LXR linux/net/ipv4/netfilter/ipt

   1/* NETMAP - static NAT mapping of IP network addresses (1:1).
   2 * The mapping can be applied to source (POSTROUTING),
   3 * destination (PREROUTING), or both (with separate rules).
   4 */
   5
   6/* (C) 2000-2001 Svenning Soerensen <svenning@post5.tele.dk>
   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
  13#include <linux/ip.h>
  14#include <linux/module.h>
  15#include <linux/netdevice.h>
  16#include <linux/netfilter.h>
  17#include <linux/netfilter_ipv4.h>
  18#include <linux/netfilter/x_tables.h>
  19#include <net/netfilter/nf_nat_rule.h>
  20
  21MODULE_LICENSE("GPL");
  22MODULE_AUTHOR("Svenning Soerensen <svenning@post5.tele.dk>");
  23MODULE_DESCRIPTION("iptables 1:1 NAT mapping of IP networks target");
  24
  25static bool
  26check(const char *tablename,
  27      const void *e,
  28      const struct xt_target *target,
  29      void *targinfo,
  30      unsigned int hook_mask)
  31{
  32        const struct nf_nat_multi_range_compat *mr = targinfo;
  33
  34        if (!(mr->range[0].flags & IP_NAT_RANGE_MAP_IPS)) {
  35                pr_debug("NETMAP:check: bad MAP_IPS.\n");
  36                return false;
  37        }
  38        if (mr->rangesize != 1) {
  39                pr_debug("NETMAP:check: bad rangesize %u.\n", mr->rangesize);
  40                return false;
  41        }
  42        return true;
  43}
  44
  45static unsigned int
  46target(struct sk_buff *skb,
  47       const struct net_device *in,
  48       const struct net_device *out,
  49       unsigned int hooknum,
  50       const struct xt_target *target,
  51       const void *targinfo)
  52{
  53        struct nf_conn *ct;
  54        enum ip_conntrack_info ctinfo;
  55        __be32 new_ip, netmask;
  56        const struct nf_nat_multi_range_compat *mr = targinfo;
  57        struct nf_nat_range newrange;
  58
  59        NF_CT_ASSERT(hooknum == NF_IP_PRE_ROUTING
  60                     || hooknum == NF_IP_POST_ROUTING
  61                     || hooknum == NF_IP_LOCAL_OUT);
  62        ct = nf_ct_get(skb, &ctinfo);
  63
  64        netmask = ~(mr->range[0].min_ip ^ mr->range[0].max_ip);
  65
  66        if (hooknum == NF_IP_PRE_ROUTING || hooknum == NF_IP_LOCAL_OUT)
  67                new_ip = ip_hdr(skb)->daddr & ~netmask;
  68        else
  69                new_ip = ip_hdr(skb)->saddr & ~netmask;
  70        new_ip |= mr->range[0].min_ip & netmask;
  71
  72        newrange = ((struct nf_nat_range)
  73                { mr->range[0].flags | IP_NAT_RANGE_MAP_IPS,
  74                  new_ip, new_ip,
  75                  mr->range[0].min, mr->range[0].max });
  76
  77        /* Hand modified range to generic setup. */
  78        return nf_nat_setup_info(ct, &newrange, hooknum);
  79}
  80
  81static struct xt_target target_module __read_mostly = {
  82        .name           = "NETMAP",
  83        .family         = AF_INET,
  84        .target         = target,
  85        .targetsize     = sizeof(struct nf_nat_multi_range_compat),
  86        .table          = "nat",
  87        .hooks          = (1 << NF_IP_PRE_ROUTING) | (1 << NF_IP_POST_ROUTING) |
  88                          (1 << NF_IP_LOCAL_OUT),
  89        .checkentry     = check,
  90        .me             = THIS_MODULE
  91};
  92
  93static int __init ipt_netmap_init(void)
  94{
  95        return xt_register_target(&target_module);
  96}
  97
  98static void __exit ipt_netmap_fini(void)
  99{
 100        xt_unregister_target(&target_module);
 101}
 102
 103module_init(ipt_netmap_init);
 104module_exit(ipt_netmap_fini);
 105