all: move network monitoring from wgengine/monitor to net/netmon

We're using it in more and more places, and it's not really specific to
our use of Wireguard (and does more just link/interface monitoring).

Also removes the separate interface we had for it in sockstats -- it's
a small enough package (we already pull in all of its dependencies
via other paths) that it's not worth the extra complexity.

Updates #7621
Updates #7850

Signed-off-by: Mihai Parparita <mihai@tailscale.com>

cmd/derper/depaware.txt

@@ -16,7 +16,7 @@ tailscale.com/cmd/derper dependencies: (generated by github.com/tailscale/depawa
         github.com/golang/protobuf/ptypes/timestamp                  from github.com/prometheus/client_model/go
         github.com/hdevalence/ed25519consensus                       from tailscale.com/tka
    L    github.com/josharian/native                                  from github.com/mdlayher/netlink+
-   L 💣 github.com/jsimonetti/rtnetlink                              from tailscale.com/net/interfaces
+   L 💣 github.com/jsimonetti/rtnetlink                              from tailscale.com/net/interfaces+
    L    github.com/jsimonetti/rtnetlink/internal/unix                from github.com/jsimonetti/rtnetlink
         github.com/klauspost/compress/flate                          from nhooyr.io/websocket
         github.com/matttproud/golang_protobuf_extensions/pbutil      from github.com/prometheus/common/expfmt
@@ -86,6 +86,7 @@ tailscale.com/cmd/derper dependencies: (generated by github.com/tailscale/depawa
      💣 tailscale.com/net/interfaces                                 from tailscale.com/net/netns+
         tailscale.com/net/netaddr                                    from tailscale.com/ipn+
         tailscale.com/net/netknob                                    from tailscale.com/net/netns
+        tailscale.com/net/netmon                                     from tailscale.com/net/sockstats
         tailscale.com/net/netns                                      from tailscale.com/derp/derphttp
         tailscale.com/net/netutil                                    from tailscale.com/client/tailscale
         tailscale.com/net/packet                                     from tailscale.com/wgengine/filter
@@ -129,7 +130,7 @@ tailscale.com/cmd/derper dependencies: (generated by github.com/tailscale/depawa
         tailscale.com/util/lineread                                  from tailscale.com/hostinfo+
         tailscale.com/util/mak                                       from tailscale.com/syncs+
         tailscale.com/util/multierr                                  from tailscale.com/health
-        tailscale.com/util/set                                       from tailscale.com/health
+        tailscale.com/util/set                                       from tailscale.com/health+
         tailscale.com/util/singleflight                              from tailscale.com/net/dnscache
         tailscale.com/util/slicesx                                   from tailscale.com/cmd/derper+
         tailscale.com/util/vizerror                                  from tailscale.com/tsweb

cmd/tailscale/depaware.txt

@@ -13,7 +13,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         github.com/google/uuid                                       from tailscale.com/util/quarantine+
         github.com/hdevalence/ed25519consensus                       from tailscale.com/tka
    L    github.com/josharian/native                                  from github.com/mdlayher/netlink+
-   L 💣 github.com/jsimonetti/rtnetlink                              from tailscale.com/net/interfaces
+   L 💣 github.com/jsimonetti/rtnetlink                              from tailscale.com/net/interfaces+
    L    github.com/jsimonetti/rtnetlink/internal/unix                from github.com/jsimonetti/rtnetlink
         github.com/kballard/go-shellquote                            from tailscale.com/cmd/tailscale/cli
         github.com/klauspost/compress/flate                          from nhooyr.io/websocket
@@ -74,6 +74,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         tailscale.com/net/netcheck                                   from tailscale.com/cmd/tailscale/cli
         tailscale.com/net/neterror                                   from tailscale.com/net/netcheck+
         tailscale.com/net/netknob                                    from tailscale.com/net/netns
+        tailscale.com/net/netmon                                     from tailscale.com/net/sockstats
         tailscale.com/net/netns                                      from tailscale.com/derp/derphttp+
         tailscale.com/net/netutil                                    from tailscale.com/client/tailscale+
         tailscale.com/net/packet                                     from tailscale.com/wgengine/filter+

cmd/tailscaled/debug.go

@@ -23,10 +23,10 @@
 	"tailscale.com/derp/derphttp"
 	"tailscale.com/ipn"
 	"tailscale.com/net/interfaces"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/tshttpproxy"
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/key"
-	"tailscale.com/wgengine/monitor"
 )
 
 var debugArgs struct {
@@ -42,7 +42,7 @@
 func debugMode(args []string) error {
 	fs := flag.NewFlagSet("debug", flag.ExitOnError)
 	fs.BoolVar(&debugArgs.ifconfig, "ifconfig", false, "If true, print network interface state")
-	fs.BoolVar(&debugArgs.monitor, "monitor", false, "If true, run link monitor forever. Precludes all other options.")
+	fs.BoolVar(&debugArgs.monitor, "monitor", false, "If true, run network monitor forever. Precludes all other options.")
 	fs.BoolVar(&debugArgs.portmap, "portmap", false, "If true, run portmap debugging. Precludes all other options.")
 	fs.StringVar(&debugArgs.getURL, "get-url", "", "If non-empty, fetch provided URL.")
 	fs.StringVar(&debugArgs.derpCheck, "derp", "", "if non-empty, test a DERP ping via named region code")
@@ -76,7 +76,7 @@ func runMonitor(ctx context.Context, loop bool) error {
 		j, _ := json.MarshalIndent(st, "", "    ")
 		os.Stderr.Write(j)
 	}
-	mon, err := monitor.New(log.Printf)
+	mon, err := netmon.New(log.Printf)
 	if err != nil {
 		return err
 	}
@@ -84,10 +84,10 @@ func runMonitor(ctx context.Context, loop bool) error {
 
 	mon.RegisterChangeCallback(func(changed bool, st *interfaces.State) {
 		if !changed {
-			log.Printf("Link monitor fired; no change")
+			log.Printf("Network monitor fired; no change")
 			return
 		}
-		log.Printf("Link monitor fired. New state:")
+		log.Printf("Network monitor fired. New state:")
 		dump(st)
 	})
 	if loop {

cmd/tailscaled/depaware.txt

@@ -240,6 +240,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/net/netcheck                                   from tailscale.com/wgengine/magicsock
         tailscale.com/net/neterror                                   from tailscale.com/net/dns/resolver+
         tailscale.com/net/netknob                                    from tailscale.com/net/netns+
+        tailscale.com/net/netmon                                     from tailscale.com/cmd/tailscaled+
         tailscale.com/net/netns                                      from tailscale.com/derp/derphttp+
      💣 tailscale.com/net/netstat                                    from tailscale.com/ipn/ipnauth+
         tailscale.com/net/netutil                                    from tailscale.com/ipn/ipnlocal+
@@ -324,7 +325,6 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/wgengine/capture                               from tailscale.com/ipn/ipnlocal+
         tailscale.com/wgengine/filter                                from tailscale.com/control/controlclient+
      💣 tailscale.com/wgengine/magicsock                             from tailscale.com/ipn/ipnlocal+
-        tailscale.com/wgengine/monitor                               from tailscale.com/control/controlclient+
         tailscale.com/wgengine/netlog                                from tailscale.com/wgengine
         tailscale.com/wgengine/netstack                              from tailscale.com/cmd/tailscaled
         tailscale.com/wgengine/router                                from tailscale.com/ipn/ipnlocal+

cmd/tailscaled/tailscaled.go

@@ -39,6 +39,7 @@
 	"tailscale.com/logtail"
 	"tailscale.com/net/dns"
 	"tailscale.com/net/dnsfallback"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/netns"
 	"tailscale.com/net/proxymux"
 	"tailscale.com/net/socks5"
@@ -59,7 +60,6 @@
 	"tailscale.com/version"
 	"tailscale.com/version/distro"
 	"tailscale.com/wgengine"
-	"tailscale.com/wgengine/monitor"
 	"tailscale.com/wgengine/netstack"
 	"tailscale.com/wgengine/router"
 )
@@ -451,18 +451,18 @@ func startIPNServer(ctx context.Context, logf logger.Logf, logID logid.PublicID)
 }
 
 func getLocalBackend(ctx context.Context, logf logger.Logf, logID logid.PublicID) (_ *ipnlocal.LocalBackend, retErr error) {
-	linkMon, err := monitor.New(logf)
+	netMon, err := netmon.New(logf)
 	if err != nil {
-		return nil, fmt.Errorf("monitor.New: %w", err)
+		return nil, fmt.Errorf("netmon.New: %w", err)
 	}
 	if logPol != nil {
-		logPol.Logtail.SetLinkMonitor(linkMon)
+		logPol.Logtail.SetNetMon(netMon)
 	}
 
 	socksListener, httpProxyListener := mustStartProxyListeners(args.socksAddr, args.httpProxyAddr)
 
 	dialer := &tsdial.Dialer{Logf: logf} // mutated below (before used)
-	e, onlyNetstack, err := createEngine(logf, linkMon, dialer)
+	e, onlyNetstack, err := createEngine(logf, netMon, dialer)
 	if err != nil {
 		return nil, fmt.Errorf("createEngine: %w", err)
 	}
@@ -551,14 +551,14 @@ func getLocalBackend(ctx context.Context, logf logger.Logf, logID logid.PublicID
 //
 // onlyNetstack is true if the user has explicitly requested that we use netstack
 // for all networking.
-func createEngine(logf logger.Logf, linkMon *monitor.Mon, dialer *tsdial.Dialer) (e wgengine.Engine, onlyNetstack bool, err error) {
+func createEngine(logf logger.Logf, netMon *netmon.Monitor, dialer *tsdial.Dialer) (e wgengine.Engine, onlyNetstack bool, err error) {
 	if args.tunname == "" {
 		return nil, false, errors.New("no --tun value specified")
 	}
 	var errs []error
 	for _, name := range strings.Split(args.tunname, ",") {
 		logf("wgengine.NewUserspaceEngine(tun %q) ...", name)
-		e, onlyNetstack, err = tryEngine(logf, linkMon, dialer, name)
+		e, onlyNetstack, err = tryEngine(logf, netMon, dialer, name)
 		if err == nil {
 			return e, onlyNetstack, nil
 		}
@@ -590,10 +590,10 @@ func handleSubnetsInNetstack() bool {
 
 var tstunNew = tstun.New
 
-func tryEngine(logf logger.Logf, linkMon *monitor.Mon, dialer *tsdial.Dialer, name string) (e wgengine.Engine, onlyNetstack bool, err error) {
+func tryEngine(logf logger.Logf, netMon *netmon.Monitor, dialer *tsdial.Dialer, name string) (e wgengine.Engine, onlyNetstack bool, err error) {
 	conf := wgengine.Config{
 		ListenPort: args.port,
-		LinkMonitor: linkMon,
+		NetMon:     netMon,
 		Dialer:     dialer,
 	}
 
