func parseIPTablesData(ruleData string) (map[string][]string, error) {
	// Split ruleData at the "COMMIT" lines; given valid input, this will result in
	// one element for each table plus an extra empty element (since the ruleData
	// should end with a "COMMIT" line).
	rawTables := strings.Split(strings.TrimPrefix(ruleData, "\n"), "COMMIT\n")
	nTables := len(rawTables) - 1