Make Weave MTU configurable and set AWS default config for jumbo frames

cmd/kops/create_cluster.go

@@ -354,30 +354,6 @@ func RunCreateCluster(f *util.Factory, out io.Writer, c *CreateClusterOptions) e
 	}
 	cluster.Spec.ConfigBase = configBase.Path()
 
-	cluster.Spec.Networking = &api.NetworkingSpec{}
-	switch c.Networking {
-	case "classic":
-		cluster.Spec.Networking.Classic = &api.ClassicNetworkingSpec{}
-	case "kubenet":
-		cluster.Spec.Networking.Kubenet = &api.KubenetNetworkingSpec{}
-	case "external":
-		cluster.Spec.Networking.External = &api.ExternalNetworkingSpec{}
-	case "cni":
-		cluster.Spec.Networking.CNI = &api.CNINetworkingSpec{}
-	case "kopeio-vxlan", "kopeio":
-		cluster.Spec.Networking.Kopeio = &api.KopeioNetworkingSpec{}
-	case "weave":
-		cluster.Spec.Networking.Weave = &api.WeaveNetworkingSpec{}
-	case "flannel":
-		cluster.Spec.Networking.Flannel = &api.FlannelNetworkingSpec{}
-	case "calico":
-		cluster.Spec.Networking.Calico = &api.CalicoNetworkingSpec{}
-	case "canal":
-		cluster.Spec.Networking.Canal = &api.CanalNetworkingSpec{}
-	default:
-		return fmt.Errorf("unknown networking mode %q", c.Networking)
-	}
-
 	glog.V(4).Infof("networking mode=%s => %s", c.Networking, fi.DebugAsJsonString(cluster.Spec.Networking))
 
 	// In future we could change the default if the flag is not specified, e.g. in 1.7 maybe the default is RBAC?
@@ -668,6 +644,37 @@ func RunCreateCluster(f *util.Factory, out io.Writer, c *CreateClusterOptions) e
 		}
 	}
 
+	cluster.Spec.Networking = &api.NetworkingSpec{}
+	switch c.Networking {
+	case "classic":
+		cluster.Spec.Networking.Classic = &api.ClassicNetworkingSpec{}
+	case "kubenet":
+		cluster.Spec.Networking.Kubenet = &api.KubenetNetworkingSpec{}
+	case "external":
+		cluster.Spec.Networking.External = &api.ExternalNetworkingSpec{}
+	case "cni":
+		cluster.Spec.Networking.CNI = &api.CNINetworkingSpec{}
+	case "kopeio-vxlan", "kopeio":
+		cluster.Spec.Networking.Kopeio = &api.KopeioNetworkingSpec{}
+	case "weave":
+		cluster.Spec.Networking.Weave = &api.WeaveNetworkingSpec{}
+
+		if cluster.Spec.CloudProvider == "aws" {
+			// AWS supports "jumbo frames" of 9001 bytes and weave adds up to 87 bytes overhead
+			// sets the default to the largest number that leaves enough overhead and is divisible by 4
+			jumboFrameMTUSize := int32(8912)
+			cluster.Spec.Networking.Weave.MTU = &jumboFrameMTUSize
+		}
+	case "flannel":
+		cluster.Spec.Networking.Flannel = &api.FlannelNetworkingSpec{}
+	case "calico":
+		cluster.Spec.Networking.Calico = &api.CalicoNetworkingSpec{}
+	case "canal":
+		cluster.Spec.Networking.Canal = &api.CanalNetworkingSpec{}
+	default:
+		return fmt.Errorf("unknown networking mode %q", c.Networking)
+	}
+
 	if c.VPCID != "" {
 		cluster.Spec.NetworkID = c.VPCID
 	}

