// SPDX-License-Identifier: GPL-2.0-only
/* Kernel module to match connection tracking information. */

/* (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2005 Netfilter Core Team <coreteam@netfilter.org>
 */

#include <linux/module.h>
#include <linux/skbuff.h>
#include <net/netfilter/nf_conntrack.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_state.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
MODULE_DESCRIPTION("ip[6]_tables connection tracking state match module");
MODULE_ALIAS("ipt_state");
MODULE_ALIAS("ip6t_state");

static bool
state_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
        const struct xt_state_info *sinfo = par->matchinfo;
        enum ip_conntrack_info ctinfo;
        unsigned int statebit;
        struct nf_conn *ct = nf_ct_get(skb, &ctinfo);

        if (ct)
                statebit = XT_STATE_BIT(ctinfo);
        else if (ctinfo == IP_CT_UNTRACKED)
                statebit = XT_STATE_UNTRACKED;
        else
                statebit = XT_STATE_INVALID;

        return (sinfo->statemask & statebit);
}

static int state_mt_check(const struct xt_mtchk_param *par)
{
        int ret;

        ret = nf_ct_netns_get(par->net, par->family);
        if (ret < 0)
                pr_info_ratelimited("cannot load conntrack support for proto=%u\n",
                                    par->family);
        return ret;
}

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

static struct xt_match state_mt_reg __read_mostly = {
        .name       = "state",
        .family     = NFPROTO_UNSPEC,
        .checkentry = state_mt_check,
        .match      = state_mt,
        .destroy    = state_mt_destroy,
        .matchsize  = sizeof(struct xt_state_info),
        .me         = THIS_MODULE,
};

static int __init state_mt_init(void)
{
        return xt_register_match(&state_mt_reg);
}

static void __exit state_mt_exit(void)
{
        xt_unregister_match(&state_mt_reg);
}

module_init(state_mt_init);
module_exit(state_mt_exit);