net/ipv4/netfilter/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
  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);