Add test cases and handle volume GUID paths

Gracefully handle errors while checking for EA and add debug logs.

changelog/unreleased/pull-4980

@@ -8,5 +8,6 @@ Restic now completely skips the attempt to fetch extended attributes
 for such volumes where it is not supported.
 
 https://github.com/restic/restic/pull/4980
+https://github.com/restic/restic/pull/4998
 https://github.com/restic/restic/issues/4955
 https://github.com/restic/restic/issues/4950

changelog/unreleased/pull-4998

@@ -1,8 +0,0 @@
-Bugfix: Fix extended attributes handling for VSS snapshots
-
-Restic was failing to backup extended attributes for VSS snapshots
-after the fix for https://github.com/restic/restic/pull/4980.
-Restic now correctly handles extended attributes for VSS snapshots.
-
-https://github.com/restic/restic/pull/4998
-https://github.com/restic/restic/pull/4980

internal/fs/ea_windows_test.go

@@ -10,6 +10,7 @@ import (
 	"os"
 	"path/filepath"
 	"reflect"
+	"strings"
 	"syscall"
 	"testing"
 	"unsafe"
@@ -245,3 +246,78 @@ func testSetGetEA(t *testing.T, path string, handle windows.Handle, testEAs []Ex
 		t.Fatalf("EAs read from path %s don't match", path)
 	}
 }
+
+func TestPathSupportsExtendedAttributes(t *testing.T) {
+	testCases := []struct {
+		name     string
+		path     string
+		expected bool
+	}{
+		{
+			name:     "System drive",
+			path:     os.Getenv("SystemDrive") + `\`,
+			expected: true,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			supported, err := PathSupportsExtendedAttributes(tc.path)
+			if err != nil {
+				t.Fatalf("Unexpected error: %v", err)
+			}
+			if supported != tc.expected {
+				t.Errorf("Expected %v, got %v for path %s", tc.expected, supported, tc.path)
+			}
+		})
+	}
+
+	// Test with an invalid path
+	_, err := PathSupportsExtendedAttributes("Z:\\NonExistentPath-UAS664da5s4dyu56das45f5as")
+	if err == nil {
+		t.Error("Expected an error for non-existent path, but got nil")
+	}
+}
+
+func TestGetVolumePathName(t *testing.T) {
+	tempDirVolume := filepath.VolumeName(os.TempDir())
+	testCases := []struct {
+		name           string
+		path           string
+		expectedPrefix string
+	}{
+		{
+			name:           "Root directory",
+			path:           os.Getenv("SystemDrive") + `\`,
+			expectedPrefix: os.Getenv("SystemDrive"),
+		},
+		{
+			name:           "Nested directory",
+			path:           os.Getenv("SystemDrive") + `\Windows\System32`,
+			expectedPrefix: os.Getenv("SystemDrive"),
+		},
+		{
+			name:           "Temp directory",
+			path:           os.TempDir() + `\`,
+			expectedPrefix: tempDirVolume,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			volumeName, err := GetVolumePathName(tc.path)
+			if err != nil {
+				t.Fatalf("Unexpected error: %v", err)
+			}
+			if !strings.HasPrefix(volumeName, tc.expectedPrefix) {
+				t.Errorf("Expected volume name to start with %s, but got %s", tc.expectedPrefix, volumeName)
+			}
+		})
+	}
+
+	// Test with an invalid path
+	_, err := GetVolumePathName("Z:\\NonExistentPath")
+	if err == nil {
+		t.Error("Expected an error for non-existent path, but got nil")
+	}
+}

internal/restic/node_windows.go

@@ -42,6 +42,7 @@ const (
 	extendedPathPrefix = `\\?\`
 	uncPathPrefix      = `\\?\UNC\`
 	globalRootPrefix   = `\\?\GLOBALROOT\`
+	volumeGUIDPrefix   = `\\?\Volume{`
 )
 
