Allow kubemark to use custom network for instance creation

cluster/kubemark/gce/config-default.sh

@@ -32,6 +32,7 @@ MASTER_ROOT_DISK_SIZE=${KUBEMARK_MASTER_ROOT_DISK_SIZE:-10GB}
 REGISTER_MASTER_KUBELET=${REGISTER_MASTER:-false}
 PREEMPTIBLE_NODE=${PREEMPTIBLE_NODE:-false}
 NODE_ACCELERATORS=${NODE_ACCELERATORS:-""}
+CREATE_CUSTOM_NETWORK=${CREATE_CUSTOM_NETWORK:-false}
 
 MASTER_OS_DISTRIBUTION=${KUBE_MASTER_OS_DISTRIBUTION:-gci}
 NODE_OS_DISTRIBUTION=${KUBE_NODE_OS_DISTRIBUTION:-gci}
@@ -44,6 +45,9 @@ if [[ "${NODE_OS_DISTRIBUTION}" == "debian" ]]; then
 fi
 
 NETWORK=${KUBE_GCE_NETWORK:-e2e}
+if [[ "${CREATE_CUSTOM_NETWORK}" == true ]]; then
+  SUBNETWORK="${SUBNETWORK:-${NETWORK}-custom-subnet}"
+fi
 INSTANCE_PREFIX="${INSTANCE_PREFIX:-"default"}"
 MASTER_NAME="${INSTANCE_PREFIX}-kubemark-master"
 AGGREGATOR_MASTER_NAME="${INSTANCE_PREFIX}-kubemark-aggregator"

test/kubemark/gce/util.sh

@@ -61,7 +61,7 @@ function create-master-instance-with-resources {
     --image-project="${MASTER_IMAGE_PROJECT}" \
     --image "${MASTER_IMAGE}" \
     --tags "${MASTER_TAG}" \
-    --subnet "${NETWORK}" \
+    --subnet "${SUBNETWORK:-${NETWORK}}" \
     --scopes "storage-ro,logging-write" \
     --boot-disk-size "${MASTER_ROOT_DISK_SIZE}" \
     --disk "name=${MASTER_NAME}-pd,device-name=master-pd,mode=rw,boot=no,auto-delete=no"