diff --git a/vendor/gopkg.in/jcmturner/rpc.v1/ndr/union.go b/vendor/gopkg.in/jcmturner/rpc.v1/ndr/union.go
new file mode 100644
index 0000000..6a657fa
--- /dev/null
+++ b/vendor/gopkg.in/jcmturner/rpc.v1/ndr/union.go
@@ -0,0 +1,57 @@
+package ndr
+
+import (
+	"errors"
+	"fmt"
+	"reflect"
+)
+
+// Union interface must be implemented by structs that will be unmarshaled into from the NDR byte stream union representation.
+// The union's discriminating tag will be passed to the SwitchFunc method.
+// The discriminating tag field must have the struct tag: `ndr:"unionTag"`
+// If the union is encapsulated the discriminating tag field must have the struct tag: `ndr:"encapsulated"`
+// The possible value fields that can be selected from must have the struct tag: `ndr:"unionField"`
+type Union interface {
+	SwitchFunc(t interface{}) string
+}
+
+// Union related constants such as struct tag values
+const (
+	unionSelectionFuncName = "SwitchFunc"
+	TagEncapsulated        = "encapsulated"
+	TagUnionTag            = "unionTag"
+	TagUnionField          = "unionField"
+)
+
+func (dec *Decoder) isUnion(field reflect.Value, tag reflect.StructTag) (r reflect.Value) {
+	ndrTag := parseTags(tag)
+	if !ndrTag.HasValue(TagUnionTag) {
+		return
+	}
+	r = field
+	// For a non-encapsulated union, the discriminant is marshalled into the transmitted data stream twice: once as the
+	// field or parameter, which is referenced by the switch_is construct, in the procedure argument list; and once as
+	// the first part of the union representation.
+	if !ndrTag.HasValue(TagEncapsulated) {
+		dec.r.Discard(int(r.Type().Size()))
+	}
+	return
+}
+
+// unionSelectedField returns the field name of which of the union values to fill
+func unionSelectedField(union, discriminant reflect.Value) (string, error) {
+	if !union.Type().Implements(reflect.TypeOf(new(Union)).Elem()) {
+		return "", errors.New("struct does not implement union interface")
+	}
+	args := []reflect.Value{discriminant}
+	// Call the SelectFunc of the union struct to find the name of the field to fill with the value selected.
+	sf := union.MethodByName(unionSelectionFuncName)
+	if !sf.IsValid() {
+		return "", fmt.Errorf("could not find a selection function called %s in the unions struct representation", unionSelectionFuncName)
+	}
+	f := sf.Call(args)
+	if f[0].Kind() != reflect.String || f[0].String() == "" {
+		return "", fmt.Errorf("the union select function did not return a string for the name of the field to fill")
+	}
+	return f[0].String(), nil
+}