// Copyright (c) Tailscale Inc & contributors

// SPDX-License-Identifier: BSD-3-Clause

package netmon

import (

"errors"

"net"

"tailscale.com/syncs"

)

type ifProps struct {

mu syncs.Mutex

name string // interface name, if known/set

index int // interface index, if known/set

}

// tsIfProps tracks the properties (name and index) of the tailscale interface.

// There is only one tailscale interface per tailscaled instance.

var tsIfProps ifProps

func (p *ifProps) tsIfName() string {

p.mu.Lock()

defer p.mu.Unlock()

return p.name

}

func (p *ifProps) tsIfIndex() int {

p.mu.Lock()

defer p.mu.Unlock()

return p.index

}

func (p *ifProps) set(ifName string, ifIndex int) {

p.mu.Lock()

defer p.mu.Unlock()

p.name = ifName

p.index = ifIndex

}

// TODO (barnstar): This doesn't need the Monitor receiver anymore but we're

// keeping it for API compatibility to avoid a breaking change.  This can be

// removed when the various clients have switched to SetTailscaleInterfaceProps

func (m *Monitor) SetTailscaleInterfaceName(ifName string) {

SetTailscaleInterfaceProps(ifName, 0)

}

// SetTailscaleInterfaceProps sets the name of the Tailscale interface and

// its index for use by various listeners/dialers. If the index is zero,

// an attempt will be made to look it up by name. This makes no attempt

// to validate that the interface exists at the time of calling.

//

// If this method is called, it is the responsibility of the caller to

// update the interface name and index if they change.

//

// This should be called as early as possible during tailscaled startup.

func SetTailscaleInterfaceProps(ifName string, ifIndex int) {

if ifIndex != 0 {

tsIfProps.set(ifName, ifIndex)

return

}

ifaces, err := net.Interfaces()

if err != nil {

return

}

for _, iface := range ifaces {

if iface.Name == ifName {

ifIndex = iface.Index

break

}

}

tsIfProps.set(ifName, ifIndex)

}

// TailscaleInterfaceName returns the name of the Tailscale interface.

// For example, "tailscale0", "tun0", "utun3", etc or an error if unset.

//

// Callers must handle errors, as the Tailscale interface

// name may not be set in some environments.

func TailscaleInterfaceName() (string, error) {

name := tsIfProps.tsIfName()

if name == "" {

return "", errors.New("Tailscale interface name not set")

}

return name, nil

}

// TailscaleInterfaceIndex returns the index of the Tailscale interface or

// an error if unset.

//

// Callers must handle errors, as the Tailscale interface

// index may not be set in some environments.

func TailscaleInterfaceIndex() (int, error) {

index := tsIfProps.tsIfIndex()

if index == 0 {

return 0, errors.New("Tailscale interface index not set")

}

return index, nil

}