Flags refactoring + custom MTU

flags/flags.go

@@ -0,0 +1,39 @@
+package flags
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/spf13/pflag"
+	"golang.zx2c4.com/wireguard/device"
+)
+
+func Parse(opts *Options) error {
+	pflag.Usage = func() {
+		fmt.Fprintf(os.Stderr, "Usage: %s [flags] <interface-name>\n", os.Args[0])
+		pflag.PrintDefaults()
+	}
+
+	pflag.IntVar(&opts.MTU, "mtu", device.DefaultMTU, "Set the MTU of the device")
+	pflag.BoolVar(&opts.Foreground, "foreground", false, "Remain in the foreground")
+	pflag.BoolVarP(&opts.ShowVersion, "version", "v", false, "Print the version number and exit")
+
+	pflag.Parse()
+
+	if opts.ShowVersion {
+		return nil
+	}
+
+	if err := setInterfaceName(opts); err != nil {
+		return err
+	}
+	return nil
+}
+
+func setInterfaceName(opts *Options) error {
+	if pflag.NArg() != 1 {
+		return fmt.Errorf("Must pass exactly one interface name, but got %d", pflag.NArg())
+	}
+	opts.InterfaceName = pflag.Arg(0)
+	return nil
+}

flags/options.go

@@ -0,0 +1,13 @@
+package flags
+
+type Options struct {
+	InterfaceName string
+
+	MTU         int
+	Foreground  bool
+	ShowVersion bool
+}
+
+func NewOptions() *Options {
+	return &Options{}
+}

go.mod

@@ -3,6 +3,7 @@ module golang.zx2c4.com/wireguard
 go 1.20
 
 require (
+	github.com/spf13/pflag v1.0.5
 	golang.org/x/crypto v0.13.0
 	golang.org/x/net v0.15.0
 	golang.org/x/sys v0.12.0

go.sum

@@ -1,5 +1,7 @@
 github.com/google/btree v1.0.1 h1:gK4Kx5IaGY9CD5sPJ36FHiBJ6ZXl0kilRiiCj+jdYp4=
 github.com/google/btree v1.0.1/go.mod h1:xXMiIv4Fb/0kKde4SpL7qlzvu5cMJDRkFDxJfI9uaxA=
+github.com/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
+github.com/spf13/pflag v1.0.5/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
 golang.org/x/crypto v0.13.0 h1:mvySKfSWJ+UKUii46M40LOvyWfN0s2U+46/jDd0e6Ck=
 golang.org/x/crypto v0.13.0/go.mod h1:y6Z2r+Rw4iayiXXAIxJIDAJ1zMW4yaTpebo8fPOliYc=
 golang.org/x/net v0.15.0 h1:ugBLEUaxABaB5AJqW9enI0ACdci2RUd4eP51NTBvuJ8=

main.go

@@ -17,6 +17,7 @@ import (
 	"golang.org/x/sys/unix"
 	"golang.zx2c4.com/wireguard/conn"
 	"golang.zx2c4.com/wireguard/device"
+	"golang.zx2c4.com/wireguard/flags"
 	"golang.zx2c4.com/wireguard/ipc"
 	"golang.zx2c4.com/wireguard/tun"
 )
@@ -32,10 +33,6 @@ const (
 	ENV_WG_PROCESS_FOREGROUND = "WG_PROCESS_FOREGROUND"
 )
 
-func printUsage() {
-	fmt.Printf("Usage: %s [-f/--foreground] INTERFACE-NAME\n", os.Args[0])
-}
-
 func warning() {
 	switch runtime.GOOS {
 	case "linux", "freebsd", "openbsd":
@@ -58,41 +55,21 @@ func warning() {
 }
 
 func main() {
-	if len(os.Args) == 2 && os.Args[1] == "--version" {
-		fmt.Printf("wireguard-go v%s\n\nUserspace WireGuard daemon for %s-%s.\nInformation available at https://www.wireguard.com.\nCopyright (C) Jason A. Donenfeld <[email protected]>.\n", Version, runtime.GOOS, runtime.GOARCH)
-		return
+	opts := flags.NewOptions()
+	if err := flags.Parse(opts); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(ExitSetupFailed)
 	}
 
-	warning()
-
-	var foreground bool
-	var interfaceName string
-	if len(os.Args) < 2 || len(os.Args) > 3 {
-		printUsage()
+	if opts.ShowVersion {
+		fmt.Printf("wireguard-go v%s\n\nUserspace WireGuard daemon for %s-%s.\nInformation available at https://www.wireguard.com.\nCopyright (C) Jason A. Donenfeld <[email protected]>.\n", Version, runtime.GOOS, runtime.GOARCH)
 		return
 	}
 
-	switch os.Args[1] {
-
-	case "-f", "--foreground":
-		foreground = true
-		if len(os.Args) != 3 {
-			printUsage()
-			return
-		}
-		interfaceName = os.Args[2]
-
-	default:
-		foreground = false
-		if len(os.Args) != 2 {
-			printUsage()
-			return
-		}
-		interfaceName = os.Args[1]
-	}
+	warning()
 
-	if !foreground {
-		foreground = os.Getenv(ENV_WG_PROCESS_FOREGROUND) == "1"
+	if !opts.Foreground {
+		opts.Foreground = os.Getenv(ENV_WG_PROCESS_FOREGROUND) == "1"
 	}
 
 	// get log level (default: info)
@@ -111,10 +88,12 @@ func main() {
 
 	// open TUN device (or use supplied fd)
 
+	interfaceName := opts.InterfaceName
+
 	tdev, err := func() (tun.Device, error) {
 		tunFdStr := os.Getenv(ENV_WG_TUN_FD)
 		if tunFdStr == "" {
-			return tun.CreateTUN(interfaceName, device.DefaultMTU)
+			return tun.CreateTUN(interfaceName, opts.MTU)
 		}
 
 		// construct tun device from supplied fd
@@ -130,7 +109,7 @@ func main() {
 		}
 
 		file := os.NewFile(uintptr(fd), "")
-		return tun.CreateTUNFromFile(file, device.DefaultMTU)
+		return tun.CreateTUNFromFile(file, opts.MTU)
 	}()
 
 	if err == nil {
@@ -176,7 +155,7 @@ func main() {
 	}
 	// daemonize the process
 
-	if !foreground {
+	if !opts.Foreground {
 		env := os.Environ()
 		env = append(env, fmt.Sprintf("%s=3", ENV_WG_TUN_FD))
 		env = append(env, fmt.Sprintf("%s=4", ENV_WG_UAPI_FD))