cmd/lopower: move lp init to newLP

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

cmd/lopower/lopower.go

@@ -16,6 +16,7 @@ import (
 	"os/signal"
 	"path/filepath"
 	"slices"
+	"sync"
 
 	"github.com/tailscale/wireguard-go/conn"
 	"github.com/tailscale/wireguard-go/device"
@@ -41,6 +42,7 @@ import (
 var (
 	wgListenPort = flag.Int("wg-port", 51820, "port number to listen on for WireGuard from the client")
 	qrListenAddr = flag.String("qr-listen", "127.0.0.1:8014", "HTTP address to serve a QR code for client's WireGuard configuration")
+	confDir      = flag.String("dir", filepath.Join(os.Getenv("HOME"), ".config/lopower"), "directory to store configuration in")
 )
 
 type config struct {
@@ -62,8 +64,8 @@ type Peer struct {
 	V6     netip.Addr
 }
 
-func storeConfig(cfg *config) {
-	path := filepath.Join(os.Getenv("HOME"), ".config/lopower/config.json")
+func (lp *lpServer) storeConfigLocked() {
+	path := filepath.Join(lp.dir, "config.json")
 	if err := os.MkdirAll(filepath.Dir(path), 0700); err != nil {
 		log.Fatalf("os.MkdirAll(%q): %v", filepath.Dir(path), err)
 	}
@@ -72,19 +74,23 @@ func storeConfig(cfg *config) {
 		log.Fatalf("os.OpenFile(%q): %v", path, err)
 	}
 	defer f.Close()
-	must.Do(json.NewEncoder(f).Encode(cfg))
+	must.Do(json.NewEncoder(f).Encode(lp.c))
 	if err := f.Close(); err != nil {
 		log.Fatalf("f.Close: %v", err)
 	}
 }
 
-func loadConfig() *config {
-	path := filepath.Join(os.Getenv("HOME"), ".config/lopower/config.json")
+func (lp *lpServer) loadConfig() {
+	path := filepath.Join(lp.dir, "config.json")
 	f, err := os.OpenFile(path, os.O_RDONLY, 0)
 	if err == nil {
+		defer f.Close()
 		var cfg *config
 		must.Do(json.NewDecoder(f).Decode(&cfg))
-		return cfg
+		lp.mu.Lock()
+		defer lp.mu.Unlock()
+		lp.c = cfg
+		return
 	}
 	if !os.IsNotExist(err) {
 		log.Fatalf("os.OpenFile(%q): %v", path, err)
@@ -98,11 +104,15 @@ func loadConfig() *config {
 	}
 	c.V4 = c.V4CIDR.Addr().Next()
 	c.V6 = c.V6CIDR.Addr().Next()
-	storeConfig(c)
-	return c
+	lp.mu.Lock()
+	defer lp.mu.Unlock()
+	lp.c = c
+	lp.storeConfigLocked()
+	return
 }
 
 func (lp *lpServer) reconfig() {
+	lp.mu.Lock()
 	wc := &wgcfg.Config{
 		Name:       "lopower0",
 		PrivateKey: lp.c.PrivKey,
@@ -121,14 +131,44 @@ func (lp *lpServer) reconfig() {
 			},
 		})
 	}
+	lp.mu.Unlock()
 	must.Do(wgcfg.ReconfigDevice(lp.d, wc, log.Printf))
 }
 
