+++ This bug was initially created as a clone of Bug #1891960 +++

Description of problem:
A customer was asking what is the specific outcome of setting the NovaIPv6 parameter to true or false on compute nodes. Our formal documentation in the Overcloud Parameters guides for OSP 10 and beyond on this parameter currently specify "Enable IPv6 features for OpenStack Compute (nova). The default value is False." [1] and [2]

After further investigation, it seems this parameter sets the use_ipv6 option flag within nova.conf. The use_ipv6 option appears to be depreciated from upstream OpenStack Ocata onwards and was specific to nova networking, which is not used in OSP 10 and beyond. Refs [3] and [4] of the upstream queens and train nova.conf - configuration options for use_ipv6 state the following:
    Assign IPv6 and IPv4 addresses when creating instances.
    Related options:
    use_neutron: this only works with nova-network.
    Warning
    This option is deprecated for removal since 16.0.0. Its value may be silently ignored in the future.
Reason
    nova-network is deprecated, as are any related configuration options.


The current entry for NovaIPv6 parameter in the Red Hat Overcloud Parameter guides is unspecific and likely misleading. It would be beneficial to at least specify in the documentation this parameter only relates to nova networking and has been depreciated. Could an OSP documentation engineer please review and revise this entry?

References:
[1] https://access.redhat.com/documentation/en-us/red_hat_openstack_platform/10/html-single/overcloud_parameters/index
[2] https://access.redhat.com/documentation/en-us/red_hat_openstack_platform/16.1/html-single/overcloud_parameters/index
[3] https://docs.openstack.org/nova/queens/configuration/config.html
[4] https://docs.openstack.org/nova/train/configuration/config.html


Version-Release number of selected component (if applicable):
RHOSP 10 --> 16.1 Overcloud Parameters formal guide

How reproducible:
N/A (documentation bug)

--- Additional comment from Artom Lifshitz on 2020-11-04 22:55:05 UTC ---

(In reply to Ben Roose from comment #0)
> Description of problem:
> A customer was asking what is the specific outcome of setting the NovaIPv6
> parameter to true or false on compute nodes. Our formal documentation in the
> Overcloud Parameters guides for OSP 10 and beyond on this parameter
> currently specify "Enable IPv6 features for OpenStack Compute (nova). The
> default value is False." [1] and [2]
> 
> After further investigation, it seems this parameter sets the use_ipv6
> option flag within nova.conf.

@Rajesh - can you confirm that is indeed the only thing the `NovaIPv6` parameters does? If so, it needs to be deprecated in anything <= OSP 16, and removed in OSP17+, as the use_ipv6 config option has been removed from Nova.

@Irinia - do we need to clone a docs BZ for this?

--- Additional comment from Irina on 2020-11-05 09:40:38 UTC ---

Hi Artom

This is a docs BZ. Maybe this issue could be cloned for the engineering work?

Thanks

Irina

--- Additional comment from Ben Roose on 2020-11-05 22:47:49 UTC ---

An FYI as the engineering and documentation teams work on this BZ:
This same customer found in OpenStack Platform 10 that the use_ipv6 option was influencing IPv6 address configuration of an instance with cloud-init. Specifically, setting use_ipv6=false in nova.conf on the underlying compute node stopped cloud-init from correctly configuring the instance IPv6 network information, but once nova.conf was set to use_ipv6=true, cloud-init did correctly configure the instance. After further investigation, it seems there is a bug in OSP 10 which requires use_ipv6=true to be set for IPv6 configuration of instances, as per Stephen Finucane's upstream code change 430910 to patch this bug [1] and [2]. Speaking with Stephen, it would seem this bug patch was not included by Red Hat until OpenStack Platform 12.

Regards,
Ben

References:
[1] https://review.opendev.org/#/c/430910/ 
[2] https://github.com/openstack/nova/commit/c0aef97c49781f2ce0aa93fd33bfac7e68ea5b97#diff-2a0c4c14c71ae11aaebe90f4c81f6dc9dad5fc38d0b8cd3d066209d54595ae90L873

--- Additional comment from Rajesh Tailor on 2020-11-06 12:13:32 UTC ---

(In reply to Artom Lifshitz from comment #1)
> (In reply to Ben Roose from comment #0)
> > Description of problem:
> > A customer was asking what is the specific outcome of setting the NovaIPv6
> > parameter to true or false on compute nodes. Our formal documentation in the
> > Overcloud Parameters guides for OSP 10 and beyond on this parameter
> > currently specify "Enable IPv6 features for OpenStack Compute (nova). The
> > default value is False." [1] and [2]
> > 
> > After further investigation, it seems this parameter sets the use_ipv6
> > option flag within nova.conf.
> 
> @Rajesh - can you confirm that is indeed the only thing the `NovaIPv6`
> parameters does? If so, it needs to be deprecated in anything <= OSP 16, and
> removed in OSP17+, as the use_ipv6 config option has been removed from Nova.

yes, and it is already removed from puppet-nova in train [1] and from THT in ussuri [2].

so we need to backport the ussuri change to train.

[1] https://review.opendev.org/#/c/658403
[2] https://review.opendev.org/#/c/715660/1

I will do the backport ASAP.
 
> @Irinia - do we need to clone a docs BZ for this?

--- Additional comment from Irina on 2020-11-06 15:09:58 UTC ---

To generate the Overcloud Params Guide and the Configuration Reference guide when the backport is complete (aiming for 16.1.4)