virtcontainers: Use only supported namespaces

Depending of the linux versions some namespaces are supported or not.
To avoid failures running containers and unit tests in old linux kernels,
only the supported namespaces should be used.

Depends-on: github.com/kata-containers/tests#1414

fixes #228

Signed-off-by: Julio Montes <julio.montes@intel.com>

virtcontainers/pkg/nsenter/nsenter.go

@@ -49,13 +49,7 @@ const (
 
 // CloneFlagsTable is exported so that consumers of this package don't need
 // to define this same table again.
-var CloneFlagsTable = map[NSType]int{
-	NSTypeCGroup: unix.CLONE_NEWCGROUP,
-	NSTypeIPC:    unix.CLONE_NEWIPC,
-	NSTypeNet:    unix.CLONE_NEWNET,
-	NSTypePID:    unix.CLONE_NEWPID,
-	NSTypeUTS:    unix.CLONE_NEWUTS,
-}
+var CloneFlagsTable = make(map[NSType]int)
 
 // Namespace describes a namespace that will be entered.
 type Namespace struct {
@@ -69,6 +63,22 @@ type nsPair struct {
 	threadNS *os.File
 }
 
+func init() {
+	var ns = map[NSType]int{
+		NSTypeCGroup: unix.CLONE_NEWCGROUP,
+		NSTypeIPC:    unix.CLONE_NEWIPC,
+		NSTypeNet:    unix.CLONE_NEWNET,
+		NSTypePID:    unix.CLONE_NEWPID,
+		NSTypeUTS:    unix.CLONE_NEWUTS,
+	}
+
+	for k, v := range ns {
+		if _, err := os.Stat(fmt.Sprint("/proc/self/ns/", string(k))); err == nil {
+			CloneFlagsTable[k] = v
+		}
+	}
+}
+
 func getNSPathFromPID(pid int, nsType NSType) string {
 	return filepath.Join(procRootPath, strconv.Itoa(pid), nsDirPath, string(nsType))
 }

virtcontainers/pkg/nsenter/nsenter_test.go

@@ -138,30 +138,31 @@ func TestSetNSWrongFileFailure(t *testing.T) {
 	assert.NotNil(t, err, "Should fail because file is not a namespace")
 }
 
-var testNamespaceList = []Namespace{
-	{
-		Type: NSTypeCGroup,
-	},
-	{
-		Type: NSTypeIPC,
-	},
-	{
-		Type: NSTypeNet,
-	},
-	{
-		Type: NSTypePID,
-	},
-	{
-		Type: NSTypeUTS,
-	},
+func supportedNamespaces() []Namespace {
+	var list []Namespace
+	var ns = []Namespace{
+		{Type: NSTypeCGroup},
+		{Type: NSTypeIPC},
+		{Type: NSTypeNet},
+		{Type: NSTypePID},
+		{Type: NSTypeUTS},
+	}
+
+	for _, n := range ns {
+		if _, err := os.Stat(fmt.Sprint("/proc/self/ns/", string(n.Type))); err == nil {
+			list = append(list, n)
+		}
+	}
+
+	return list
 }
 
 func testToRunNil() error {
 	return nil
 }
 
 func TestNsEnterEmptyPathAndPIDFromNSListFailure(t *testing.T) {
-	err := NsEnter(testNamespaceList, testToRunNil)
+	err := NsEnter(supportedNamespaces(), testToRunNil)
 	assert.NotNil(t, err, "Should fail because neither a path nor a PID"+
 		" has been provided by every namespace of the list")
 }
@@ -172,7 +173,7 @@ func TestNsEnterEmptyNamespaceListSuccess(t *testing.T) {
 }
 
 func TestNsEnterSuccessful(t *testing.T) {
-	nsList := testNamespaceList
+	nsList := supportedNamespaces()
 	sleepDuration := 60
 
 	cloneFlags := 0