1/*
2 * This is a module which is used for rejecting packets.
3 */
4
5/* (C) 1999-2001 Paul `Rusty' Russell
6 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
11 */
12#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
13#include <linux/module.h>
14#include <linux/skbuff.h>
15#include <linux/slab.h>
16#include <linux/ip.h>
17#include <linux/udp.h>
18#include <linux/icmp.h>
19#include <net/icmp.h>
20#include <linux/netfilter/x_tables.h>
21#include <linux/netfilter_ipv4/ip_tables.h>
22#include <linux/netfilter_ipv4/ipt_REJECT.h>
23#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
24#include <linux/netfilter_bridge.h>
25#endif
26
27#include <net/netfilter/ipv4/nf_reject.h>
28
29MODULE_LICENSE("GPL");
30MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
31MODULE_DESCRIPTION("Xtables: packet \"rejection\" target for IPv4");
32
33static unsigned int
34reject_tg(struct sk_buff *skb, const struct xt_action_param *par)
35{
36	const struct ipt_reject_info *reject = par->targinfo;
37
38	switch (reject->with) {
39	case IPT_ICMP_NET_UNREACHABLE:
40		nf_send_unreach(skb, ICMP_NET_UNREACH);
41		break;
42	case IPT_ICMP_HOST_UNREACHABLE:
43		nf_send_unreach(skb, ICMP_HOST_UNREACH);
44		break;
45	case IPT_ICMP_PROT_UNREACHABLE:
46		nf_send_unreach(skb, ICMP_PROT_UNREACH);
47		break;
48	case IPT_ICMP_PORT_UNREACHABLE:
49		nf_send_unreach(skb, ICMP_PORT_UNREACH);
50		break;
51	case IPT_ICMP_NET_PROHIBITED:
52		nf_send_unreach(skb, ICMP_NET_ANO);
53		break;
54	case IPT_ICMP_HOST_PROHIBITED:
55		nf_send_unreach(skb, ICMP_HOST_ANO);
56		break;
57	case IPT_ICMP_ADMIN_PROHIBITED:
58		nf_send_unreach(skb, ICMP_PKT_FILTERED);
59		break;
60	case IPT_TCP_RESET:
61		nf_send_reset(skb, par->hooknum);
62	case IPT_ICMP_ECHOREPLY:
63		/* Doesn't happen. */
64		break;
65	}
66
67	return NF_DROP;
68}
69
70static int reject_tg_check(const struct xt_tgchk_param *par)
71{
72	const struct ipt_reject_info *rejinfo = par->targinfo;
73	const struct ipt_entry *e = par->entryinfo;
74
75	if (rejinfo->with == IPT_ICMP_ECHOREPLY) {
76		pr_info("ECHOREPLY no longer supported.\n");
77		return -EINVAL;
78	} else if (rejinfo->with == IPT_TCP_RESET) {
79		/* Must specify that it's a TCP packet */
80		if (e->ip.proto != IPPROTO_TCP ||
81		    (e->ip.invflags & XT_INV_PROTO)) {
82			pr_info("TCP_RESET invalid for non-tcp\n");
83			return -EINVAL;
84		}
85	}
86	return 0;
87}
88
89static struct xt_target reject_tg_reg __read_mostly = {
90	.name		= "REJECT",
91	.family		= NFPROTO_IPV4,
92	.target		= reject_tg,
93	.targetsize	= sizeof(struct ipt_reject_info),
94	.table		= "filter",
95	.hooks		= (1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD) |
96			  (1 << NF_INET_LOCAL_OUT),
97	.checkentry	= reject_tg_check,
98	.me		= THIS_MODULE,
99};
100
101static int __init reject_tg_init(void)
102{
103	return xt_register_target(&reject_tg_reg);
104}
105
106static void __exit reject_tg_exit(void)
107{
108	xt_unregister_target(&reject_tg_reg);
109}
110
111module_init(reject_tg_init);
112module_exit(reject_tg_exit);
113