 // mknod is not supported on Windows.
@@ -422,15 +423,21 @@ func checkAndStoreEASupport(path string) (isEASupportedVolume bool, err error) {
 		}
 		// If not found, check if EA is supported with manually prepared volume name
 		isEASupportedVolume, err = fs.PathSupportsExtendedAttributes(volumeName + `\`)
-		// If the prepared volume name is not valid, we will next fetch the actual volume name.
+		// If the prepared volume name is not valid, we will fetch the actual volume name next.
 		if err != nil && !errors.Is(err, windows.DNS_ERROR_INVALID_NAME) {
-			return false, err
+			debug.Log("Error checking if extended attributes are supported for prepared volume name %s: %v", volumeName, err)
+			// There can be multiple errors like path does not exist, bad network path, etc.
+			// We just gracefully disallow extended attributes for cases.
+			return false, nil
 		}
 	}
 	// If an entry is not found, get the actual volume name using the GetVolumePathName function
 	volumeNameActual, err := fs.GetVolumePathName(path)
 	if err != nil {
-		return false, err
+		debug.Log("Error getting actual volume name %s for path %s: %v", volumeName, path, err)
+		// There can be multiple errors like path does not exist, bad network path, etc.
+		// We just gracefully disallow extended attributes for cases.
+		return false, nil
 	}
 	if volumeNameActual != volumeName {
 		// If the actual volume name is different, check cache for the actual volume name
@@ -441,11 +448,19 @@ func checkAndStoreEASupport(path string) (isEASupportedVolume bool, err error) {
 		}
 		// If the actual volume name is different and is not in the map, again check if the new volume supports extended attributes with the actual volume name
 		isEASupportedVolume, err = fs.PathSupportsExtendedAttributes(volumeNameActual + `\`)
+		// Debug log for cases where the prepared volume name is not valid
 		if err != nil {
-			return false, err
+			debug.Log("Error checking if extended attributes are supported for actual volume name %s: %v", volumeNameActual, err)
+			// There can be multiple errors like path does not exist, bad network path, etc.
+			// We just gracefully disallow extended attributes for cases.
+			return false, nil
+		} else {
+			debug.Log("Checking extended attributes. Prepared volume name: %s, actual volume name: %s, isEASupportedVolume: %v, err: %v", volumeName, volumeNameActual, isEASupportedVolume, err)
 		}
 	}
+	if volumeNameActual != "" {
 		eaSupportedVolumesMap.Store(volumeNameActual, isEASupportedVolume)
+	}
 	return isEASupportedVolume, err
 }
 
@@ -460,6 +475,7 @@ func prepareVolumeName(path string) (volumeName string, err error) {
 			volumeName = filepath.VolumeName(path)
 		}
 	} else {
+		if !strings.HasPrefix(path, volumeGUIDPrefix) { // Handle volume GUID path
 			if strings.HasPrefix(path, uncPathPrefix) {
 				// Convert \\?\UNC\ extended path to standard path to get the volume name correctly
 				path = `\\` + path[len(uncPathPrefix):]
@@ -473,6 +489,7 @@ func prepareVolumeName(path string) (volumeName string, err error) {
 					return "", fmt.Errorf("failed to get absolute path: %w", err)
 				}
 			}
+		}
 		volumeName = filepath.VolumeName(path)
 	}
 	return volumeName, nil

internal/restic/node_windows_test.go

@@ -12,6 +12,7 @@ import (
 	"strings"
 	"syscall"
 	"testing"
+	"time"
 
