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/* Shared library add-on to iptables to add connection limit support. */
#include <stdio.h>
#include <netdb.h>
#include <string.h>
#include <stdlib.h>
#include <stddef.h>
#include <getopt.h>
#include <iptables.h>
#include <linux/netfilter_ipv4/ip_conntrack.h>
#include <linux/netfilter_ipv4/ipt_connlimit.h>
/* Function which prints out usage message. */
static void
help(void)
{
printf(
"connlimit v%s options:\n"
"[!] --connlimit-above n match if the number of existing tcp connections is (not) above n\n"
" --connlimit-mask n group hosts using mask\n"
"\n", IPTABLES_VERSION);
}
static struct option opts[] = {
{ "connlimit-above", 1, 0, '1' },
{ "connlimit-mask", 1, 0, '2' },
{0}
};
/* 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_connlimit_info *info = (struct ipt_connlimit_info*)(*match)->data;
int i;
if (0 == (*flags & 2)) {
/* set default mask unless we've already seen a mask option */
info->mask = htonl(0xFFFFFFFF);
}
switch (c) {
case '1':
check_inverse(optarg, &invert, &optind, 0);
info->limit = atoi(argv[optind-1]);
info->inverse = invert;
*flags |= 1;
break;
case '2':
i = atoi(argv[optind-1]);
if ((i < 0) || (i > 32))
exit_error(PARAMETER_PROBLEM,
"--connlimit-mask must be between 0 and 32");
if (i == 0)
info->mask = 0;
else
info->mask = htonl(0xFFFFFFFF << (32 - i));
*flags |= 2;
break;
default:
return 0;
}
return 1;
}
/* Final check */
static void final_check(unsigned int flags)
{
if (!flags & 1)
exit_error(PARAMETER_PROBLEM, "You must specify `--connlimit-above'");
}
static int
count_bits(u_int32_t mask)
{
int i, bits;
for (bits = 0, i = 31; i >= 0; i--) {
if (mask & htonl((u_int32_t)1 << i)) {
bits++;
continue;
}
break;
}
return bits;
}
/* Prints out the matchinfo. */
static void
print(const struct ipt_ip *ip,
const struct ipt_entry_match *match,
int numeric)
{
struct ipt_connlimit_info *info = (struct ipt_connlimit_info*)match->data;
printf("#conn/%d %s %d ", count_bits(info->mask),
info->inverse ? "<" : ">", info->limit);
}
/* Saves the matchinfo in parsable form to stdout. */
static void save(const struct ipt_ip *ip, const struct ipt_entry_match *match)
{
struct ipt_connlimit_info *info = (struct ipt_connlimit_info*)match->data;
printf("%s--connlimit-above %d ",info->inverse ? "! " : "",info->limit);
printf("--connlimit-mask %d ",count_bits(info->mask));
}
static struct iptables_match connlimit = {
.name = "connlimit",
.version = IPTABLES_VERSION,
.size = IPT_ALIGN(sizeof(struct ipt_connlimit_info)),
.userspacesize = offsetof(struct ipt_connlimit_info,data),
.help = help,
.parse = parse,
.final_check = final_check,
.print = print,
.save = save,
.extra_opts = opts
};
void _init(void)
{
register_match(&connlimit);
}
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