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/* Shared library add-on to iptables for the TTL target
* (C) 2000 by Harald Welte <laforge@gnumonks.org>
*
* $Id$
*
* This program is distributed under the terms of GNU GPL
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <getopt.h>
#include <iptables.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv4/ipt_TTL.h>
#define IPT_TTL_USED 1
static void help(void)
{
printf(
"TTL target v%s options\n"
" --ttl-set value Set TTL to <value 0-255>\n"
" --ttl-dec value Decrement TTL by <value 1-255>\n"
" --ttl-inc value Increment TTL by <value 1-255>\n"
, IPTABLES_VERSION);
}
static int parse(int c, char **argv, int invert, unsigned int *flags,
const void *entry,
struct xt_entry_target **target)
{
struct ipt_TTL_info *info = (struct ipt_TTL_info *) (*target)->data;
unsigned int 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, NULL, 0))
exit_error(PARAMETER_PROBLEM,
"TTL: unexpected `!'");
if (string_to_number(optarg, 0, 255, &value) == -1)
exit_error(PARAMETER_PROBLEM,
"TTL: Expected value between 0 and 255");
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;
}
static void final_check(unsigned int flags)
{
if (!(flags & IPT_TTL_USED))
exit_error(PARAMETER_PROBLEM,
"TTL: You must specify an action");
}
static void save(const void *ip,
const struct xt_entry_target *target)
{
const struct ipt_TTL_info *info =
(struct ipt_TTL_info *) target->data;
switch (info->mode) {
case IPT_TTL_SET:
printf("--ttl-set ");
break;
case IPT_TTL_DEC:
printf("--ttl-dec ");
break;
case IPT_TTL_INC:
printf("--ttl-inc ");
break;
}
printf("%u ", info->ttl);
}
static void print(const void *ip,
const struct xt_entry_target *target, int numeric)
{
const struct ipt_TTL_info *info =
(struct ipt_TTL_info *) target->data;
printf("TTL ");
switch (info->mode) {
case IPT_TTL_SET:
printf("set to ");
break;
case IPT_TTL_DEC:
printf("decrement by ");
break;
case IPT_TTL_INC:
printf("increment by ");
break;
}
printf("%u ", info->ttl);
}
static const struct option opts[] = {
{ "ttl-set", 1, NULL, '1' },
{ "ttl-dec", 1, NULL, '2' },
{ "ttl-inc", 1, NULL, '3' },
{ }
};
static struct iptables_target TTL = {
.next = NULL,
.name = "TTL",
.version = IPTABLES_VERSION,
.size = IPT_ALIGN(sizeof(struct ipt_TTL_info)),
.userspacesize = IPT_ALIGN(sizeof(struct ipt_TTL_info)),
.help = &help,
.parse = &parse,
.final_check = &final_check,
.print = &print,
.save = &save,
.extra_opts = opts
};
void _init(void)
{
register_target(&TTL);
}
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