Add basic support for "global_physnet_mtu" and "path_mtu" options.

I've added basic support for "global_physnet_mtu" and "path_mtu"
options by allowing to configure them via charm parameters.

Change-Id: Ia95533418ccd4b7d1b96270633193ea34b1edecb
Partial-Bug: 1650579

config.yaml

@@ -118,6 +118,10 @@ options:
       The MTU size for interfaces managed by neutron. If unset or set to
       0, no value will be applied. This value will be provided to
       neutron-plugin-api relations.
+      .
+      NOTE: This option is deprecated and will be removed in Newton.
+      Please use the system-wide global-physnet-mtu setting which the
+      agents will take into account when wiring VIFs.
   neutron-plugin:
     default: ovs
     type: string
@@ -623,3 +627,23 @@ options:
     default:
     description: |
       The default type for a tenant network e.g. vxlan, vlan, gre etc
+  global-physnet-mtu:
+    type: int
+    default: 1500
+    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.
+      .
+      NOTE: This options is available starting from Mitaka release.
+  path-mtu:
+    type: int
+    default: 
+    description: |
+      Maximum size of an IP packet (MTU) that can traverse the
+      underlying physical network infrastructure without fragmentation
+      when using an overlay/tunnel protocol. This option allows
+      specifying a physical network MTU value that differs from the
+      default global-physnet-mtu value.

hooks/neutron_api_context.py

@@ -300,6 +300,14 @@ class NeutronCCContext(context.NeutronContext):
         else:
             ctxt['enable_hyperv'] = False
 
+        if release >= 'mitaka':
+            if config('global-physnet-mtu'):
+                ctxt['global_physnet_mtu'] = config('global-physnet-mtu')
+                if config('path-mtu'):
+                    ctxt['path_mtu'] = config('path-mtu')
+                else:
+                    ctxt['path_mtu'] = config('global-physnet-mtu')
+
         return ctxt
 
 

templates/mitaka/ml2_conf.ini

@@ -0,0 +1,59 @@
+# mitaka
+###############################################################################
+# [ WARNING ]
+# Configuration file maintained by Juju. Local changes may be overwritten.  
+###############################################################################
+[ml2]
+{% if enable_ml2_port_security -%}
+extension_drivers=port_security
+{% endif -%}
+
+{% if neutron_plugin == 'Calico' -%}
+type_drivers = local,flat
+mechanism_drivers = calico
+{% else -%}
+type_drivers = {{ tenant_network_types }}
+tenant_network_types = {{ tenant_network_types }}
+{% if enable_sriov %}
+mechanism_drivers = openvswitch,l2population,sriovnicswitch
+{% elif enable_hyperv %}
+mechanism_drivers = openvswitch,hyperv,l2population
+{% else %}
+mechanism_drivers = openvswitch,l2population
+{% endif %}
+
+{% if path_mtu -%}
+path_mtu = {{ path_mtu }}
+{% endif -%}
+
+[ml2_type_gre]
+tunnel_id_ranges = 1:1000
+
+[ml2_type_vxlan]
+vni_ranges = {{ vni_ranges }}
+
+[ml2_type_vlan]
+network_vlan_ranges = {{ vlan_ranges }}
+
+[ml2_type_flat]
+flat_networks = {{ network_providers }}
+
+[ovs]
+enable_tunneling = True
+local_ip = {{ local_ip }}
+
+[agent]
+tunnel_types = {{ overlay_network_type }}
+{% endif -%}
+
+[securitygroup]
+{% if neutron_security_groups -%}
+enable_security_group = True
+{% if neutron_plugin == 'Calico' -%}
+firewall_driver = neutron.agent.linux.iptables_firewall.IptablesFirewallDriver
+{% else -%}
+firewall_driver = neutron.agent.linux.iptables_firewall.OVSHybridIptablesFirewallDriver
+{% endif -%}
+{% else -%}
+enable_security_group = False
+{% endif -%}

templates/mitaka/neutron.conf

@@ -71,6 +71,10 @@ notify_nova_on_port_data_changes = True
 
 {% include "section-zeromq" %}
 
+{% if global_physnet_mtu -%}
+global_physnet_mtu = {{ global_physnet_mtu }}
+{% endif -%}
+
 [quotas]
 {% if quota_driver -%}
 quota_driver = {{ quota_driver }}