1// Copyright 2017 Google Inc.  All rights reserved.
 2// Use of this source code is governed by a BSD-style
 3// license that can be found in the LICENSE file.
 4
 5// +build !js
 6
 7package uuid
 8
 9import "net"
10
11var interfaces []net.Interface // cached list of interfaces
12
13// getHardwareInterface returns the name and hardware address of interface name.
14// If name is "" then the name and hardware address of one of the system's
15// interfaces is returned.  If no interfaces are found (name does not exist or
16// there are no interfaces) then "", nil is returned.
17//
18// Only addresses of at least 6 bytes are returned.
19func getHardwareInterface(name string) (string, []byte) {
20	if interfaces == nil {
21		var err error
22		interfaces, err = net.Interfaces()
23		if err != nil {
24			return "", nil
25		}
26	}
27	for _, ifs := range interfaces {
28		if len(ifs.HardwareAddr) >= 6 && (name == "" || name == ifs.Name) {
29			return ifs.Name, ifs.HardwareAddr
30		}
31	}
32	return "", nil
33}