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/* Shared library add-on to iptables to add TTL matching support
* (C) 2000 by Harald Welte <laforge@gnumonks.org>
*
* $Id: libipt_ttl.c,v 1.4 2002/02/25 11:25:41 laforge Exp $
*
* This program is released under the terms of GNU GPL */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <getopt.h>
#include <iptables.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv4/ipt_ttl.h>
static void help(void)
{
printf(
"TTL match v%s options:\n"
" --ttl-eq value Match time to live value\n"
" --ttl-lt value Match TTL < value\n"
" --ttl-gt value Match TTL > value\n"
, NETFILTER_VERSION);
}
static void init(struct ipt_entry_match *m, unsigned int *nfcache)
{
/* caching not yet implemented */
*nfcache |= NFC_UNKNOWN;
}
static int parse(int c, char **argv, int invert, unsigned int *flags,
const struct ipt_entry *entry, unsigned int *nfcache,
struct ipt_entry_match **match)
{
struct ipt_ttl_info *info = (struct ipt_ttl_info *) (*match)->data;
u_int8_t value;
check_inverse(optarg, &invert, &optind, 0);
value = atoi(argv[optind-1]);
if (*flags)
exit_error(PARAMETER_PROBLEM,
"Can't specify TTL option twice");
if (!optarg)
exit_error(PARAMETER_PROBLEM,
"ttl: You must specify a value");
switch (c) {
case '2':
if (invert)
info->mode = IPT_TTL_NE;
else
info->mode = IPT_TTL_EQ;
/* is 0 allowed? */
info->ttl = value;
*flags = 1;
break;
case '3':
if (invert)
exit_error(PARAMETER_PROBLEM,
"ttl: unexpected `!'");
info->mode = IPT_TTL_LT;
info->ttl = value;
*flags = 1;
break;
case '4':
if (invert)
exit_error(PARAMETER_PROBLEM,
"ttl: unexpected `!'");
info->mode = IPT_TTL_GT;
info->ttl = value;
*flags = 1;
break;
default:
return 0;
}
return 1;
}
static void final_check(unsigned int flags)
{
if (!flags)
exit_error(PARAMETER_PROBLEM,
"TTL match: You must specify one of "
"`--ttl-eq', `--ttl-lt', `--ttl-gt");
}
static void print(const struct ipt_ip *ip,
const struct ipt_entry_match *match,
int numeric)
{
const struct ipt_ttl_info *info =
(struct ipt_ttl_info *) match->data;
printf("TTL match ");
switch (info->mode) {
case IPT_TTL_EQ:
printf("TTL == ");
break;
case IPT_TTL_NE:
printf("TTL != ");
break;
case IPT_TTL_LT:
printf("TTL < ");
break;
case IPT_TTL_GT:
printf("TTL > ");
break;
}
printf("%u ", info->ttl);
}
static void save(const struct ipt_ip *ip,
const struct ipt_entry_match *match)
{
const struct ipt_ttl_info *info =
(struct ipt_ttl_info *) match->data;
switch (info->mode) {
case IPT_TTL_EQ:
printf("--ttl-eq ");
break;
case IPT_TTL_NE:
printf("! --ttl-eq ");
break;
case IPT_TTL_LT:
printf("--ttl-lt ");
break;
case IPT_TTL_GT:
printf("--ttl-gt ");
break;
default:
/* error */
break;
}
printf("%u ", info->ttl);
}
static struct option opts[] = {
{ "ttl", 1, 0, '2' },
{ "ttl-eq", 1, 0, '2'},
{ "ttl-lt", 1, 0, '3'},
{ "ttl-gt", 1, 0, '4'},
{ 0 }
};
static
struct iptables_match ttl = {
NULL,
"ttl",
NETFILTER_VERSION,
IPT_ALIGN(sizeof(struct ipt_ttl_info)),
IPT_ALIGN(sizeof(struct ipt_ttl_info)),
&help,
&init,
&parse,
&final_check,
&print,
&save,
opts
};
void _init(void)
{
register_match(&ttl);
}
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