virtcontainers: Add support for ephemeral volumes

Ephemeral volumes should not be passed at 9pfs mounts.
They should be created inside the VM.

This patch disables ephemeral volumes from getting
mounted as 9pfs from the host and instead a corresponding
tmpfs is created inside the VM.

Fixes : #61

Signed-off-by: Harshal Patil <harshal.patil@in.ibm.com>

cli/utils.go

@@ -15,7 +15,10 @@ import (
 	"strings"
 )
 
-const unknown = "<<unknown>>"
+const (
+	unknown     = "<<unknown>>"
+	k8sEmptyDir = "kubernetes.io~empty-dir"
+)
 
 // variables to allow tests to modify the values
 var (
@@ -43,6 +46,26 @@ func getFileContents(file string) (string, error) {
 	return string(bytes), nil
 }
 
+// IsEphemeralStorage returns true if the given path
+// to the storage belongs to kubernetes ephemeral storage
+//
+// This method depends on a specific path used by k8s
+// to detect if it's of type ephemeral. As of now,
+// this is a very k8s specific solution that works
+// but in future there should be a better way for this
+// method to determine if the path is for ephemeral
+// volume type
+func IsEphemeralStorage(path string) bool {
+	splitSourceSlice := strings.Split(path, "/")
+	if len(splitSourceSlice) > 1 {
+		storageType := splitSourceSlice[len(splitSourceSlice)-2]
+		if storageType == k8sEmptyDir {
+			return true
+		}
+	}
+	return false
+}
+
 func getKernelVersion() (string, error) {
 	contents, err := getFileContents(procVersion)
 	if err != nil {