Creating a load balancer doesn't validate a minimum number of ips when the subnet is specified

[Quentin GROLLEAU]

When a customer is creating a loadbalancer specifying the subnet_id, no check on the minimal numbers of ips is done. May be we can add one like when network_id is specify ?

Reproducer :
 ❯ openstack ip availability show 0072ced1-8fd5-4731-aa69-f4c96e364730
+------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------+
| Field | Value |
+------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------+
| id | 0072ced1-8fd5-4731-aa69-f4c96e364730 |
| name | None |
| network_id | 0072ced1-8fd5-4731-aa69-f4c96e364730 |
| network_name | Test_Octavia_minimum |
| project_id | ba9d9c29dda84eaf8d96f3c95647d748 |
| subnet_ip_availability | cidr='10.0.0.0/28', ip_version='4', subnet_id='44730f99-f265-4205-80f7-54da3fe4f159', subnet_name='private_subnet', total_ips='13', used_ips='14' |
| tenant_id | ba9d9c29dda84eaf8d96f3c95647d748 |
| total_ips | 13 |
| used_ips | 14 |
+------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------+
 ❯ openstack loadbalancer create --vip-subnet-id 44730f99-f265-4205-80f7-54da3fe4f159 --name LB_port_test_minimum

Provider 'amphora' reports error: No more IP addresses available on network 0072ced1-8fd5-4731-aa69-f4c96e364730.
Neutron server returns request_ids: ['req-fac2ab96-a057-4a61-9a87-77f9da0f8c97'] (HTTP 500) (Request-ID: req-faf25c71-c05f-41f5-954b-7497c89697c8)

Instead, shouldn't we return a 400 error like when we specify the network :

❯ openstack loadbalancer create --vip-subnet-id 44730f99-f265-4205-80f7-54da3fe4f159 --name LB_port_test_minimum
Validation failure: Subnet(s) in the supplied network do not contain enough available IPs. (HTTP 400) (Request-ID: req-d13d0ee0-553d-42cb-8b1b-7fc4ffb84f3e)

[Gregory Thiemonge (gthiemonge)]

Thanks for reporting it, yes, we could check that there are enough IP addresses on vip_subnet_id

Additional note:

there's another issue in https://opendev.org/openstack/octavia/src/commit/860d2f6aadfba9cef2c695d072dd48e29a7e85c8/octavia/api/v2/controllers/load_balancer.py#L151-L161

we get the number of required IP addresses based on CONF.controller_worker.loadbalancer_topology but the default topology may be overridden by a flavor, we need to fix that too

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/octavia/+/898803