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
26 MODULE_LICENSE("GPL");
27 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
28 MODULE_DESCRIPTION("Xtables: packet \"rejection\" target for IPv4");
29
30 static unsigned int
31 reject_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
69 static 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
88 static 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
100 static int __init reject_tg_init(void)
101 {
102 return xt_register_target(&reject_tg_reg);
103 }
104
105 static void __exit reject_tg_exit(void)
106 {
107 xt_unregister_target(&reject_tg_reg);
108 }
109
110 module_init(reject_tg_init);
111 module_exit(reject_tg_exit);
112
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