Public bug reported:
This was found as a UT regression failure in the x/group-based-policy
project, but I think the same issue applies to the auto-allocated-
topology workflow (or any feature that creates a network at the plugin
or DB layer instead of at the REST layer). The exception seen is this:
File
"/home/zuul/src/opendev.org/x/group-based-policy/.tox/py36/lib/python3.6/site-packages/neutron/plugins/ml2/plugin.py",
line 1053, in create_network
result, mech_context = self._create_network_db(context, network)
File
"/home/zuul/src/opendev.org/x/group-based-policy/gbpservice/neutron/plugins/ml2plus/plugin.py",
line 333, in _create_network_db
context, network)
File
"/home/zuul/src/opendev.org/x/group-based-policy/.tox/py36/lib/python3.6/site-packages/neutron/plugins/ml2/plugin.py",
line 1013, in _create_network_db
net_db.mtu = self._get_network_mtu(net_db)
File
"/home/zuul/src/opendev.org/x/group-based-policy/.tox/py36/lib/python3.6/site-packages/neutron/plugins/ml2/plugin.py",
line 995, in _get_network_mtu
raise exc.InvalidInput(error_message=msg)
neutron_lib.exceptions.InvalidInput: Invalid input for operation: Requested MTU
is too big, maximum is 1000.
The UT limits the network MTU using configuration file settings:
https://opendev.org/x/group-based-policy/src/branch/master/gbpservice/neutron/tests/unit/services/grouppolicy/test_aim_mapping_driver.py#L2951-L2952
The regression happens because a default MTU for the DB layer was
introduced in this patch: https://review.opendev.org/#/c/679399/
The default value used is the DEFAULT_NETWORK_MTU constant from neutron-
lib (1500). This is different than the default value installed by the
REST layer (0). When the network MTU is constrained using configuration
files, it gets to this code path:
https://opendev.org/openstack/neutron/src/branch/master/neutron/plugins/ml2/plugin.py#L992-L1002
Since the DB layer has set the default to 1500 instead of 0, this
exception gets triggered, even though the caller at the plugin layer
didn't specify a value for the MTU.
One possible fix is to have the DB layer use a value of 0 for the
default instead of DEFAULT_NETWORK_MTU.
** Affects: neutron
Importance: Undecided
Assignee: Thomas Bachman (bachman)
Status: In Progress
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https://bugs.launchpad.net/bugs/1896933
Title:
Exception when plugin creates a network without specifying the MTU
Status in neutron:
In Progress
Bug description:
This was found as a UT regression failure in the x/group-based-policy
project, but I think the same issue applies to the auto-allocated-
topology workflow (or any feature that creates a network at the plugin
or DB layer instead of at the REST layer). The exception seen is this:
File
"/home/zuul/src/opendev.org/x/group-based-policy/.tox/py36/lib/python3.6/site-packages/neutron/plugins/ml2/plugin.py",
line 1053, in create_network
result, mech_context = self._create_network_db(context, network)
File
"/home/zuul/src/opendev.org/x/group-based-policy/gbpservice/neutron/plugins/ml2plus/plugin.py",
line 333, in _create_network_db
context, network)
File
"/home/zuul/src/opendev.org/x/group-based-policy/.tox/py36/lib/python3.6/site-packages/neutron/plugins/ml2/plugin.py",
line 1013, in _create_network_db
net_db.mtu = self._get_network_mtu(net_db)
File
"/home/zuul/src/opendev.org/x/group-based-policy/.tox/py36/lib/python3.6/site-packages/neutron/plugins/ml2/plugin.py",
line 995, in _get_network_mtu
raise exc.InvalidInput(error_message=msg)
neutron_lib.exceptions.InvalidInput: Invalid input for operation: Requested
MTU is too big, maximum is 1000.
The UT limits the network MTU using configuration file settings:
https://opendev.org/x/group-based-policy/src/branch/master/gbpservice/neutron/tests/unit/services/grouppolicy/test_aim_mapping_driver.py#L2951-L2952
The regression happens because a default MTU for the DB layer was
introduced in this patch: https://review.opendev.org/#/c/679399/
The default value used is the DEFAULT_NETWORK_MTU constant from
neutron-lib (1500). This is different than the default value installed
by the REST layer (0). When the network MTU is constrained using
configuration files, it gets to this code path:
https://opendev.org/openstack/neutron/src/branch/master/neutron/plugins/ml2/plugin.py#L992-L1002
Since the DB layer has set the default to 1500 instead of 0, this
exception gets triggered, even though the caller at the plugin layer
didn't specify a value for the MTU.
One possible fix is to have the DB layer use a value of 0 for the
default instead of DEFAULT_NETWORK_MTU.
To manage notifications about this bug go to:
https://bugs.launchpad.net/neutron/+bug/1896933/+
