net/ipv4/netfilter/ipt_REJECT.c

   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 <[email protected]>
   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
  29 MODULE_LICENSE("GPL");
  30 MODULE_AUTHOR("Netfilter Core Team <[email protected]>");
  31 MODULE_DESCRIPTION("Xtables: packet \"rejection\" target for IPv4");
  32
  33 static unsigned int
  34 reject_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
  71 static 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
  90 static 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
 102 static int __init reject_tg_init(void)
 103 {
 104         return xt_register_target(&reject_tg_reg);
 105 }
 106
 107 static void __exit reject_tg_exit(void)
 108 {
 109         xt_unregister_target(&reject_tg_reg);
 110 }
 111
 112 module_init(reject_tg_init);
 113 module_exit(reject_tg_exit);