implemented child process

config/config.go

@@ -40,7 +40,7 @@ type Configuration struct {
 type Host struct {
 	Crypto    string `validate:"required,oneof=None Blake2s"`
 	SharedKey string `validate:"required_if=Crypto Blake2s"`
-	MTU       uint
+	MTU       uint `validate:"required,min=576"`
 }
 
 type Peer struct {

main.go

@@ -28,6 +28,7 @@ func main() {
 		// 2) create a tun adapter
 		// 3) spawn a child
 		// 4) exit
+
 		o, err := flags.ParseFlags()
 		if err != nil {
 			if errors.Is(err, flags.PrintedHelpErr) {
@@ -56,8 +57,40 @@ func main() {
 			if err := os.Setenv(ENV_NC_CONFIG_PATH, o.ConfigFile); err != nil {
 				panic(err)
 			}
+			log.Println("switching to foreground")
 			goto FOREGROUND
 		}
+
+		files := make([]*os.File, 4)
+		files[0], _ = os.Open(os.DevNull) // stdin
+		files[1], _ = os.Open(os.DevNull) // stderr
+		files[2], _ = os.Open(os.DevNull) // stdout
+		files[3] = t.File()
+
+		env := os.Environ()
+		env = append(env, fmt.Sprintf("%s=3", ENV_NC_TUN_FD))
+		env = append(env, fmt.Sprintf("%s=%s", ENV_NC_CONFIG_PATH, o.ConfigFile))
+
+		attr := os.ProcAttr{
+			Env:   env,
+			Files: files,
+		}
+
+		path, err := os.Executable()
+		if err != nil {
+			panic(err)
+		}
+
+		process, err := os.StartProcess(
+			path,
+			os.Args,
+			&attr,
+		)
+		if err != nil {
+			panic(err)
+		}
+
+		_ = process.Release()
 		return
 	}
 

tun/tun.go

@@ -51,7 +51,7 @@ func NewFromFile(fd uintptr, mtu int) (ss *SourceSink, err error) {
 
 
 			if strings.Contains(iface.Flags.String(), "up") {
-				log.Println("wgtun is up")
+				log.Println("tun is up")
 				ss.up = true
 				return
 			}
@@ -77,7 +77,7 @@ func (t *SourceSink) Source() (proxy.Packet, error) {
 
 	buf := make([]byte, t.mtu)
 
-	read, err := t.tun.Read(buf, t.mtu)
+	read, err := t.tun.Read(buf, 4)
 	if err != nil {
 		return nil, err
 	}
@@ -97,7 +97,7 @@ func (t *SourceSink) Sink(packet proxy.Packet) error {
 		t.upMu.Unlock()
 	}
 
-	_, err := t.tun.Write(packet.Contents(), t.mtu)
+	_, err := t.tun.Write(packet.Contents(), 4)
 	if err != nil {
 		switch err.(type) {
 		case *os.PathError: