diff --git a/unum/vendor/golang.org/x/net/internal/nettest/helper_bsd.go b/unum/vendor/golang.org/x/net/internal/nettest/helper_bsd.go
new file mode 100644
index 0000000..a6e433b
--- /dev/null
+++ b/unum/vendor/golang.org/x/net/internal/nettest/helper_bsd.go
@@ -0,0 +1,53 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd netbsd openbsd
+
+package nettest
+
+import (
+	"runtime"
+	"strconv"
+	"strings"
+	"syscall"
+)
+
+var darwinVersion int
+
+func init() {
+	if runtime.GOOS == "darwin" {
+		// See http://support.apple.com/kb/HT1633.
+		s, err := syscall.Sysctl("kern.osrelease")
+		if err != nil {
+			return
+		}
+		ss := strings.Split(s, ".")
+		if len(ss) == 0 {
+			return
+		}
+		darwinVersion, _ = strconv.Atoi(ss[0])
+	}
+}
+
+func supportsIPv6MulticastDeliveryOnLoopback() bool {
+	switch runtime.GOOS {
+	case "freebsd":
+		// See http://www.freebsd.org/cgi/query-pr.cgi?pr=180065.
+		// Even after the fix, it looks like the latest
+		// kernels don't deliver link-local scoped multicast
+		// packets correctly.
+		return false
+	case "darwin":
+		return !causesIPv6Crash()
+	default:
+		return true
+	}
+}
+
+func causesIPv6Crash() bool {
+	// We see some kernel crash when running IPv6 with IP-level
+	// options on Darwin kernel version 12 or below.
+	// See golang.org/issues/17015.
+	return darwinVersion < 13
+}