Merge pull request #28673 from cheld/add-cni-config

Automatic merge from submit-queue

add default flannel configuration for cni

I added a default flannel configuration for cni.

So hyperkube can be started with:
```
--network-plugin=kubenet
```
or with flannel:

```
--network-plugin=cni
--network-plugin-dir=/etc/cni/net.d
```

Requires update of cni binaries to 0.3.0 or later to work. See also https://github.com/kubernetes/kubernetes/issues/27603

This PR is intended to support multi-node Hyperkube 
https://github.com/kubernetes/kube-deploy/pull/115



CC @zreigz  

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cluster/images/hyperkube/Dockerfile

@@ -68,6 +68,9 @@ ADD https://storage.googleapis.com/kubernetes-release/easy-rsa/easy-rsa.tar.gz /
 # Copy the cni folder into /opt/
 COPY cni /opt/cni
 
+# Copy overlay configuration to default directory
+COPY cni-conf /etc/cni/net.d
+
 # Create symlinks for each hyperkube server
 # TODO: this is unreliable for now (e.g. running "/kubelet" panics)
 # Also, it doesn't work for other architectures

cluster/images/hyperkube/cni-conf/10-containernet.conf

@@ -0,0 +1,9 @@
+{
+  "name": "containernet",
+  "type": "flannel",
+  "delegate": {
+        "bridge": "cni0",
+        "mtu": 1450,
+        "isDefaultGateway": true
+    }
+}

cluster/images/hyperkube/cni-conf/99-loopback.conf

@@ -0,0 +1,3 @@
+{
+    "type": "loopback"
+}