// SPDX-License-Identifier: GPL-2.0-only
/*
 * This is a module which is used for rejecting packets.
 */

/* (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/ip.h>
#include <linux/udp.h>
#include <linux/icmp.h>
#include <net/icmp.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv4/ipt_REJECT.h>
#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
#include <linux/netfilter_bridge.h>
#endif

#include <net/netfilter/ipv4/nf_reject.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
MODULE_DESCRIPTION("Xtables: packet \"rejection\" target for IPv4");

static unsigned int
reject_tg(struct sk_buff *skb, const struct xt_action_param *par)
{
        const struct ipt_reject_info *reject = par->targinfo;
        int hook = xt_hooknum(par);

        switch (reject->with) {
        case IPT_ICMP_NET_UNREACHABLE:
                nf_send_unreach(skb, ICMP_NET_UNREACH, hook);
                break;
        case IPT_ICMP_HOST_UNREACHABLE:
                nf_send_unreach(skb, ICMP_HOST_UNREACH, hook);
                break;
        case IPT_ICMP_PROT_UNREACHABLE:
                nf_send_unreach(skb, ICMP_PROT_UNREACH, hook);
                break;
        case IPT_ICMP_PORT_UNREACHABLE:
                nf_send_unreach(skb, ICMP_PORT_UNREACH, hook);
                break;
        case IPT_ICMP_NET_PROHIBITED:
                nf_send_unreach(skb, ICMP_NET_ANO, hook);
                break;
        case IPT_ICMP_HOST_PROHIBITED:
                nf_send_unreach(skb, ICMP_HOST_ANO, hook);
                break;
        case IPT_ICMP_ADMIN_PROHIBITED:
                nf_send_unreach(skb, ICMP_PKT_FILTERED, hook);
                break;
        case IPT_TCP_RESET:
                nf_send_reset(xt_net(par), par->state->sk, skb, hook);
                break;
        case IPT_ICMP_ECHOREPLY:
                /* Doesn't happen. */
                break;
        }

        return NF_DROP;
}

static int reject_tg_check(const struct xt_tgchk_param *par)
{
        const struct ipt_reject_info *rejinfo = par->targinfo;
        const struct ipt_entry *e = par->entryinfo;

        if (rejinfo->with == IPT_ICMP_ECHOREPLY) {
                pr_info_ratelimited("ECHOREPLY no longer supported.\n");
                return -EINVAL;
        } else if (rejinfo->with == IPT_TCP_RESET) {
                /* Must specify that it's a TCP packet */
                if (e->ip.proto != IPPROTO_TCP ||
                    (e->ip.invflags & XT_INV_PROTO)) {
                        pr_info_ratelimited("TCP_RESET invalid for non-tcp\n");
                        return -EINVAL;
                }
        }
        return 0;
}

static struct xt_target reject_tg_reg __read_mostly = {
        .name           = "REJECT",
        .family         = NFPROTO_IPV4,
        .target         = reject_tg,
        .targetsize     = sizeof(struct ipt_reject_info),
        .table          = "filter",
        .hooks          = (1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD) |
                          (1 << NF_INET_LOCAL_OUT),
        .checkentry     = reject_tg_check,
        .me             = THIS_MODULE,
};

static int __init reject_tg_init(void)
{
        return xt_register_target(&reject_tg_reg);
}

static void __exit reject_tg_exit(void)
{
        xt_unregister_target(&reject_tg_reg);
}

module_init(reject_tg_init);
module_exit(reject_tg_exit);