LXR linux/net/ipv4/netfilter/ipt

   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
  38        switch (reject->with) {
  39        case IPT_ICMP_NET_UNREACHABLE:
  40                nf_send_unreach(skb, ICMP_NET_UNREACH);
  41                break;
  42        case IPT_ICMP_HOST_UNREACHABLE:
  43                nf_send_unreach(skb, ICMP_HOST_UNREACH);
  44                break;
  45        case IPT_ICMP_PROT_UNREACHABLE:
  46                nf_send_unreach(skb, ICMP_PROT_UNREACH);
  47                break;
  48        case IPT_ICMP_PORT_UNREACHABLE:
  49                nf_send_unreach(skb, ICMP_PORT_UNREACH);
  50                break;
  51        case IPT_ICMP_NET_PROHIBITED:
  52                nf_send_unreach(skb, ICMP_NET_ANO);
  53                break;
  54        case IPT_ICMP_HOST_PROHIBITED:
  55                nf_send_unreach(skb, ICMP_HOST_ANO);
  56                break;
  57        case IPT_ICMP_ADMIN_PROHIBITED:
  58                nf_send_unreach(skb, ICMP_PKT_FILTERED);
  59                break;
  60        case IPT_TCP_RESET:
  61                nf_send_reset(skb, par->hooknum);
  62        case IPT_ICMP_ECHOREPLY:
  63                /* Doesn't happen. */
  64                break;
  65        }
  66
  67        return NF_DROP;
  68}
  69
  70static int reject_tg_check(const struct xt_tgchk_param *par)
  71{
  72        const struct ipt_reject_info *rejinfo = par->targinfo;
  73        const struct ipt_entry *e = par->entryinfo;
  74
  75        if (rejinfo->with == IPT_ICMP_ECHOREPLY) {
  76                pr_info("ECHOREPLY no longer supported.\n");
  77                return -EINVAL;
  78        } else if (rejinfo->with == IPT_TCP_RESET) {
  79                /* Must specify that it's a TCP packet */
  80                if (e->ip.proto != IPPROTO_TCP ||
  81                    (e->ip.invflags & XT_INV_PROTO)) {
  82                        pr_info("TCP_RESET invalid for non-tcp\n");
  83                        return -EINVAL;
  84                }
  85        }
  86        return 0;
  87}
  88
  89static struct xt_target reject_tg_reg __read_mostly = {
  90        .name           = "REJECT",
  91        .family         = NFPROTO_IPV4,
  92        .target         = reject_tg,
  93        .targetsize     = sizeof(struct ipt_reject_info),
  94        .table          = "filter",
  95        .hooks          = (1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD) |
  96                          (1 << NF_INET_LOCAL_OUT),
  97        .checkentry     = reject_tg_check,
  98        .me             = THIS_MODULE,
  99};
 100
 101static int __init reject_tg_init(void)
 102{
 103        return xt_register_target(&reject_tg_reg);
 104}
 105
 106static void __exit reject_tg_exit(void)
 107{
 108        xt_unregister_target(&reject_tg_reg);
 109}
 110
 111module_init(reject_tg_init);
 112module_exit(reject_tg_exit);
 113