Add ML2/OVN security group logging documentation

Previously there was a guide on how the network logging feature worked,
but it was centered around ML2/OVS. This adds more details and
information on how to create and manage network log objects when using
ML2/OVN.

Change-Id: I0eca448d79488ff66203fee7999b1df31f5ed44d
Signed-off-by: Elvira García <egarciar@redhat.com>

doc/source/admin/config-logging.rst

@@ -8,16 +8,170 @@ Packet logging service is designed as a Neutron plug-in that captures network
 packets for relevant resources (e.g. security group or firewall group) when the
 registered events occur.
 
-.. image:: figures/logging-framework.png
-   :width: 100%
-   :alt: Packet Logging Framework
+--------------
+ML2/OVN Driver
+--------------
+
 
 Supported loggable resource types
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-From Rocky release, both of ``security_group`` and ``firewall_group`` are
-supported as resource types in Neutron packet logging framework.
+From the Wallaby release the ML2/OVN driver supports the ``security_group``
+resource.
 
+The following diagram shows a mapping from Neutron security group framework to
+the ACLs, which are the resources where we enable the logging when using
+ML2/OVN. Each security group rule maps to an ACL associated to a port group
+that contains all the ports belonging to the security group.
+
+
+.. image:: figures/secgrouprule-to-acl.png
+   :width: 100%
+   :alt: Packet Logging Framework with ML2/OVS
+
+.. _contributors documentation: https://docs.openstack.org/neutron/latest/contributor/internals/ovn/ovn_network_logging.html
+
+For more details on the developing peculiarities of this implementation, you
+can check the `contributors documentation`_.
+
+Service Configuration
+~~~~~~~~~~~~~~~~~~~~~
+
+To enable the logging service, add ``log`` to the ``service_plugins`` setting
+in ``/etc/neutron/neutron.conf``:
+
+.. code-block:: none
+
+     service_plugins = router,metering,log
+
+It is possible to set parameters in ml2_conf.ini to tune how we want to log the
+packets by modifying ``rate_limit`` and ``burst_limit`` in section
+``[network_log]`` in ``/etc/neutron/plugins/ml2/ml2_conf.ini``:
+
+* ``rate_limit`` - Limit the packet rate of the logs that are sent to the OVN
+  controller, in packets per second. The higher the number, the more logs we
+  will get in the log file.
+
+* ``burst_limit`` - Increase the packet rate limit by the specified value for a
+  short period of time.
+
+.. code-block:: ini
+
+     [network_log]
+     rate_limit = 150
+     burst_limit = 50
+
+.. note::
+
+     There is a minimum value for these parameters. For ``rate_limit`` it is
+     100 and for ``burst_limit`` it is 25.
+
+In order to make the changes to rate and burst effective, restart the
+neutron-server service. To ensure the configuration for rate and burst was
+updated, check the meter-band table on the OVN Northbound database. You need to
+create at least one log object to see the meter band entry created.
+
+.. code-block:: console
+
+     $ ovn-nbctl list meter-band
+
+
+Service workflow
+~~~~~~~~~~~~~~~~
+Create a logging resource with security group as resource type:
+
+.. code-block:: console
+
+   $ openstack network log create --resource-type security_group \
+   --resource sg1 --event ALL log1
+
+     +-----------------+--------------------------------------+
+     | Field           | Value                                |
+     +-----------------+--------------------------------------+
+     | Description     |                                      |
+     | Enabled         | True                                 |
+     | Event           | ALL                                  |
+     | ID              | 67b1f618-0b89-4b9c-b3e4-9378b4472175 |
+     | Name            | log1                                 |
+     | Project         | 74731b187a824a8d9b85a12b6eacbcbb     |
+     | Resource        | 387494cb-392a-4760-8c36-09be2fdb0b49 |
+     | Target          | None                                 |
+     | Type            | security_group                       |
+     | created_at      | 2023-07-31T09:44:34Z                 |
+     | revision_number | 0                                    |
+     | tenant_id       | 74731b187a824a8d9b85a12b6eacbcbb     |
+     | updated_at      | 2023-07-31T09:44:34Z                 |
+     +-----------------+--------------------------------------+
+
+
+.. note::
+
+     Due to the internal design of the ML2/OVN driver, there is one ACL that
+     aggregates all dropped traffic, instead of having one drop ACL per
+     security group. Since the smallest logging unit in OVN is the ACL, that
+     means that if we choose to log DROP traffic, we will get traffic logged
+     from all security groups.
+
+     If we choose to log ALL traffic, we will get the accepted traffic
+     from the selected security group, but the dropped traffic from all
+     security groups.
+
+     This can change in following releases if the ACL management is redesigned
+     in OVN.
+
+
+.. warning::
+
+   We cannot assign individual ports when using ML2/OVN, so the ``--target``
+   parameter is not used.
+
+
+Just as with ML2/OVS, we can enable or disable logging objects at runtime. If
+we have two objects targeted to log the same resource, as long as one of them
+is enabled, the resource will be logged on the logfile.
+
+
+Understanding the logging
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+In ML2/OVN we find the packet monitoring logging recorded on each
+``ovn-controller.log`` file within the compute nodes. This means that we will
+have as many logfiles as compute nodes, because each OVN controller has the
+capacity of logging only the traffic they manage. The location of the OVN
+controller log may differ depending on the distribution, please consult your
+installation documentation for more details. The format of the logging is:
+
+
+.. code-block:: console
+
+   2023-01-08T17:57:28.283002425+00:00 stderr F
+   2023-01-08T17:57:28Z|00094|acl_log(ovn_pinctrl0)|INFO|
+   name="neutron-e9ebf19c-3d84-49ae-a81e-7a01035a8768", verdict=allow,
+   severity=info, direction=to-lport: icmp, vlan_tci=0x0000,
+   dl_src=fa:16:3e:d3:b4:48, dl_dst=fa:16:3e:9a:d9:7d, nw_src=10.0.0.67,
+   nw_dst=192.168.100.11, nw_tos=0, nw_ecn=0, nw_ttl=63, nw_frag=no,
+   icmp_type=8, icmp_code=0
+
+In this example, the name is ``neutron-<security group log object ID>``. We can
+also see the verdict, the severity, the direction of the datagram and the
+content.
+
+
+
+--------------
+ML2/OVS Driver
+--------------
+
+.. image:: figures/logging-framework.png
+   :width: 100%
+   :alt: Packet Logging Framework with ML2/OVS
+
+
+Supported loggable resource types
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+From Rocky Release, the ML2/OVS driver supports both ``security_group`` and
+``firewall_group`` as resource types in the Neutron packet logging framework.
 
 Service Configuration
 ~~~~~~~~~~~~~~~~~~~~~