/* Shared library add-on to iptables to add simple non load-balancing SNAT support. */
#include <stdbool.h>
#include <stdio.h>
#include <netdb.h>
#include <string.h>
#include <stdlib.h>
#include <getopt.h>
#include <xtables.h>
#include <net/netfilter/nf_nat.h>
/* For 64bit kernel / 32bit userspace */
#include <linux/netfilter_ipv4/ipt_SAME.h>

static void SAME_help(void)
{
	printf(
"SAME target options:\n"
" --to <ipaddr>-<ipaddr>\n"
"				Addresses to map source to.\n"
"				 May be specified more than\n"
"				  once for multiple ranges.\n"
" --nodst\n"
"				Don't use destination-ip in\n"
"				           source selection\n"
" --random\n"
"				Randomize source port\n");
}

static const struct option SAME_opts[] = {
	{.name = "to",     .has_arg = true,  .val = '1'},
	{.name = "nodst",  .has_arg = false, .val = '2'},
	{.name = "random", .has_arg = false, .val = '3'},
	XT_GETOPT_TABLEEND,
};

/* Parses range of IPs */
static void
parse_to(char *arg, struct nf_nat_range *range)
{
	char *dash;
	const struct in_addr *ip;

	range->flags |= IP_NAT_RANGE_MAP_IPS;
	dash = strchr(arg, '-');

	if (dash)
		*dash = '\0';

	ip = xtables_numeric_to_ipaddr(arg);
	if (!ip)
		xtables_error(PARAMETER_PROBLEM, "Bad IP address \"%s\"\n",
			   arg);
	range->min_ip = ip->s_addr;

	if (dash) {
		ip = xtables_numeric_to_ipaddr(dash+1);
		if (!ip)
			xtables_error(PARAMETER_PROBLEM, "Bad IP address \"%s\"\n",
				   dash+1);
	}
	range->max_ip = ip->s_addr;
	if (dash)
		if (range->min_ip > range->max_ip)
			xtables_error(PARAMETER_PROBLEM, "Bad IP range \"%s-%s\"\n",
				   arg, dash+1);
}

#define IPT_SAME_OPT_TO			0x01
#define IPT_SAME_OPT_NODST		0x02
#define IPT_SAME_OPT_RANDOM		0x04

static int SAME_parse(int c, char **argv, int invert, unsigned int *flags,
                      const void *entry, struct xt_entry_target **target)
{
	struct ipt_same_info *mr
		= (struct ipt_same_info *)(*target)->data;
	unsigned int count;

	switch (c) {
	case '1':
		if (mr->rangesize == IPT_SAME_MAX_RANGE)
			xtables_error(PARAMETER_PROBLEM,
				   "Too many ranges specified, maximum "
				   "is %i ranges.\n",
				   IPT_SAME_MAX_RANGE);
		if (xtables_check_inverse(optarg, &invert, NULL, 0, argv))
			xtables_error(PARAMETER_PROBLEM,
				   "Unexpected `!' after --to");

		parse_to(optarg, &mr->range[mr->rangesize]);
		/* WTF do we need this for? */
		if (*flags & IPT_SAME_OPT_RANDOM)
			mr->range[mr->rangesize].flags 
				|= IP_NAT_RANGE_PROTO_RANDOM;
		mr->rangesize++;
		*flags |= IPT_SAME_OPT_TO;
		break;
		
	case '2':
		if (*flags & IPT_SAME_OPT_NODST)
			xtables_error(PARAMETER_PROBLEM,
				   "Can't specify --nodst twice");
		
		mr->info |= IPT_SAME_NODST;
		*flags |= IPT_SAME_OPT_NODST;
		break;

	case '3':	
		*flags |= IPT_SAME_OPT_RANDOM;
		for (count=0; count < mr->rangesize; count++)
			mr->range[count].flags |= IP_NAT_RANGE_PROTO_RANDOM;
		break;
	}
	
	return 1;
}

static void SAME_check(unsigned int flags)
{
	if (!(flags & IPT_SAME_OPT_TO))
		xtables_error(PARAMETER_PROBLEM,
			   "SAME needs --to");
}

static void SAME_print(const void *ip, const struct xt_entry_target *target,
                       int numeric)
{
	unsigned int count;
	const struct ipt_same_info *mr = (const void *)target->data;
	int random_selection = 0;
	
	printf(" same:");

	for (count = 0; count < mr->rangesize; count++) {
		const struct nf_nat_range *r = &mr->range[count];
		struct in_addr a;

		a.s_addr = r->min_ip;

		printf("%s", xtables_ipaddr_to_numeric(&a));
		a.s_addr = r->max_ip;
		
		if (r->min_ip != r->max_ip)
			printf("-%s", xtables_ipaddr_to_numeric(&a));
		if (r->flags & IP_NAT_RANGE_PROTO_RANDOM) 
			random_selection = 1;
	}
	
	if (mr->info & IPT_SAME_NODST)
		printf(" nodst");

	if (random_selection)
		printf(" random");
}

static void SAME_save(const void *ip, const struct xt_entry_target *target)
{
	unsigned int count;
	const struct ipt_same_info *mr = (const void *)target->data;
	int random_selection = 0;

	for (count = 0; count < mr->rangesize; count++) {
		const struct nf_nat_range *r = &mr->range[count];
		struct in_addr a;

		a.s_addr = r->min_ip;
		printf(" --to %s", xtables_ipaddr_to_numeric(&a));
		a.s_addr = r->max_ip;

		if (r->min_ip != r->max_ip)
			printf("-%s", xtables_ipaddr_to_numeric(&a));
		if (r->flags & IP_NAT_RANGE_PROTO_RANDOM) 
			random_selection = 1;
	}
	
	if (mr->info & IPT_SAME_NODST)
		printf(" --nodst");

	if (random_selection)
		printf(" --random");
}

static struct xtables_target same_tg_reg = {
	.name		= "SAME",
	.version	= XTABLES_VERSION,
	.family		= NFPROTO_IPV4,
	.size		= XT_ALIGN(sizeof(struct ipt_same_info)),
	.userspacesize	= XT_ALIGN(sizeof(struct ipt_same_info)),
	.help		= SAME_help,
	.parse		= SAME_parse,
	.final_check	= SAME_check,
	.print		= SAME_print,
	.save		= SAME_save,
	.extra_opts	= SAME_opts,
};

void _init(void)
{
	xtables_register_target(&same_tg_reg);
}