### Files

``````/*
* Copyright (c) 2006-2013 Patrick McHardy <kaber@trash.net>
*/

#include <math.h>
#include <stdio.h>
#include <string.h>
#include <xtables.h>
#include <linux/netfilter/xt_statistic.h>

enum {
O_MODE = 0,
O_PROBABILITY,
O_EVERY,
O_PACKET,
F_PROBABILITY = 1 << O_PROBABILITY,
F_EVERY       = 1 << O_EVERY,
F_PACKET      = 1 << O_PACKET,
};

static void statistic_help(void)
{
printf(
"statistic match options:\n"
" --mode mode                    Match mode (random, nth)\n"
" random mode:\n"
"[!] --probability p		 Probability\n"
" nth mode:\n"
"[!] --every n			 Match every nth packet\n"
" --packet p			 Initial counter value (0 <= p <= n-1, default 0)\n");
}

#define s struct xt_statistic_info
static const struct xt_option_entry statistic_opts[] = {
{.name = "mode", .id = O_MODE, .type = XTTYPE_STRING,
.flags = XTOPT_MAND},
{.name = "probability", .id = O_PROBABILITY, .type = XTTYPE_DOUBLE,
.flags = XTOPT_INVERT, .min = 0, .max = 1,
.excl = F_EVERY | F_PACKET},
{.name = "every", .id = O_EVERY, .type = XTTYPE_UINT32, .min = 1,
.flags = XTOPT_INVERT | XTOPT_PUT, XTOPT_POINTER(s, u.nth.every),
.excl = F_PROBABILITY, .also = F_PACKET},
{.name = "packet", .id = O_PACKET, .type = XTTYPE_UINT32,
.flags = XTOPT_PUT, XTOPT_POINTER(s, u.nth.packet),
.excl = F_PROBABILITY, .also = F_EVERY},
XTOPT_TABLEEND,
};
#undef s

static void statistic_parse(struct xt_option_call *cb)
{
struct xt_statistic_info *info = cb->data;

if (cb->invert)
info->flags |= XT_STATISTIC_INVERT;

xtables_option_parse(cb);
switch (cb->entry->id) {
case O_MODE:
if (strcmp(cb->arg, "random") == 0)
info->mode = XT_STATISTIC_MODE_RANDOM;
else if (strcmp(cb->arg, "nth") == 0)
info->mode = XT_STATISTIC_MODE_NTH;
else
cb->arg);
break;
case O_PROBABILITY:
info->u.random.probability = lround(0x80000000 * cb->val.dbl);
break;
case O_EVERY:
--info->u.nth.every;
break;
}
}

static void statistic_check(struct xt_fcheck_call *cb)
{
struct xt_statistic_info *info = cb->data;

if (info->mode == XT_STATISTIC_MODE_RANDOM &&
!(cb->xflags & F_PROBABILITY))
xtables_error(PARAMETER_PROBLEM,
"--probability must be specified when using "
"random mode");
if (info->mode == XT_STATISTIC_MODE_NTH &&
!(cb->xflags & (F_EVERY | F_PACKET)))
xtables_error(PARAMETER_PROBLEM,
"--every and --packet must be specified when "
"using nth mode");

/* at this point, info->u.nth.every have been decreased. */
if (info->u.nth.packet > info->u.nth.every)
xtables_error(PARAMETER_PROBLEM,
"the --packet p must be 0 <= p <= n-1");

info->u.nth.count = info->u.nth.every - info->u.nth.packet;
}

static void print_match(const struct xt_statistic_info *info, char *prefix)
{
switch (info->mode) {
case XT_STATISTIC_MODE_RANDOM:
printf(" %smode random%s %sprobability %.11f", prefix,
(info->flags & XT_STATISTIC_INVERT) ? " !" : "",
prefix,
1.0 * info->u.random.probability / 0x80000000);
break;
case XT_STATISTIC_MODE_NTH:
printf(" %smode nth%s %severy %u", prefix,
(info->flags & XT_STATISTIC_INVERT) ? " !" : "",
prefix,
info->u.nth.every + 1);
if (info->u.nth.packet || *prefix)
printf(" %spacket %u", prefix, info->u.nth.packet);
break;
}
}

static void
statistic_print(const void *ip, const struct xt_entry_match *match, int numeric)
{
const struct xt_statistic_info *info = (const void *)match->data;

printf(" statistic");
print_match(info, "");
}

static void statistic_save(const void *ip, const struct xt_entry_match *match)
{
const struct xt_statistic_info *info = (const void *)match->data;

print_match(info, "--");
}

static int statistic_xlate(struct xt_xlate *xl,
const struct xt_xlate_mt_params *params)
{
const struct xt_statistic_info *info =
(struct xt_statistic_info *)params->match->data;

switch (info->mode) {
case XT_STATISTIC_MODE_RANDOM:
return 0;
case XT_STATISTIC_MODE_NTH:
xt_xlate_add(xl, "numgen inc mod %u %s%u",
info->u.nth.every + 1,
info->flags & XT_STATISTIC_INVERT ? "!= " : "",
info->u.nth.packet);
break;
}

return 1;
}

static struct xtables_match statistic_match = {
.family		= NFPROTO_UNSPEC,
.name		= "statistic",
.version	= XTABLES_VERSION,
.size		= XT_ALIGN(sizeof(struct xt_statistic_info)),
.userspacesize	= offsetof(struct xt_statistic_info, u.nth.count),
.help		= statistic_help,
.x6_parse	= statistic_parse,
.x6_fcheck	= statistic_check,
.print		= statistic_print,
.save		= statistic_save,
.x6_options	= statistic_opts,
.xlate		= statistic_xlate,
};

void _init(void)
{
xtables_register_match(&statistic_match);
}
``````