2022-03-10 16:36:23 UTC
Target Upstream Version:

Attachments (Terms of Use)

System ID Private Priority Status Summary Last Updated
Github openshift machine-config-operator pull 2914 0 None open [WIP] Bug 2035199: add support for IPv6 and multiple routes to the same destination when setting MTU on routes during MT... 2022-01-18 09:22:58 UTC
Red Hat Product Errata RHSA-2022:0056 0 None None None 2022-03-10 16:36:34 UTC

Description Riccardo Ravaioli 2021-12-23 09:20:10 UTC
The network manager dispatcher script found in mtu-migration-dispatcher.yaml does not currently support IPv6 routes, but it should. MTU migration should support both IPv4 and IPv6 clusters.

Comment 2 Mike Fiedler 2022-01-26 15:33:48 UTC
@@rravaiol Can you provide a reproducer for the problem?

Comment 3 Riccardo Ravaioli 2022-01-26 16:25:33 UTC
Hi Mike, the problem was that the bash function set_mtu_on_dev_routes only applied to ipv4 routes:

... so in an IPv6 single-stack cluster the dispatcher script above would do absolutely nothing. In order to see this happening, the whole MTU migration procedure should be triggered on an IPv6 cluster.

For instance, following the accepted proposal (https://github.com/openshift/enhancements/pull/963), we can *decrease* the cluster (and host) MTU as in the example in https://github.com/openshift/enhancements/blob/master/enhancements/network/allow-mtu-changes.md#mtu-decrease-example. After the first rolling reboot, we should see a change in host routes (on each node) that go through br-ex or the physical interface on the host(this is for ovn-k, while for sdn we only consider routes going through the default gateway interface): these routes should now have an MTU value equal to `MTU.Machine.To` that the user specified when triggering the MTU migration. 

Prior to the fix for this BZ, if we did the MTU migration on an IPv6 cluster, after the first rolling reboot we would see no MTU at all on these host routes.

Comment 8 errata-xmlrpc 2022-03-10 16:36:23 UTC
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (Moderate: OpenShift Container Platform 4.10.3 security update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.


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