/*
 * Shared library add-on to iptables to add TPROXY target support.
 *
 * Copyright (C) 2002-2008 BalaBit IT Ltd.
 */
#include <getopt.h>
#include <stdbool.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <limits.h>

#include <iptables.h>
#include <xtables.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_TPROXY.h>

static const struct option tproxy_tg_opts[] = {
	{ .name = "on-port", .has_arg = 1, .val = '1'},
	{ .name = "on-ip", .has_arg = 1, .val = '2'},
	{ .name = "tproxy-mark", .has_arg = 1, .val = '3'},
	{NULL},
};

enum {
	PARAM_ONPORT = 1 << 0,
	PARAM_ONIP = 1 << 1,
	PARAM_MARK = 1 << 2,
};

static void tproxy_tg_help(void)
{
	printf(
"TPROXY target options:\n"
"  --on-port port		    Redirect connection to port, or the original port if 0\n"
"  --on-ip ip			    Optionally redirect to the given IP\n"
"  --tproxy-mark value[/mask]	    Mark packets with the given value/mask\n\n");
}

static void parse_tproxy_lport(const char *s, struct xt_tproxy_target_info *info)
{
	unsigned int lport;

	if (string_to_number(s, 0, 65535, &lport) != -1)
		info->lport = htons(lport);
	else
		param_act(P_BAD_VALUE, "TPROXY", "--on-port", s);
}

static void parse_tproxy_laddr(const char *s, struct xt_tproxy_target_info *info)
{
	struct in_addr *laddr;

	if ((laddr = numeric_to_ipaddr(s)) == NULL)
		param_act(P_BAD_VALUE, "TPROXY", "--on-ip", s);

	info->laddr = laddr->s_addr;
}

static void parse_tproxy_mark(char *s, struct xt_tproxy_target_info *info)
{
	unsigned int value, mask = ~0U;
	char *end;

	if (!strtonum(s, &end, &value, 0, UINT_MAX))
		param_act(P_BAD_VALUE, "TPROXY", "--tproxy-mark", s);
	if (*end == '/')
		if (!strtonum(end + 1, &end, &mask, 0, UINT_MAX))
			param_act(P_BAD_VALUE, "TPROXY", "--tproxy-mark", s);
	if (*end != '\0')
		param_act(P_BAD_VALUE, "TPROXY", "--tproxy-mark", s);

	info->mark_mask = mask;
	info->mark_value = value;
}

static int tproxy_tg_parse(int c, char **argv, int invert, unsigned int *flags,
			const void *entry, struct xt_entry_target **target)
{
	struct xt_tproxy_target_info *tproxyinfo = (void *)(*target)->data;

	switch (c) {
	case '1':
		param_act(P_ONLY_ONCE, "TPROXY", "--on-port", *flags & PARAM_ONPORT);
		param_act(P_NO_INVERT, "TPROXY", "--on-port", invert);
		parse_tproxy_lport(optarg, tproxyinfo);
		*flags |= PARAM_ONPORT;
		return 1;
	case '2':
		param_act(P_ONLY_ONCE, "TPROXY", "--on-ip", *flags & PARAM_ONIP);
		param_act(P_NO_INVERT, "TPROXY", "--on-ip", invert);
		parse_tproxy_laddr(optarg, tproxyinfo);
		*flags |= PARAM_ONIP;
		return 1;
	case '3':
		param_act(P_ONLY_ONCE, "TPROXY", "--tproxy-mark", *flags & PARAM_MARK);
		param_act(P_NO_INVERT, "TPROXY", "--tproxy-mark", invert);
		parse_tproxy_mark(optarg, tproxyinfo);
		*flags |= PARAM_MARK;
		return 1;
	}

	return 0;
}

static void tproxy_tg_check(unsigned int flags)
{
	if (!(flags & PARAM_ONPORT))
		exit_error(PARAMETER_PROBLEM,
			   "TPROXY target: Parameter --on-port is required");
}

static void tproxy_tg_print(const void *ip, const struct xt_entry_target *target,
			 int numeric)
{
	const struct xt_tproxy_target_info *info = (const void *)target->data;
	printf("TPROXY redirect %s:%u mark 0x%x/0x%x",
	       ipaddr_to_numeric((const struct in_addr *)&info->laddr),
	       ntohs(info->lport), (unsigned int)info->mark_value,
	       (unsigned int)info->mark_mask);
}

static void tproxy_tg_save(const void *ip, const struct xt_entry_target *target)
{
	const struct xt_tproxy_target_info *info = (const void *)target->data;

	printf("--on-port %u ", ntohs(info->lport));
	printf("--on-ip %s ",
	       ipaddr_to_numeric((const struct in_addr *)&info->laddr));
	printf("--tproxy-mark 0x%x/0x%x ",
	       (unsigned int)info->mark_value, (unsigned int)info->mark_mask);
}

static struct xtables_target tproxy_tg_reg = {
	.name	       = "TPROXY",
	.family	       = AF_INET,
	.version       = XTABLES_VERSION,
	.size	       = XT_ALIGN(sizeof(struct xt_tproxy_target_info)),
	.userspacesize = XT_ALIGN(sizeof(struct xt_tproxy_target_info)),
	.help	       = tproxy_tg_help,
	.parse	       = tproxy_tg_parse,
	.final_check   = tproxy_tg_check,
	.print	       = tproxy_tg_print,
	.save	       = tproxy_tg_save,
	.extra_opts    = tproxy_tg_opts,
};

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