net/ipv4/netfilter/ipt_MASQUERADE.c

   1 /* Masquerade.  Simple mapping which alters range to a local IP address
   2    (depending on route). */
   3
   4 /* (C) 1999-2001 Paul `Rusty' Russell
   5  * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  12 #include <linux/types.h>
  13 #include <linux/inetdevice.h>
  14 #include <linux/ip.h>
  15 #include <linux/timer.h>
  16 #include <linux/module.h>
  17 #include <linux/netfilter.h>
  18 #include <net/protocol.h>
  19 #include <net/ip.h>
  20 #include <net/checksum.h>
  21 #include <net/route.h>
  22 #include <linux/netfilter_ipv4.h>
  23 #include <linux/netfilter/x_tables.h>
  24 #include <net/netfilter/nf_nat.h>
  25 #include <net/netfilter/ipv4/nf_nat_masquerade.h>
  26
  27 MODULE_LICENSE("GPL");
  28 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  29 MODULE_DESCRIPTION("Xtables: automatic-address SNAT");
  30
  31 /* FIXME: Multiple targets. --RR */
  32 static int masquerade_tg_check(const struct xt_tgchk_param *par)
  33 {
  34         const struct nf_nat_ipv4_multi_range_compat *mr = par->targinfo;
  35
  36         if (mr->range[0].flags & NF_NAT_RANGE_MAP_IPS) {
  37                 pr_debug("bad MAP_IPS.\n");
  38                 return -EINVAL;
  39         }
  40         if (mr->rangesize != 1) {
  41                 pr_debug("bad rangesize %u\n", mr->rangesize);
  42                 return -EINVAL;
  43         }
  44         return 0;
  45 }
  46
  47 static unsigned int
  48 masquerade_tg(struct sk_buff *skb, const struct xt_action_param *par)
  49 {
  50         struct nf_nat_range range;
  51         const struct nf_nat_ipv4_multi_range_compat *mr;
  52
  53         mr = par->targinfo;
  54         range.flags = mr->range[0].flags;
  55         range.min_proto = mr->range[0].min;
  56         range.max_proto = mr->range[0].max;
  57
  58         return nf_nat_masquerade_ipv4(skb, par->hooknum, &range, par->out);
  59 }
  60
  61 static struct xt_target masquerade_tg_reg __read_mostly = {
  62         .name           = "MASQUERADE",
  63         .family         = NFPROTO_IPV4,
  64         .target         = masquerade_tg,
  65         .targetsize     = sizeof(struct nf_nat_ipv4_multi_range_compat),
  66         .table          = "nat",
  67         .hooks          = 1 << NF_INET_POST_ROUTING,
  68         .checkentry     = masquerade_tg_check,
  69         .me             = THIS_MODULE,
  70 };
  71
  72 static int __init masquerade_tg_init(void)
  73 {
  74         int ret;
  75
  76         ret = xt_register_target(&masquerade_tg_reg);
  77
  78         if (ret == 0)
  79                 nf_nat_masquerade_ipv4_register_notifier();
  80
  81         return ret;
  82 }
  83
  84 static void __exit masquerade_tg_exit(void)
  85 {
  86         xt_unregister_target(&masquerade_tg_reg);
  87         nf_nat_masquerade_ipv4_unregister_notifier();
  88 }
  89
  90 module_init(masquerade_tg_init);
  91 module_exit(masquerade_tg_exit);