Description of problem:

For this OOO config:

parameter_defaults:
  NeutronL3AgentExtensions: 'conntrack_helper,port_forwarding'

As defined in THT:

From openstack-tripleo-heat-templates/deployment/neutron/neutron-l3-container-puppet.yaml 

  NeutronL3AgentExtensions:
    default: ""
    description: |
        Comma-separated list of extensions enabled for the Neutron L3 agent.
    type: comma_delimited_list

Results in this hiera data:

# hiera -c /etc/puppet/hiera.yaml neutron::agents::l3::extensions
["conntrack_helper", "port_forwarding"]

However, the resulting config via puppet is:

[root@overcloud-controller-0 ~]# crudini --get /var/lib/config-data/puppet-generated/neutron/etc/neutron/l3_agent.ini agent extensions
conntrack_helper


From the puppet module:

/etc/puppet/modules/neutron/manifests/agents/l3.pp

# [*extensions*]
#   (optional) L3 agent extensions to enable.
#   Defaults to $::os_service_default
#

...

  neutron_l3_agent_config {
    'DEFAULT/debug':                            value => $debug;
    'DEFAULT/interface_driver':                 value => $interface_driver;
    'DEFAULT/gateway_external_network_id':      value => $gateway_external_network_id;
    'DEFAULT/handle_internal_only_routers':     value => $handle_internal_only_routers;
    'DEFAULT/metadata_port':                    value => $metadata_port;
    'DEFAULT/periodic_interval':                value => $periodic_interval;
    'DEFAULT/periodic_fuzzy_delay':             value => $periodic_fuzzy_delay;
    'DEFAULT/enable_metadata_proxy':            value => $enable_metadata_proxy;
    'DEFAULT/agent_mode':                       value => $agent_mode;
    'DEFAULT/radvd_user':                       value => $radvd_user;
    'agent/availability_zone':                  value => $availability_zone;
    'agent/extensions':                         value => $extensions;
  }


It seems the puppet module need to handle the array and join it before setting the agent/extensions value.

Version-Release number of selected component (if applicable):
16.1 current
 rpm -q puppet-neutron
puppet-neutron-15.5.1-1.20201113235652.el8ost.noarch


How reproducible:
100%

Steps to Reproduce:
1. see above example

Actual results:
puppet-neutron only sets l3 agent/extensions to first element in list.

Expected results:
Comma-separated list of extensions enabled for the Neutron L3 agent