ipt_REJECT.c

  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);