@@ -633,7 +633,7 @@ func tryEngine(logf logger.Logf, linkMon *monitor.Mon, dialer *tsdial.Dialer, na
 			return e, false, err
 		}
 
-		r, err := router.New(logf, dev, linkMon)
+		r, err := router.New(logf, dev, netMon)
 		if err != nil {
 			dev.Close()
 			return nil, false, fmt.Errorf("creating router: %w", err)

control/controlclient/direct.go

@@ -37,6 +37,7 @@
 	"tailscale.com/net/dnscache"
 	"tailscale.com/net/dnsfallback"
 	"tailscale.com/net/interfaces"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/netutil"
 	"tailscale.com/net/tlsdial"
 	"tailscale.com/net/tsdial"
@@ -54,7 +55,6 @@
 	"tailscale.com/util/multierr"
 	"tailscale.com/util/singleflight"
 	"tailscale.com/util/systemd"
-	"tailscale.com/wgengine/monitor"
 )
 
 // Direct is the client that connects to a tailcontrol server for a node.
@@ -67,7 +67,7 @@ type Direct struct {
 	newDecompressor        func() (Decompressor, error)
 	keepAlive              bool
 	logf                   logger.Logf
-	linkMon                *monitor.Mon // or nil
+	netMon                 *netmon.Monitor // or nil
 	discoPubKey            key.DiscoPublic
 	getMachinePrivKey      func() (key.MachinePrivate, error)
 	debugFlags             []string
@@ -113,7 +113,7 @@ type Options struct {
 	HTTPTestClient       *http.Client                 // optional HTTP client to use (for tests only)
 	NoiseTestClient      *http.Client                 // optional HTTP client to use for noise RPCs (tests only)
 	DebugFlags           []string                     // debug settings to send to control
-	LinkMonitor          *monitor.Mon                 // optional link monitor
+	NetMon               *netmon.Monitor              // optional network monitor
 	PopBrowserURL        func(url string)             // optional func to open browser
 	OnClientVersion      func(*tailcfg.ClientVersion) // optional func to inform GUI of client version status
 	OnControlTime        func(time.Time)              // optional func to notify callers of new time from control
@@ -241,7 +241,7 @@ func NewDirect(opts Options) (*Direct, error) {
 		discoPubKey:            opts.DiscoPublicKey,
 		debugFlags:             opts.DebugFlags,
 		keepSharerAndUserSplit: opts.KeepSharerAndUserSplit,
-		linkMon:                opts.LinkMonitor,
+		netMon:                 opts.NetMon,
 		skipIPForwardingCheck:  opts.SkipIPForwardingCheck,
 		pinger:                 opts.Pinger,
 		popBrowser:             opts.PopBrowserURL,
@@ -871,8 +871,8 @@ func (c *Direct) sendMapRequest(ctx context.Context, maxPolls int, readOnly bool
 		ReadOnly: readOnly && !allowStream,
 	}
 	var extraDebugFlags []string
-	if hi != nil && c.linkMon != nil && !c.skipIPForwardingCheck &&
+	if hi != nil && c.netMon != nil && !c.skipIPForwardingCheck &&
-		ipForwardingBroken(hi.RoutableIPs, c.linkMon.InterfaceState()) {
+		ipForwardingBroken(hi.RoutableIPs, c.netMon.InterfaceState()) {
 		extraDebugFlags = append(extraDebugFlags, "warn-ip-forwarding-off")
 	}
 	if health.RouterHealth() != nil {

ipn/ipnlocal/local.go

@@ -142,7 +142,7 @@ type LocalBackend struct {
 	store                 ipn.StateStore
 	dialer                *tsdial.Dialer // non-nil
 	backendLogID          logid.PublicID
-	unregisterLinkMon     func()
+	unregisterNetMon      func()
 	unregisterHealthWatch func()
 	portpoll              *portlist.Poller // may be nil
 	portpollOnce          sync.Once        // guards starting readPoller
@@ -330,12 +330,12 @@ func NewLocalBackend(logf logger.Logf, logID logid.PublicID, store ipn.StateStor
 	b.statusChanged = sync.NewCond(&b.statusLock)
 	b.e.SetStatusCallback(b.setWgengineStatus)
 
-	linkMon := e.GetLinkMonitor()
+	netMon := e.GetNetMon()
-	b.prevIfState = linkMon.InterfaceState()
+	b.prevIfState = netMon.InterfaceState()
 	// Call our linkChange code once with the current state, and
 	// then also whenever it changes:
-	b.linkChange(false, linkMon.InterfaceState())
+	b.linkChange(false, netMon.InterfaceState())
-	b.unregisterLinkMon = linkMon.RegisterChangeCallback(b.linkChange)
+	b.unregisterNetMon = netMon.RegisterChangeCallback(b.linkChange)
 
 	b.unregisterHealthWatch = health.RegisterWatcher(b.onHealthChange)
 
@@ -499,7 +499,7 @@ func (b *LocalBackend) maybePauseControlClientLocked() {
 	b.cc.SetPaused((b.state == ipn.Stopped && b.netMap != nil) || !networkUp)
 }
 
-// linkChange is our link monitor callback, called whenever the network changes.
+// linkChange is our network monitor callback, called whenever the network changes.
 // major is whether ifst is different than earlier.
 func (b *LocalBackend) linkChange(major bool, ifst *interfaces.State) {
 	b.mu.Lock()
@@ -576,7 +576,7 @@ func (b *LocalBackend) Shutdown() {
 		b.sockstatLogger.Shutdown()
 	}
 
-	b.unregisterLinkMon()
+	b.unregisterNetMon()
 	b.unregisterHealthWatch()
 	if cc != nil {
 		cc.Shutdown()
@@ -1423,7 +1423,7 @@ func (b *LocalBackend) Start(opts ipn.Options) error {
 		HTTPTestClient:       httpTestClient,
 		DiscoPublicKey:       discoPublic,
 		DebugFlags:           debugFlags,
-		LinkMonitor:          b.e.GetLinkMonitor(),
+		NetMon:               b.e.GetNetMon(),
 		Pinger:               b,
 		PopBrowserURL:        b.tellClientToBrowseToURL,
 		OnClientVersion:      b.onClientVersion,

ipn/ipnlocal/serve.go

@@ -143,7 +143,7 @@ func (s *serveListener) Run() {
 }
 
 func (s *serveListener) shouldWarnAboutListenError(err error) bool {
-	if !s.b.e.GetLinkMonitor().InterfaceState().HasIP(s.ap.Addr()) {
+	if !s.b.e.GetNetMon().InterfaceState().HasIP(s.ap.Addr()) {
 		// Machine likely doesn't have IPv6 enabled (or the IP is still being
 		// assigned). No need to warn. Notably, WSL2 (Issue 6303).
 		return false

ipn/localapi/localapi.go

@@ -34,6 +34,7 @@
 	"tailscale.com/ipn/ipnlocal"
 	"tailscale.com/ipn/ipnstate"
 	"tailscale.com/logtail"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/netutil"
 	"tailscale.com/net/portmapper"
 	"tailscale.com/tailcfg"
@@ -46,7 +47,6 @@
 	"tailscale.com/util/httpm"
 	"tailscale.com/util/mak"
 	"tailscale.com/version"
-	"tailscale.com/wgengine/monitor"
 )
 
 type localAPIHandler func(*Handler, http.ResponseWriter, *http.Request)
@@ -695,7 +695,7 @@ func (h *Handler) serveDebugPortmap(w http.ResponseWriter, r *http.Request) {
 	})
 	defer c.Close()
 
-	linkMon, err := monitor.New(logger.WithPrefix(logf, "monitor: "))
+	netMon, err := netmon.New(logger.WithPrefix(logf, "monitor: "))
 	if err != nil {
 		logf("error creating monitor: %v", err)
 		return
@@ -707,14 +707,14 @@ func (h *Handler) serveDebugPortmap(w http.ResponseWriter, r *http.Request) {
 			self = netip.MustParseAddr(b)
 			return gw, self, true
 		}
-		return linkMon.GatewayAndSelfIP()
+		return netMon.GatewayAndSelfIP()
 	}
 
 	c.SetGatewayLookupFunc(gatewayAndSelfIP)
 
 	gw, selfIP, ok := gatewayAndSelfIP()
 	if !ok {
-		logf("no gateway or self IP; %v", linkMon.InterfaceState())
+		logf("no gateway or self IP; %v", netMon.InterfaceState())
 		return
 	}
 	logf("gw=%v; self=%v", gw, selfIP)

logtail/logtail.go

@@ -24,11 +24,11 @@
 	"tailscale.com/envknob"
 	"tailscale.com/logtail/backoff"
 	"tailscale.com/net/interfaces"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/sockstats"
 	tslogger "tailscale.com/types/logger"
 	"tailscale.com/types/logid"
 	"tailscale.com/util/set"
-	"tailscale.com/wgengine/monitor"
 )
 
 // DefaultHost is the default host name to upload logs to when
@@ -179,7 +179,7 @@ type Logger struct {
 	url            string
 	lowMem         bool
 	skipClientTime bool
-	linkMonitor    *monitor.Mon
+	netMonitor     *netmon.Monitor
 	buffer         Buffer
 	drainWake      chan struct{}        // signal to speed up drain
 	flushDelayFn   func() time.Duration // negative or zero return value to upload aggressively, or >0 to batch at this delay
@@ -214,12 +214,12 @@ func (l *Logger) SetVerbosityLevel(level int) {
 	atomic.StoreInt64(&l.stderrLevel, int64(level))
 }
 
