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	int hook = par->hooknum;
38
39	switch (reject->with) {
40	case IPT_ICMP_NET_UNREACHABLE:
41		nf_send_unreach(skb, ICMP_NET_UNREACH, hook);
42		break;
43	case IPT_ICMP_HOST_UNREACHABLE:
44		nf_send_unreach(skb, ICMP_HOST_UNREACH, hook);
45		break;
46	case IPT_ICMP_PROT_UNREACHABLE:
47		nf_send_unreach(skb, ICMP_PROT_UNREACH, hook);
48		break;
49	case IPT_ICMP_PORT_UNREACHABLE:
50		nf_send_unreach(skb, ICMP_PORT_UNREACH, hook);
51		break;
52	case IPT_ICMP_NET_PROHIBITED:
53		nf_send_unreach(skb, ICMP_NET_ANO, hook);
54		break;
55	case IPT_ICMP_HOST_PROHIBITED:
56		nf_send_unreach(skb, ICMP_HOST_ANO, hook);
57		break;
58	case IPT_ICMP_ADMIN_PROHIBITED:
59		nf_send_unreach(skb, ICMP_PKT_FILTERED, hook);
60		break;
61	case IPT_TCP_RESET:
62		nf_send_reset(skb, hook);
63	case IPT_ICMP_ECHOREPLY:
64		/* Doesn't happen. */
65		break;
66	}
67
68	return NF_DROP;
69}
70
71static int reject_tg_check(const struct xt_tgchk_param *par)
72{
73	const struct ipt_reject_info *rejinfo = par->targinfo;
74	const struct ipt_entry *e = par->entryinfo;
75
76	if (rejinfo->with == IPT_ICMP_ECHOREPLY) {
77		pr_info("ECHOREPLY no longer supported.\n");
78		return -EINVAL;
79	} else if (rejinfo->with == IPT_TCP_RESET) {
80		/* Must specify that it's a TCP packet */
81		if (e->ip.proto != IPPROTO_TCP ||
82		    (e->ip.invflags & XT_INV_PROTO)) {
83			pr_info("TCP_RESET invalid for non-tcp\n");
84			return -EINVAL;
85		}
86	}
87	return 0;
88}
89
90static struct xt_target reject_tg_reg __read_mostly = {
91	.name		= "REJECT",
92	.family		= NFPROTO_IPV4,
93	.target		= reject_tg,
94	.targetsize	= sizeof(struct ipt_reject_info),
95	.table		= "filter",
96	.hooks		= (1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD) |
97			  (1 << NF_INET_LOCAL_OUT),
98	.checkentry	= reject_tg_check,
99	.me		= THIS_MODULE,
100};
101
102static int __init reject_tg_init(void)
103{
104	return xt_register_target(&reject_tg_reg);
105}
106
107static void __exit reject_tg_exit(void)
108{
109	xt_unregister_target(&reject_tg_reg);
110}
111
112module_init(reject_tg_init);
113module_exit(reject_tg_exit);
114