Basic platform?

Former-commit-id: 423e18edc3

dns/platform/examples/example_usage.go

@@ -0,0 +1,236 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"net/netip"
+	"os"
+	"os/signal"
+	"syscall"
+	"time"
+
+	"github.com/your-org/olm/dns/platform"
+)
+
+func main() {
+	// Example 1: Automatic detection and DNS override
+	exampleAutoDetection()
+
+	// Example 2: Manual platform selection
+	// exampleManualSelection()
+
+	// Example 3: Get current system DNS
+	// exampleGetCurrentDNS()
+}
+
+// exampleAutoDetection demonstrates automatic detection of the best DNS configurator
+func exampleAutoDetection() {
+	fmt.Println("=== Example 1: Automatic Detection ===")
+
+	// On Linux/Unix, provide an interface name for better detection
+	// On macOS, the interface name is ignored
+	// On Windows, provide the interface GUID
+	ifaceName := "eth0" // Change this to your interface name
+
+	configurator, err := platform.DetectBestConfigurator(ifaceName)
+	if err != nil {
+		log.Fatalf("Failed to detect DNS configurator: %v", err)
+	}
+
+	fmt.Printf("Using DNS configurator: %s\n", configurator.Name())
+
+	// Get current DNS servers before changing
+	currentDNS, err := configurator.GetCurrentDNS()
+	if err != nil {
+		log.Printf("Warning: Could not get current DNS: %v", err)
+	} else {
+		fmt.Printf("Current DNS servers: %v\n", currentDNS)
+	}
+
+	// Set new DNS servers
+	newDNS := []netip.Addr{
+		netip.MustParseAddr("1.1.1.1"),     // Cloudflare
+		netip.MustParseAddr("8.8.8.8"),     // Google
+	}
+
+	fmt.Printf("Setting DNS servers to: %v\n", newDNS)
+	originalDNS, err := configurator.SetDNS(newDNS)
+	if err != nil {
+		log.Fatalf("Failed to set DNS: %v", err)
+	}
+
+	fmt.Printf("Original DNS servers (backed up): %v\n", originalDNS)
+
+	// Set up signal handling for graceful shutdown
+	sigChan := make(chan os.Signal, 1)
+	signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM)
+
+	// Run for 30 seconds or until interrupted
+	fmt.Println("\nDNS override active. Press Ctrl+C to restore original DNS.")
+	fmt.Println("Waiting 30 seconds...")
+
+	select {
+	case <-time.After(30 * time.Second):
+		fmt.Println("\nTimeout reached.")
+	case sig := <-sigChan:
+		fmt.Printf("\nReceived signal: %v\n", sig)
+	}
+
+	// Restore original DNS
+	fmt.Println("Restoring original DNS servers...")
+	if err := configurator.RestoreDNS(); err != nil {
+		log.Fatalf("Failed to restore DNS: %v", err)
+	}
+
+	fmt.Println("DNS restored successfully!")
+}
+
+// exampleManualSelection demonstrates manual selection of DNS configurator
+func exampleManualSelection() {
+	fmt.Println("=== Example 2: Manual Selection ===")
+
+	// Linux - systemd-resolved
+	configurator, err := platform.NewSystemdResolvedDNSConfigurator("eth0")
+	if err != nil {
+		log.Fatalf("Failed to create systemd-resolved configurator: %v", err)
+	}
+
+	fmt.Printf("Using: %s\n", configurator.Name())
+
+	newDNS := []netip.Addr{
+		netip.MustParseAddr("1.1.1.1"),
+	}
+
+	originalDNS, err := configurator.SetDNS(newDNS)
+	if err != nil {
+		log.Fatalf("Failed to set DNS: %v", err)
+	}
+
+	fmt.Printf("Changed from %v to %v\n", originalDNS, newDNS)
+
+	// Restore after 10 seconds
+	time.Sleep(10 * time.Second)
+	configurator.RestoreDNS()
+}
+
+// exampleGetCurrentDNS demonstrates getting current system DNS
+func exampleGetCurrentDNS() {
+	fmt.Println("=== Example 3: Get Current DNS ===")
+
+	configurator, err := platform.DetectBestConfigurator("eth0")
+	if err != nil {
+		log.Fatalf("Failed to detect configurator: %v", err)
+	}
+
+	servers, err := configurator.GetCurrentDNS()
+	if err != nil {
+		log.Fatalf("Failed to get DNS: %v", err)
+	}
+
+	fmt.Printf("Current DNS servers (%s):\n", configurator.Name())
+	for i, server := range servers {
+		fmt.Printf("  %d. %s\n", i+1, server)
+	}
+}
+
+// Platform-specific examples
+
+// exampleLinuxFile demonstrates direct file manipulation on Linux
+func exampleLinuxFile() {
+	configurator, err := platform.NewFileDNSConfigurator()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	newDNS := []netip.Addr{
+		netip.MustParseAddr("8.8.8.8"),
+	}
+
+	originalDNS, err := configurator.SetDNS(newDNS)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	defer configurator.RestoreDNS()
+
+	fmt.Printf("Changed from %v to %v\n", originalDNS, newDNS)
+	time.Sleep(10 * time.Second)
+}
+
+// exampleLinuxNetworkManager demonstrates NetworkManager on Linux
+func exampleLinuxNetworkManager() {
+	if !platform.IsNetworkManagerAvailable() {
+		fmt.Println("NetworkManager is not available")
+		return
+	}
+
+	configurator, err := platform.NewNetworkManagerDNSConfigurator("eth0")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	newDNS := []netip.Addr{
+		netip.MustParseAddr("1.1.1.1"),
+	}
+
+	originalDNS, err := configurator.SetDNS(newDNS)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	defer configurator.RestoreDNS()
+
+	fmt.Printf("Changed from %v to %v\n", originalDNS, newDNS)
+	time.Sleep(10 * time.Second)
+}
+
+// exampleMacOS demonstrates macOS DNS override
+func exampleMacOS() {
+	configurator, err := platform.NewDarwinDNSConfigurator()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	newDNS := []netip.Addr{
+		netip.MustParseAddr("1.1.1.1"),
+		netip.MustParseAddr("1.0.0.1"),
+	}
+
+	originalDNS, err := configurator.SetDNS(newDNS)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	defer configurator.RestoreDNS()
+
+	fmt.Printf("Changed from %v to %v\n", originalDNS, newDNS)
+	time.Sleep(10 * time.Second)
+}
+
+// exampleWindows demonstrates Windows DNS override
+func exampleWindows() {
+	// You need to get the interface GUID first
+	// This can be obtained from:
+	// - ipconfig /all (look for the interface's GUID)
+	// - registry: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces
+	guid := "{YOUR-INTERFACE-GUID-HERE}"
+
+	configurator, err := platform.NewWindowsDNSConfigurator(guid)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	newDNS := []netip.Addr{
+		netip.MustParseAddr("1.1.1.1"),
+	}
+
+	originalDNS, err := configurator.SetDNS(newDNS)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	defer configurator.RestoreDNS()
+
+	fmt.Printf("Changed from %v to %v\n", originalDNS, newDNS)
+	time.Sleep(10 * time.Second)
+}