/* 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 <linux/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_ipv4_multi_range_compat *mr = (struct nf_nat_ipv4_multi_range_compat *)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_ipv4_multi_range_compat *mr = cb->data;

	struct nf_nat_ipv4_range *range = &mr->range[0];

	xtables_option_parse(cb);

	range->flags |= NF_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_ipv4_multi_range_compat *mr = (const void *)target->data;

	const struct nf_nat_ipv4_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_print(const void *ip, const struct xt_entry_target *target,

			 int numeric)

{

	printf(" to:");

	__NETMAP_print(ip, target, numeric);

}

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_ipv4_multi_range_compat)),

	.userspacesize	= XT_ALIGN(sizeof(struct nf_nat_ipv4_multi_range_compat)),

	.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);

}