-// SetLinkMonitor sets the optional the link monitor.
+// SetNetMon sets the optional the network monitor.
 //
 // It should not be changed concurrently with log writes and should
 // only be set once.
-func (l *Logger) SetLinkMonitor(lm *monitor.Mon) {
+func (l *Logger) SetNetMon(lm *netmon.Monitor) {
-	l.linkMonitor = lm
+	l.netMonitor = lm
 }
 
 // SetSockstatsLabel sets the label used in sockstat logs to identify network traffic from this logger.
@@ -403,16 +403,16 @@ func (l *Logger) uploading(ctx context.Context) {
 }
 
 func (l *Logger) internetUp() bool {
-	if l.linkMonitor == nil {
+	if l.netMonitor == nil {
 		// No way to tell, so assume it is.
 		return true
 	}
-	return l.linkMonitor.InterfaceState().AnyInterfaceUp()
+	return l.netMonitor.InterfaceState().AnyInterfaceUp()
 }
 
 func (l *Logger) awaitInternetUp(ctx context.Context) {
 	upc := make(chan bool, 1)
-	defer l.linkMonitor.RegisterChangeCallback(func(changed bool, st *interfaces.State) {
+	defer l.netMonitor.RegisterChangeCallback(func(changed bool, st *interfaces.State) {
 		if st.AnyInterfaceUp() {
 			select {
 			case upc <- true:

net/dns/manager.go

@@ -18,12 +18,12 @@
 	"golang.org/x/exp/slices"
 	"tailscale.com/health"
 	"tailscale.com/net/dns/resolver"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/tsdial"
 	"tailscale.com/types/dnstype"
 	"tailscale.com/types/logger"
 	"tailscale.com/util/clientmetric"
 	"tailscale.com/util/dnsname"
-	"tailscale.com/wgengine/monitor"
 )
 
 var (
@@ -64,14 +64,14 @@ type Manager struct {
 }
 
 // NewManagers created a new manager from the given config.
-func NewManager(logf logger.Logf, oscfg OSConfigurator, linkMon *monitor.Mon, dialer *tsdial.Dialer, linkSel resolver.ForwardLinkSelector) *Manager {
+func NewManager(logf logger.Logf, oscfg OSConfigurator, netMon *netmon.Monitor, dialer *tsdial.Dialer, linkSel resolver.ForwardLinkSelector) *Manager {
 	if dialer == nil {
 		panic("nil Dialer")
 	}
 	logf = logger.WithPrefix(logf, "dns: ")
 	m := &Manager{
 		logf:     logf,
-		resolver: resolver.New(logf, linkMon, linkSel, dialer),
+		resolver: resolver.New(logf, netMon, linkSel, dialer),
 		os:       oscfg,
 	}
 	m.ctx, m.ctxCancel = context.WithCancel(context.Background())

net/dns/resolver/forwarder.go

@@ -25,6 +25,7 @@
 	"tailscale.com/net/dns/publicdns"
 	"tailscale.com/net/dnscache"
 	"tailscale.com/net/neterror"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/netns"
 	"tailscale.com/net/sockstats"
 	"tailscale.com/net/tsdial"
@@ -34,7 +35,6 @@
 	"tailscale.com/util/cloudenv"
 	"tailscale.com/util/dnsname"
 	"tailscale.com/version"
-	"tailscale.com/wgengine/monitor"
 )
 
 // headerBytes is the number of bytes in a DNS message header.
@@ -176,7 +176,7 @@ type resolverAndDelay struct {
 // forwarder forwards DNS packets to a number of upstream nameservers.
 type forwarder struct {
 	logf    logger.Logf
-	linkMon *monitor.Mon
+	netMon  *netmon.Monitor
 	linkSel ForwardLinkSelector // TODO(bradfitz): remove this when tsdial.Dialer absorbs it
 	dialer  *tsdial.Dialer
 
@@ -206,10 +206,10 @@ func init() {
 	rand.Seed(time.Now().UnixNano())
 }
 
-func newForwarder(logf logger.Logf, linkMon *monitor.Mon, linkSel ForwardLinkSelector, dialer *tsdial.Dialer) *forwarder {
+func newForwarder(logf logger.Logf, netMon *netmon.Monitor, linkSel ForwardLinkSelector, dialer *tsdial.Dialer) *forwarder {
 	f := &forwarder{
 		logf:    logger.WithPrefix(logf, "forward: "),
-		linkMon: linkMon,
+		netMon:  netMon,
 		linkSel: linkSel,
 		dialer:  dialer,
 	}
@@ -355,7 +355,7 @@ func (f *forwarder) packetListener(ip netip.Addr) (nettype.PacketListenerWithNet
 		return stdNetPacketListener, nil
 	}
 	lc := new(net.ListenConfig)
-	if err := initListenConfig(lc, f.linkMon, linkName); err != nil {
+	if err := initListenConfig(lc, f.netMon, linkName); err != nil {
 		return nil, err
 	}
 	return nettype.MakePacketListenerWithNetIP(lc), nil
@@ -763,7 +763,7 @@ func (f *forwarder) forwardWithDestChan(ctx context.Context, query packet, respo
 	}
 }
 
-var initListenConfig func(_ *net.ListenConfig, _ *monitor.Mon, tunName string) error
+var initListenConfig func(_ *net.ListenConfig, _ *netmon.Monitor, tunName string) error
 
 // nameFromQuery extracts the normalized query name from bs.
 func nameFromQuery(bs []byte) (dnsname.FQDN, error) {

net/dns/resolver/macios_ext.go

@@ -9,15 +9,15 @@
 	"errors"
 	"net"
 
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/netns"
-	"tailscale.com/wgengine/monitor"
 )
 
 func init() {
 	initListenConfig = initListenConfigNetworkExtension
 }
 
-func initListenConfigNetworkExtension(nc *net.ListenConfig, mon *monitor.Mon, tunName string) error {
+func initListenConfigNetworkExtension(nc *net.ListenConfig, mon *netmon.Monitor, tunName string) error {
 	nif, ok := mon.InterfaceState().Interface[tunName]
 	if !ok {
 		return errors.New("utun not found")

net/dns/resolver/tsdns.go

@@ -26,6 +26,7 @@
 	"tailscale.com/envknob"
 	"tailscale.com/net/dns/resolvconffile"
 	"tailscale.com/net/netaddr"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/tsaddr"
 	"tailscale.com/net/tsdial"
 	"tailscale.com/syncs"
@@ -34,7 +35,6 @@
 	"tailscale.com/util/clientmetric"
 	"tailscale.com/util/cloudenv"
 	"tailscale.com/util/dnsname"
-	"tailscale.com/wgengine/monitor"
 )
 
 const dnsSymbolicFQDN = "magicdns.localhost-tailscale-daemon."
@@ -179,7 +179,7 @@ func WriteRoutes(w *bufio.Writer, routes map[dnsname.FQDN][]*dnstype.Resolver) {
 // it delegates to upstream nameservers if any are set.
 type Resolver struct {
 	logf               logger.Logf
-	linkMon            *monitor.Mon     // or nil
+	netMon             *netmon.Monitor  // or nil
 	dialer             *tsdial.Dialer   // non-nil
 	saveConfigForTests func(cfg Config) // used in tests to capture resolver config
 	// forwarder forwards requests to upstream nameservers.
@@ -205,20 +205,20 @@ type ForwardLinkSelector interface {
 }
 
 // New returns a new resolver.
-// linkMon optionally specifies a link monitor to use for socket rebinding.
+// netMon optionally specifies a network monitor to use for socket rebinding.
-func New(logf logger.Logf, linkMon *monitor.Mon, linkSel ForwardLinkSelector, dialer *tsdial.Dialer) *Resolver {
+func New(logf logger.Logf, netMon *netmon.Monitor, linkSel ForwardLinkSelector, dialer *tsdial.Dialer) *Resolver {
 	if dialer == nil {
 		panic("nil Dialer")
 	}
 	r := &Resolver{
 		logf:     logger.WithPrefix(logf, "resolver: "),
-		linkMon:  linkMon,
+		netMon:   netMon,
 		closed:   make(chan struct{}),
 		hostToIP: map[dnsname.FQDN][]netip.Addr{},
 		ipToHost: map[netip.Addr]dnsname.FQDN{},
 		dialer:   dialer,
 	}
-	r.forwarder = newForwarder(r.logf, linkMon, linkSel, dialer)
+	r.forwarder = newForwarder(r.logf, netMon, linkSel, dialer)
 	return r
 }
 

net/dns/resolver/tsdns_test.go

@@ -24,11 +24,11 @@
 	miekdns "github.com/miekg/dns"
 	dns "golang.org/x/net/dns/dnsmessage"
 	"tailscale.com/net/netaddr"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/tsdial"
 	"tailscale.com/tstest"
 	"tailscale.com/types/dnstype"
 	"tailscale.com/util/dnsname"
-	"tailscale.com/wgengine/monitor"
 )
 
 var (
@@ -315,7 +315,7 @@ func TestRDNSNameToIPv6(t *testing.T) {
 }
 
 func newResolver(t testing.TB) *Resolver {
-	return New(t.Logf, nil /* no link monitor */, nil /* no link selector */, new(tsdial.Dialer))
+	return New(t.Logf, nil /* no network monitor */, nil /* no link selector */, new(tsdial.Dialer))
 }
 
 func TestResolveLocal(t *testing.T) {
@@ -997,7 +997,7 @@ func TestMarshalResponseFormatError(t *testing.T) {
 
 func TestForwardLinkSelection(t *testing.T) {
 	configCall := make(chan string, 1)
-	tstest.Replace(t, &initListenConfig, func(nc *net.ListenConfig, mon *monitor.Mon, tunName string) error {
+	tstest.Replace(t, &initListenConfig, func(nc *net.ListenConfig, mon *netmon.Monitor, tunName string) error {
 		select {
 		case configCall <- tunName:
 			return nil

net/interfaces/interfaces.go

@@ -351,12 +351,6 @@ func (s *State) String() string {
 	return sb.String()
 }
 
-// ChangeFunc is a callback function (usually registered with
-// wgengine/monitor's Mon) that's called when the network
-// changed. The changed parameter is whether the network changed
-// enough for State to have changed since the last callback.
-type ChangeFunc func(changed bool, state *State)
-
 // An InterfaceFilter indicates whether EqualFiltered should use i when deciding whether two States are equal.
 // ips are all the IPPrefixes associated with i.
 type InterfaceFilter func(i Interface, ips []netip.Prefix) bool

net/interfaces/interfaces_linux.go

@@ -167,8 +167,8 @@ func defaultRoute() (d DefaultRouteDetails, err error) {
 	// /proc/net/route. Use netlink to find the default route.
 	//
 	// TODO(bradfitz): this allocates a fair bit. We should track
-	// this in wgengine/monitor instead and have
+	// this in net/interfaces/monitor instead and have
-	// interfaces.GetState take a link monitor or similar so the
+	// interfaces.GetState take a netmon.Monitor or similar so the
 	// routing table can be cached and the monitor's existing
 	// subscription to route changes can update the cached state,
 	// rather than querying the whole thing every time like

net/netmon/netmon.go

@@ -4,7 +4,7 @@
 // Package monitor provides facilities for monitoring network
 // interface and route changes. It primarily exists to know when
 // portable devices move between different networks.
-package monitor
+package netmon
 
 import (
 	"encoding/json"
@@ -48,15 +48,15 @@ type osMon interface {
 	IsInterestingInterface(iface string) bool
 }
 