+func newLP(ctx context.Context) *lpServer {
+	logf := log.Printf
+	deviceLogger := &device.Logger{
+		Verbosef: logger.Discard,
+		Errorf:   logf,
+	}
+	lp := &lpServer{
+		dir: *confDir,
+	}
+	lp.loadConfig()
+	lp.initNetstack(ctx)
+	nst := &nsTUN{
+		lp:      lp,
+		closeCh: make(chan struct{}),
+		evChan:  make(chan tun.Event),
+	}
+	wgdev := wgcfg.NewDevice(nst, conn.NewDefaultBind(), deviceLogger)
+	defer wgdev.Close()
+	lp.d = wgdev
+	must.Do(wgdev.Up())
+	lp.reconfig()
+	lp.startTSNet(ctx)
+	return lp
+}
+
 type lpServer struct {
-	c      *config
+	dir    string
+	tsnet  *tsnet.Server
 	d      *device.Device
 	ns     *stack.Stack
 	linkEP *channel.Endpoint
+
+	mu sync.Mutex // protects following
+	c  *config
 }
 
 // MaxPacketSize is the maximum size (in bytes)
@@ -161,9 +201,12 @@ func (lp *lpServer) initNetstack(ctx context.Context) error {
 	ns.SetSpoofing(nicID, true)
 
 	var routes []tcpip.Route
+	lp.mu.Lock()
+	v4, v6 := lp.c.V4, lp.c.V6
+	lp.mu.Unlock()
 
 	{
-		prefix := tcpip.AddrFrom4Slice(lp.c.V4.AsSlice()).WithPrefix()
+		prefix := tcpip.AddrFrom4Slice(v4.AsSlice()).WithPrefix()
 		if tcpProb := ns.AddProtocolAddress(nicID, tcpip.ProtocolAddress{
 			Protocol:          ipv4.ProtocolNumber,
 			AddressWithPrefix: prefix,
@@ -181,7 +224,7 @@ func (lp *lpServer) initNetstack(ctx context.Context) error {
 		})
 	}
 	{
-		prefix := tcpip.AddrFrom16(lp.c.V6.As16()).WithPrefix()
+		prefix := tcpip.AddrFrom16(v6.As16()).WithPrefix()
 		if tcpProb := ns.AddProtocolAddress(nicID, tcpip.ProtocolAddress{
 			Protocol:          ipv6.ProtocolNumber,
 			AddressWithPrefix: prefix,
@@ -290,19 +333,20 @@ func (t *nsTUN) Name() (string, error)    { return "nstun", nil }
 func (t *nsTUN) Events() <-chan tun.Event { return t.evChan }
 func (t *nsTUN) BatchSize() int           { return 1 }
 
-func startTSNet(ctx context.Context) {
+func (lp *lpServer) startTSNet(ctx context.Context) {
 	hostname, err := os.Hostname()
 	if err != nil {
 		log.Fatal(err)
 	}
 
-	ts := &tsnet.Server{
+	lp.tsnet = &tsnet.Server{
+		Dir:       filepath.Join(lp.dir, "tsnet"),
 		Hostname:  hostname,
 		UserLogf:  log.Printf,
 		Ephemeral: false,
 	}
 
-	if _, err := ts.Up(ctx); err != nil {
+	if _, err := lp.tsnet.Up(ctx); err != nil {
 		log.Fatal(err)
 	}
 }
@@ -310,29 +354,10 @@ func startTSNet(ctx context.Context) {
 func main() {
 	flag.Parse()
 
-	logf := log.Printf
-	deviceLogger := &device.Logger{
-		Verbosef: logger.Discard,
-		Errorf:   logf,
-	}
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
-	lp := &lpServer{
-		c: loadConfig(),
-	}
-	lp.initNetstack(ctx)
-	nst := &nsTUN{
-		lp:      lp,
-		closeCh: make(chan struct{}),
-		evChan:  make(chan tun.Event),
-	}
-	wgdev := wgcfg.NewDevice(nst, conn.NewDefaultBind(), deviceLogger)
-	defer wgdev.Close()
-	lp.d = wgdev
-	must.Do(wgdev.Up())
-	lp.reconfig()
-
-	// startTSNet(ctx)
+	lp := newLP(ctx)
+	_ = lp
 
 	sigCh := make(chan os.Signal, 1)
 	signal.Notify(sigCh, unix.SIGTERM, os.Interrupt)