Add TripleO Heat Template Parameters for Neutron Tenant MTU

This change adds the TripleO Heat Parameters and Puppet hieradata
to support setting the MTU for Neutron tenant networks. A new
parameter, NeutronTenantMtu is introduced, and this gets used for
the NeutronDnsmasqOptions and in Puppet hieradata.

NeutronTenantMtu is also used in the Puppet hieradata for both the
compute and control nodes. Two values are set:

nova::compute::network_device_mtu

which sets /etc/nova/nova.conf: network_device_mtu = <NeutronTenantMtu>

neutron::network_device_mtu

which sets in /etc/neutron/neutron.conf:
network_device_mtu = <NeutronTenantMtu>

finally, the NeutronDnsmasqOptions parameter becomes a str_format
that maps the NeutronTenantMtu onto the DHCP options,
so a default of 'dhcp-option-force=26,%MTU%' would be formatted to
'dhcp-option-force=26,1300' if NeutronTenantMtu were 1300.

This will set dnsmasq to serve an MTU via DHCP that matches the
NeutronTenantMtu:

/etc/neutron/dnsmasq-neutron.conf:dhcp-option-force=26,1300

Typically, you would change all three of these settings to use small
or jumbo frames in VMs. When using tunneling, NeutronTenantMtu
should be set at least 50 bytes smaller than the physical network
MTU in order to make room for tunneling overhead.

Note that this change does not support setting the MTU on veth
interfaces if veth patches are used to br-int instead of OVS
patches.

Change-Id: I38840e082ee01dc3b6fc78e1dd97f53fa4e63039

1 files changed, 21 insertions, 3 deletions

diff --git a/overcloud.yaml b/overcloud.yaml
index 673bf506..a71fb2fe 100644
--- a/overcloud.yaml
+++ b/overcloud.yaml
@@ -168,6 +168,15 @@ parameters:
     description: Shared secret to prevent spoofing
     type: string
     hidden: true
+  NeutronTenantMtu:
+    description: >
+      The default MTU for tenant networks. For VXLAN/GRE tunneling, this should
+      be at least 50 bytes smaller than the MTU on the physical network. This
+      value will be used to set the MTU on the virtual Ethernet device.
+      This value will be used to construct the NeutronDnsmasqOptions, since that
+      will determine the MTU that is assigned to the VM host through DHCP.
+    default: "1400"
+    type: string
   NeutronTunnelTypes:
     default: 'vxlan'
     description: |
@@ -498,8 +507,11 @@ parameters:
     type: number
     default: 4096
   NeutronDnsmasqOptions:
-    default: 'dhcp-option-force=26,1400'
-    description: Dnsmasq options for neutron-dhcp-agent. The default value here forces MTU to be set to 1400 to account for the tunnel overhead.
+    default: 'dhcp-option-force=26,%MTU%'
+    description: >
+      Dnsmasq options for neutron-dhcp-agent. The default value here forces MTU
+      to be set to the value of NeutronTenantMtu, which should be set to account
+      for tunnel overhead.
     type: string
   NeutronPublicInterfaceDefaultRoute:
     default: ''
@@ -898,6 +910,7 @@ resources:
           NeutronPublicInterfaceIP: {get_param: NeutronPublicInterfaceIP}
           NeutronFlatNetworks: {get_param: NeutronFlatNetworks}
           NeutronBridgeMappings: {get_param: NeutronBridgeMappings}
+          NeutronTenantMtu: {get_param: NeutronTenantMtu}
           NeutronExternalNetworkBridge: {get_param: NeutronExternalNetworkBridge}
           NeutronEnableIsolatedMetadata: {get_param: NeutronEnableIsolatedMetadata}
           NeutronEnableTunnelling: {get_param: NeutronEnableTunnelling}
@@ -907,7 +920,11 @@ resources:
           NeutronPublicInterfaceDefaultRoute: {get_param: NeutronPublicInterfaceDefaultRoute}
           NeutronPublicInterfaceRawDevice: {get_param: NeutronPublicInterfaceRawDevice}
           NeutronPassword: {get_param: NeutronPassword}
-          NeutronDnsmasqOptions: {get_param: NeutronDnsmasqOptions}
+          NeutronDnsmasqOptions:
+            str_replace:
+              template: {get_param: NeutronDnsmasqOptions}
+              params:
+                '%MTU%': {get_param: NeutronTenantMtu}
           NeutronDVR: {get_param: NeutronDVR}
           NeutronMetadataProxySharedSecret: {get_param: NeutronMetadataProxySharedSecret}
           NeutronAgentMode: {get_param: NeutronAgentMode}
@@ -996,6 +1013,7 @@ resources:
           KeystoneAdminApiVirtualIP: {get_attr: [VipMap, net_ip_map, {get_param: [ServiceNetMap, KeystoneAdminApiNetwork]}]}
           KeystonePublicApiVirtualIP: {get_attr: [VipMap, net_ip_map, {get_param: [ServiceNetMap, KeystonePublicApiNetwork]}]}
           NeutronBridgeMappings: {get_param: NeutronBridgeMappings}
+          NeutronTenantMtu: {get_param: NeutronTenantMtu}
           NeutronEnableTunnelling: {get_param: NeutronEnableTunnelling}
           NeutronEnableL2Pop : {get_param: NeutronEnableL2Pop}
           NeutronFlatNetworks: {get_param: NeutronFlatNetworks}