"ml2_vlan_allocations.vlan_id" value should be checked in the DB backend

[Rodolfo Alonso]

As reported by some users [1], the Neutron table "ml2_vlan_allocations" contains allocations with vlan_id=0.

A VLAN ID with value 0 is not accepted by Neutron during the parsing of config option "network_vlan_ranges". "NetworkVlanRangeError" exception is raised.

Despite of this check, the DB, somehow, has a register with vlan_id=0:

> select * from ml2_vlan_allocations;
+------------------+---------+-----------+
| physical_network | vlan_id | allocated |
+------------------+---------+-----------+
| tenant ......... | ..... 0 | ....... 1 |
...

A DB backend check should disable any writing operation with vlan_id out of the allowed VLAN tags [1, 4094]

[1] https://bugzilla.redhat.com/show_bug.cgi?id=1716857

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/717083

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/717083
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=795aa6b9fa792ec31c211cb690cae905c067dcf5
Submitter: Zuul
Branch: master

commit 795aa6b9fa792ec31c211cb690cae905c067dcf5
Author: Rodolfo Alonso Hernandez <email address hidden>
Date: Tue Apr 28 09:07:07 2020 +0000

    Limit ml2_vlan_allocations.vlan_id value in DB backend

    Limit "ml2_vlan_allocations.vlan_id" values stored in the DB by
    adding a check constraint in the DB engine. This check will
    verify that vlan_id is in the interval [1, 4094].

    Change-Id: Ie6453cb7a2ef0c43baf540c49a03079f4c8d3818
    Closes-Bug: #1870400