 	"github.com/restic/restic/internal/errors"
 	"github.com/restic/restic/internal/fs"
@@ -329,3 +330,198 @@ func TestRestoreExtendedAttributes(t *testing.T) {
 		}
 	}
 }
+
+func TestPrepareVolumeName(t *testing.T) {
+	currentVolume := filepath.VolumeName(func() string {
+		// Get the current working directory
+		pwd, err := os.Getwd()
+		if err != nil {
+			t.Fatalf("Failed to get current working directory: %v", err)
+		}
+		return pwd
+	}())
+	// Create a temporary directory for the test
+	tempDir, err := os.MkdirTemp("", "restic_test_"+time.Now().Format("20060102150405"))
+	if err != nil {
+		t.Fatalf("Failed to create temp directory: %v", err)
+	}
+	defer os.RemoveAll(tempDir)
+
+	// Create a long file name
+	longFileName := `\Very\Long\Path\That\Exceeds\260\Characters\` + strings.Repeat(`\VeryLongFolderName`, 20) + `\\LongFile.txt`
+	longFilePath := filepath.Join(tempDir, longFileName)
+
+	tempDirVolume := filepath.VolumeName(tempDir)
+	// Create the file
+	content := []byte("This is a test file with a very long name.")
+	err = os.MkdirAll(filepath.Dir(longFilePath), 0755)
+	test.OK(t, err)
+	if err != nil {
+		t.Fatalf("Failed to create long folder: %v", err)
+	}
+	err = os.WriteFile(longFilePath, content, 0644)
+	test.OK(t, err)
+	if err != nil {
+		t.Fatalf("Failed to create long file: %v", err)
+	}
+	osVolumeGUIDPath := getOSVolumeGUIDPath(t)
+	osVolumeGUIDVolume := filepath.VolumeName(osVolumeGUIDPath)
+
+	testCases := []struct {
+		name                string
+		path                string
+		expectedVolume      string
+		expectError         bool
+		expectedEASupported bool
+		isRealPath          bool
+	}{
+		{
+			name:                "Network drive path",
+			path:                `Z:\Shared\Documents`,
+			expectedVolume:      `Z:`,
+			expectError:         false,
+			expectedEASupported: false,
+		},
+		{
+			name:                "Subst drive path",
+			path:                `X:\Virtual\Folder`,
+			expectedVolume:      `X:`,
+			expectError:         false,
+			expectedEASupported: false,
+		},
+		{
+			name:                "Windows reserved path",
+			path:                `\\.\` + os.Getenv("SystemDrive") + `\System32\drivers\etc\hosts`,
+			expectedVolume:      `\\.\` + os.Getenv("SystemDrive"),
+			expectError:         false,
+			expectedEASupported: true,
+			isRealPath:          true,
+		},
+		{
+			name:                "Long UNC path",
+			path:                `\\?\UNC\LongServerName\VeryLongShareName\DeepPath\File.txt`,
+			expectedVolume:      `\\LongServerName\VeryLongShareName`,
+			expectError:         false,
+			expectedEASupported: false,
+		},
+		{
+			name:                "Volume GUID path",
+			path:                osVolumeGUIDPath,
+			expectedVolume:      osVolumeGUIDVolume,
+			expectError:         false,
+			expectedEASupported: true,
+			isRealPath:          true,
+		},
+		{
+			name:                "Volume GUID path with subfolder",
+			path:                osVolumeGUIDPath + `\Windows`,
+			expectedVolume:      osVolumeGUIDVolume,
+			expectError:         false,
+			expectedEASupported: true,
+			isRealPath:          true,
+		},
+		{
+			name:                "Standard path",
+			path:                os.Getenv("SystemDrive") + `\Users\`,
+			expectedVolume:      os.Getenv("SystemDrive"),
+			expectError:         false,
+			expectedEASupported: true,
+			isRealPath:          true,
+		},
+		{
+			name:                "Extended length path",
+			path:                longFilePath,
+			expectedVolume:      tempDirVolume,
+			expectError:         false,
+			expectedEASupported: true,
+			isRealPath:          true,
+		},
+		{
+			name:                "UNC path",
+			path:                `\\server\share\folder`,
+			expectedVolume:      `\\server\share`,
+			expectError:         false,
+			expectedEASupported: false,
+		},
+		{
+			name:                "Extended UNC path",
+			path:                `\\?\UNC\server\share\folder`,
+			expectedVolume:      `\\server\share`,
+			expectError:         false,
+			expectedEASupported: false,
+		},
+		{
+			name:                "Volume Shadow Copy path",
+			path:                `\\?\GLOBALROOT\Device\HarddiskVolumeShadowCopy1\Users\test`,
+			expectedVolume:      `\\?\GLOBALROOT\Device\HarddiskVolumeShadowCopy1`,
+			expectError:         false,
+			expectedEASupported: false,
+		},
+		{
+			name: "Relative path",
+			path: `folder\subfolder`,
+
+			expectedVolume:      currentVolume, // Get current volume
+			expectError:         false,
+			expectedEASupported: true,
+		},
+		{
+			name:                "Empty path",
+			path:                ``,
+			expectedVolume:      currentVolume,
+			expectError:         false,
+			expectedEASupported: true,
+			isRealPath:          false,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			isEASupported, err := checkAndStoreEASupport(tc.path)
+			test.OK(t, err)
+			test.Equals(t, tc.expectedEASupported, isEASupported)
+
+			volume, err := prepareVolumeName(tc.path)
+
+			if tc.expectError {
+				test.Assert(t, err != nil, "Expected an error, but got none")
+			} else {
+				test.OK(t, err)
+			}
+			test.Equals(t, tc.expectedVolume, volume)
+
+			if tc.isRealPath {
+				isEASupportedVolume, err := fs.PathSupportsExtendedAttributes(volume + `\`)
+				// If the prepared volume name is not valid, we will next fetch the actual volume name.
+				test.OK(t, err)
+
+				test.Equals(t, tc.expectedEASupported, isEASupportedVolume)
+
+				actualVolume, err := fs.GetVolumePathName(tc.path)
+				test.OK(t, err)
+				test.Equals(t, tc.expectedVolume, actualVolume)
+			}
+		})
+	}
+}
+
+func getOSVolumeGUIDPath(t *testing.T) string {
+	// Get the path of the OS drive (usually C:\)
+	osDrive := os.Getenv("SystemDrive") + "\\"
+
+	// Convert to a volume GUID path
+	volumeName, err := windows.UTF16PtrFromString(osDrive)
+	test.OK(t, err)
+	if err != nil {
+		return ""
+	}
+
+	var volumeGUID [windows.MAX_PATH]uint16
+	err = windows.GetVolumeNameForVolumeMountPoint(volumeName, &volumeGUID[0], windows.MAX_PATH)
+	test.OK(t, err)
+	if err != nil {
+		return ""
+	}
+
+	return windows.UTF16ToString(volumeGUID[:])
+}