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/* Shared library add-on to iptables to add static NAT support.
Author: Svenning Soerensen <svenning@post5.tele.dk>
*/
#include <stdio.h>
#include <netdb.h>
#include <string.h>
#include <stdlib.h>
#include <getopt.h>
#include <xtables.h>
#include <net/netfilter/nf_nat.h>
#define MODULENAME "NETMAP"
enum {
O_TO = 0,
};
static const struct xt_option_entry NETMAP_opts[] = {
{.name = "to", .id = O_TO, .type = XTTYPE_HOSTMASK,
.flags = XTOPT_MAND},
XTOPT_TABLEEND,
};
static void NETMAP_help(void)
{
printf(MODULENAME" target options:\n"
" --%s address[/mask]\n"
" Network address to map to.\n\n",
NETMAP_opts[0].name);
}
static int
netmask2bits(uint32_t netmask)
{
uint32_t bm;
int bits;
netmask = ntohl(netmask);
for (bits = 0, bm = 0x80000000; netmask & bm; netmask <<= 1)
bits++;
if (netmask)
return -1; /* holes in netmask */
return bits;
}
static void NETMAP_init(struct xt_entry_target *t)
{
struct nf_nat_multi_range *mr = (struct nf_nat_multi_range *)t->data;
/* Actually, it's 0, but it's ignored at the moment. */
mr->rangesize = 1;
}
static void NETMAP_parse(struct xt_option_call *cb)
{
struct nf_nat_multi_range *mr = cb->data;
struct nf_nat_range *range = &mr->range[0];
xtables_option_parse(cb);
range->flags |= IP_NAT_RANGE_MAP_IPS;
range->min_ip = cb->val.haddr.ip & cb->val.hmask.ip;
range->max_ip = range->min_ip | ~cb->val.hmask.ip;
}
static void NETMAP_print(const void *ip, const struct xt_entry_target *target,
int numeric)
{
const struct nf_nat_multi_range *mr = (const void *)target->data;
const struct nf_nat_range *r = &mr->range[0];
struct in_addr a;
int bits;
a.s_addr = r->min_ip;
printf("%s", xtables_ipaddr_to_numeric(&a));
a.s_addr = ~(r->min_ip ^ r->max_ip);
bits = netmask2bits(a.s_addr);
if (bits < 0)
printf("/%s", xtables_ipaddr_to_numeric(&a));
else
printf("/%d", bits);
}
static void NETMAP_save(const void *ip, const struct xt_entry_target *target)
{
printf(" --%s ", NETMAP_opts[0].name);
NETMAP_print(ip, target, 0);
}
static struct xtables_target netmap_tg_reg = {
.name = MODULENAME,
.version = XTABLES_VERSION,
.family = NFPROTO_IPV4,
.size = XT_ALIGN(sizeof(struct nf_nat_multi_range)),
.userspacesize = XT_ALIGN(sizeof(struct nf_nat_multi_range)),
.help = NETMAP_help,
.init = NETMAP_init,
.x6_parse = NETMAP_parse,
.print = NETMAP_print,
.save = NETMAP_save,
.x6_options = NETMAP_opts,
};
void _init(void)
{
xtables_register_target(&netmap_tg_reg);
}
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