docs/networking.md

@@ -101,6 +101,19 @@ Daemonset installation for K8s 1.4.x or 1.5.x.
 $ kubectl create -f https://git.io/weave-kube
 ```
 
+### Configuring Weave MTU
+
+The Weave MTU is configurable by editing the cluster and setting `mtu` option in the weave configuration.
+AWS VPCs support jumbo frames, so on cluster creation kops sets the weave MTU to 8912 bytes (9001 minus overhead).
+
+```
+spec:
+  networking:
+    weave:
+      mtu: 8912
+```
+
+
 ### Calico Example for CNI and Network Policy
 
 #### Installing Calico on a new Cluster

pkg/apis/kops/networking.go

@@ -54,6 +54,7 @@ type KopeioNetworkingSpec struct {
 
 // Weave declares that we want Weave networking
 type WeaveNetworkingSpec struct {
+	MTU *int32 `json:"mtu,omitempty"`
 }
 
 // Flannel declares that we want Flannel networking

pkg/apis/kops/v1alpha1/networking.go

@@ -54,6 +54,7 @@ type KopeioNetworkingSpec struct {
 
 // Weave declares that we want Weave networking
 type WeaveNetworkingSpec struct {
+	MTU *int32 `json:"mtu,omitempty"`
 }
 
 // Flannel declares that we want Flannel networking

pkg/apis/kops/v1alpha1/zz_generated.conversion.go

@@ -1765,6 +1765,7 @@ func Convert_kops_RBACAuthorizationSpec_To_v1alpha1_RBACAuthorizationSpec(in *ko
 }
 
 func autoConvert_v1alpha1_WeaveNetworkingSpec_To_kops_WeaveNetworkingSpec(in *WeaveNetworkingSpec, out *kops.WeaveNetworkingSpec, s conversion.Scope) error {
+	out.MTU = in.MTU
 	return nil
 }
 
@@ -1773,6 +1774,7 @@ func Convert_v1alpha1_WeaveNetworkingSpec_To_kops_WeaveNetworkingSpec(in *WeaveN
 }
 
 func autoConvert_kops_WeaveNetworkingSpec_To_v1alpha1_WeaveNetworkingSpec(in *kops.WeaveNetworkingSpec, out *WeaveNetworkingSpec, s conversion.Scope) error {
+	out.MTU = in.MTU
 	return nil
 }
 

pkg/apis/kops/v1alpha2/networking.go

@@ -54,6 +54,7 @@ type KopeioNetworkingSpec struct {
 
 // Weave declares that we want Weave networking
 type WeaveNetworkingSpec struct {
+	MTU *int32 `json:"mtu,omitempty"`
 }
 
 // Flannel declares that we want Flannel networking

pkg/apis/kops/v1alpha2/zz_generated.conversion.go

@@ -1919,6 +1919,7 @@ func Convert_kops_TopologySpec_To_v1alpha2_TopologySpec(in *kops.TopologySpec, o
 }
 
 func autoConvert_v1alpha2_WeaveNetworkingSpec_To_kops_WeaveNetworkingSpec(in *WeaveNetworkingSpec, out *kops.WeaveNetworkingSpec, s conversion.Scope) error {
+	out.MTU = in.MTU
 	return nil
 }
 
@@ -1927,6 +1928,7 @@ func Convert_v1alpha2_WeaveNetworkingSpec_To_kops_WeaveNetworkingSpec(in *WeaveN
 }
 
 func autoConvert_kops_WeaveNetworkingSpec_To_v1alpha2_WeaveNetworkingSpec(in *kops.WeaveNetworkingSpec, out *WeaveNetworkingSpec, s conversion.Scope) error {
+	out.MTU = in.MTU
 	return nil
 }
 

upup/models/cloudup/resources/addons/networking.weave/k8s-1.6.yaml.template

@@ -97,6 +97,11 @@ spec:
             limits:
               cpu: 100m
               memory: 200Mi
+          {{if .Networking.Weave.MTU }}
+          env:
+            - name: WEAVE_MTU
+              value: "{{ .Networking.Weave.MTU }}"
+          {{end}}
         - name: weave-npc
           image: weaveworks/weave-npc:1.9.4
           resources:

upup/models/cloudup/resources/addons/networking.weave/pre-k8s-1.6.yaml.template

@@ -58,6 +58,11 @@ spec:
             limits:
               cpu: 100m
               memory: 200Mi
+          {{if .Networking.Weave.MTU }}
+          env:
+            - name: WEAVE_MTU
+              value: "{{ .Networking.Weave.MTU }}"
+          {{end}}
         - name: weave-npc
           image: weaveworks/weave-npc:1.9.4
           resources:

upup/pkg/fi/cloudup/bootstrapchannelbuilder.go

@@ -241,7 +241,9 @@ func (b *BootstrapChannelBuilder) buildManifest() (*channelsapi.Addons, map[stri
 
 	if b.cluster.Spec.Networking.Weave != nil {
 		key := "networking.weave"
-		version := "1.9.4"
+
+		// 1.9.5-kops.1 = 1.9.4 with WEAVE_MTU configured
+		version := "1.9.5-kops.1"
 
 		{
 			location := key + "/pre-k8s-1.6.yaml"