Use mtu of Tenant network to control neutron global_physnet_mtu

Change: I11e38f82eb9040f77412fe8ad200fcc48031e2f8 introduced mtu
property for composable networks. This change set the MTU of the
Tenant network as the global_physnet_mtu for neutron, unless the
NeutronGlobalPhysnetMtu is overridden. The default MTU used if
no MTU is defined for the Tenant network is 1500. (The same
default was previously used for the NeutronGlobalPhysnetMtu
parameter.)

Change-Id: I5e60d52ad571e1cdb3b82cd1d9947e33fa682bf8

environments/network-environment-v6.j2.yaml

@@ -56,6 +56,14 @@ parameter_defaults:
   # Routes to add to host_routes property of the subnets in neutron.
   {{network.name}}Routes: {{network.routes_ipv6|default([])}}
 {%-     endif %}
+{%-     if network.name == 'Tenant' %}
+  # MTU of the underlying physical network. Neutron uses this value to
+  # calculate MTU for all virtual network components. For flat and VLAN
+  # networks, neutron uses this value without modification. For overlay
+  # networks such as VXLAN, neutron automatically subtracts the overlay
+  # protocol overhead from this value.
+  TenantNetPhysnetMtu: {{network.mtu|default('1500')}}
+{%-     endif %}
 {% endfor %}
 {#- FIXME: These global parameters should be defined in a YAML file, e.g. network_data.yaml. #}
   # Define the DNS servers (maximum 2) for the overcloud nodes

environments/network-environment.j2.yaml

@@ -54,6 +54,14 @@ parameter_defaults:
   # Routes to add to host_routes property of the subnets in neutron.
   {{network.name}}Routes: {{network.routes|default([])}}
 {%-     endif %}
+{%-     if network.name == 'Tenant' %}
+  # MTU of the underlying physical network. Neutron uses this value to
+  # calculate MTU for all virtual network components. For flat and VLAN
+  # networks, neutron uses this value without modification. For overlay
+  # networks such as VXLAN, neutron automatically subtracts the overlay
+  # protocol overhead from this value.
+  TenantNetPhysnetMtu: {{network.mtu|default('1500')}}
+{%-     endif %}
 {% endfor %}
 {#- FIXME: These global parameters should be defined in a YAML file, e.g. network_data.yaml. #}
   # Define the DNS servers (maximum 2) for the overcloud nodes

puppet/services/neutron-base.yaml

@@ -49,6 +49,16 @@ parameters:
         Remove configuration that is not generated by TripleO. Used to avoid
         configuration remnants after upgrades.
   NeutronGlobalPhysnetMtu:
+    type: number
+    default: 0
+    description: |
+        MTU of the underlying physical network. Neutron uses this value to
+        calculate MTU for all virtual network components. For flat and VLAN
+        networks, neutron uses this value without modification. For overlay
+        networks such as VXLAN, neutron automatically subtracts the overlay
+        protocol overhead from this value.
+        (If this is not changed TenantNetPhysnetMtu will be used.)
+  TenantNetPhysnetMtu:
     type: number
     default: 1500
     description: |
@@ -57,6 +67,8 @@ parameters:
         networks, neutron uses this value without modification. For overlay
         networks such as VXLAN, neutron automatically subtracts the overlay
         protocol overhead from this value.
+        (The mtu setting of the Tenant network in network_data.yaml
+        control's this parameter.)
   NeutronDBSyncExtraParams:
     default: ''
     description: |
@@ -125,6 +137,7 @@ conditions:
   dhcp_agents_zero: {equals : [{get_param: NeutronDhcpAgentsPerNetwork}, 0]}
   service_debug_unset: {equals : [{get_param: NeutronDebug}, '']}
   internal_tls_enabled: {equals: [{get_param: EnableInternalTLS}, true]}
+  global_physnet_mtu_unset: {equals: [{get_param: NeutronGlobalPhysnetMtu}, 0]}
 
 outputs:
   role_data:
@@ -155,7 +168,11 @@ outputs:
             neutron::db::database_db_max_retries: -1
             neutron::db::database_max_retries: -1
             neutron::db::sync::db_sync_timeout: {get_param: DatabaseSyncTimeout}
-            neutron::global_physnet_mtu: {get_param: NeutronGlobalPhysnetMtu}
+            neutron::global_physnet_mtu:
+              if:
+              - global_physnet_mtu_unset
+              - {get_param: TenantNetPhysnetMtu}
+              - {get_param: NeutronGlobalPhysnetMtu}
             neutron::db::sync::extra_params: {get_param: NeutronDBSyncExtraParams}
             neutron::vlan_transparent: {get_param: EnableVLANTransparency}
           - if:

releasenotes/notes/set-tenant-net-mtu-as-neutron-global-physnet-mtu-5e3515a97e8e0367.yaml

@@ -0,0 +1,10 @@
+---
+features:
+  - |
+    The MTU defined for the ``Tenant`` network in network_data is now used to
+    set neutron's ``global_physnet_mtu`` unless the ``NeutronGlobalPhysnetMtu``
+    parameter is used to override the default. (Neutron uses the
+    ``global_physnet_mtu`` value to calculate MTU for all virtual network
+    components. For flat and VLAN networks, neutron uses this value without
+    modification. For overlay networks such as VXLAN, neutron automatically
+    subtracts the overlay protocol overhead from this value.)