[Bug 2077430] [NEW] [OVN] two routers connected to the same network does not work properly

[Damian Dąbrowski]

Public bug reported:


# Problem Description

I have:

- 2 VMs connected to inner-net
- inner-router(with default gateway in outer-net and a port in inner-net)
- outer router(with default gateway in public network and a port in outer-net)

NOTE: I don't have any static routes defined for these routers.

Graphical visualization can be found here:
https://i.ibb.co/gzjd604/Screenshot-from-2024-08-20-13-26-55.png

This scenario works perfectly fine for OVS ML2 driver(VMs have Internet
connectivity), but not for OVN.

I noticed that gateway port for inner-router is DOWN(you can see this on
the above screenshot) which looks quite suspicious.

I applied https://review.opendev.org/c/openstack/neutron/+/907504 but it
didn't solve the problem.

# How to reproduce the issue

(assuming that you have a test environment with 'public' network already
defined)

```
openstack network create outer-net --external --disable-port-security
openstack subnet create --network outer-net --subnet-range 10.10.0.0/24 outer-subnet
openstack router create outer-router --external-gateway public
openstack router add subnet outer-router outer-subnet

openstack network create inner-net --disable-port-security
openstack subnet create --network inner-net --subnet-range 10.0.0.0/24 inner-subnet
openstack router create --external-gateway outer-net inner-router
openstack router add subnet inner-router inner-subnet

openstack server create \
--network inner-net \
--image 'cirros' \
--flavor 'tempest1' \
vm-inner-1
```

Then, log in to vm-inner-1 and try to ping 8.8.8.8.
For OVS it works, for OVN it doesn't.

** Affects: neutron (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/2077430

Title:
  [OVN] two routers connected to the same network does not work properly

Status in neutron package in Ubuntu:
  New

Bug description:
  
  # Problem Description

  I have:

  - 2 VMs connected to inner-net
  - inner-router(with default gateway in outer-net and a port in inner-net)
  - outer router(with default gateway in public network and a port in outer-net)

  NOTE: I don't have any static routes defined for these routers.

  Graphical visualization can be found here:
  https://i.ibb.co/gzjd604/Screenshot-from-2024-08-20-13-26-55.png

  This scenario works perfectly fine for OVS ML2 driver(VMs have
  Internet connectivity), but not for OVN.

  I noticed that gateway port for inner-router is DOWN(you can see this
  on the above screenshot) which looks quite suspicious.

  I applied https://review.opendev.org/c/openstack/neutron/+/907504 but
  it didn't solve the problem.

  # How to reproduce the issue

  (assuming that you have a test environment with 'public' network
  already defined)

  ```
  openstack network create outer-net --external --disable-port-security
  openstack subnet create --network outer-net --subnet-range 10.10.0.0/24 outer-subnet
  openstack router create outer-router --external-gateway public
  openstack router add subnet outer-router outer-subnet

  openstack network create inner-net --disable-port-security
  openstack subnet create --network inner-net --subnet-range 10.0.0.0/24 inner-subnet
  openstack router create --external-gateway outer-net inner-router
  openstack router add subnet inner-router inner-subnet

  openstack server create \
  --network inner-net \
  --image 'cirros' \
  --flavor 'tempest1' \
  vm-inner-1
  ```

  Then, log in to vm-inner-1 and try to ping 8.8.8.8.
  For OVS it works, for OVN it doesn't.

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