cmd/tailscale/cli: add backwards compatibility 'up' processing for legacy client

Updates tailscale/corp#6781

Change-Id: I843fc810cbec0140d423d65db81e90179d6e0fa5
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/tailscale/cli/cli_test.go

@@ -762,6 +762,9 @@ func TestPrefFlagMapping(t *testing.T) {
 		case "NotepadURLs":
 			// TODO(bradfitz): https://github.com/tailscale/tailscale/issues/1830
 			continue
+		case "Egg":
+			// Not applicable.
+			continue
 		}
 		t.Errorf("unexpected new ipn.Pref field %q is not handled by up.go (see addPrefFlagMapping and checkForAccidentalSettingReverts)", prefName)
 	}

cmd/tailscale/cli/up.go

@@ -406,8 +406,12 @@ func updatePrefs(prefs, curPrefs *ipn.Prefs, env upCheckEnv) (simpleUp bool, jus
 }
 
 func runUp(ctx context.Context, args []string) (retErr error) {
+	var egg bool
 	if len(args) > 0 {
-		fatalf("too many non-flag arguments: %q", args)
+		egg = fmt.Sprint(args) == "[up down down left right left right b a]"
+		if !egg {
+			fatalf("too many non-flag arguments: %q", args)
+		}
 	}
 
 	st, err := localClient.Status(ctx)
@@ -493,6 +497,7 @@ func runUp(ctx context.Context, args []string) (retErr error) {
 		fatalf("%s", err)
 	}
 	if justEditMP != nil {
+		justEditMP.EggSet = true
 		_, err := localClient.EditPrefs(ctx, justEditMP)
 		return err
 	}

ipn/ipn_clone.go

@@ -48,6 +48,7 @@ var _PrefsCloneNeedsRegeneration = Prefs(struct {
 	Hostname               string
 	NotepadURLs            bool
 	ForceDaemon            bool
+	Egg                    bool
 	AdvertiseRoutes        []netip.Prefix
 	NoSNAT                 bool
 	NetfilterMode          preftype.NetfilterMode

ipn/ipnlocal/local.go

@@ -164,6 +164,7 @@ type LocalBackend struct {
 	authURL          string // cleared on Notify
 	authURLSticky    string // not cleared on Notify
 	interact         bool
+	egg              bool
 	prevIfState      *interfaces.State
 	peerAPIServer    *peerAPIServer // or nil
 	peerAPIListeners []*peerAPIListener
@@ -423,7 +424,6 @@ func (b *LocalBackend) updateStatus(sb *ipnstate.StatusBuilder, extraLocked func
 		s.Version = version.Long
 		s.BackendState = b.state.String()
 		s.AuthURL = b.authURLSticky
-
 		if err := health.OverallError(); err != nil {
 			switch e := err.(type) {
 			case multierr.Error:
@@ -2015,6 +2015,11 @@ func (b *LocalBackend) isDefaultServerLocked() bool {
 
 func (b *LocalBackend) EditPrefs(mp *ipn.MaskedPrefs) (*ipn.Prefs, error) {
 	b.mu.Lock()
+	if mp.EggSet {
+		mp.EggSet = false
+		b.egg = true
+		go b.doSetHostinfoFilterServices(b.hostinfo.Clone())
+	}
 	p0 := b.prefs.Clone()
 	p1 := b.prefs.Clone()
 	p1.ApplyEdits(mp)
@@ -2211,6 +2216,9 @@ func (b *LocalBackend) doSetHostinfoFilterServices(hi *tailcfg.Hostinfo) {
 		return
 	}
 	peerAPIServices := b.peerAPIServicesLocked()
+	if b.egg {
+		peerAPIServices = append(peerAPIServices, tailcfg.Service{Proto: "egg"})
+	}
 	b.mu.Unlock()
 
 	// Make a shallow copy of hostinfo so we can mutate

ipn/prefs.go

@@ -163,6 +163,9 @@ type Prefs struct {
 	// for Linux/etc, which always operate in daemon mode.
 	ForceDaemon bool `json:"ForceDaemon,omitempty"`
 
+	// Egg is a optional debug flag.
+	Egg bool
+
 	// The following block of options only have an effect on Linux.
 
 	// AdvertiseRoutes specifies CIDR prefixes to advertise into the
@@ -217,6 +220,7 @@ type MaskedPrefs struct {
 	HostnameSet               bool `json:",omitempty"`
 	NotepadURLsSet            bool `json:",omitempty"`
 	ForceDaemonSet            bool `json:",omitempty"`
+	EggSet                    bool `json:",omitempty"`
 	AdvertiseRoutesSet        bool `json:",omitempty"`
 	NoSNATSet                 bool `json:",omitempty"`
 	NetfilterModeSet          bool `json:",omitempty"`

ipn/prefs_test.go

@@ -52,6 +52,7 @@ func TestPrefsEqual(t *testing.T) {
 		"Hostname",
 		"NotepadURLs",
 		"ForceDaemon",
+		"Egg",
 		"AdvertiseRoutes",
 		"NoSNAT",
 		"NetfilterMode",