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[Bug 2100294] [NEW] [ovn] Changing gateway for IPv6 subnet updates wrong routes family

To: yahoo-eng-team@xxxxxxxxxxxxxxxxxxx
From: Dmitriy Rabotyagov <2100294@xxxxxxxxxxxxxxxxxx>
Date: Wed, 26 Feb 2025 16:05:47 -0000
Reply-to: Bug 2100294 <2100294@xxxxxxxxxxxxxxxxxx>
Sender: noreply@xxxxxxxxxxxxx

Public bug reported:

Description
===========

In case of updating a gateway address for IPv6 subnet Neutron does add a
"default" route for all routers towards IPv6 address to IPv4 routes.


How to reproduce
================

Assuming, you have an IPv6 network and a router in that network.

root@os-control01-neutron-ovn-northd-container-1b10accf:/# ovn-nbctl --no-leader-only lr-route-list neutron-5ab4b663-4ded-4625-8665-ee9c4454cb58
IPv4 Routes
Route Table <main>:
                0.0.0.0/0              172.29.248.1  dst-ip

IPv6 Routes
Route Table <main>:
                     ::/0         2001:db8:300:1:: dst-ip
root@os-control01-neutron-ovn-northd-container-1b10accf:/#

Now, you update the gateway for the subnet:
openstack subnet set --gateway 2001:db8:300:1::1 7a4d7935-db7c-415b-9006-acc1b62634f0

As a result, following state of the LR is recieved:
root@os-control01-neutron-ovn-northd-container-1b10accf:/# ovn-nbctl --no-leader-only lr-route-list neutron-5ab4b663-4ded-4625-8665-ee9c4454cb58
IPv4 Routes
Route Table <main>:
                0.0.0.0/0              172.29.248.1 dst-ip ecmp
                0.0.0.0/0        2001:db8:300:1::1 dst-ip ecmp

IPv6 Routes
Route Table <main>:
                     ::/0         2001:db8:300:1:: dst-ip

** Affects: neutron
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/2100294

Title:
  [ovn] Changing gateway for IPv6 subnet updates wrong routes family

Status in neutron:
  New

Bug description:
  Description
  ===========

  In case of updating a gateway address for IPv6 subnet Neutron does add
  a "default" route for all routers towards IPv6 address to IPv4 routes.

  
  How to reproduce
  ================

  Assuming, you have an IPv6 network and a router in that network.

  root@os-control01-neutron-ovn-northd-container-1b10accf:/# ovn-nbctl --no-leader-only lr-route-list neutron-5ab4b663-4ded-4625-8665-ee9c4454cb58
  IPv4 Routes
  Route Table <main>:
                  0.0.0.0/0              172.29.248.1  dst-ip

  IPv6 Routes
  Route Table <main>:
                       ::/0         2001:db8:300:1:: dst-ip
  root@os-control01-neutron-ovn-northd-container-1b10accf:/#

  Now, you update the gateway for the subnet:
  openstack subnet set --gateway 2001:db8:300:1::1 7a4d7935-db7c-415b-9006-acc1b62634f0

  As a result, following state of the LR is recieved:
  root@os-control01-neutron-ovn-northd-container-1b10accf:/# ovn-nbctl --no-leader-only lr-route-list neutron-5ab4b663-4ded-4625-8665-ee9c4454cb58
  IPv4 Routes
  Route Table <main>:
                  0.0.0.0/0              172.29.248.1 dst-ip ecmp
                  0.0.0.0/0        2001:db8:300:1::1 dst-ip ecmp

  IPv6 Routes
  Route Table <main>:
                       ::/0         2001:db8:300:1:: dst-ip

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