cmd/cli: get static DNS using syscall

cmd/cli/os_windows.go

@@ -13,14 +13,15 @@ import (
 	"sync"
 
 	"golang.org/x/sys/windows"
+	"golang.org/x/sys/windows/registry"
 	"golang.zx2c4.com/wireguard/windows/tunnel/winipcfg"
 
 	ctrldnet "github.com/Control-D-Inc/ctrld/internal/net"
 )
 
 const (
-	v4InterfaceKeyPathFormat = `HKLM:\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\`
-	v6InterfaceKeyPathFormat = `HKLM:\SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters\Interfaces\`
+	v4InterfaceKeyPathFormat = `SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\`
+	v6InterfaceKeyPathFormat = `SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters\Interfaces\`
 )
 
 var (
@@ -177,25 +178,31 @@ func currentDNS(iface *net.Interface) []string {
 func currentStaticDNS(iface *net.Interface) ([]string, error) {
 	luid, err := winipcfg.LUIDFromIndex(uint32(iface.Index))
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("winipcfg.LUIDFromIndex: %w", err)
 	}
 	guid, err := luid.GUID()
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("luid.GUID: %w", err)
 	}
 	var ns []string
 	for _, path := range []string{v4InterfaceKeyPathFormat, v6InterfaceKeyPathFormat} {
-		interfaceKeyPath := path + guid.String()
 		found := false
+		interfaceKeyPath := path + guid.String()
+		k, err := registry.OpenKey(registry.LOCAL_MACHINE, interfaceKeyPath, registry.QUERY_VALUE)
+		if err != nil {
+			return nil, fmt.Errorf("%s: %w", interfaceKeyPath, err)
+		}
 		for _, key := range []string{"NameServer", "ProfileNameServer"} {
 			if found {
 				continue
 			}
-			cmd := fmt.Sprintf(`Get-ItemPropertyValue -Path "%s" -Name "%s"`, interfaceKeyPath, key)
-			out, err := powershell(cmd)
-			if err == nil && len(out) > 0 {
+			value, _, err := k.GetStringValue(key)
+			if err != nil && !errors.Is(err, registry.ErrNotExist) {
+				return nil, fmt.Errorf("%s: %w", key, err)
+			}
+			if len(value) > 0 {
 				found = true
-				for _, e := range strings.Split(string(out), ",") {
+				for _, e := range strings.Split(value, ",") {
 					ns = append(ns, strings.TrimRight(e, "\x00"))
 				}
 			}

cmd/cli/os_windows_test.go

@@ -0,0 +1,68 @@
+package cli
+
+import (
+	"fmt"
+	"net"
+	"slices"
+	"strings"
+	"testing"
+	"time"
+
+	"golang.zx2c4.com/wireguard/windows/tunnel/winipcfg"
+)
+
+func Test_currentStaticDNS(t *testing.T) {
+	iface, err := net.InterfaceByName(defaultIfaceName())
+	if err != nil {
+		t.Fatal(err)
+	}
+	start := time.Now()
+	staticDns, err := currentStaticDNS(iface)
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Logf("Using Windows API takes: %d", time.Since(start).Milliseconds())
+
+	start = time.Now()
+	staticDnsPowershell, err := currentStaticDnsPowershell(iface)
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Logf("Using Powershell takes: %d", time.Since(start).Milliseconds())
+
+	slices.Sort(staticDns)
+	slices.Sort(staticDnsPowershell)
+	if !slices.Equal(staticDns, staticDnsPowershell) {
+		t.Fatalf("result mismatch, want: %v, got: %v", staticDnsPowershell, staticDns)
+	}
+}
+
+func currentStaticDnsPowershell(iface *net.Interface) ([]string, error) {
+	luid, err := winipcfg.LUIDFromIndex(uint32(iface.Index))
+	if err != nil {
+		return nil, err
+	}
+	guid, err := luid.GUID()
+	if err != nil {
+		return nil, err
+	}
+	var ns []string
+	for _, path := range []string{"HKLM:\\" + v4InterfaceKeyPathFormat, "HKLM:\\" + v6InterfaceKeyPathFormat} {
+		interfaceKeyPath := path + guid.String()
+		found := false
+		for _, key := range []string{"NameServer", "ProfileNameServer"} {
+			if found {
+				continue
+			}
+			cmd := fmt.Sprintf(`Get-ItemPropertyValue -Path "%s" -Name "%s"`, interfaceKeyPath, key)
+			out, err := powershell(cmd)
+			if err == nil && len(out) > 0 {
+				found = true
+				for _, e := range strings.Split(string(out), ",") {
+					ns = append(ns, strings.TrimRight(e, "\x00"))
+				}
+			}
+		}
+	}
+	return ns, nil
+}