Description of problem:
Filed as Bug Deputy.
I'm not 100% sure if this failure is due to tobiko or to neutron. More investigation would be necessary. Hopefully these inputs are useful.

In the gate DFG-network-neutron-17.1_director-rhel-virthost-3cont_2comp-ml2ovs-ipv4-vxlan- tobiko-tempest-nossl-ovsfirewall we find that in both
tobiko_faults-neutron_1_02_create_neutron_resources_neutron and tobiko_faults-neutron_1_06_verify_neutron_resources_neutron this tests are failing without being able to reach the final server.

Test_2_ping_vlan_port_after_restart
Test_1_ping_vlan_port
Test_0_vlan_ip_addresses

Fail with:

Traceback (most recent call last):
File "/home/stack/src/x/tobiko/tobiko/tests/scenario/neutron/test_trunk.py", line 90, in test_2_ping_vlan_port_after_restart
self.stack.assert_vlan_is_reachable()
File "/home/stack/src/x/tobiko/tobiko/openstack/stacks/_vlan.py", line 103, in assert_vlan_is_reachable
ping.assert_reachable_hosts(fixed_ips,
File "/home/stack/src/x/tobiko/tobiko/shell/ping/_assert.py", line 27, in assert_reachable_hosts
_ping.wait_for_ping_hosts(hosts, **params)
File "/home/stack/src/x/tobiko/tobiko/shell/ping/_ping.py", line 100, in wait_for_ping_hosts
raise _exception.UnreachableHostsException(
tobiko.shell.ping._exception.UnreachableHostsException: timeout of 900.0 seconds expired after 904.4510264396667 seconds waiting for host(s) Selection([IPAddress('10.100.4.30'), IPAddress('fc00::4:f816:3eff:feb5:46e4')]) to return ping messages

Looking at the logs of the controllers for this gate [0] I found:
In server.log.1.gz, many logs with the following 404 error:

2023-06-14 03:03:50.900 16 INFO neutron.services.segments.plugin [-] Segment 81a4475f-9e3b-4aae-843b-527dd359530e resource provider not found; error: Placement Client Error (4xx): {"errors": [

{"status": 404, "title": "Not Found", "detail": "The resource could not be found.\n\n No resource provider with uuid 81a4475f-9e3b-4aae-843b-527dd359530e found for delete ", "request_id": "req-9338d486-ebd4-4426-9c87-99815fcd44aa"}

]}

And also many "subnet is already being modified" errors:
2023-06-14 03:03:24.873 20 ERROR oslo_messaging.rpc.server raise exception
2023-06-14 03:03:24.873 20 ERROR oslo_messaging.rpc.server neutron_lib.exceptions.SubnetInUse: Unable to complete operation on subnet 49eb8a84-9d6e-44ed-b9e5-77a57d8a955d: This subnet is being modified by another concurrent operation.

Version-Release number of selected component (if applicable):
17.1

How reproducible:
Not sure, we should check the next build of DFG-network-neutron-17.1_director-rhel-virthost-3cont_2comp-ml2ovs-ipv4-vxlan-tobiko-tempest-nossl-ovsfirewall [1]

[0] http://rhos-ci-logs.lab.eng.tlv2.redhat.com/logs/rcj/DFG-network-neutron-17.1_director-rhel-virthost-3cont_2comp-ml2ovs-ipv4-vxlan-tobiko-tempest-nossl-ovsfirewall/33/

[1] https://rhos-ci-jenkins.lab.eng.tlv2.redhat.com/job/DFG-network-neutron-17.1_director-rhel-virthost-3cont_2comp-ml2ovs-ipv4-vxlan-tobiko-tempest-nossl-ovsfirewall/

Actual results:
Test_2_ping_vlan_port_after_restart
Test_1_ping_vlan_port
Test_0_vlan_ip_addresses
fails in both tobiko_faults-neutron_1_02_create_neutron_resources_neutron and tobiko_faults-neutron_1_06_verify_neutron_resources_neutron
Expected results:
Test are successful