Default flag change in netaddr breaks (at least) unit tests

[Takashi Kajinami]

netaddr 1.0.0 changed the default parsing mode from INET_ATON to INET_PTON[1]. This was initially added to netaddr.IPAddress and then later was applied to netaddr.IPNetwork in 1.1.0 [2]

While we attempted to bump netaddr to 1.0.1, we noticed this change broke some of the unit tests in neutron.

https://zuul.opendev.org/t/openstack/build/8cfad48dcfb84be893fe78a1f965c5e6

(example)
```
neutron.tests.unit.agent.l3.extensions.test_ndp_proxy.NDPProxyExtensionDVRTestCase.test__get_snat_idx_ipv4
----------------------------------------------------------------------------------------------------------

Captured traceback:
~~~~~~~~~~~~~~~~~~~
    Traceback (most recent call last):
      File "/home/zuul/src/opendev.org/openstack/neutron/.tox/py311/lib/python3.11/site-packages/netaddr/ip/__init__.py", line 346, in __init__
    self._value = self._module.str_to_int(addr, flags)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      File "/home/zuul/src/opendev.org/openstack/neutron/.tox/py311/lib/python3.11/site-packages/netaddr/strategy/ipv4.py", line 120, in str_to_int
    raise error
    netaddr.core.AddrFormatError: '101.12.13.00' is not a valid IPv4 address string!

During handling of the above exception, another exception occurred:

    Traceback (most recent call last):
      File "/home/zuul/src/opendev.org/openstack/neutron/.tox/py311/lib/python3.11/site-packages/netaddr/ip/__init__.py", line 1019, in __init__
    value, prefixlen = parse_ip_network(module, addr, flags)
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      File "/home/zuul/src/opendev.org/openstack/neutron/.tox/py311/lib/python3.11/site-packages/netaddr/ip/__init__.py", line 899, in parse_ip_network
    ip = IPAddress(val1, module.version, flags=INET_PTON)
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      File "/home/zuul/src/opendev.org/openstack/neutron/.tox/py311/lib/python3.11/site-packages/netaddr/ip/__init__.py", line 348, in __init__
    raise AddrFormatError(
    netaddr.core.AddrFormatError: base address '101.12.13.00' is not IPv4

During handling of the above exception, another exception occurred:

    Traceback (most recent call last):
      File "/home/zuul/src/opendev.org/openstack/neutron/neutron/tests/base.py", line 178, in func
    return f(self, *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^
      File "/home/zuul/src/opendev.org/openstack/neutron/neutron/tests/base.py", line 178, in func
    return f(self, *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^
      File "/home/zuul/src/opendev.org/openstack/neutron/neutron/tests/unit/agent/l3/test_dvr_local_router.py", line 549, in test__get_snat_idx_ipv4
    snat_idx = ri._get_snat_idx(ip_cidr)
               ^^^^^^^^^^^^^^^^^^^^^^^^^
      File "/home/zuul/src/opendev.org/openstack/neutron/neutron/agent/l3/dvr_local_router.py", line 412, in _get_snat_idx
    net = netaddr.IPNetwork(ip_cidr)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^
      File "/home/zuul/src/opendev.org/openstack/neutron/.tox/py311/lib/python3.11/site-packages/netaddr/ip/__init__.py", line 1028, in __init__
    raise AddrFormatError('invalid IPNetwork %s' % (addr,))
    netaddr.core.AddrFormatError: invalid IPNetwork 101.12.13.00/24
```

An "easy" fix is adding flags=INET_ATON to all places. (note that INET_ATON was added in netaddr 0.10.0) but I'd like to ask someone from the neutron team to look into this and check whether we really have to use INET_ATON or fix unit test side to apply the more strict rule.

[1] https://netaddr.readthedocs.io/en/latest/changes.html#release-1-0-0
[2] https://netaddr.readthedocs.io/en/latest/changes.html#release-1-1-0

[Rodolfo Alonso (rodolfo-alonso-hernandez)]

Patch: https://review.opendev.org/c/openstack/neutron/+/909317

[Dr. Jens Harbott (j-harbott)]

One thing to discuss is whether the API allowing "101.12.13.00/24" was actually a bug or whether it needs to be considered an (undocumented?) feature and changing to the stricter verification would be a regression.

[Rodolfo Alonso (rodolfo-alonso-hernandez)]

Added to the "on-demand" section of tomorrow's meeting: https://wiki.openstack.org/wiki/Network/Meetings#On_Demand_Agenda

[Takashi Kajinami (kajinamit)]

Please note this may affect wider patterns which were previously accepted.

For example with netaddr < 1.0.0, "10/8" is a valid representation of subnet and is translated to 10.0.0.0/8 .

Type "help", "copyright", "credits" or "license" for more information.
>>> import netaddr
>>> netaddr.IPNetwork('10/8')
IPNetwork('10.0.0.0/8')

However with netaddr >= 1.0.0, which uses INET_PTON, this is no longer accepted

>>> import netaddr
>>> netaddr.IPNetwork('10/8')
Traceback (most recent call last):
  File "/home/tkajinam/venv/lib/python3.11/site-packages/netaddr/strategy/ipv4.py", line 124, in str_to_int
    return _struct.unpack('>I', _inet_pton(AF_INET, addr))[0]
                                ^^^^^^^^^^^^^^^^^^^^^^^^^
OSError: illegal IP address string passed to inet_pton

Currently with netaddr < 1.0.0, neutron supports that INET_ATON compliant format.

