103 lines
2.5 KiB
Go
103 lines
2.5 KiB
Go
// Copyright 2016 Google Inc. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package uuid
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import (
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"net"
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"sync"
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)
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var (
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nodeMu sync.Mutex
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interfaces []net.Interface // cached list of interfaces
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ifname string // name of interface being used
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nodeID [6]byte // hardware for version 1 UUIDs
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zeroID [6]byte // nodeID with only 0's
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)
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// NodeInterface returns the name of the interface from which the NodeID was
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// derived. The interface "user" is returned if the NodeID was set by
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// SetNodeID.
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func NodeInterface() string {
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defer nodeMu.Unlock()
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nodeMu.Lock()
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return ifname
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}
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// SetNodeInterface selects the hardware address to be used for Version 1 UUIDs.
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// If name is "" then the first usable interface found will be used or a random
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// Node ID will be generated. If a named interface cannot be found then false
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// is returned.
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//
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// SetNodeInterface never fails when name is "".
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func SetNodeInterface(name string) bool {
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defer nodeMu.Unlock()
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nodeMu.Lock()
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return setNodeInterface(name)
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}
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func setNodeInterface(name string) bool {
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if interfaces == nil {
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var err error
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interfaces, err = net.Interfaces()
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if err != nil && name != "" {
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return false
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}
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}
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for _, ifs := range interfaces {
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if len(ifs.HardwareAddr) >= 6 && (name == "" || name == ifs.Name) {
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copy(nodeID[:], ifs.HardwareAddr)
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ifname = ifs.Name
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return true
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}
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}
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// We found no interfaces with a valid hardware address. If name
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// does not specify a specific interface generate a random Node ID
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// (section 4.1.6)
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if name == "" {
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randomBits(nodeID[:])
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return true
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}
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return false
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}
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// NodeID returns a slice of a copy of the current Node ID, setting the Node ID
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// if not already set.
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func NodeID() []byte {
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defer nodeMu.Unlock()
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nodeMu.Lock()
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if nodeID == zeroID {
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setNodeInterface("")
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}
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nid := nodeID
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return nid[:]
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}
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// SetNodeID sets the Node ID to be used for Version 1 UUIDs. The first 6 bytes
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// of id are used. If id is less than 6 bytes then false is returned and the
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// Node ID is not set.
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func SetNodeID(id []byte) bool {
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if len(id) < 6 {
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return false
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}
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defer nodeMu.Unlock()
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nodeMu.Lock()
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copy(nodeID[:], id)
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ifname = "user"
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return true
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}
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// NodeID returns the 6 byte node id encoded in uuid. It returns nil if uuid is
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// not valid. The NodeID is only well defined for version 1 and 2 UUIDs.
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func (uuid UUID) NodeID() []byte {
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if len(uuid) != 16 {
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return nil
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}
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var node [6]byte
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copy(node[:], uuid[10:])
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return node[:]
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}
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