Merge pull request #42147 from bowei/ip-alias-2

Automatic merge from submit-queue

Add support for IP aliases for pod IPs (GCP alpha feature)

```release-note
Adds support for allocation of pod IPs via IP aliases.

# Adds KUBE_GCE_ENABLE_IP_ALIASES flag to the cluster up scripts (`kube-{up,down}.sh`).

KUBE_GCE_ENABLE_IP_ALIASES=true will enable allocation of PodCIDR ips
using the ip alias mechanism rather than using routes. This feature is currently
only available on GCE.

## Usage
$ CLUSTER_IP_RANGE=10.100.0.0/16 KUBE_GCE_ENABLE_IP_ALIASES=true bash -x cluster/kube-up.sh

# Adds CloudAllocator to the node CIDR allocator (kubernetes-controller manager).

If CIDRAllocatorType is set to `CloudCIDRAllocator`, then allocation
of CIDR allocation instead is done by the external cloud provider and
the node controller is only responsible for reflecting the allocation
into the node spec.

- Splits off the rangeAllocator from the cidr_allocator.go file.
- Adds cloudCIDRAllocator, which is used when the cloud provider allocates
  the CIDR ranges externally. (GCE support only)
- Updates RBAC permission for node controller to include PATCH
```

cluster/common.sh

@@ -723,6 +723,17 @@ EOF
 FEATURE_GATES: $(yaml-quote ${FEATURE_GATES})
 EOF
   fi
+
+  if [ -n "${PROVIDER_VARS:-}" ]; then
+    local var_name
+    local var_value
+
+    for var_name in ${PROVIDER_VARS}; do
+      eval "local var_value=\$(yaml-quote \${${var_name}})"
+      echo "${var_name}: ${var_value}" >>$file
+    done
+  fi
+
   if [[ "${master}" == "true" ]]; then
     # Master-only env vars.
     cat >>$file <<EOF