rem: if (check_inverse(optarg, &invert))
add: if (check_inverse(optarg, &invert, NULL, 0))
context: static int parse(int c, char **argv, int invert, unsigned int *flags,		const struct ipt_entry *entry,		struct ipt_entry_target **target){	struct ipt_TTL_info *info = (struct ipt_TTL_info *) (*target)->data;	u_int8_t value;	if (*flags & IPT_TTL_USED) {		exit_error(PARAMETER_PROBLEM, 				"Can't specify TTL option twice");	}	if (!optarg) 		exit_error(PARAMETER_PROBLEM, 				"TTL: You must specify a value");	if (check_inverse(optarg, &invert))		exit_error(PARAMETER_PROBLEM,				"TTL: unexpected `!'");		value = atoi(optarg);	switch (c) {		case '1':			info->mode = IPT_TTL_SET;			break;		case '2':			if (value == 0) {				exit_error(PARAMETER_PROBLEM,					"TTL: decreasing by 0?");			}			info->mode = IPT_TTL_DEC;			break;		case '3':			if (value == 0) {				exit_error(PARAMETER_PROBLEM,					"TTL: increasing by 0?");			}			info->mode = IPT_TTL_INC;			break;		default:			return 0;	}		info->ttl = value;	*flags |= IPT_TTL_USED;	return 1;}