ipn: temporary support for loading legacy relaynode configs.

Signed-off-by: David Anderson <dave@natulte.net>

cmd/tailscaled/tailscaled.go

@@ -80,6 +80,7 @@ func main() {
 		SocketPath:         *socketpath,
 		StatePath:          *statepath,
 		AutostartStateKey:  globalStateKey,
+		LegacyConfigPath:   "/var/lib/tailscale/relay.conf",
 		SurviveDisconnects: true,
 	}
 	err = ipnserver.Run(context.Background(), logf, pol.PublicID.String(), opts, e)

ipn/backend.go

@@ -82,6 +82,14 @@ type Options struct {
 	//    an initial overwrite of backend state with Prefs.
 	StateKey StateKey
 	Prefs    *Prefs
+	// LegacyConfigPath optionally specifies the old-style relaynode
+	// relay.conf location. If both LegacyConfigPath and StateKey are
+	// specified and the requested state doesn't exist in the backend
+	// store, the backend migrates the config from LegacyConfigPath.
+	//
+	// TODO(danderson): remove some time after the transition to
+	// tailscaled is done.
+	LegacyConfigPath string
 	// Notify is called when backend events happen.
 	Notify func(Notify) `json:"-"`
 }

ipn/ipnserver/server.go

@@ -43,6 +43,15 @@ type Options struct {
 	// using the given StateKey. If empty, the agent stays idle and
 	// waits for a frontend to start it.
 	AutostartStateKey ipn.StateKey
+	// LegacyConfigPath optionally specifies the old-style relaynode
+	// relay.conf location. If both LegacyConfigPath and
+	// AutostartStateKey are specified and the requested state doesn't
+	// exist in the backend store, the backend migrates the config
+	// from LegacyConfigPath.
+	//
+	// TODO(danderson): remove some time after the transition to
+	// tailscaled is done.
+	LegacyConfigPath string
 	// SurviveDisconnects specifies how the server reacts to its
 	// frontend disconnecting. If true, the server keeps running on
 	// its existing state, and accepts new frontend connections. If
@@ -115,6 +124,7 @@ func Run(rctx context.Context, logf logger.Logf, logid string, opts Options, e w
 			Start: &ipn.StartArgs{
 				Opts: ipn.Options{
 					StateKey:         opts.AutostartStateKey,
+					LegacyConfigPath: opts.LegacyConfigPath,
 				},
 			},
 		})

ipn/local.go

@@ -150,7 +150,7 @@ func (b *LocalBackend) Start(opts Options) error {
 	b.hiCache = hi
 	b.state = NoState
 
-	if err := b.loadStateWithLock(opts.StateKey, opts.Prefs); err != nil {
+	if err := b.loadStateWithLock(opts.StateKey, opts.Prefs, opts.LegacyConfigPath); err != nil {
 		b.mu.Unlock()
 		return fmt.Errorf("loading requested state: %v", err)
 	}
@@ -360,7 +360,7 @@ func (b *LocalBackend) popBrowserAuthNow() {
 	}
 }
 
-func (b *LocalBackend) loadStateWithLock(key StateKey, prefs *Prefs) error {
+func (b *LocalBackend) loadStateWithLock(key StateKey, prefs *Prefs, legacyPath string) error {
 	if prefs == nil && key == "" {
 		panic("state key and prefs are both unset")
 	}
@@ -386,9 +386,14 @@ func (b *LocalBackend) loadStateWithLock(key StateKey, prefs *Prefs) error {
 	bs, err := b.store.ReadState(key)
 	if err != nil {
 		if err == ErrStateNotExist {
+			if legacyPath != "" {
+				b.prefs = *LoadPrefs(legacyPath, true)
+				b.logf("Imported state from relaynode for %q", key)
+			} else {
 				b.prefs = NewPrefs()
-			b.stateKey = key
 				b.logf("Created empty state for %q", key)
+			}
+			b.stateKey = key
 			return nil
 		}
 		return fmt.Errorf("store.ReadState(%q): %v", key, err)