-// Mon represents a monitoring instance.
+// Monitor represents a monitoring instance.
-type Mon struct {
+type Monitor struct {
 	logf   logger.Logf
 	om     osMon // nil means not supported on this platform
 	change chan struct{}
 	stop   chan struct{} // closed on Stop
 
 	mu         sync.Mutex // guards all following fields
-	cbs        set.HandleSet[interfaces.ChangeFunc]
+	cbs        set.HandleSet[ChangeFunc]
 	ruleDelCB  set.HandleSet[RuleDeleteCallback]
 	ifState    *interfaces.State
 	gwValid    bool       // whether gw and gwSelfIP are valid
@@ -70,12 +70,17 @@ type Mon struct {
 	timeJumped bool // whether we need to send a changed=true after a big time jump
 }
 
+// ChangeFunc is a callback function registered with Monitor that's called when the
+// network changed. The changed parameter is whether the network changed
+// enough for State to have changed since the last callback.
+type ChangeFunc func(changed bool, state *interfaces.State)
+
 // New instantiates and starts a monitoring instance.
 // The returned monitor is inactive until it's started by the Start method.
 // Use RegisterChangeCallback to get notified of network changes.
-func New(logf logger.Logf) (*Mon, error) {
+func New(logf logger.Logf) (*Monitor, error) {
 	logf = logger.WithPrefix(logf, "monitor: ")
-	m := &Mon{
+	m := &Monitor{
 		logf:     logf,
 		change:   make(chan struct{}, 1),
 		stop:     make(chan struct{}),
@@ -102,13 +107,13 @@ func New(logf logger.Logf) (*Mon, error) {
 // interfaces.
 //
 // The returned value is owned by Mon; it must not be modified.
-func (m *Mon) InterfaceState() *interfaces.State {
+func (m *Monitor) InterfaceState() *interfaces.State {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 	return m.ifState
 }
 
-func (m *Mon) interfaceStateUncached() (*interfaces.State, error) {
+func (m *Monitor) interfaceStateUncached() (*interfaces.State, error) {
 	return interfaces.GetState()
 }
 
@@ -117,7 +122,7 @@ func (m *Mon) interfaceStateUncached() (*interfaces.State, error) {
 //
 // It's the same as interfaces.LikelyHomeRouterIP, but it caches the
 // result until the monitor detects a network change.
-func (m *Mon) GatewayAndSelfIP() (gw, myIP netip.Addr, ok bool) {
+func (m *Monitor) GatewayAndSelfIP() (gw, myIP netip.Addr, ok bool) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 	if m.gwValid {
@@ -133,7 +138,7 @@ func (m *Mon) GatewayAndSelfIP() (gw, myIP netip.Addr, ok bool) {
 // RegisterChangeCallback adds callback to the set of parties to be
 // notified (in their own goroutine) when the network state changes.
 // To remove this callback, call unregister (or close the monitor).
-func (m *Mon) RegisterChangeCallback(callback interfaces.ChangeFunc) (unregister func()) {
+func (m *Monitor) RegisterChangeCallback(callback ChangeFunc) (unregister func()) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 	handle := m.cbs.Add(callback)
@@ -153,7 +158,7 @@ func (m *Mon) RegisterChangeCallback(callback interfaces.ChangeFunc) (unregister
 // RegisterRuleDeleteCallback adds callback to the set of parties to be
 // notified (in their own goroutine) when a Linux ip rule is deleted.
 // To remove this callback, call unregister (or close the monitor).
-func (m *Mon) RegisterRuleDeleteCallback(callback RuleDeleteCallback) (unregister func()) {
+func (m *Monitor) RegisterRuleDeleteCallback(callback RuleDeleteCallback) (unregister func()) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 	handle := m.ruleDelCB.Add(callback)
@@ -166,7 +171,7 @@ func (m *Mon) RegisterRuleDeleteCallback(callback RuleDeleteCallback) (unregiste
 
 // Start starts the monitor.
 // A monitor can only be started & closed once.
-func (m *Mon) Start() {
+func (m *Monitor) Start() {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 	if m.started || m.closed {
@@ -187,7 +192,7 @@ func (m *Mon) Start() {
 }
 
 // Close closes the monitor.
-func (m *Mon) Close() error {
+func (m *Monitor) Close() error {
 	m.mu.Lock()
 	if m.closed {
 		m.mu.Unlock()
@@ -218,7 +223,7 @@ func (m *Mon) Close() error {
 // change and re-check the state of the network. Any registered
 // ChangeFunc callbacks will be called within the event coalescing
 // period (under a fraction of a second).
-func (m *Mon) InjectEvent() {
+func (m *Monitor) InjectEvent() {
 	select {
 	case m.change <- struct{}{}:
 	default:
@@ -228,7 +233,7 @@ func (m *Mon) InjectEvent() {
 	}
 }
 
-func (m *Mon) stopped() bool {
+func (m *Monitor) stopped() bool {
 	select {
 	case <-m.stop:
 		return true
@@ -239,7 +244,7 @@ func (m *Mon) stopped() bool {
 
 // pump continuously retrieves messages from the connection, notifying
 // the change channel of changes, and stopping when a stop is issued.
-func (m *Mon) pump() {
+func (m *Monitor) pump() {
 	defer m.goroutines.Done()
 	for !m.stopped() {
 		msg, err := m.om.Receive()
@@ -263,7 +268,7 @@ func (m *Mon) pump() {
 	}
 }
 
-func (m *Mon) notifyRuleDeleted(rdm ipRuleDeletedMessage) {
+func (m *Monitor) notifyRuleDeleted(rdm ipRuleDeletedMessage) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 	for _, cb := range m.ruleDelCB {
@@ -274,13 +279,13 @@ func (m *Mon) notifyRuleDeleted(rdm ipRuleDeletedMessage) {
 // isInterestingInterface reports whether the provided interface should be
 // considered when checking for network state changes.
 // The ips parameter should be the IPs of the provided interface.
-func (m *Mon) isInterestingInterface(i interfaces.Interface, ips []netip.Prefix) bool {
+func (m *Monitor) isInterestingInterface(i interfaces.Interface, ips []netip.Prefix) bool {
 	return m.om.IsInterestingInterface(i.Name) && interfaces.UseInterestingInterfaces(i, ips)
 }
 
 // debounce calls the callback function with a delay between events
 // and exits when a stop is issued.
-func (m *Mon) debounce() {
+func (m *Monitor) debounce() {
 	defer m.goroutines.Done()
 	for {
 		select {
@@ -343,7 +348,7 @@ func wallTime() time.Time {
 	return time.Now().Round(0)
 }
 
-func (m *Mon) pollWallTime() {
+func (m *Monitor) pollWallTime() {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 	if m.closed {
@@ -365,7 +370,7 @@ func (m *Mon) pollWallTime() {
 // checkWallTimeAdvanceLocked reports whether wall time jumped more than 150% of
 // pollWallTimeInterval, indicating we probably just came out of sleep. Once a
 // time jump is detected it must be reset by calling resetTimeJumpedLocked.
-func (m *Mon) checkWallTimeAdvanceLocked() bool {
+func (m *Monitor) checkWallTimeAdvanceLocked() bool {
 	if !shouldMonitorTimeJump {
 		panic("unreachable") // if callers are correct
 	}
@@ -378,7 +383,7 @@ func (m *Mon) checkWallTimeAdvanceLocked() bool {
 }
 
 // resetTimeJumpedLocked consumes the signal set by checkWallTimeAdvanceLocked.
-func (m *Mon) resetTimeJumpedLocked() {
+func (m *Monitor) resetTimeJumpedLocked() {
 	m.timeJumped = false
 }
 

net/netmon/netmon_darwin.go

@@ -1,7 +1,7 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
-package monitor
+package netmon
 
 import (
 	"fmt"
@@ -24,7 +24,7 @@ type unspecifiedMessage struct{
 
 func (unspecifiedMessage) ignore() bool { return false }
 
-func newOSMon(logf logger.Logf, _ *Mon) (osMon, error) {
+func newOSMon(logf logger.Logf, _ *Monitor) (osMon, error) {
 	fd, err := unix.Socket(unix.AF_ROUTE, unix.SOCK_RAW, 0)
 	if err != nil {
 		return nil, err

net/netmon/netmon_darwin_test.go

@@ -1,7 +1,7 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
-package monitor
+package netmon
 
 import (
 	"encoding/hex"

net/netmon/netmon_freebsd.go

@@ -1,7 +1,7 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
-package monitor
+package netmon
 
 import (
 	"bufio"
@@ -24,7 +24,7 @@ type devdConn struct {
 	conn net.Conn
 }
 
-func newOSMon(logf logger.Logf, m *Mon) (osMon, error) {
+func newOSMon(logf logger.Logf, m *Monitor) (osMon, error) {
 	conn, err := net.Dial("unixpacket", "/var/run/devd.seqpacket.pipe")
 	if err != nil {
 		logf("devd dial error: %v, falling back to polling method", err)

net/netmon/netmon_linux.go

@@ -3,7 +3,7 @@
 
 //go:build !android
 
-package monitor
+package netmon
 
 import (
 	"net"
@@ -44,7 +44,7 @@ type nlConn struct {
 	addrCache map[uint32]map[netip.Addr]bool
 }
 