```
[root@localhost ~]# openstack subnet create --debug --network testnetwork --subnet-range 10/8 testsubnet
...
REQ: curl -g -i -X POST http://127.0.0.1:9696/v2.0/subnets -H "Content-Type: application/json" -H "User-Agent: openstacksdk/2.1.0 keystoneauth1/5.5.0 python-requests/2.25.1 CPython/3.9.18" -H "X-Auth-Token: {SHA256}f5f8310eff9da291b1ed3a851365033bc771153d5f148ecd59b969d2d32ce32a" -d '{"subnet": {"name": "testsubnet", "network_id": "156e8829-3b7c-45b1-8678-c35d625e0af4", "ip_version": 4, "cidr": "10/8"}}'
http://127.0.0.1:9696 "POST /v2.0/subnets HTTP/1.1" 201 608
RESP: [201] Connection: keep-alive Content-Length: 608 Content-Type: application/json Date: Tue, 20 Feb 2024 15:10:06 GMT X-Openstack-Request-Id: req-455d7d7b-8de3-45ab-b75c-a6b9f505838d
RESP BODY: {"subnet":{"id":"3ba2fa27-5931-4acc-bba5-3383232cd112","name":"testsubnet","tenant_id":"2e1290f8bdc44d35bce981db68fb54a2","network_id":"156e8829-3b7c-45b1-8678-c35d625e0af4","ip_version":4,"subnetpool_id":null,"enable_dhcp":true,"ipv6_ra_mode":null,"ipv6_address_mode":null,"gateway_ip":"10.0.0.1","cidr":"10.0.0.0/8","allocation_pools":[{"start":"10.0.0.2","end":"10.255.255.254"}],"host_routes":[],"dns_nameservers":[],"description":"","service_types":[],"tags":[],"created_at":"2024-02-20T15:10:05Z","updated_at":"2024-02-20T15:10:05Z","revision_number":0,"project_id":"2e1290f8bdc44d35bce981db68fb54a2"}}
POST call to network for http://127.0.0.1:9696/v2.0/subnets used request id req-455d7d7b-8de3-45ab-b75c-a6b9f505838d
+----------------------+--------------------------------------+
| Field | Value |
+----------------------+--------------------------------------+
| allocation_pools | 10.0.0.2-10.255.255.254 |
| cidr | 10.0.0.0/8 |
| created_at | 2024-02-20T15:10:05Z |
| description | |
| dns_nameservers | |
| dns_publish_fixed_ip | None |
| enable_dhcp | True |
| gateway_ip | 10.0.0.1 |
| host_routes | |
| id | 3ba2fa27-5931-4acc-bba5-3383232cd112...

[Takashi Kajinami (kajinamit)]

While we can recover the previous behavior by setting flags arg for IPAddress, I noticed there is no equivalent mechanism for IPNetwork ...

EDIT: I proposed https://github.com/netaddr/netaddr/pull/377

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/neutron/+/909317
Committed: https://opendev.org/openstack/neutron/commit/2ed9834047897d6b13a09ffa9cbeed2a4c0cc65b
Submitter: "Zuul (22348)"
Branch: master

commit 2ed9834047897d6b13a09ffa9cbeed2a4c0cc65b
Author: Dr. Jens Harbott <email address hidden>
Date: Sun Feb 18 12:42:40 2024 +0100

    Fix invalid IP address representation in unit test

    An IP address may not have a leading zero in any of its octets, this is
    getting enforced by the latest netaddr library.

    Partial-Bug: 2054203
    Change-Id: I15cd049de1511a9b52e8e28bccec87060c2f1411

[OpenStack Infra (hudson-openstack)]

Related fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/neutron-lib/+/910331