#include <stdio.h>

#include <netdb.h>

#include <string.h>

#include <stdlib.h>

#include <xtables.h>

#include <iptables.h>

#include <limits.h> /* INT_MAX in ip_tables.h */

#include <linux/netfilter_ipv4/ip_tables.h>

#include <linux/netfilter/nf_nat.h>

enum {

	O_TO_SRC = 0,

	O_RANDOM,

	O_RANDOM_FULLY,

	O_PERSISTENT,

	O_X_TO_SRC,

	F_TO_SRC       = 1 << O_TO_SRC,

	F_RANDOM       = 1 << O_RANDOM,

	F_RANDOM_FULLY = 1 << O_RANDOM_FULLY,

	F_X_TO_SRC     = 1 << O_X_TO_SRC,

};

/* Source NAT data consists of a multi-range, indicating where to map

   to. */

struct ipt_natinfo

{

	struct xt_entry_target t;

	struct nf_nat_ipv4_multi_range_compat mr;

};

static void SNAT_help(void)

{

	printf(

"SNAT target options:\n"

" --to-source [<ipaddr>[-<ipaddr>]][:port[-port]]\n"

"				Address to map source to.\n"

"[--random] [--random-fully] [--persistent]\n");

}

static const struct xt_option_entry SNAT_opts[] = {

	{.name = "to-source", .id = O_TO_SRC, .type = XTTYPE_STRING,

	 .flags = XTOPT_MAND | XTOPT_MULTI},

	{.name = "random", .id = O_RANDOM, .type = XTTYPE_NONE},

	{.name = "random-fully", .id = O_RANDOM_FULLY, .type = XTTYPE_NONE},

	{.name = "persistent", .id = O_PERSISTENT, .type = XTTYPE_NONE},

	XTOPT_TABLEEND,

};

static struct ipt_natinfo *

append_range(struct ipt_natinfo *info, const struct nf_nat_ipv4_range *range)

{

	unsigned int size;

	/* One rangesize already in struct ipt_natinfo */

	size = XT_ALIGN(sizeof(*info) + info->mr.rangesize * sizeof(*range));

	info = realloc(info, size);

	if (!info)

		xtables_error(OTHER_PROBLEM, "Out of memory\n");

	info->t.u.target_size = size;

	info->mr.range[info->mr.rangesize] = *range;

	info->mr.rangesize++;

	return info;

}

/* Ranges expected in network order. */

static struct xt_entry_target *

parse_to(const char *orig_arg, int portok, struct ipt_natinfo *info)

{

	struct nf_nat_ipv4_range range;

	char *arg, *colon, *dash, *error;

	const struct in_addr *ip;

	arg = strdup(orig_arg);

	if (arg == NULL)

		xtables_error(RESOURCE_PROBLEM, "strdup");

	memset(&range, 0, sizeof(range));

	colon = strchr(arg, ':');

	if (colon) {

		int port;

		if (!portok)

			xtables_error(PARAMETER_PROBLEM,

				   "Need TCP, UDP, SCTP or DCCP with port specification");

		range.flags |= NF_NAT_RANGE_PROTO_SPECIFIED;

		port = atoi(colon+1);

		if (port <= 0 || port > 65535)

			xtables_error(PARAMETER_PROBLEM,

				   "Port `%s' not valid\n", colon+1);

		error = strchr(colon+1, ':');

		if (error)

			xtables_error(PARAMETER_PROBLEM,

				   "Invalid port:port syntax - use dash\n");

		dash = strchr(colon, '-');

		if (!dash) {

			range.min.tcp.port

				= range.max.tcp.port

				= htons(port);

		} else {

			int maxport;

			maxport = atoi(dash + 1);

			if (maxport <= 0 || maxport > 65535)

				xtables_error(PARAMETER_PROBLEM,

					   "Port `%s' not valid\n", dash+1);

			if (maxport < port)

				/* People are stupid. */

				xtables_error(PARAMETER_PROBLEM,

					   "Port range `%s' funky\n", colon+1);

			range.min.tcp.port = htons(port);

			range.max.tcp.port = htons(maxport);

		}

		/* Starts with a colon? No IP info...*/

		if (colon == arg) {

			free(arg);

			return &(append_range(info, &range)->t);

		}

		*colon = '\0';

	}

	range.flags |= NF_NAT_RANGE_MAP_IPS;

	dash = strchr(arg, '-');

	if (colon && dash && dash > colon)

		dash = NULL;

	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;

	} else

		range.max_ip = range.min_ip;

	free(arg);

	return &(append_range(info, &range)->t);

}

static void SNAT_parse(struct xt_option_call *cb)

{

	const struct ipt_entry *entry = cb->xt_entry;

	struct ipt_natinfo *info = (void *)(*cb->target);

	int portok;

	if (entry->ip.proto == IPPROTO_TCP

	    || entry->ip.proto == IPPROTO_UDP

	    || entry->ip.proto == IPPROTO_SCTP

	    || entry->ip.proto == IPPROTO_DCCP

	    || entry->ip.proto == IPPROTO_ICMP)

		portok = 1;

	else

		portok = 0;

	xtables_option_parse(cb);

	switch (cb->entry->id) {

	case O_TO_SRC:

		if (cb->xflags & F_X_TO_SRC) {

			if (!kernel_version)

				get_kernel_version();

			if (kernel_version > LINUX_VERSION(2, 6, 10))

				xtables_error(PARAMETER_PROBLEM,

					   "SNAT: Multiple --to-source not supported");