-func newOSMon(logf logger.Logf, m *Mon) (osMon, error) {
+func newOSMon(logf logger.Logf, m *Monitor) (osMon, error) {
 	conn, err := netlink.Dial(unix.NETLINK_ROUTE, &netlink.Config{
 		// Routes get us most of the events of interest, but we need
 		// address as well to cover things like DHCP deciding to give

net/netmon/netmon_linux_test.go

@@ -1,7 +1,7 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
-package monitor
+package netmon
 
 import (
 	"net"

net/netmon/netmon_polling.go

@@ -3,13 +3,13 @@
 
 //go:build (!linux && !freebsd && !windows && !darwin) || android
 
-package monitor
+package netmon
 
 import (
 	"tailscale.com/types/logger"
 )
 
-func newOSMon(logf logger.Logf, m *Mon) (osMon, error) {
+func newOSMon(logf logger.Logf, m *Monitor) (osMon, error) {
 	return newPollingMon(logf, m)
 }
 

net/netmon/netmon_test.go

@@ -1,7 +1,7 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
-package monitor
+package netmon
 
 import (
 	"flag"

net/netmon/netmon_windows.go

@@ -1,7 +1,7 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
-package monitor
+package netmon
 
 import (
 	"context"
@@ -44,7 +44,7 @@ type winMon struct {
 	noDeadlockTicker *time.Ticker
 }
 
-func newOSMon(logf logger.Logf, _ *Mon) (osMon, error) {
+func newOSMon(logf logger.Logf, _ *Monitor) (osMon, error) {
 	m := &winMon{
 		logf:             logf,
 		messagec:         make(chan eventMessage, 1),

net/netmon/polling.go

@@ -3,7 +3,7 @@
 
 //go:build !windows && !darwin
 
-package monitor
+package netmon
 
 import (
 	"bytes"
@@ -17,7 +17,7 @@
 	"tailscale.com/types/logger"
 )
 
-func newPollingMon(logf logger.Logf, m *Mon) (osMon, error) {
+func newPollingMon(logf logger.Logf, m *Monitor) (osMon, error) {
 	return &pollingMon{
 		logf: logf,
 		m:    m,
@@ -30,7 +30,7 @@ func newPollingMon(logf logger.Logf, m *Mon) (osMon, error) {
 // of anything to subscribe to.
 type pollingMon struct {
 	logf logger.Logf
-	m    *Mon
+	m    *Monitor
 
 	closeOnce sync.Once
 	stop      chan struct{}

net/sockstats/sockstats.go

@@ -11,7 +11,7 @@
 import (
 	"context"
 
-	"tailscale.com/net/interfaces"
+	"tailscale.com/net/netmon"
 	"tailscale.com/types/logger"
 )
 
@@ -107,17 +107,10 @@ func GetValidation() *ValidationSockStats {
 	return getValidation()
 }
 
-// LinkMonitor is the interface for the parts of wgengine/mointor's Mon that we
+// SetNetMon configures the sockstats package to monitor the active
-// need, to avoid the dependency.
-type LinkMonitor interface {
-	InterfaceState() *interfaces.State
-	RegisterChangeCallback(interfaces.ChangeFunc) (unregister func())
-}
-
-// SetLinkMonitor configures the sockstats package to monitor the active
 // interface, so that per-interface stats can be collected.
-func SetLinkMonitor(lm LinkMonitor) {
+func SetNetMon(lm *netmon.Monitor) {
-	setLinkMonitor(lm)
+	setNetMon(lm)
 }
 
 // DebugInfo returns a string containing debug information about the tracked

net/sockstats/sockstats_noop.go

@@ -8,6 +8,7 @@
 import (
 	"context"
 
+	"tailscale.com/net/netmon"
 	"tailscale.com/types/logger"
 )
 
@@ -29,7 +30,7 @@ func getValidation() *ValidationSockStats {
 	return nil
 }
 
-func setLinkMonitor(lm LinkMonitor) {
+func setNetMon(lm *netmon.Monitor) {
 }
 
 func debugInfo() string {

net/sockstats/sockstats_tsgo.go

@@ -16,6 +16,7 @@
 	"time"
 
 	"tailscale.com/net/interfaces"
+	"tailscale.com/net/netmon"
 	"tailscale.com/types/logger"
 	"tailscale.com/util/clientmetric"
 )
@@ -84,7 +85,7 @@ func withSockStats(ctx context.Context, label Label, logf logger.Logf) context.C
 			rxBytesCellularMetric: clientmetric.NewCounter(fmt.Sprintf("sockstats_rx_bytes_cellular_%s", label)),
 		}
 
-		// We might be called before setLinkMonitor has been called (and we've
+		// We might be called before setNetMon has been called (and we've
 		// had a chance to populate knownInterfaces). In that case, we'll have
 		// to get the list of interfaces ourselves.
 		if len(sockStats.knownInterfaces) == 0 {
@@ -248,7 +249,7 @@ func getValidation() *ValidationSockStats {
 	return r
 }
 
-func setLinkMonitor(lm LinkMonitor) {
+func setNetMon(lm *netmon.Monitor) {
 	sockStats.mu.Lock()
 	defer sockStats.mu.Unlock()
 

net/tsdial/tsdial.go

@@ -20,11 +20,11 @@
 	"tailscale.com/net/dnscache"
 	"tailscale.com/net/interfaces"
 	"tailscale.com/net/netknob"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/netns"
 	"tailscale.com/types/logger"
 	"tailscale.com/types/netmap"
 	"tailscale.com/util/mak"
-	"tailscale.com/wgengine/monitor"
 )
 
 // Dialer dials out of tailscaled, while taking care of details while
@@ -54,8 +54,8 @@ type Dialer struct {
 	closed           bool
 	dns              dnsMap
 	tunName          string // tun device name
-	linkMon           *monitor.Mon
+	netMon           *netmon.Monitor
-	linkMonUnregister func()
+	netMonUnregister func()
 	exitDNSDoHBase   string                 // non-empty if DoH-proxying exit node in use; base URL+path (without '?')
 	dnsCache         *dnscache.MessageCache // nil until first non-empty SetExitDNSDoH
 	nextSysConnID    int
@@ -117,9 +117,9 @@ func (d *Dialer) Close() error {
 	d.mu.Lock()
 	defer d.mu.Unlock()
 	d.closed = true
-	if d.linkMonUnregister != nil {
+	if d.netMonUnregister != nil {
-		d.linkMonUnregister()
+		d.netMonUnregister()
-		d.linkMonUnregister = nil
+		d.netMonUnregister = nil
 	}
 	for _, c := range d.activeSysConns {
 		c.Close()
@@ -128,15 +128,15 @@ func (d *Dialer) Close() error {
 	return nil
 }
 
-func (d *Dialer) SetLinkMonitor(mon *monitor.Mon) {
+func (d *Dialer) SetNetMon(mon *netmon.Monitor) {
 	d.mu.Lock()
 	defer d.mu.Unlock()
-	if d.linkMonUnregister != nil {
+	if d.netMonUnregister != nil {
-		go d.linkMonUnregister()
+		go d.netMonUnregister()
-		d.linkMonUnregister = nil
+		d.netMonUnregister = nil
 	}
-	d.linkMon = mon
+	d.netMon = mon
-	d.linkMonUnregister = d.linkMon.RegisterChangeCallback(d.linkChanged)
+	d.netMonUnregister = d.netMon.RegisterChangeCallback(d.linkChanged)
 }
 
 func (d *Dialer) linkChanged(major bool, state *interfaces.State) {
@@ -163,10 +163,10 @@ func (d *Dialer) closeSysConn(id int) {
 }
 
 func (d *Dialer) interfaceIndexLocked(ifName string) (index int, ok bool) {
-	if d.linkMon == nil {
+	if d.netMon == nil {
 		return 0, false
 	}
-	st := d.linkMon.InterfaceState()
+	st := d.netMon.InterfaceState()
 	iface, ok := st.Interface[ifName]
 	if !ok {
 		return 0, false

tsnet/tsnet.go

@@ -42,6 +42,7 @@
 	"tailscale.com/logtail"
 	"tailscale.com/logtail/filch"
 	"tailscale.com/net/memnet"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/proxymux"
 	"tailscale.com/net/socks5"
 	"tailscale.com/net/tsdial"
@@ -51,7 +52,6 @@
 	"tailscale.com/types/nettype"
 	"tailscale.com/util/mak"
 	"tailscale.com/wgengine"
-	"tailscale.com/wgengine/monitor"
 	"tailscale.com/wgengine/netstack"
 )
 
@@ -106,7 +106,7 @@ type Server struct {
 	initErr          error
 	lb               *ipnlocal.LocalBackend
 	netstack         *netstack.Impl
-	linkMon          *monitor.Mon
+	netMon           *netmon.Monitor
 	rootPath         string // the state directory
 	hostname         string
 	shutdownCtx      context.Context
@@ -356,8 +356,8 @@ func (s *Server) Close() error {
 	if s.lb != nil {
 		s.lb.Shutdown()
 	}
-	if s.linkMon != nil {
+	if s.netMon != nil {
-		s.linkMon.Close()
+		s.netMon.Close()
 	}
 	if s.dialer != nil {
 		s.dialer.Close()
@@ -476,16 +476,16 @@ func (s *Server) start() (reterr error) {
 		return err
 	}
 
