chore(usbgadget): update usbgadget config only when needed (#474)

internal/usbgadget/changeset_symlink.go

@@ -0,0 +1,136 @@
+package usbgadget
+
+import (
+	"fmt"
+	"os"
+	"path"
+	"path/filepath"
+	"reflect"
+
+	"github.com/rs/zerolog"
+)
+
+type symlink struct {
+	Path   string
+	Target string
+}
+
+func compareSymlinks(expected []symlink, actual []symlink) bool {
+	if len(expected) != len(actual) {
+		return false
+	}
+
+	return reflect.DeepEqual(expected, actual)
+}
+
+func checkIfSymlinksInOrder(fc *FileChange, logger *zerolog.Logger) (FileState, error) {
+	if logger == nil {
+		logger = defaultLogger
+	}
+	l := logger.With().Str("path", fc.Path).Logger()
+
+	if fc.ParamSymlinks == nil || len(fc.ParamSymlinks) == 0 {
+		return FileStateUnknown, fmt.Errorf("no symlinks to check")
+	}
+
+	fi, err := os.Lstat(fc.Path)
+
+	if err != nil {
+		if os.IsNotExist(err) {
+			return FileStateAbsent, nil
+		} else {
+			l.Warn().Err(err).Msg("failed to stat file")
+			return FileStateUnknown, fmt.Errorf("failed to stat file")
+		}
+	}
+
+	if !fi.IsDir() {
+		return FileStateUnknown, fmt.Errorf("file is not a directory")
+	}
+
+	files, err := os.ReadDir(fc.Path)
+	symlinks := make([]symlink, 0)
+	if err != nil {
+		return FileStateUnknown, fmt.Errorf("failed to read directory")
+	}
+
+	for _, file := range files {
+		if file.Type()&os.ModeSymlink != os.ModeSymlink {
+			continue
+		}
+
+		path := filepath.Join(fc.Path, file.Name())
+		target, err := os.Readlink(path)
+		if err != nil {
+			return FileStateUnknown, fmt.Errorf("failed to read symlink")
+		}
+
+		if !filepath.IsAbs(target) {
+			target = filepath.Join(fc.Path, target)
+			newTarget, err := filepath.Abs(target)
+			if err != nil {
+				return FileStateUnknown, fmt.Errorf("failed to get absolute path")
+			}
+			target = newTarget
+		}
+
+		symlinks = append(symlinks, symlink{
+			Path:   path,
+			Target: target,
+		})
+	}
+
+	// compare the symlinks with the expected symlinks
+	if compareSymlinks(fc.ParamSymlinks, symlinks) {
+		return FileStateSymlinkInOrderConfigFS, nil
+	}
+
+	l.Trace().Interface("expected", fc.ParamSymlinks).Interface("actual", symlinks).Msg("symlinks are not in order")
+
+	return FileStateSymlinkNotInOrderConfigFS, nil
+}
+
+func recreateSymlinks(fc *FileChange, logger *zerolog.Logger) error {
+	if logger == nil {
+		logger = defaultLogger
+	}
+	// remove all symlinks
+	files, err := os.ReadDir(fc.Path)
+	if err != nil {
+		return fmt.Errorf("failed to read directory")
+	}
+
+	l := logger.With().Str("path", fc.Path).Logger()
+	l.Info().Msg("recreate symlinks")
+
+	for _, file := range files {
+		if file.Type()&os.ModeSymlink != os.ModeSymlink {
+			continue
+		}
+		l.Info().Str("name", file.Name()).Msg("remove symlink")
+		err := os.Remove(path.Join(fc.Path, file.Name()))
+		if err != nil {
+			return fmt.Errorf("failed to remove symlink")
+		}
+	}
+
+	l.Info().Interface("param-symlinks", fc.ParamSymlinks).Msg("create symlinks")
+
+	// create the symlinks
+	for _, symlink := range fc.ParamSymlinks {
+		l.Info().Str("name", symlink.Path).Str("target", symlink.Target).Msg("create symlink")
+
+		path := symlink.Path
+		if !filepath.IsAbs(path) {
+			path = filepath.Join(fc.Path, path)
+		}
+
+		err := os.Symlink(symlink.Target, path)
+		if err != nil {
+			l.Warn().Err(err).Msg("failed to create symlink")
+			return fmt.Errorf("failed to create symlink")
+		}
+	}
+
+	return nil
+}