[client] Cleanup firewall state on startup (#2768)

client/server/state.go

@@ -0,0 +1,37 @@
+package server
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/hashicorp/go-multierror"
+
+	nberrors "github.com/netbirdio/netbird/client/errors"
+	"github.com/netbirdio/netbird/client/internal/statemanager"
+)
+
+// restoreResidualConfig checks if the client was not shut down in a clean way and restores residual state if required.
+// Otherwise, we might not be able to connect to the management server to retrieve new config.
+func restoreResidualState(ctx context.Context) error {
+	path := statemanager.GetDefaultStatePath()
+	if path == "" {
+		return nil
+	}
+
+	mgr := statemanager.New(path)
+
+	// register the states we are interested in restoring
+	registerStates(mgr)
+
+	var merr *multierror.Error
+	if err := mgr.PerformCleanup(); err != nil {
+		merr = multierror.Append(merr, fmt.Errorf("perform cleanup: %w", err))
+	}
+
+	// persist state regardless of cleanup outcome. It could've succeeded partially
+	if err := mgr.PersistState(ctx); err != nil {
+		merr = multierror.Append(merr, fmt.Errorf("persist state: %w", err))
+	}
+
+	return nberrors.FormatErrorOrNil(merr)
+}