-	s.linkMon, err = monitor.New(logf)
+	s.netMon, err = netmon.New(logf)
 	if err != nil {
 		return err
 	}
-	closePool.add(s.linkMon)
+	closePool.add(s.netMon)
 
 	s.dialer = &tsdial.Dialer{Logf: logf} // mutated below (before used)
 	eng, err := wgengine.NewUserspaceEngine(logf, wgengine.Config{
 		ListenPort: 0,
-		LinkMonitor: s.linkMon,
+		NetMon:     s.netMon,
 		Dialer:     s.dialer,
 	})
 	if err != nil {

tstest/integration/tailscaled_deps_test_darwin.go

@@ -24,6 +24,7 @@
 	_ "tailscale.com/net/dns"
 	_ "tailscale.com/net/dnsfallback"
 	_ "tailscale.com/net/interfaces"
+	_ "tailscale.com/net/netmon"
 	_ "tailscale.com/net/netns"
 	_ "tailscale.com/net/proxymux"
 	_ "tailscale.com/net/socks5"
@@ -47,7 +48,6 @@
 	_ "tailscale.com/version"
 	_ "tailscale.com/version/distro"
 	_ "tailscale.com/wgengine"
-	_ "tailscale.com/wgengine/monitor"
 	_ "tailscale.com/wgengine/netstack"
 	_ "tailscale.com/wgengine/router"
 )

tstest/integration/tailscaled_deps_test_freebsd.go

@@ -24,6 +24,7 @@
 	_ "tailscale.com/net/dns"
 	_ "tailscale.com/net/dnsfallback"
 	_ "tailscale.com/net/interfaces"
+	_ "tailscale.com/net/netmon"
 	_ "tailscale.com/net/netns"
 	_ "tailscale.com/net/proxymux"
 	_ "tailscale.com/net/socks5"
@@ -47,7 +48,6 @@
 	_ "tailscale.com/version"
 	_ "tailscale.com/version/distro"
 	_ "tailscale.com/wgengine"
-	_ "tailscale.com/wgengine/monitor"
 	_ "tailscale.com/wgengine/netstack"
 	_ "tailscale.com/wgengine/router"
 )

tstest/integration/tailscaled_deps_test_linux.go

@@ -24,6 +24,7 @@
 	_ "tailscale.com/net/dns"
 	_ "tailscale.com/net/dnsfallback"
 	_ "tailscale.com/net/interfaces"
+	_ "tailscale.com/net/netmon"
 	_ "tailscale.com/net/netns"
 	_ "tailscale.com/net/proxymux"
 	_ "tailscale.com/net/socks5"
@@ -47,7 +48,6 @@
 	_ "tailscale.com/version"
 	_ "tailscale.com/version/distro"
 	_ "tailscale.com/wgengine"
-	_ "tailscale.com/wgengine/monitor"
 	_ "tailscale.com/wgengine/netstack"
 	_ "tailscale.com/wgengine/router"
 )

tstest/integration/tailscaled_deps_test_openbsd.go

@@ -24,6 +24,7 @@
 	_ "tailscale.com/net/dns"
 	_ "tailscale.com/net/dnsfallback"
 	_ "tailscale.com/net/interfaces"
+	_ "tailscale.com/net/netmon"
 	_ "tailscale.com/net/netns"
 	_ "tailscale.com/net/proxymux"
 	_ "tailscale.com/net/socks5"
@@ -47,7 +48,6 @@
 	_ "tailscale.com/version"
 	_ "tailscale.com/version/distro"
 	_ "tailscale.com/wgengine"
-	_ "tailscale.com/wgengine/monitor"
 	_ "tailscale.com/wgengine/netstack"
 	_ "tailscale.com/wgengine/router"
 )

tstest/integration/tailscaled_deps_test_windows.go

@@ -32,6 +32,7 @@
 	_ "tailscale.com/net/dns"
 	_ "tailscale.com/net/dnsfallback"
 	_ "tailscale.com/net/interfaces"
+	_ "tailscale.com/net/netmon"
 	_ "tailscale.com/net/netns"
 	_ "tailscale.com/net/proxymux"
 	_ "tailscale.com/net/socks5"
@@ -56,7 +57,6 @@
 	_ "tailscale.com/version/distro"
 	_ "tailscale.com/wf"
 	_ "tailscale.com/wgengine"
-	_ "tailscale.com/wgengine/monitor"
 	_ "tailscale.com/wgengine/netstack"
 	_ "tailscale.com/wgengine/router"
 )

wgengine/bench/wg.go

@@ -40,7 +40,7 @@ func setupWGTest(b *testing.B, logf logger.Logf, traf *TrafficGen, a1, a2 netip.
 	}
 	e1, err := wgengine.NewUserspaceEngine(l1, wgengine.Config{
 		Router:     router.NewFake(l1),
-		LinkMonitor: nil,
+		NetMon:     nil,
 		ListenPort: 0,
 		Tun:        t1,
 	})
@@ -64,7 +64,7 @@ func setupWGTest(b *testing.B, logf logger.Logf, traf *TrafficGen, a1, a2 netip.
 	}
 	e2, err := wgengine.NewUserspaceEngine(l2, wgengine.Config{
 		Router:     router.NewFake(l2),
-		LinkMonitor: nil,
+		NetMon:     nil,
 		ListenPort: 0,
 		Tun:        t2,
 	})

wgengine/magicsock/magicsock.go

@@ -47,6 +47,7 @@
 	"tailscale.com/net/netaddr"
 	"tailscale.com/net/netcheck"
 	"tailscale.com/net/neterror"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/netns"
 	"tailscale.com/net/packet"
 	"tailscale.com/net/portmapper"
@@ -69,7 +70,6 @@
 	"tailscale.com/util/uniq"
 	"tailscale.com/version"
 	"tailscale.com/wgengine/capture"
-	"tailscale.com/wgengine/monitor"
 )
 
 const (
@@ -279,7 +279,7 @@ type Conn struct {
 	idleFunc               func() time.Duration // nil means unknown
 	testOnlyPacketListener nettype.PacketListener
 	noteRecvActivity       func(key.NodePublic) // or nil, see Options.NoteRecvActivity
-	linkMon                *monitor.Mon         // or nil
+	netMon                 *netmon.Monitor      // or nil
 
 	// ================================================================
 	// No locking required to access these fields, either because
@@ -573,9 +573,9 @@ type Options struct {
 	// not hold Conn.mu while calling it.
 	NoteRecvActivity func(key.NodePublic)
 
-	// LinkMonitor is the link monitor to use.
+	// NetMon is the network monitor to use.
 	// With one, the portmapper won't be used.
-	LinkMonitor *monitor.Mon
+	NetMon *netmon.Monitor
 }
 
 func (o *Options) logf() logger.Logf {
@@ -643,10 +643,10 @@ func NewConn(opts Options) (*Conn, error) {
 	c.testOnlyPacketListener = opts.TestOnlyPacketListener
 	c.noteRecvActivity = opts.NoteRecvActivity
 	c.portMapper = portmapper.NewClient(logger.WithPrefix(c.logf, "portmapper: "), nil, c.onPortMapChanged)
-	if opts.LinkMonitor != nil {
+	if opts.NetMon != nil {
-		c.portMapper.SetGatewayLookupFunc(opts.LinkMonitor.GatewayAndSelfIP)
+		c.portMapper.SetGatewayLookupFunc(opts.NetMon.GatewayAndSelfIP)
 	}
-	c.linkMon = opts.LinkMonitor
+	c.netMon = opts.NetMon
 
 	if err := c.rebind(keepCurrentPort); err != nil {
 		return nil, err
@@ -3369,8 +3369,8 @@ func (c *Conn) Rebind() {
 	}
 
 	var ifIPs []netip.Prefix
-	if c.linkMon != nil {
+	if c.netMon != nil {
-		st := c.linkMon.InterfaceState()
+		st := c.netMon.InterfaceState()
 		defIf := st.DefaultRouteInterface
 		ifIPs = st.InterfaceIPs[defIf]
 		c.logf("Rebind; defIf=%q, ips=%v", defIf, ifIPs)

wgengine/router/router.go

@@ -10,9 +10,9 @@
 	"reflect"
 
 	"github.com/tailscale/wireguard-go/tun"
+	"tailscale.com/net/netmon"
 	"tailscale.com/types/logger"
 	"tailscale.com/types/preftype"
-	"tailscale.com/wgengine/monitor"
 )
 
 // Router is responsible for managing the system network stack.
@@ -34,11 +34,11 @@ type Router interface {
 // New returns a new Router for the current platform, using the
 // provided tun device.
 //
-// If linkMon is nil, it's not used. It's currently (2021-07-20) only
+// If netMon is nil, it's not used. It's currently (2021-07-20) only
 // used on Linux in some situations.
-func New(logf logger.Logf, tundev tun.Device, linkMon *monitor.Mon) (Router, error) {
+func New(logf logger.Logf, tundev tun.Device, netMon *netmon.Monitor) (Router, error) {
 	logf = logger.WithPrefix(logf, "router: ")
-	return newUserspaceRouter(logf, tundev, linkMon)
+	return newUserspaceRouter(logf, tundev, netMon)
 }
 
 // Cleanup restores the system network configuration to its original state

wgengine/router/router_darwin.go

@@ -5,12 +5,12 @@
 
 import (
 	"github.com/tailscale/wireguard-go/tun"
+	"tailscale.com/net/netmon"
 	"tailscale.com/types/logger"
-	"tailscale.com/wgengine/monitor"
 )
 
-func newUserspaceRouter(logf logger.Logf, tundev tun.Device, linkMon *monitor.Mon) (Router, error) {
+func newUserspaceRouter(logf logger.Logf, tundev tun.Device, netMon *netmon.Monitor) (Router, error) {
-	return newUserspaceBSDRouter(logf, tundev, linkMon)
+	return newUserspaceBSDRouter(logf, tundev, netMon)
 }
 
 func cleanup(logger.Logf, string) {

wgengine/router/router_default.go

@@ -10,11 +10,11 @@
 	"runtime"
 
 	"github.com/tailscale/wireguard-go/tun"
+	"tailscale.com/net/netmon"
 	"tailscale.com/types/logger"
-	"tailscale.com/wgengine/monitor"
 )
 
-func newUserspaceRouter(logf logger.Logf, tunDev tun.Device, linkMon *monitor.Mon) (Router, error) {
+func newUserspaceRouter(logf logger.Logf, tunDev tun.Device, netMon *netmon.Monitor) (Router, error) {
 	return nil, fmt.Errorf("unsupported OS %q", runtime.GOOS)
 }
 

wgengine/router/router_freebsd.go

@@ -5,8 +5,8 @@
 
 import (
 	"github.com/tailscale/wireguard-go/tun"
+	"tailscale.com/net/netmon"
 	"tailscale.com/types/logger"
-	"tailscale.com/wgengine/monitor"
 )
 
