Bug 2019938

Summary:	router ports gateway_mtu option should not always be set
Product:	Red Hat OpenStack	Reporter:	Elvira <egarciar>
Component:	python-networking-ovn	Assignee:	Elvira <egarciar>
Status:	CLOSED ERRATA	QA Contact:	Eduardo Olivares <eolivare>
Severity:	high	Docs Contact:
Priority:	high
Version:	16.2 (Train)	CC:	apevec, lhh, majopela, scohen
Target Milestone:	z2	Keywords:	AutomationBlocker, Triaged
Target Release:	16.2 (Train on RHEL 8.4)
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	python-networking-ovn-7.4.2-2.20220113214852.a2eba10.el8ost	Doc Type:	No Doc Update
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2022-03-23 22:12:24 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Elvira 2021-11-03 16:41:17 UTC

Copied from eolivare's previous description on BZ2018459, which is now only used as Test-only track of the Core OVN. This BZ was separated from there since we agreed that there are 2 separate tasks: 1. Test the Core OVN fix 2. Fix how neutron sets the gateway_mtu.

Description of problem:
This bug is a consequence of the investigation of the core ovn bug BZ2017424
See comments 2 and 3 from that bug.
In comment 3, Numan explains that gateway_mtu should not be set in some cases:
"If a neutron router is connected to a provider network 'A' and private geneve networks.  If the mtu of private networks (1442 in normal cases) is lesser than that of provider network (1500), then there is no need for neutron ml2ovn to set options:gateway_mtu=1500 even if the config option to enable gateway mtu is set."


AFAIU, the original issue from BZ2017424 is going to be fixed in OVS, but the change requested in this bug could also help to fix the issue and, in any case, could have a positive performance impact.


Version-Release number of selected component (if applicable):
RHOS-16.2-RHEL-8-20211013.n.1

How reproducible:
100% (See BZ2017424 description)

Steps to Reproduce:
See BZ2017424 description

Comment 2 Elvira 2021-12-10 14:31:43 UTC

Commit merged automatically in rhos-16.2-trunk-patches. Fixed in python-networking-ovn-7.4.2-2.20211209154612.933c1ba.el8osttrunk

Comment 12 errata-xmlrpc 2022-03-23 22:12:24 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 (Release of components for Red Hat OpenStack Platform 16.2.2), and where to find the updated
files, follow the link below.

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

https://access.redhat.com/errata/RHBA-2022:1001