1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * This is a module which is used for rejecting packets.
4 */
5
6/* (C) 1999-2001 Paul `Rusty' Russell
7 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
8 */
9#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
10#include <linux/module.h>
11#include <linux/skbuff.h>
12#include <linux/slab.h>
13#include <linux/ip.h>
14#include <linux/udp.h>
15#include <linux/icmp.h>
16#include <net/icmp.h>
17#include <linux/netfilter/x_tables.h>
18#include <linux/netfilter_ipv4/ip_tables.h>
19#include <linux/netfilter_ipv4/ipt_REJECT.h>
20#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
21#include <linux/netfilter_bridge.h>
22#endif
23
24#include <net/netfilter/ipv4/nf_reject.h>
25
26MODULE_LICENSE("GPL");
27MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
28MODULE_DESCRIPTION("Xtables: packet \"rejection\" target for IPv4");
29
30static unsigned int
31reject_tg(struct sk_buff *skb, const struct xt_action_param *par)
32{
33	const struct ipt_reject_info *reject = par->targinfo;
34	int hook = xt_hooknum(par);
35
36	switch (reject->with) {
37	case IPT_ICMP_NET_UNREACHABLE:
38		nf_send_unreach(skb, ICMP_NET_UNREACH, hook);
39		break;
40	case IPT_ICMP_HOST_UNREACHABLE:
41		nf_send_unreach(skb, ICMP_HOST_UNREACH, hook);
42		break;
43	case IPT_ICMP_PROT_UNREACHABLE:
44		nf_send_unreach(skb, ICMP_PROT_UNREACH, hook);
45		break;
46	case IPT_ICMP_PORT_UNREACHABLE:
47		nf_send_unreach(skb, ICMP_PORT_UNREACH, hook);
48		break;
49	case IPT_ICMP_NET_PROHIBITED:
50		nf_send_unreach(skb, ICMP_NET_ANO, hook);
51		break;
52	case IPT_ICMP_HOST_PROHIBITED:
53		nf_send_unreach(skb, ICMP_HOST_ANO, hook);
54		break;
55	case IPT_ICMP_ADMIN_PROHIBITED:
56		nf_send_unreach(skb, ICMP_PKT_FILTERED, hook);
57		break;
58	case IPT_TCP_RESET:
59		nf_send_reset(xt_net(par), par->state->sk, skb, hook);
60		break;
61	case IPT_ICMP_ECHOREPLY:
62		/* Doesn't happen. */
63		break;
64	}
65
66	return NF_DROP;
67}
68
69static int reject_tg_check(const struct xt_tgchk_param *par)
70{
71	const struct ipt_reject_info *rejinfo = par->targinfo;
72	const struct ipt_entry *e = par->entryinfo;
73
74	if (rejinfo->with == IPT_ICMP_ECHOREPLY) {
75		pr_info_ratelimited("ECHOREPLY no longer supported.\n");
76		return -EINVAL;
77	} else if (rejinfo->with == IPT_TCP_RESET) {
78		/* Must specify that it's a TCP packet */
79		if (e->ip.proto != IPPROTO_TCP ||
80		    (e->ip.invflags & XT_INV_PROTO)) {
81			pr_info_ratelimited("TCP_RESET invalid for non-tcp\n");
82			return -EINVAL;
83		}
84	}
85	return 0;
86}
87
88static struct xt_target reject_tg_reg __read_mostly = {
89	.name		= "REJECT",
90	.family		= NFPROTO_IPV4,
91	.target		= reject_tg,
92	.targetsize	= sizeof(struct ipt_reject_info),
93	.table		= "filter",
94	.hooks		= (1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD) |
95			  (1 << NF_INET_LOCAL_OUT),
96	.checkentry	= reject_tg_check,
97	.me		= THIS_MODULE,
98};
99
100static int __init reject_tg_init(void)
101{
102	return xt_register_target(&reject_tg_reg);
103}
104
105static void __exit reject_tg_exit(void)
106{
107	xt_unregister_target(&reject_tg_reg);
108}
109
110module_init(reject_tg_init);
111module_exit(reject_tg_exit);
112