add vendor

vendor/golang.org/x/net/ipv6/helper.go

@@ -0,0 +1,39 @@
+// Copyright 2013 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.
+
+package ipv6
+
+import (
+	"errors"
+	"net"
+)
+
+var (
+	errMissingAddress  = errors.New("missing address")
+	errHeaderTooShort  = errors.New("header too short")
+	errInvalidConnType = errors.New("invalid conn type")
+	errOpNoSupport     = errors.New("operation not supported")
+	errNoSuchInterface = errors.New("no such interface")
+)
+
+func boolint(b bool) int {
+	if b {
+		return 1
+	}
+	return 0
+}
+
+func netAddrToIP16(a net.Addr) net.IP {
+	switch v := a.(type) {
+	case *net.UDPAddr:
+		if ip := v.IP.To16(); ip != nil && ip.To4() == nil {
+			return ip
+		}
+	case *net.IPAddr:
+		if ip := v.IP.To16(); ip != nil && ip.To4() == nil {
+			return ip
+		}
+	}
+	return nil
+}