openstack/neutron
Code Issues Proposed changes

Update OVN gaps document

Browse Source 
Recently we closed some of the gaps between ML2/OVS and ML2/OVN,
like for example:

* Support for the QoS DSCP,
* Support for the Layer 3 IPs QoS,
* Fix bugs [1] and [2] related to the OVN DNS resolution.

This patch updates documented gaps by removing those points from the
gaps list.
It also adds some links to the WIP patches for other of the gaps on that
list.

[1] https://bugs.launchpad.net/neutron/+bug/1951816
[2] https://bugs.launchpad.net/neutron/+bug/1950686

Change-Id: I0e670ef0a87300182ba83f350a84d28bf8d31eb9
This commit is contained in:
Slawek Kaplonski 2022-05-18 11:34:07 +02:00
parent e35188ef3d
commit 76a1206888
1 changed files with 21 additions and 32 deletions

53
doc/source/ovn/gaps.rst

@ -8,23 +8,11 @@ It is not a complete list, but is enough to be used as a starting point for
implementors working on closing these gaps. A TODO list for OVN is located
at [1]_.
* QoS DSCP support
Currently ML2/OVS supports QoS DSCP tagging and egress bandwidth limiting.
Those are basic QoS features that while integrated in the OVS/OVN C core
are not integrated (or fully tested) in the neutron OVN mechanism driver.
* QoS for Layer 3 IPs
Currently the Neutron L3-agent supports floating IP and gateway IP bandwidth
limiting based on Linux TC. OVN L3 plugin supports floating IP bandwidth
limiting based on the OVN's QoS rules.
Neutron OVN backend does not yet support bandwidth limiting for gateway IP.
* QoS Minimum Bandwidth support
Currently ML2/OVS supports QoS Minimum Bandwidth limiting, but it is
not supported in OVN.
The work on this is in progress. Details can be found at [2]_ and [3]_.
* BGP support
@ -37,18 +25,19 @@ at [1]_.
The core OVN DHCP server implementation does not have support for
sending different boot options based on the ``gpxe`` DHCP Option
(no. 175). Also, Ironic uses dnsmasq syntax when configuring the DHCP
options for Neutron [2]_ which is not understood by the OVN driver.
options for Neutron [4]_ which is not understood by the OVN driver.
Work on that is in progress currently, see [5]_ and [6]_.
* QoS minimum bandwidth allocation in Placement API
ML2/OVN integration with the Nova placement API to provide guaranteed
minimum bandwidth for ports [3]_.
minimum bandwidth for ports [7]_. Work in progress, see [8]_
* IPv6 Prefix Delegation
Currently ML2/OVN doesn't implement IPv6 prefix delegation. OVN logical
routers have this capability implemented in [4]_ and we have an open RFE to
fill this gap [5]_.
routers have this capability implemented in [9]_ and we have an open RFE to
fill this gap [10]_.
* East/West Fragmentation
@ -62,31 +51,31 @@ at [1]_.
from instances to reach the DHCP agent. For OVN this traffic has to be explicitly
allowed by security group rules attached to the instance. Note that the default
security group does allow all outgoing traffic, so this only becomes relevant
when using custom security groups [6]_.
when using custom security groups [11]_. Proposed patch is [12]_ but it
needs to be revived and updated.
* DNS resolution for instances
OVN cannot use the host's networking for DNS resolution, so Case 2b in [7]_ can
OVN cannot use the host's networking for DNS resolution, so Case 2b in [13]_ can
only be used when additional DHCP agents are deployed. For Case 2a a different
configuration option has to be used in ``ml2_conf.ini``::
[ovn]
dns_servers = 203.0.113.8, 198.51.100.53
Note that this option currently only works for IPv4 nameservers [8]_.
In addition, with ML2/OVS setting the name-server option for a subnet to ``0.0.0.0``
or ``::`` respectively has the effect that no nameservers are announced via DHCP for
this subnet. This currently does not work with OVN [9]_.
References
----------
.. [1] https://github.com/ovn-org/ovn/blob/master/TODO.rst
.. [2] https://github.com/openstack/ironic/blob/123cb22c731f93d0c608d791b41e05884fe18c04/ironic/common/pxe_utils.py#L447-L462>
.. [3] https://specs.openstack.org/openstack/neutron-specs/specs/rocky/minimum-bandwidth-allocation-placement-api.html
.. [4] https://patchwork.ozlabs.org/project/openvswitch/patch/6aec0fb280f610a2083fbb6c61e251b1d237b21f.1576840560.git.lorenzo.bianconi@redhat.com/
.. [5] https://bugs.launchpad.net/neutron/+bug/1895972
.. [6] https://bugs.launchpad.net/neutron/+bug/1926515
.. [7] https://docs.openstack.org/neutron/latest/admin/config-dns-res.html
.. [8] https://bugs.launchpad.net/neutron/+bug/1951816
.. [9] https://bugs.launchpad.net/neutron/+bug/1950686
.. [2] https://bugzilla.redhat.com/show_bug.cgi?id=2060310
.. [3] https://review.opendev.org/c/openstack/neutron/+/842292
.. [4] https://github.com/openstack/ironic/blob/123cb22c731f93d0c608d791b41e05884fe18c04/ironic/common/pxe_utils.py#L447-L462>
.. [5] https://review.opendev.org/c/openstack/neutron/+/840287
.. [6] https://review.opendev.org/c/openstack/neutron/+/840316
.. [7] https://specs.openstack.org/openstack/neutron-specs/specs/rocky/minimum-bandwidth-allocation-placement-api.html
.. [8] https://review.opendev.org/c/openstack/neutron/+/786478
.. [9] https://patchwork.ozlabs.org/project/openvswitch/patch/6aec0fb280f610a2083fbb6c61e251b1d237b21f.1576840560.git.lorenzo.bianconi@redhat.com/
.. [10] https://bugs.launchpad.net/neutron/+bug/1895972
.. [11] https://bugs.launchpad.net/neutron/+bug/1926515
.. [12] https://review.opendev.org/c/openstack/neutron/+/788594
.. [13] https://docs.openstack.org/neutron/latest/admin/config-dns-res.html