cmd/tailscale/cli: plumb TUN mode into tailscale web template

UI works remains, but data is there now.

Updates #4015

Change-Id: Ib91e94718b655ad60a63596e59468f3b3b102306
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/tailscale/cli/web.go

@@ -58,6 +58,7 @@ type tmplData struct {
 	AdvertiseExitNode bool
 	AdvertiseRoutes   string
 	LicensesURL       string
+	TUNMode           bool
 }
 
 var webCmd = &ffcli.Command{
@@ -338,7 +339,7 @@ func webHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	st, err := localClient.Status(ctx)
+	st, err := localClient.StatusWithoutPeers(ctx)
 	if err != nil {
 		http.Error(w, err.Error(), http.StatusInternalServerError)
 		return
@@ -408,6 +409,7 @@ func webHandler(w http.ResponseWriter, r *http.Request) {
 		Status:       st.BackendState,
 		DeviceName:   deviceName,
 		LicensesURL:  licensesURL(),
+		TUNMode:      st.TUN,
 	}
 	exitNodeRouteV4 := netip.MustParsePrefix("0.0.0.0/0")
 	exitNodeRouteV6 := netip.MustParsePrefix("::/0")

ipn/ipnlocal/local.go

@@ -579,6 +579,7 @@ func (b *LocalBackend) updateStatus(sb *ipnstate.StatusBuilder, extraLocked func
 	defer b.mu.Unlock()
 	sb.MutateStatus(func(s *ipnstate.Status) {
 		s.Version = version.Long
+		s.TUN = !wgengine.IsNetstack(b.e)
 		s.BackendState = b.state.String()
 		s.AuthURL = b.authURLSticky
 		if err := health.OverallError(); err != nil {

ipn/ipnstate/ipnstate.go

@@ -31,6 +31,10 @@ type Status struct {
 	// Version is the daemon's long version (see version.Long).
 	Version string
 
+	// TUN is whether /dev/net/tun (or equivalent kernel interface) is being
+	// used. If false, it's running in userspace mode.
+	TUN bool
+
 	// BackendState is an ipn.State string value:
 	//  "NoState", "NeedsLogin", "NeedsMachineAuth", "Stopped",
 	//  "Starting", "Running".