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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 <xtables.h>
#include <linux/netfilter/xt_connlimit.h>
static void connlimit_help(void)
{
printf(
"connlimit match options:\n"
"[!] --connlimit-above n match if the number of existing "
" connections is (not) above n\n"
" --connlimit-mask n group hosts using mask\n");
}
static const struct option connlimit_opts[] = {
{"connlimit-above", 1, NULL, 'A'},
{"connlimit-mask", 1, NULL, 'M'},
{ .name = NULL }
};
static void connlimit_init(struct xt_entry_match *match)
{
struct xt_connlimit_info *info = (void *)match->data;
/* This will also initialize the v4 mask correctly */
memset(info->v6_mask, 0xFF, sizeof(info->v6_mask));
}
static void prefix_to_netmask(u_int32_t *mask, unsigned int prefix_len)
{
if (prefix_len == 0) {
mask[0] = mask[1] = mask[2] = mask[3] = 0;
} else if (prefix_len <= 32) {
mask[0] <<= 32 - prefix_len;
mask[1] = mask[2] = mask[3] = 0;
} else if (prefix_len <= 64) {
mask[1] <<= 32 - (prefix_len - 32);
mask[2] = mask[3] = 0;
} else if (prefix_len <= 96) {
mask[2] <<= 32 - (prefix_len - 64);
mask[3] = 0;
} else if (prefix_len <= 128) {
mask[3] <<= 32 - (prefix_len - 96);
}
mask[0] = htonl(mask[0]);
mask[1] = htonl(mask[1]);
mask[2] = htonl(mask[2]);
mask[3] = htonl(mask[3]);
}
static int connlimit_parse(int c, char **argv, int invert, unsigned int *flags,
struct xt_connlimit_info *info, unsigned int family)
{
char *err;
int i;
switch (c) {
case 'A':
if (*flags & 0x1)
xtables_error(PARAMETER_PROBLEM,
"--connlimit-above may be given only once");
*flags |= 0x1;
xtables_check_inverse(optarg, &invert, &optind, 0, argv);
info->limit = strtoul(optarg, NULL, 0);
info->inverse = invert;
break;
case 'M':
if (*flags & 0x2)
xtables_error(PARAMETER_PROBLEM,
"--connlimit-mask may be given only once");
*flags |= 0x2;
i = strtoul(optarg, &err, 0);
if (family == NFPROTO_IPV6) {
if (i > 128 || *err != '\0')
xtables_error(PARAMETER_PROBLEM,
"--connlimit-mask must be between "
"0 and 128");
prefix_to_netmask(info->v6_mask, i);
} else {
if (i > 32 || *err != '\0')
xtables_error(PARAMETER_PROBLEM,
"--connlimit-mask must be between "
"0 and 32");
if (i == 0)
info->v4_mask = 0;
else
info->v4_mask = htonl(0xFFFFFFFF << (32 - i));
}
break;
default:
return 0;
}
return 1;
}
static int connlimit_parse4(int c, char **argv, int invert,
unsigned int *flags, const void *entry,
struct xt_entry_match **match)
{
return connlimit_parse(c, argv, invert, flags,
(void *)(*match)->data, NFPROTO_IPV4);
}
static int connlimit_parse6(int c, char **argv, int invert,
unsigned int *flags, const void *entry,
struct xt_entry_match **match)
{
return connlimit_parse(c, argv, invert, flags,
(void *)(*match)->data, NFPROTO_IPV6);
}
static void connlimit_check(unsigned int flags)
{
if (!(flags & 0x1))
xtables_error(PARAMETER_PROBLEM,
"You must specify \"--connlimit-above\"");
}
static unsigned int count_bits4(u_int32_t mask)
{
unsigned int bits = 0;
for (mask = ~ntohl(mask); mask != 0; mask >>= 1)
++bits;
return 32 - bits;
}
static unsigned int count_bits6(const u_int32_t *mask)
{
unsigned int bits = 0, i;
u_int32_t tmp[4];
for (i = 0; i < 4; ++i)
for (tmp[i] = ~ntohl(mask[i]); tmp[i] != 0; tmp[i] >>= 1)
++bits;
return 128 - bits;
}
static void connlimit_print4(const void *ip,
const struct xt_entry_match *match, int numeric)
{
const struct xt_connlimit_info *info = (const void *)match->data;
printf("#conn/%u %s %u ", count_bits4(info->v4_mask),
info->inverse ? "<=" : ">", info->limit);
}
static void connlimit_print6(const void *ip,
const struct xt_entry_match *match, int numeric)
{
const struct xt_connlimit_info *info = (const void *)match->data;
printf("#conn/%u %s %u ", count_bits6(info->v6_mask),
info->inverse ? "<=" : ">", info->limit);
}
static void connlimit_save4(const void *ip, const struct xt_entry_match *match)
{
const struct xt_connlimit_info *info = (const void *)match->data;
printf("%s--connlimit-above %u --connlimit-mask %u ",
info->inverse ? "! " : "", info->limit,
count_bits4(info->v4_mask));
}
static void connlimit_save6(const void *ip, const struct xt_entry_match *match)
{
const struct xt_connlimit_info *info = (const void *)match->data;
printf("%s--connlimit-above %u --connlimit-mask %u ",
info->inverse ? "! " : "", info->limit,
count_bits6(info->v6_mask));
}
static struct xtables_match connlimit_mt_reg[] = {
{
.name = "connlimit",
.family = NFPROTO_IPV4,
.version = XTABLES_VERSION,
.size = XT_ALIGN(sizeof(struct xt_connlimit_info)),
.userspacesize = offsetof(struct xt_connlimit_info, data),
.help = connlimit_help,
.init = connlimit_init,
.parse = connlimit_parse4,
.final_check = connlimit_check,
.print = connlimit_print4,
.save = connlimit_save4,
.extra_opts = connlimit_opts,
},
{
.name = "connlimit",
.family = NFPROTO_IPV6,
.version = XTABLES_VERSION,
.size = XT_ALIGN(sizeof(struct xt_connlimit_info)),
.userspacesize = offsetof(struct xt_connlimit_info, data),
.help = connlimit_help,
.init = connlimit_init,
.parse = connlimit_parse6,
.final_check = connlimit_check,
.print = connlimit_print6,
.save = connlimit_save6,
.extra_opts = connlimit_opts,
},
};
void _init(void)
{
xtables_register_matches(connlimit_mt_reg, ARRAY_SIZE(connlimit_mt_reg));
}
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