restic: extract Node filesystem code to fs package

internal/fs/node_xattr.go

@@ -0,0 +1,131 @@
+//go:build darwin || freebsd || linux || solaris
+// +build darwin freebsd linux solaris
+
+package fs
+
+import (
+	"fmt"
+	"os"
+	"syscall"
+
+	"github.com/restic/restic/internal/debug"
+	"github.com/restic/restic/internal/errors"
+	"github.com/restic/restic/internal/restic"
+
+	"github.com/pkg/xattr"
+)
+
+// getxattr retrieves extended attribute data associated with path.
+func getxattr(path, name string) ([]byte, error) {
+	b, err := xattr.LGet(path, name)
+	return b, handleXattrErr(err)
+}
+
+// listxattr retrieves a list of names of extended attributes associated with the
+// given path in the file system.
+func listxattr(path string) ([]string, error) {
+	l, err := xattr.LList(path)
+	return l, handleXattrErr(err)
+}
+
+func IsListxattrPermissionError(err error) bool {
+	var xerr *xattr.Error
+	if errors.As(err, &xerr) {
+		return xerr.Op == "xattr.list" && errors.Is(xerr.Err, os.ErrPermission)
+	}
+	return false
+}
+
+// setxattr associates name and data together as an attribute of path.
+func setxattr(path, name string, data []byte) error {
+	return handleXattrErr(xattr.LSet(path, name, data))
+}
+
+// removexattr removes the attribute name from path.
+func removexattr(path, name string) error {
+	return handleXattrErr(xattr.LRemove(path, name))
+}
+
+func handleXattrErr(err error) error {
+	switch e := err.(type) {
+	case nil:
+		return nil
+
+	case *xattr.Error:
+		// On Linux, xattr calls on files in an SMB/CIFS mount can return
+		// ENOATTR instead of ENOTSUP.
+		switch e.Err {
+		case syscall.ENOTSUP, xattr.ENOATTR:
+			return nil
+		}
+		return errors.WithStack(e)
+
+	default:
+		return errors.WithStack(e)
+	}
+}
+
+// nodeRestoreGenericAttributes is no-op.
+func nodeRestoreGenericAttributes(node *restic.Node, _ string, warn func(msg string)) error {
+	return restic.HandleAllUnknownGenericAttributesFound(node.GenericAttributes, warn)
+}
+
+// nodeFillGenericAttributes is a no-op.
+func nodeFillGenericAttributes(_ *restic.Node, _ string, _ os.FileInfo, _ *statT) (allowExtended bool, err error) {
+	return true, nil
+}
+
+func nodeRestoreExtendedAttributes(node *restic.Node, path string) error {
+	expectedAttrs := map[string]struct{}{}
+	for _, attr := range node.ExtendedAttributes {
+		err := setxattr(path, attr.Name, attr.Value)
+		if err != nil {
+			return err
+		}
+		expectedAttrs[attr.Name] = struct{}{}
+	}
+
+	// remove unexpected xattrs
+	xattrs, err := listxattr(path)
+	if err != nil {
+		return err
+	}
+	for _, name := range xattrs {
+		if _, ok := expectedAttrs[name]; ok {
+			continue
+		}
+		if err := removexattr(path, name); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func nodeFillExtendedAttributes(node *restic.Node, path string, ignoreListError bool) error {
+	xattrs, err := listxattr(path)
+	debug.Log("fillExtendedAttributes(%v) %v %v", path, xattrs, err)
+	if err != nil {
+		if ignoreListError && IsListxattrPermissionError(err) {
+			return nil
+		}
+		return err
+	}
+
+	node.ExtendedAttributes = make([]restic.ExtendedAttribute, 0, len(xattrs))
+	for _, attr := range xattrs {
+		attrVal, err := getxattr(path, attr)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "can not obtain extended attribute %v for %v:\n", attr, path)
+			continue
+		}
+		attr := restic.ExtendedAttribute{
+			Name:  attr,
+			Value: attrVal,
+		}
+
+		node.ExtendedAttributes = append(node.ExtendedAttributes, attr)
+	}
+
+	return nil
+}