linux/net/ipv4/netfilter/ipt_REJECT.c
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   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(par->net, 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