From a56711796fb1f67904436f1f3b38772d79dde666 Mon Sep 17 00:00:00 2001
From: Cuong Manh Le <cuong@windscribe.com>
Date: Wed, 20 Nov 2024 21:39:01 +0700
Subject: [PATCH] cmd/cli: set DNS using Windows API

---
 cmd/cli/os_windows.go | 55 +++++++++++++++++++++++++++++++------------
 1 file changed, 40 insertions(+), 15 deletions(-)

diff --git a/cmd/cli/os_windows.go b/cmd/cli/os_windows.go
index b9412b6..1a22b0f 100644
--- a/cmd/cli/os_windows.go
+++ b/cmd/cli/os_windows.go
@@ -4,12 +4,13 @@ import (
 	"errors"
 	"fmt"
 	"net"
+	"net/netip"
 	"os"
 	"slices"
-	"strconv"
 	"strings"
 	"sync"
 
+	"golang.org/x/sys/windows"
 	"golang.zx2c4.com/wireguard/windows/tunnel/winipcfg"
 
 	ctrldnet "github.com/Control-D-Inc/ctrld/internal/net"
@@ -30,14 +31,6 @@ func setDnsIgnoreUnusableInterface(iface *net.Interface, nameservers []string) e
 	return setDNS(iface, nameservers)
 }
 
-func setDnsPowershellCmd(iface *net.Interface, nameservers []string) string {
-	nss := make([]string, 0, len(nameservers))
-	for _, ns := range nameservers {
-		nss = append(nss, strconv.Quote(ns))
-	}
-	return fmt.Sprintf("Set-DnsClientServerAddress -InterfaceIndex %d -ServerAddresses (%s)", iface.Index, strings.Join(nss, ","))
-}
-
 // setDNS sets the dns server for the provided network interface
 func setDNS(iface *net.Interface, nameservers []string) error {
 	if len(nameservers) == 0 {
@@ -65,9 +58,36 @@ func setDNS(iface *net.Interface, nameservers []string) error {
 			}
 		}
 	})
-	out, err := powershell(setDnsPowershellCmd(iface, nameservers))
+	luid, err := winipcfg.LUIDFromIndex(uint32(iface.Index))
 	if err != nil {
-		return fmt.Errorf("%w: %s", err, string(out))
+		return fmt.Errorf("setDNS: %w", err)
+	}
+	var (
+		serversV4 []netip.Addr
+		serversV6 []netip.Addr
+	)
+	for _, ns := range nameservers {
+		if addr, err := netip.ParseAddr(ns); err == nil {
+			if addr.Is4() {
+				serversV4 = append(serversV4, addr)
+			} else {
+				serversV6 = append(serversV6, addr)
+			}
+		}
+	}
+
+	if len(serversV4) == 0 && len(serversV6) == 0 {
+		return errors.New("invalid DNS nameservers")
+	}
+	if len(serversV4) > 0 {
+		if err := luid.SetDNS(windows.AF_INET, serversV4, nil); err != nil {
+			return fmt.Errorf("could not set DNS ipv4: %w", err)
+		}
+	}
+	if len(serversV6) > 0 {
+		if err := luid.SetDNS(windows.AF_INET6, serversV6, nil); err != nil {
+			return fmt.Errorf("could not set DNS ipv6: %w", err)
+		}
 	}
 	return nil
 }
@@ -96,11 +116,16 @@ func resetDNS(iface *net.Interface) error {
 		}
 	})
 
-	// Restoring DHCP settings.
-	cmd := fmt.Sprintf("Set-DnsClientServerAddress -InterfaceIndex %d -ResetServerAddresses", iface.Index)
-	out, err := powershell(cmd)
+	luid, err := winipcfg.LUIDFromIndex(uint32(iface.Index))
 	if err != nil {
-		return fmt.Errorf("%w: %s", err, string(out))
+		return fmt.Errorf("resetDNS: %w", err)
+	}
+	// Restoring DHCP settings.
+	if err := luid.SetDNS(windows.AF_INET, nil, nil); err != nil {
+		return fmt.Errorf("could not reset DNS ipv4: %w", err)
+	}
+	if err := luid.SetDNS(windows.AF_INET6, nil, nil); err != nil {
+		return fmt.Errorf("could not reset DNS ipv6: %w", err)
 	}
 
 	// If there's static DNS saved, restoring it.