 // For now this router only supports the userspace WireGuard implementations.
@@ -14,8 +14,8 @@
 // Work is currently underway for an in-kernel FreeBSD implementation of wireguard
 // https://svnweb.freebsd.org/base?view=revision&revision=357986
 
-func newUserspaceRouter(logf logger.Logf, tundev tun.Device, linkMon *monitor.Mon) (Router, error) {
+func newUserspaceRouter(logf logger.Logf, tundev tun.Device, netMon *netmon.Monitor) (Router, error) {
-	return newUserspaceBSDRouter(logf, tundev, linkMon)
+	return newUserspaceBSDRouter(logf, tundev, netMon)
 }
 
 func cleanup(logf logger.Logf, interfaceName string) {

wgengine/router/router_linux.go

@@ -24,12 +24,12 @@
 	"golang.org/x/sys/unix"
 	"golang.org/x/time/rate"
 	"tailscale.com/envknob"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/tsaddr"
 	"tailscale.com/types/logger"
 	"tailscale.com/types/preftype"
 	"tailscale.com/util/multierr"
 	"tailscale.com/version/distro"
-	"tailscale.com/wgengine/monitor"
 )
 
 const (
@@ -94,8 +94,8 @@ type linuxRouter struct {
 	closed           atomic.Bool
 	logf             func(fmt string, args ...any)
 	tunname          string
-	linkMon          *monitor.Mon
+	netMon           *netmon.Monitor
-	unregLinkMon     func()
+	unregNetMon      func()
 	addrs            map[netip.Prefix]bool
 	routes           map[netip.Prefix]bool
 	localRoutes      map[netip.Prefix]bool
@@ -121,7 +121,7 @@ type linuxRouter struct {
 	cmd  commandRunner
 }
 
-func newUserspaceRouter(logf logger.Logf, tunDev tun.Device, linkMon *monitor.Mon) (Router, error) {
+func newUserspaceRouter(logf logger.Logf, tunDev tun.Device, netMon *netmon.Monitor) (Router, error) {
 	tunname, err := tunDev.Name()
 	if err != nil {
 		return nil, err
@@ -156,15 +156,15 @@ func newUserspaceRouter(logf logger.Logf, tunDev tun.Device, linkMon *monitor.Mo
 		ambientCapNetAdmin: useAmbientCaps(),
 	}
 
-	return newUserspaceRouterAdvanced(logf, tunname, linkMon, ipt4, ipt6, cmd, supportsV6, supportsV6NAT)
+	return newUserspaceRouterAdvanced(logf, tunname, netMon, ipt4, ipt6, cmd, supportsV6, supportsV6NAT)
 }
 
-func newUserspaceRouterAdvanced(logf logger.Logf, tunname string, linkMon *monitor.Mon, netfilter4, netfilter6 netfilterRunner, cmd commandRunner, supportsV6, supportsV6NAT bool) (Router, error) {
+func newUserspaceRouterAdvanced(logf logger.Logf, tunname string, netMon *netmon.Monitor, netfilter4, netfilter6 netfilterRunner, cmd commandRunner, supportsV6, supportsV6NAT bool) (Router, error) {
 	r := &linuxRouter{
 		logf:          logf,
 		tunname:       tunname,
 		netfilterMode: netfilterOff,
-		linkMon:       linkMon,
+		netMon:        netMon,
 
 		v6Available:    supportsV6,
 		v6NATAvailable: supportsV6NAT,
@@ -336,8 +336,8 @@ func (r *linuxRouter) useIPCommand() bool {
 	return !ok
 }
 
-// onIPRuleDeleted is the callback from the link monitor for when an IP policy
+// onIPRuleDeleted is the callback from the network monitor for when an IP
-// rule is deleted. See Issue 1591.
+// policy rule is deleted. See Issue 1591.
 //
 // If an ip rule is deleted (with pref number 52xx, as Tailscale sets), then
 // set a timer to restore our rules, in case they were deleted. The timer lets
@@ -372,8 +372,8 @@ func (r *linuxRouter) onIPRuleDeleted(table uint8, priority uint32) {
 }
 
 func (r *linuxRouter) Up() error {
-	if r.unregLinkMon == nil && r.linkMon != nil {
+	if r.unregNetMon == nil && r.netMon != nil {
-		r.unregLinkMon = r.linkMon.RegisterRuleDeleteCallback(r.onIPRuleDeleted)
+		r.unregNetMon = r.netMon.RegisterRuleDeleteCallback(r.onIPRuleDeleted)
 	}
 	if err := r.addIPRules(); err != nil {
 		return fmt.Errorf("adding IP rules: %w", err)
@@ -390,8 +390,8 @@ func (r *linuxRouter) Up() error {
 
 func (r *linuxRouter) Close() error {
 	r.closed.Store(true)
-	if r.unregLinkMon != nil {
+	if r.unregNetMon != nil {
-		r.unregLinkMon()
+		r.unregNetMon()
 	}
 	if err := r.downInterface(); err != nil {
 		return err

wgengine/router/router_linux_test.go

@@ -21,9 +21,9 @@
 	"github.com/tailscale/wireguard-go/tun"
 	"github.com/vishvananda/netlink"
 	"golang.org/x/exp/slices"
+	"tailscale.com/net/netmon"
 	"tailscale.com/tstest"
 	"tailscale.com/types/logger"
-	"tailscale.com/wgengine/monitor"
 )
 
 func TestRouterStates(t *testing.T) {
@@ -320,7 +320,7 @@ func TestRouterStates(t *testing.T) {
 		},
 	}
 
-	mon, err := monitor.New(logger.Discard)
+	mon, err := netmon.New(logger.Discard)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -659,7 +659,7 @@ func createTestTUN(t *testing.T) tun.Device {
 
 type linuxTest struct {
 	tun       tun.Device
-	mon       *monitor.Mon
+	mon       *netmon.Monitor
 	r         *linuxRouter
 	logOutput tstest.MemLogger
 }
@@ -684,7 +684,7 @@ func newLinuxRootTest(t *testing.T) *linuxTest {
 
 	logf := lt.logOutput.Logf
 
-	mon, err := monitor.New(logger.Discard)
+	mon, err := netmon.New(logger.Discard)
 	if err != nil {
 		lt.Close()
 		t.Fatal(err)

wgengine/router/router_openbsd.go

@@ -12,8 +12,8 @@
 
 	"github.com/tailscale/wireguard-go/tun"
 	"go4.org/netipx"
+	"tailscale.com/net/netmon"
 	"tailscale.com/types/logger"
-	"tailscale.com/wgengine/monitor"
 )
 
 // For now this router only supports the WireGuard userspace implementation.
@@ -22,14 +22,14 @@
 
 type openbsdRouter struct {
 	logf    logger.Logf
-	linkMon *monitor.Mon
+	netMon  *netmon.Monitor
 	tunname string
 	local4  netip.Prefix
 	local6  netip.Prefix
 	routes  map[netip.Prefix]struct{}
 }
 
-func newUserspaceRouter(logf logger.Logf, tundev tun.Device, linkMon *monitor.Mon) (Router, error) {
+func newUserspaceRouter(logf logger.Logf, tundev tun.Device, netMon *netmon.Monitor) (Router, error) {
 	tunname, err := tundev.Name()
 	if err != nil {
 		return nil, err
@@ -37,7 +37,7 @@ func newUserspaceRouter(logf logger.Logf, tundev tun.Device, linkMon *monitor.Mo
 
 	return &openbsdRouter{
 		logf:    logf,
-		linkMon: linkMon,
+		netMon:  netMon,
 		tunname: tunname,
 	}, nil
 }

wgengine/router/router_userspace_bsd.go

@@ -14,21 +14,21 @@
 
 	"github.com/tailscale/wireguard-go/tun"
 	"go4.org/netipx"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/tsaddr"
 	"tailscale.com/types/logger"
 	"tailscale.com/version"
-	"tailscale.com/wgengine/monitor"
 )
 
 type userspaceBSDRouter struct {
 	logf    logger.Logf
-	linkMon *monitor.Mon
+	netMon  *netmon.Monitor
 	tunname string
 	local   []netip.Prefix
 	routes  map[netip.Prefix]bool
 }
 
-func newUserspaceBSDRouter(logf logger.Logf, tundev tun.Device, linkMon *monitor.Mon) (Router, error) {
+func newUserspaceBSDRouter(logf logger.Logf, tundev tun.Device, netMon *netmon.Monitor) (Router, error) {
 	tunname, err := tundev.Name()
 	if err != nil {
 		return nil, err
@@ -36,7 +36,7 @@ func newUserspaceBSDRouter(logf logger.Logf, tundev tun.Device, linkMon *monitor
 
 	return &userspaceBSDRouter{
 		logf:    logf,
-		linkMon: linkMon,
+		netMon:  netMon,
 		tunname: tunname,
 	}, nil
 }

wgengine/router/router_windows.go

@@ -22,19 +22,19 @@
 	"golang.zx2c4.com/wireguard/windows/tunnel/winipcfg"
 	"tailscale.com/logtail/backoff"
 	"tailscale.com/net/dns"
+	"tailscale.com/net/netmon"
 	"tailscale.com/types/logger"
-	"tailscale.com/wgengine/monitor"
 )
 
 type winRouter struct {
 	logf                func(fmt string, args ...any)
-	linkMon             *monitor.Mon // may be nil
+	netMon              *netmon.Monitor // may be nil
 	nativeTun           *tun.NativeTun
 	routeChangeCallback *winipcfg.RouteChangeCallback
 	firewall            *firewallTweaker
 }
 
-func newUserspaceRouter(logf logger.Logf, tundev tun.Device, linkMon *monitor.Mon) (Router, error) {
+func newUserspaceRouter(logf logger.Logf, tundev tun.Device, netMon *netmon.Monitor) (Router, error) {
 	nativeTun := tundev.(*tun.NativeTun)
 	luid := winipcfg.LUID(nativeTun.LUID())
 	guid, err := luid.GUID()
@@ -44,7 +44,7 @@ func newUserspaceRouter(logf logger.Logf, tundev tun.Device, linkMon *monitor.Mo
 
 	return &winRouter{
 		logf:      logf,
-		linkMon:   linkMon,
+		netMon:    netMon,
 		nativeTun: nativeTun,
 		firewall: &firewallTweaker{
 			logf:    logger.WithPrefix(logf, "firewall: "),

wgengine/userspace.go

@@ -28,6 +28,7 @@
 	"tailscale.com/net/dns/resolver"
 	"tailscale.com/net/flowtrack"
 	"tailscale.com/net/interfaces"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/packet"
 	"tailscale.com/net/sockstats"
 	"tailscale.com/net/tsaddr"
@@ -48,7 +49,6 @@
 	"tailscale.com/wgengine/capture"
 	"tailscale.com/wgengine/filter"
 	"tailscale.com/wgengine/magicsock"
-	"tailscale.com/wgengine/monitor"
 	"tailscale.com/wgengine/netlog"
 	"tailscale.com/wgengine/router"
 	"tailscale.com/wgengine/wgcfg"
@@ -95,9 +95,9 @@ type userspaceEngine struct {
 	confListenPort   uint16 // original conf.ListenPort
 	dns              *dns.Manager
 	magicConn        *magicsock.Conn
-	linkMon           *monitor.Mon
+	netMon           *netmon.Monitor
-	linkMonOwned      bool       // whether we created linkMon (and thus need to close it)
+	netMonOwned      bool       // whether we created netMon (and thus need to close it)
-	linkMonUnregister func()     // unsubscribes from changes; used regardless of linkMonOwned
+	netMonUnregister func()     // unsubscribes from changes; used regardless of netMonOwned
 	birdClient       BIRDClient // or nil
 
 	testMaybeReconfigHook func() // for tests; if non-nil, fires if maybeReconfigWireguardLocked called
@@ -199,9 +199,9 @@ type Config struct {
 	// If nil, a fake OSConfigurator that does nothing is used.
 	DNS dns.OSConfigurator
 
-	// LinkMonitor optionally provides an existing link monitor to re-use.
+	// NetMon optionally provides an existing network monitor to re-use.
-	// If nil, a new link monitor is created.
+	// If nil, a new network monitor is created.
-	LinkMonitor *monitor.Mon
+	NetMon *netmon.Monitor
 
 	// Dialer is the dialer to use for outbound connections.
 	// If nil, a new Dialer is created
@@ -316,34 +316,34 @@ func NewUserspaceEngine(logf logger.Logf, conf Config) (_ Engine, reterr error)
 	e.isLocalAddr.Store(tsaddr.NewContainsIPFunc(nil))
 	e.isDNSIPOverTailscale.Store(tsaddr.NewContainsIPFunc(nil))
 
-	if conf.LinkMonitor != nil {
+	if conf.NetMon != nil {
-		e.linkMon = conf.LinkMonitor
+		e.netMon = conf.NetMon
 	} else {
-		mon, err := monitor.New(logf)
+		mon, err := netmon.New(logf)
 		if err != nil {
 			return nil, err
 		}
 		closePool.add(mon)
-		e.linkMon = mon
+		e.netMon = mon
-		e.linkMonOwned = true
+		e.netMonOwned = true
 	}
 
 	tunName, _ := conf.Tun.Name()
 	conf.Dialer.SetTUNName(tunName)
-	conf.Dialer.SetLinkMonitor(e.linkMon)
+	conf.Dialer.SetNetMon(e.netMon)
-	e.dns = dns.NewManager(logf, conf.DNS, e.linkMon, conf.Dialer, fwdDNSLinkSelector{e, tunName})
+	e.dns = dns.NewManager(logf, conf.DNS, e.netMon, conf.Dialer, fwdDNSLinkSelector{e, tunName})
 
 	// TODO: there's probably a better place for this
-	sockstats.SetLinkMonitor(e.linkMon)
+	sockstats.SetNetMon(e.netMon)
 
-	logf("link state: %+v", e.linkMon.InterfaceState())
+	logf("link state: %+v", e.netMon.InterfaceState())
 
-	unregisterMonWatch := e.linkMon.RegisterChangeCallback(func(changed bool, st *interfaces.State) {
+	unregisterMonWatch := e.netMon.RegisterChangeCallback(func(changed bool, st *interfaces.State) {
 		tshttpproxy.InvalidateCache()
 		e.linkChange(changed, st)
 	})
 	closePool.addFunc(unregisterMonWatch)
-	e.linkMonUnregister = unregisterMonWatch
+	e.netMonUnregister = unregisterMonWatch
 
 	endpointsFn := func(endpoints []tailcfg.Endpoint) {
 		e.mu.Lock()
@@ -359,7 +359,7 @@ func NewUserspaceEngine(logf logger.Logf, conf Config) (_ Engine, reterr error)
 		DERPActiveFunc:   e.RequestStatus,
 		IdleFunc:         e.tundev.IdleDuration,
 		NoteRecvActivity: e.noteRecvActivity,
-		LinkMonitor:      e.linkMon,
+		NetMon:           e.netMon,
 	}
 
 	var err error
@@ -368,7 +368,7 @@ func NewUserspaceEngine(logf logger.Logf, conf Config) (_ Engine, reterr error)
 		return nil, fmt.Errorf("wgengine: %v", err)
 	}
 	closePool.add(e.magicConn)
-	e.magicConn.SetNetworkUp(e.linkMon.InterfaceState().AnyInterfaceUp())
+	e.magicConn.SetNetworkUp(e.netMon.InterfaceState().AnyInterfaceUp())
 
 	tsTUNDev.SetDiscoKey(e.magicConn.DiscoPublicKey())
 
@@ -455,8 +455,8 @@ func NewUserspaceEngine(logf logger.Logf, conf Config) (_ Engine, reterr error)
 	if err := e.router.Set(nil); err != nil {
 		return nil, fmt.Errorf("router.Set(nil): %w", err)
 	}
-	e.logf("Starting link monitor...")
+	e.logf("Starting network monitor...")
-	e.linkMon.Start()
+	e.netMon.Start()
 
 	e.logf("Engine created.")
 	return e, nil
@@ -1094,9 +1094,9 @@ func (e *userspaceEngine) Close() {
 	r := bufio.NewReader(strings.NewReader(""))
 	e.wgdev.IpcSetOperation(r)
 	e.magicConn.Close()
-	e.linkMonUnregister()
+	e.netMonUnregister()
-	if e.linkMonOwned {
+	if e.netMonOwned {
-		e.linkMon.Close()
+		e.netMon.Close()
 	}
 	e.dns.Down()
 	e.router.Close()
@@ -1119,15 +1119,15 @@ func (e *userspaceEngine) Wait() {
 	<-e.waitCh
 }
 
-func (e *userspaceEngine) GetLinkMonitor() *monitor.Mon {
+func (e *userspaceEngine) GetNetMon() *netmon.Monitor {
-	return e.linkMon
+	return e.netMon
 }
 
 // LinkChange signals a network change event. It's currently
-// (2021-03-03) only called on Android. On other platforms, linkMon
+// (2021-03-03) only called on Android. On other platforms, netMon
 // generates link change events for us.
 func (e *userspaceEngine) LinkChange(_ bool) {
-	e.linkMon.InjectEvent()
+	e.netMon.InjectEvent()
 }
 
 func (e *userspaceEngine) linkChange(changed bool, cur *interfaces.State) {

wgengine/watchdog.go

@@ -18,6 +18,7 @@
 	"tailscale.com/ipn/ipnstate"
 	"tailscale.com/net/dns"
 	"tailscale.com/net/dns/resolver"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/tstun"
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/key"
@@ -25,7 +26,6 @@
 	"tailscale.com/wgengine/capture"
 	"tailscale.com/wgengine/filter"
 	"tailscale.com/wgengine/magicsock"
-	"tailscale.com/wgengine/monitor"
 	"tailscale.com/wgengine/router"
 	"tailscale.com/wgengine/wgcfg"
 )
@@ -126,8 +126,8 @@ func (e *watchdogEngine) watchdog(name string, fn func()) {
 func (e *watchdogEngine) Reconfig(cfg *wgcfg.Config, routerCfg *router.Config, dnsCfg *dns.Config, debug *tailcfg.Debug) error {
 	return e.watchdogErr("Reconfig", func() error { return e.wrap.Reconfig(cfg, routerCfg, dnsCfg, debug) })
 }
-func (e *watchdogEngine) GetLinkMonitor() *monitor.Mon {
+func (e *watchdogEngine) GetNetMon() *netmon.Monitor {
-	return e.wrap.GetLinkMonitor()
+	return e.wrap.GetNetMon()
 }
 func (e *watchdogEngine) GetFilter() *filter.Filter {
 	return e.wrap.GetFilter()

wgengine/wgengine.go

@@ -10,12 +10,12 @@
 
 	"tailscale.com/ipn/ipnstate"
 	"tailscale.com/net/dns"
+	"tailscale.com/net/netmon"
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/key"
 	"tailscale.com/types/netmap"
 	"tailscale.com/wgengine/capture"
 	"tailscale.com/wgengine/filter"
-	"tailscale.com/wgengine/monitor"
 	"tailscale.com/wgengine/router"
 	"tailscale.com/wgengine/wgcfg"
 )
@@ -92,8 +92,8 @@ type Engine interface {
 	// WireGuard status changes.
 	SetStatusCallback(StatusCallback)
 
-	// GetLinkMonitor returns the link monitor.
+	// GetNetMon returns the network monitor.
-	GetLinkMonitor() *monitor.Mon
+	GetNetMon() *netmon.Monitor
 
 	// RequestStatus requests a WireGuard status update right
 	// away, sent to the callback registered via SetStatusCallback.
@@ -119,7 +119,7 @@ type Engine interface {
 	//
 	// Deprecated: don't use this method. It was removed shortly
 	// before the Tailscale 1.6 release when we remembered that
-	// Android doesn't use the Linux-based link monitor and has
+	// Android doesn't use the Linux-based network monitor and has
 	// its own mechanism that uses LinkChange. Android is the only
 	// caller of this method now. Don't add more.
 	LinkChange(isExpensive bool)