// SPDX-License-Identifier: GPL-2.0-only
/* Masquerade.  Simple mapping which alters range to a local IP address
   (depending on route). */

/* (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/netfilter/x_tables.h>
#include <net/netfilter/nf_nat.h>
#include <net/netfilter/nf_nat_masquerade.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
MODULE_DESCRIPTION("Xtables: automatic-address SNAT");

/* FIXME: Multiple targets. --RR */
static int masquerade_tg_check(const struct xt_tgchk_param *par)
{
        const struct nf_nat_ipv4_multi_range_compat *mr = par->targinfo;

        if (mr->range[0].flags & NF_NAT_RANGE_MAP_IPS) {
                pr_debug("bad MAP_IPS.\n");
                return -EINVAL;
        }
        if (mr->rangesize != 1) {
                pr_debug("bad rangesize %u\n", mr->rangesize);
                return -EINVAL;
        }
        return nf_ct_netns_get(par->net, par->family);
}

static unsigned int
masquerade_tg(struct sk_buff *skb, const struct xt_action_param *par)
{
        struct nf_nat_range2 range;
        const struct nf_nat_ipv4_multi_range_compat *mr;

        mr = par->targinfo;
        range.flags = mr->range[0].flags;
        range.min_proto = mr->range[0].min;
        range.max_proto = mr->range[0].max;

        return nf_nat_masquerade_ipv4(skb, xt_hooknum(par), &range,
                                      xt_out(par));
}

static void masquerade_tg_destroy(const struct xt_tgdtor_param *par)
{
        nf_ct_netns_put(par->net, par->family);
}

#if IS_ENABLED(CONFIG_IPV6)
static unsigned int
masquerade_tg6(struct sk_buff *skb, const struct xt_action_param *par)
{
        return nf_nat_masquerade_ipv6(skb, par->targinfo, xt_out(par));
}

static int masquerade_tg6_checkentry(const struct xt_tgchk_param *par)
{
        const struct nf_nat_range2 *range = par->targinfo;

        if (range->flags & NF_NAT_RANGE_MAP_IPS)
                return -EINVAL;

        return nf_ct_netns_get(par->net, par->family);
}
#endif

static struct xt_target masquerade_tg_reg[] __read_mostly = {
        {
#if IS_ENABLED(CONFIG_IPV6)
                .name           = "MASQUERADE",
                .family         = NFPROTO_IPV6,
                .target         = masquerade_tg6,
                .targetsize     = sizeof(struct nf_nat_range),
                .table          = "nat",
                .hooks          = 1 << NF_INET_POST_ROUTING,
                .checkentry     = masquerade_tg6_checkentry,
                .destroy        = masquerade_tg_destroy,
                .me             = THIS_MODULE,
        }, {
#endif
                .name           = "MASQUERADE",
                .family         = NFPROTO_IPV4,
                .target         = masquerade_tg,
                .targetsize     = sizeof(struct nf_nat_ipv4_multi_range_compat),
                .table          = "nat",
                .hooks          = 1 << NF_INET_POST_ROUTING,
                .checkentry     = masquerade_tg_check,
                .destroy        = masquerade_tg_destroy,
                .me             = THIS_MODULE,
        }
};

static int __init masquerade_tg_init(void)
{
        int ret;

        ret = xt_register_targets(masquerade_tg_reg,
                                  ARRAY_SIZE(masquerade_tg_reg));
        if (ret)
                return ret;

        ret = nf_nat_masquerade_inet_register_notifiers();
        if (ret) {
                xt_unregister_targets(masquerade_tg_reg,
                                      ARRAY_SIZE(masquerade_tg_reg));
                return ret;
        }

        return ret;
}

static void __exit masquerade_tg_exit(void)
{
        xt_unregister_targets(masquerade_tg_reg, ARRAY_SIZE(masquerade_tg_reg));
        nf_nat_masquerade_inet_unregister_notifiers();
}

module_init(masquerade_tg_init);
module_exit(masquerade_tg_exit);
#if IS_ENABLED(CONFIG_IPV6)
MODULE_ALIAS("ip6t_MASQUERADE");
#endif
MODULE_ALIAS("ipt_MASQUERADE");