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 = xt_hooknum(par);
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(xt_net(par), 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_ratelimited("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_ratelimited("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