		}

		*cb->target = parse_to(cb->arg, portok, info);

		cb->xflags |= F_X_TO_SRC;

		break;

	case O_PERSISTENT:

		info->mr.range[0].flags |= NF_NAT_RANGE_PERSISTENT;

		break;

	}

}

static void SNAT_fcheck(struct xt_fcheck_call *cb)

{

	static const unsigned int f = F_TO_SRC | F_RANDOM;

	static const unsigned int r = F_TO_SRC | F_RANDOM_FULLY;

	struct nf_nat_ipv4_multi_range_compat *mr = cb->data;

	if ((cb->xflags & f) == f)

		mr->range[0].flags |= NF_NAT_RANGE_PROTO_RANDOM;

	if ((cb->xflags & r) == r)

		mr->range[0].flags |= NF_NAT_RANGE_PROTO_RANDOM_FULLY;

}

static void print_range(const struct nf_nat_ipv4_range *r)

{

	if (r->flags & NF_NAT_RANGE_MAP_IPS) {

		struct in_addr a;

		a.s_addr = r->min_ip;

		printf("%s", xtables_ipaddr_to_numeric(&a);;

		if (r->max_ip != r->min_ip) {

			a.s_addr = r->max_ip;

			printf("-%s", xtables_ipaddr_to_numeric(&a);;

		}

	}

	if (r->flags & NF_NAT_RANGE_PROTO_SPECIFIED) {

		printf(":");

		printf("%hu", ntohs(r->min.tcp.port));

		if (r->max.tcp.port != r->min.tcp.port)

			printf("-%hu", ntohs(r->max.tcp.port));

	}

}

static void SNAT_print(const void *ip, const struct xt_entry_target *target,

                       int numeric)

{

	const struct ipt_natinfo *info = (const void *)target;

	unsigned int i = 0;

	printf(" to:");

	for (i = 0; i < info->mr.rangesize; i++) {

		print_range(&info->mr.range[i]);

		if (info->mr.range[i].flags & NF_NAT_RANGE_PROTO_RANDOM)

			printf(" random");

		if (info->mr.range[i].flags & NF_NAT_RANGE_PROTO_RANDOM_FULLY)

			printf(" random-fully");

		if (info->mr.range[i].flags & NF_NAT_RANGE_PERSISTENT)

			printf(" persistent");

	}

}

static void SNAT_save(const void *ip, const struct xt_entry_target *target)

{

	const struct ipt_natinfo *info = (const void *)target;

	unsigned int i = 0;

	for (i = 0; i < info->mr.rangesize; i++) {

		printf(" --to-source ");

		print_range(&info->mr.range[i]);

		if (info->mr.range[i].flags & NF_NAT_RANGE_PROTO_RANDOM)

			printf(" --random");

		if (info->mr.range[i].flags & NF_NAT_RANGE_PROTO_RANDOM_FULLY)

			printf(" --random-fully");

		if (info->mr.range[i].flags & NF_NAT_RANGE_PERSISTENT)

			printf(" --persistent");

	}

}

static void print_range_xlate(const struct nf_nat_ipv4_range *r,

			      struct xt_xlate *xl)

{

	if (r->flags & NF_NAT_RANGE_MAP_IPS) {

		struct in_addr a;

		a.s_addr = r->min_ip;

		xt_xlate_add(xl, "%s", xtables_ipaddr_to_numeric(&a);;

		if (r->max_ip != r->min_ip) {

			a.s_addr = r->max_ip;

			xt_xlate_add(xl, "-%s", xtables_ipaddr_to_numeric(&a);;

		}

	}

	if (r->flags & NF_NAT_RANGE_PROTO_SPECIFIED) {

		xt_xlate_add(xl, ":");

		xt_xlate_add(xl, "%hu", ntohs(r->min.tcp.port));

		if (r->max.tcp.port != r->min.tcp.port)

			xt_xlate_add(xl, "-%hu", ntohs(r->max.tcp.port));

	}

}

static int SNAT_xlate(struct xt_xlate *xl,

		      const struct xt_xlate_tg_params *params)

{

	const struct ipt_natinfo *info = (const void *)params->target;

	unsigned int i = 0;

	bool sep_need = false;

	const char *sep = " ";

	for (i = 0; i < info->mr.rangesize; i++) {

		xt_xlate_add(xl, "snat to ");

		print_range_xlate(&info->mr.range[i], xl);

		if (info->mr.range[i].flags & NF_NAT_RANGE_PROTO_RANDOM) {

			xt_xlate_add(xl, " random");

			sep_need = true;

		}

		if (info->mr.range[i].flags & NF_NAT_RANGE_PROTO_RANDOM_FULLY) {

			if (sep_need)

				sep = ",";

			xt_xlate_add(xl, "%sfully-random", sep);

			sep_need = true;

		}

		if (info->mr.range[i].flags & NF_NAT_RANGE_PERSISTENT) {

			if (sep_need)

				sep = ",";

			xt_xlate_add(xl, "%spersistent", sep);

		}

	}

	return 1;

}

static struct xtables_target snat_tg_reg = {

	.name		= "SNAT",

	.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		= SNAT_help,

	.x6_parse	= SNAT_parse,

	.x6_fcheck	= SNAT_fcheck,

	.print		= SNAT_print,

	.save		= SNAT_save,

	.x6_options	= SNAT_opts,

	.xlate		= SNAT_xlate,

};

void _init(void)

{

	xtables_register_target(&snat_tg_reg);

}