handle review comments

lib/auth/auth.go

@@ -1512,17 +1512,13 @@ func (a *Server) runPeriodicOperations() {
 									if _, err := a.Services.UpdateNode(a.closeCtx, srv); err != nil && !trace.IsCompareFailed(err) {
 										logger.WarnContext(a.closeCtx, "failed to update SSH server hostname", "error", err)
 									}
-								}
-
-								// If the hostname has been replaced by a sanitized version, revert it back to the original
-								// if the original is valid under the most recent rules.
-								if oldHostname, ok := srv.GetLabel(replacedHostnameLabel); ok && validServerHostname(oldHostname) {
-									switch s := srv.(type) {
-									case *types.ServerV2:
-										s.Spec.Hostname = oldHostname
-										delete(s.Metadata.Labels, replacedHostnameLabel)
-									default:
-										return false, trace.BadParameter("invalid server provided")
+								} else if oldHostname, ok := srv.GetLabel(replacedHostnameLabel); ok && validServerHostname(oldHostname) {
+									// If the hostname has been replaced by a sanitized version, revert it back to the original
+									// if the original is valid under the most recent rules.
+									logger := a.logger.With("server", srv.GetName(), "old_hostname", oldHostname, "sanitized_hostname", srv.GetHostname())
+									if err := restoreSanitizedHostname(srv); err != nil {
+										logger.WarnContext(a.closeCtx, "failed to restore sanitized static SSH server hostname", "error", err)
+										return false, nil
 									}
 									if _, err := a.Services.UpdateNode(a.closeCtx, srv); err != nil && !trace.IsCompareFailed(err) {
 										log.Warnf("Failed to update node hostname: %v", err)
@@ -5688,6 +5684,26 @@ func sanitizeHostname(server types.Server) error {
 	return nil
 }
 
+// restoreSanitizedHostname restores the original hostname of a server and removes the label.
+func restoreSanitizedHostname(server types.Server) error {
+	oldHostname, ok := server.GetLabels()[replacedHostnameLabel]
+	// if the label is not present or the hostname is invalid under the most recent rules, do nothing.
+	if !ok || !validServerHostname(oldHostname) {
+		return nil
+	}
+
+	switch s := server.(type) {
+	case *types.ServerV2:
+		// restore the original hostname and remove the label.
+		s.Spec.Hostname = oldHostname
+		delete(s.Metadata.Labels, replacedHostnameLabel)
+	default:
+		return trace.BadParameter("invalid server provided")
+	}
+
+	return nil
+}
+
 // UpsertNode implements [services.Presence] by delegating to [Server.Services]
 // and potentially emitting a [usagereporter] event.
 func (a *Server) UpsertNode(ctx context.Context, server types.Server) (*types.KeepAlive, error) {