Reviewed: https://review.opendev.org/c/openstack/neutron/+/901753
Committed:
https://opendev.org/openstack/neutron/commit/114ca0f1be8c10915d7e755e68ac2117f7db78e7
Submitter: "Zuul (22348)"
Branch: master
commit 114ca0f1be8c10915d7e755e68ac2117f7db78e7
Author: Lucas Alvares Gomes <lucasago...@gmail.com>
Date: Wed Nov 22 13:05:24 2023 +0000
Fix IGMP inconsistency across drivers
Prior to this patch, ML2/OVS and ML2/OVN had inconsistent IGMP
configurations. Neutron only exposed one configuration option for IGMP:
igmp_snooping_enabled.
Other features such as IGMP flood, IGMP flood reports and IGMP flood
unregistered were hardcoded differently on each driver (see LP#2044272
for a more details).
These hardcoded values has led to many changes over the years tweaking
them to work on different scenarios but they were never final because
the fix for one case would break the other.
This patch introduces 3 new configuration options for these other IGMP
features that can be enabled or disabled on both backends. Operators
can now fine tune their deployments in the way that will work for them.
As a consequence of the hardcoded values for each driver we had to break
some defaults and, in the case of ML2/OVS, if operators want to keep
things as they were before this patch they will need to enable the new
mcast_flood and mcast_flood_unregistered configuration options.
That said, the for ML2/OVS there was also an inconsistency with the help
string of igmp_snooping_enabled configuration option as it mentioned
that enabling snooping would disable flooding to unregistered ports but
that was not true anymore after the fix [0].
[0] https://bugs.launchpad.net/neutron/+bug/1884723
Closes-Bug: #2044272
Change-Id: Ic4dde46aa0ea2b03362329c87341c83b24d32176
Signed-off-by: Lucas Alvares Gomes <lucasago...@gmail.com>
** Changed in: neutron
Status: In Progress => Fix Released
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https://bugs.launchpad.net/bugs/2044272
Title:
Inconsistent IGMP configuration across drivers
Status in neutron:
Fix Released
Bug description:
Currently there's only one configuration available for IGMP in
Neutron: [ovs]/igmp_snooping_enable.
By enabling this we will get different behaviors on ML2/OVN and
ML2/OVS because the rest of the igmp configuration: "mcast-snooping-
flood", "mcast-snooping-flood-reports" and "mcast-snooping-disable-
flood-unregistered" are hard coded with different values in both
drivers.
For example, in the help string for the [ovs]/igmp_snooping_enable it
says [0]:
"""
... Setting this option to True will also enable the Open vSwitch
mcast-snooping-disable-flood-unregistered flag...
"""
But that's only true for ML2/OVN nowadays where it was changed in 2020
[1] to match the behavior of ML2/OVS. But, in 2021, ML2/OVS changed
this behavior again [2] and now this has caused another issue with one
of our customers.
Right now, ML2/OVN will disable the flooding to unregistered ports and
ML2/OVS will enable it.
This back and forth changing IGMP values is not new [3], this patch
for example disables the "mcast-snooping-flood-reports" in ML2/OVN
where it was hard coded as enabled before. The patch [4] is what
enabled "mcast-snooping-flood" and "mcast-snooping-flood-reports" for
OVN provnet ports. Then patch [1] disabled "mcast-snooping-flood-
reports" for OVN provnet ports... And so on... It's messy.
The fact is that, since Neutron exposes only one configuration for
IGMP but the backend offers a total of 4 config options we will never
get it right. There will always be a use case that will have problems
with these hard coded settings and we will have to keep changing it
indefinitely.
This LP is proposing making a definitive and final change for IGMP in
Neutron by exposing all these knobs to the operators via config
options. I know in OpenStack nowadays we strive to have fewer
configuration options where possible but, I think this is one case
where this should not be applicable because of the many ways multicast
can be configured on each deployment.
As part of this work tho, we will have to change the defaults of one
of the drivers to make them consistent again and I would argue, given
the help string for igmp_snooping_enable, that everything should be
disabled by default.
[0]
https://github.com/openstack/neutron/blob/2be4343756863f252c8289e2ca3e7afe71f566c4/neutron/conf/agent/ovs_conf.py#L41-L46
[1] https://review.opendev.org/c/openstack/neutron/+/762818
[2] https://review.opendev.org/c/openstack/neutron/+/766360
[3] https://review.opendev.org/c/openstack/neutron/+/888127
[4] https://review.opendev.org/c/openstack/neutron/+/779258
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