Description of problem:

Keystone provides a configuration option that allows users to page LDAP responses [0].

You can disable paging by setting page_size to 0, which should return all query data from LDAP in a single response.

I have an AD server with 10,000 users and I have paging set to 1,000. I am able to list users and verified paging is actually working.

If I disable paging by setting it to 0, the request errors:

2020-09-17 21:03:46.836 45 ERROR keystone.server.flask.application raise exception.LDAPSizeLimitExceeded()
2020-09-17 21:03:46.836 45 ERROR keystone.server.flask.application keystone.exception.LDAPSizeLimitExceeded: Number of User/Group entities returned by LDAP exceeded size limit. Contact your LDAP administrator.

However, if I set page_size to 100000, the request succeeds, even though I'm requesting all 10,000 users with page sizes of 100000.

I would expect to be able to disable paging without seeing the error since I'm able to request all LDAP users with huge page sizes.

[0] https://docs.openstack.org/keystone/latest/configuration/config-options.html#ldap.page_size

Version-Release number of selected component (if applicable):
OSP16.1


How reproducible:


Steps to Reproduce:
1. Configure Active Directory as the LDAP backend on Keystone
2. Configure ldap.page_size=0 (which means that the paging are disabled)
3.

Actual results:
2020-09-17 21:03:46.836 45 ERROR keystone.server.flask.application raise exception.LDAPSizeLimitExceeded()
2020-09-17 21:03:46.836 45 ERROR keystone.server.flask.application keystone.exception.LDAPSizeLimitExceeded: Number of User/Group entities returned by LDAP exceeded size limit. Contact your LDAP administrator.

Expected results: Paging is disabled for Active Directory when you're using it as LDAP backend on Keystone


Additional info: