cmd/tailscaled: add `-state=mem:` to support creation of an ephemeral node.

RELNOTE=`tailscaled --state=mem:` registers as an ephemeral node and
does not store state to disk.

Signed-off-by: Maisem Ali <maisem@tailscale.com>

cmd/tailscaled/tailscaled.go

@@ -28,6 +28,7 @@ import (
 	"time"
 
 	"inet.af/netaddr"
+	"tailscale.com/control/controlclient"
 	"tailscale.com/envknob"
 	"tailscale.com/ipn"
 	"tailscale.com/ipn/ipnserver"
@@ -123,7 +124,7 @@ func main() {
 	flag.StringVar(&args.httpProxyAddr, "outbound-http-proxy-listen", "", `optional [ip]:port to run an outbound HTTP proxy (e.g. "localhost:8080")`)
 	flag.StringVar(&args.tunname, "tun", defaultTunName(), `tunnel interface name; use "userspace-networking" (beta) to not use TUN`)
 	flag.Var(flagtype.PortValue(&args.port, 0), "port", "UDP port to listen on for WireGuard and peer-to-peer traffic; 0 means automatically select")
-	flag.StringVar(&args.statepath, "state", paths.DefaultTailscaledStateFile(), "absolute path of state file; use 'kube:<secret-name>' to use Kubernetes secrets or 'arn:aws:ssm:...' to store in AWS SSM. If empty and --statedir is provided, the default is <statedir>/tailscaled.state")
+	flag.StringVar(&args.statepath, "state", paths.DefaultTailscaledStateFile(), "absolute path of state file; use 'kube:<secret-name>' to use Kubernetes secrets or 'arn:aws:ssm:...' to store in AWS SSM; use 'mem:' to not store state and register as an emphemeral node. If empty and --statedir is provided, the default is <statedir>/tailscaled.state")
 	flag.StringVar(&args.statedir, "statedir", "", "path to directory for storage of config state, TLS certs, temporary incoming Taildrop files, etc. If empty, it's derived from --state when possible.")
 	flag.StringVar(&args.socketpath, "socket", paths.DefaultTailscaledSocket(), "path of the service unix socket")
 	flag.StringVar(&args.birdSocketPath, "bird-socket", "", "path of the bird unix socket")
@@ -238,8 +239,19 @@ func ipnServerOpts() (o ipnserver.Options) {
 			o.VarRoot = dir
 		}
 	}
+	if strings.HasPrefix(statePathOrDefault(), "mem:") {
+		// Register as an ephemeral node.
+		o.LoginFlags = controlclient.LoginEphemeral
+	}
 
 	switch goos {
+	case "js":
+		// The js/wasm client has no state storage so for now
+		// treat all interactive logins as ephemeral.
+		// TODO(bradfitz): if we start using browser LocalStorage
+		// or something, then rethink this.
+		o.LoginFlags = controlclient.LoginEphemeral
+		fallthrough
 	default:
 		o.SurviveDisconnects = true
 		o.AutostartStateKey = ipn.GlobalDaemonStateKey

ipn/ipnlocal/local.go

@@ -136,6 +136,7 @@ type LocalBackend struct {
 	prevIfState      *interfaces.State
 	peerAPIServer    *peerAPIServer // or nil
 	peerAPIListeners []*peerAPIListener
+	loginFlags       controlclient.LoginFlags
 	incomingFiles    map[*incomingFile]bool
 	// directFileRoot, if non-empty, means to write received files
 	// directly to this directory, without staging them in an
@@ -166,7 +167,7 @@ type clientGen func(controlclient.Options) (controlclient.Client, error)
 // but is not actually running.
 //
 // If dialer is nil, a new one is made.
-func NewLocalBackend(logf logger.Logf, logid string, store ipn.StateStore, dialer *tsdial.Dialer, e wgengine.Engine) (*LocalBackend, error) {
+func NewLocalBackend(logf logger.Logf, logid string, store ipn.StateStore, dialer *tsdial.Dialer, e wgengine.Engine, loginFlags controlclient.LoginFlags) (*LocalBackend, error) {
 	if e == nil {
 		panic("ipn.NewLocalBackend: engine must not be nil")
 	}
@@ -199,6 +200,7 @@ func NewLocalBackend(logf logger.Logf, logid string, store ipn.StateStore, diale
 		state:          ipn.NoState,
 		portpoll:       portpoll,
 		gotPortPollRes: make(chan struct{}),
+		loginFlags:     loginFlags,
 	}
 
 	// Default filter blocks everything and logs nothing, until Start() is called.
@@ -1569,13 +1571,14 @@ func (b *LocalBackend) InServerMode() bool {
 }
 
 // Login implements Backend.
+// As of 2022-02-17, this is only exists for tests.
 func (b *LocalBackend) Login(token *tailcfg.Oauth2Token) {
 	b.mu.Lock()
 	b.assertClientLocked()
 	cc := b.cc
 	b.mu.Unlock()
 
-	cc.Login(token, controlclient.LoginInteractive)
+	cc.Login(token, b.loginFlags|controlclient.LoginInteractive)
 }
 
 // StartLoginInteractive implements Backend. It requests a new
@@ -1594,15 +1597,7 @@ func (b *LocalBackend) StartLoginInteractive() {
 	if url != "" {
 		b.popBrowserAuthNow()
 	} else {
-		flags := controlclient.LoginInteractive
-		if runtime.GOOS == "js" {
-			// The js/wasm client has no state storage so for now
-			// treat all interactive logins as ephemeral.
-			// TODO(bradfitz): if we start using browser LocalStorage
-			// or something, then rethink this.
-			flags |= controlclient.LoginEphemeral
-		}
-		cc.Login(nil, flags)
+		cc.Login(nil, b.loginFlags|controlclient.LoginInteractive)
 	}
 }
 

ipn/ipnlocal/local_test.go

@@ -463,7 +463,7 @@ func TestLazyMachineKeyGeneration(t *testing.T) {
 		t.Fatalf("NewFakeUserspaceEngine: %v", err)
 	}
 	t.Cleanup(eng.Close)
-	lb, err := NewLocalBackend(logf, "logid", store, nil, eng)
+	lb, err := NewLocalBackend(logf, "logid", store, nil, eng, 0)
 	if err != nil {
 		t.Fatalf("NewLocalBackend: %v", err)
 	}

ipn/ipnlocal/loglines_test.go

@@ -54,7 +54,7 @@ func TestLocalLogLines(t *testing.T) {
 	}
 	t.Cleanup(e.Close)
 
-	lb, err := NewLocalBackend(logf, idA.String(), store, nil, e)
+	lb, err := NewLocalBackend(logf, idA.String(), store, nil, e, 0)
 	if err != nil {
 		t.Fatal(err)
 	}

ipn/ipnlocal/state_test.go

@@ -293,7 +293,7 @@ func TestStateMachine(t *testing.T) {
 
 	cc := newMockControl(t)
 	t.Cleanup(func() { cc.preventLog.Set(true) }) // hacky way to pacify issue 3020
-	b, err := NewLocalBackend(logf, "logid", store, nil, e)
+	b, err := NewLocalBackend(logf, "logid", store, nil, e, 0)
 	if err != nil {
 		t.Fatalf("NewLocalBackend: %v", err)
 	}
@@ -954,7 +954,7 @@ func TestWGEngineStatusRace(t *testing.T) {
 	eng, err := wgengine.NewFakeUserspaceEngine(logf, 0)
 	c.Assert(err, qt.IsNil)
 	t.Cleanup(eng.Close)
-	b, err := NewLocalBackend(logf, "logid", new(ipn.MemoryStore), nil, eng)
+	b, err := NewLocalBackend(logf, "logid", new(ipn.MemoryStore), nil, eng, 0)
 	c.Assert(err, qt.IsNil)
 
 	cc := newMockControl(t)

ipn/ipnserver/server.go

@@ -85,6 +85,9 @@ type Options struct {
 	// the actual definition of "disconnect" is when the
 	// connection count transitions from 1 to 0.
 	SurviveDisconnects bool
+
+	// LoginFlags specifies the LoginFlags to pass to the client.
+	LoginFlags controlclient.LoginFlags
 }
 
 // Server is an IPN backend and its set of 0 or more active localhost
@@ -660,6 +663,8 @@ func tryWindowsAppDataMigration(logf logger.Logf, path string) string {
 // Special cases:
 //
 //   * empty string means to use an in-memory store
+//   * if the string begins with "mem:", the suffix
+//     is ignored and an in-memory store is used.
 //   * if the string begins with "kube:", the suffix
 //     is a Kubernetes secret name
 //   * if the string begins with "arn:", the value is
@@ -668,9 +673,12 @@ func StateStore(path string, logf logger.Logf) (ipn.StateStore, error) {
 	if path == "" {
 		return &ipn.MemoryStore{}, nil
 	}
+	const memPrefix = "mem:"
 	const kubePrefix = "kube:"
 	const arnPrefix = "arn:"
 	switch {
+	case strings.HasPrefix(path, memPrefix):
+		return &ipn.MemoryStore{}, nil
 	case strings.HasPrefix(path, kubePrefix):
 		secretName := strings.TrimPrefix(path, kubePrefix)
 		store, err := ipn.NewKubeStore(secretName)
@@ -797,7 +805,7 @@ func Run(ctx context.Context, logf logger.Logf, ln net.Listener, store ipn.State
 //
 // To start it, use the Server.Run method.
 func New(logf logger.Logf, logid string, store ipn.StateStore, eng wgengine.Engine, dialer *tsdial.Dialer, serverModeUser *user.User, opts Options) (*Server, error) {
-	b, err := ipnlocal.NewLocalBackend(logf, logid, store, dialer, eng)
+	b, err := ipnlocal.NewLocalBackend(logf, logid, store, dialer, eng, opts.LoginFlags)
 	if err != nil {
 		return nil, fmt.Errorf("NewLocalBackend: %v", err)
 	}

tsnet/tsnet.go

@@ -54,6 +54,10 @@ type Server struct {
 	// log.Printf is used.
 	Logf logger.Logf
 
+	// Ephemeral, if true, specifies that the instance should register
+	// as an Ephemeral node (https://tailscale.com/kb/1111/ephemeral-nodes/).
+	Emphemeral bool
+
 	initOnce sync.Once
 	initErr  error
 	lb       *ipnlocal.LocalBackend
@@ -173,7 +177,11 @@ func (s *Server) start() error {
 	}
 	logid := "tslib-TODO"
 
-	lb, err := ipnlocal.NewLocalBackend(logf, logid, store, s.dialer, eng)
+	loginFlags := controlclient.LoginDefault
+	if s.Emphemeral {
+		loginFlags = controlclient.LoginEphemeral
+	}
+	lb, err := ipnlocal.NewLocalBackend(logf, logid, store, s.dialer, eng, loginFlags)
 	if err != nil {
 		return fmt.Errorf("NewLocalBackend: %v", err)
 	}

tstest/integration/tailscaled_deps_test_darwin.go

@@ -13,6 +13,7 @@ import (
 	// process and can cache a prior success when a dependency changes.
 	_ "inet.af/netaddr"
 	_ "tailscale.com/chirp"
+	_ "tailscale.com/control/controlclient"
 	_ "tailscale.com/derp/derphttp"
 	_ "tailscale.com/envknob"
 	_ "tailscale.com/ipn"

tstest/integration/tailscaled_deps_test_freebsd.go

@@ -13,6 +13,7 @@ import (
 	// process and can cache a prior success when a dependency changes.
 	_ "inet.af/netaddr"
 	_ "tailscale.com/chirp"
+	_ "tailscale.com/control/controlclient"
 	_ "tailscale.com/derp/derphttp"
 	_ "tailscale.com/envknob"
 	_ "tailscale.com/ipn"

tstest/integration/tailscaled_deps_test_linux.go

@@ -13,6 +13,7 @@ import (
 	// process and can cache a prior success when a dependency changes.
 	_ "inet.af/netaddr"
 	_ "tailscale.com/chirp"
+	_ "tailscale.com/control/controlclient"
 	_ "tailscale.com/derp/derphttp"
 	_ "tailscale.com/envknob"
 	_ "tailscale.com/ipn"

tstest/integration/tailscaled_deps_test_openbsd.go

@@ -13,6 +13,7 @@ import (
 	// process and can cache a prior success when a dependency changes.
 	_ "inet.af/netaddr"
 	_ "tailscale.com/chirp"
+	_ "tailscale.com/control/controlclient"
 	_ "tailscale.com/derp/derphttp"
 	_ "tailscale.com/envknob"
 	_ "tailscale.com/ipn"

tstest/integration/tailscaled_deps_test_windows.go

@@ -16,6 +16,7 @@ import (
 	_ "golang.org/x/sys/windows/svc/mgr"
 	_ "golang.zx2c4.com/wireguard/windows/tunnel/winipcfg"
 	_ "inet.af/netaddr"
+	_ "tailscale.com/control/controlclient"
 	_ "tailscale.com/derp/derphttp"
 	_ "tailscale.com/envknob"
 	_ "tailscale.com/ipn"