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/*
Shared library add-on to iptables to add match support for random match.
This file is distributed under the terms of the GNU General Public
License (GPL). Copies of the GPL can be obtained from:
ftp://prep.ai.mit.edu/pub/gnu/GPL
2001-10-14 Fabrice MARIE <fabrice@celestix.com> : initial development.
*/
#include <stdio.h>
#include <netdb.h>
#include <string.h>
#include <stdlib.h>
#include <syslog.h>
#include <getopt.h>
#include <iptables.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv4/ipt_random.h>
/**
* The kernel random routing returns numbers between 0 and 255.
* To ease the task of the user in choosing the probability
* of matching, we want him to be able to use percentages.
* Therefore we have to accept numbers in percentage here,
* turn them into number between 0 and 255 for the kernel module,
* and turn them back to percentages when we print/save
* the rule.
*/
/* Function which prints out usage message. */
static void
help(void)
{
printf(
"random v%s options:\n"
" [--average] percent The probability in percentage of the match\n"
" If ommited, a probability of 50%% percent is set.\n"
" Percentage must be within : 1 <= percent <= 99.\n\n",
NETFILTER_VERSION);
}
static struct option opts[] = {
{ "average", 1, 0, '1' },
{ 0 }
};
/* Initialize the target. */
static void
init(struct ipt_entry_match *m, unsigned int *nfcache)
{
struct ipt_rand_info *randinfo = (struct ipt_rand_info *)(m)->data;
*nfcache |= NFC_UNKNOWN;
/* We assign the average to be 50 which is our default value */
/* 50 * 2.55 = 128 */
randinfo->average = 128;
}
#define IPT_RAND_OPT_AVERAGE 0x01
/* Function which parses command options; returns true if it
ate an option */
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_rand_info *randinfo = (struct ipt_rand_info *)(*match)->data;
unsigned int num;
switch (c) {
case '1':
/* check for common mistakes... */
if (invert)
exit_error(PARAMETER_PROBLEM,
"Can't specify ! --average");
if (*flags & IPT_RAND_OPT_AVERAGE)
exit_error(PARAMETER_PROBLEM,
"Can't specify --average twice");
/* Remember, this function will interpret a leading 0 to be
Octal, a leading 0x to be hexdecimal... */
if (string_to_number(optarg, 1, 99, &num) == -1 || num < 1)
exit_error(PARAMETER_PROBLEM,
"bad --average `%s', must be between 1 and 99", optarg);
/* assign the values */
randinfo->average = (int)(num * 2.55);
*flags |= IPT_RAND_OPT_AVERAGE;
break;
default:
return 0;
}
return 1;
}
/* Final check; nothing. */
static void final_check(unsigned int flags)
{
}
/* Prints out the targinfo. */
static void
print(const struct ipt_ip *ip,
const struct ipt_entry_match *match,
int numeric)
{
const struct ipt_rand_info *randinfo
= (const struct ipt_rand_info *)match->data;
div_t result = div((randinfo->average*100), 255);
if (result.rem > 127) /* round up... */
++result.quot;
printf(" random %u%% ", result.quot);
}
/* Saves the union ipt_targinfo in parsable form to stdout. */
static void
save(const struct ipt_ip *ip, const struct ipt_entry_match *match)
{
const struct ipt_rand_info *randinfo
= (const struct ipt_rand_info *)match->data;
div_t result = div((randinfo->average *100), 255);
if (result.rem > 127) /* round up... */
++result.quot;
printf("--average %u ", result.quot);
}
struct iptables_match rand_match
= { NULL,
"random",
NETFILTER_VERSION,
IPT_ALIGN(sizeof(struct ipt_rand_info)),
IPT_ALIGN(sizeof(struct ipt_rand_info)),
&help,
&init,
&parse,
&final_check,
&print,
&save,
opts
};
void _init(void)
{
register_match(&rand_match);
}
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