libct/configs/validate: add IOPriority.Class validation

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

libcontainer/configs/validate/validator.go

@@ -406,5 +406,13 @@ func ioPriority(config *configs.Config) error {
 	if priority < 0 || priority > 7 {
 		return fmt.Errorf("invalid ioPriority.Priority: %d", priority)
 	}
+
+	switch class := config.IOPriority.Class; class {
+	case specs.IOPRIO_CLASS_RT, specs.IOPRIO_CLASS_BE, specs.IOPRIO_CLASS_IDLE:
+		// Valid class, do nothing.
+	default:
+		return fmt.Errorf("invalid ioPriority.Class: %q", class)
+	}
+
 	return nil
 }

libcontainer/configs/validate/validator_test.go

@@ -847,15 +847,21 @@ func TestValidateIOPriority(t *testing.T) {
 	testCases := []struct {
 		isErr    bool
 		priority int
+		class    specs.IOPriorityClass
 	}{
-		{isErr: false, priority: 0},
-		{isErr: false, priority: 7},
-		{isErr: true, priority: -1},
+		{isErr: false, priority: 0, class: specs.IOPRIO_CLASS_IDLE},
+		{isErr: false, priority: 7, class: specs.IOPRIO_CLASS_RT},
+		{isErr: false, priority: 3, class: specs.IOPRIO_CLASS_BE},
+		// Invalid priority.
+		{isErr: true, priority: -1, class: specs.IOPRIO_CLASS_BE},
+		// Invalid class.
+		{isErr: true, priority: 3, class: specs.IOPriorityClass("IOPRIO_CLASS_WOW")},
 	}
 
 	for _, tc := range testCases {
 		ioPriroty := configs.IOPriority{
 			Priority: tc.priority,
+			Class:    tc.class,
 		}
 		config := &configs.Config{
 			Rootfs:     "/var",