release/src-rt/linux/linux-2.6/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
  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 <net/netfilter/nf_nat_rule.h>
  23 #include <linux/netfilter_ipv4.h>
  24 #include <linux/netfilter/x_tables.h>
  25 #include <linux/netfilter_ipv4.h>
  26
  27 MODULE_LICENSE("GPL");
  28 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  29 MODULE_DESCRIPTION("iptables MASQUERADE target module");
  30
  31 #if 0
  32 #define DEBUGP printk
  33 #else
  34 #define DEBUGP(format, args...)
  35 #endif
  36
  37 /* FIXME: Multiple targets. --RR */
  38 static int
  39 masquerade_check(const char *tablename,
  40                  const void *e,
  41                  const struct xt_target *target,
  42                  void *targinfo,
  43                  unsigned int hook_mask)
  44 {
  45         const struct nf_nat_multi_range_compat *mr = targinfo;
  46
  47         if (mr->range[0].flags & IP_NAT_RANGE_MAP_IPS) {
  48                 DEBUGP("masquerade_check: bad MAP_IPS.\n");
  49                 return 0;
  50         }
  51         if (mr->rangesize != 1) {
  52                 DEBUGP("masquerade_check: bad rangesize %u.\n", mr->rangesize);
  53                 return 0;
  54         }
  55         return 1;
  56 }
  57
  58 static unsigned int
  59 masquerade_target(struct sk_buff *skb,
  60                   const struct net_device *in,
  61                   const struct net_device *out,
  62                   unsigned int hooknum,
  63                   const struct xt_target *target,
  64                   const void *targinfo)
  65 {
  66         struct nf_conn *ct;
  67         struct nf_conn_nat *nat;
  68         enum ip_conntrack_info ctinfo;
  69         struct nf_nat_range newrange;
  70         const struct nf_nat_multi_range_compat *mr;
  71         struct rtable *rt;
  72         __be32 newsrc;
  73
  74         NF_CT_ASSERT(hooknum == NF_IP_POST_ROUTING);
  75
  76         ct = nf_ct_get(skb, &ctinfo);
  77         nat = nfct_nat(ct);
  78
  79         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED
  80                             || ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY));
  81
  82         /* Mark the connection as cone if we have such rule configured */
  83         nat->info.nat_type |= (skb->nfcache & NFC_IP_CONE_NAT) ? NFC_IP_CONE_NAT:0;
  84
  85         /* Source address is 0.0.0.0 - locally generated packet that is
  86          * probably not supposed to be masqueraded.
  87          */
  88         if (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip == 0)
  89                 return NF_ACCEPT;
  90
  91         mr = targinfo;
  92         rt = (struct rtable *)skb->dst;
  93         newsrc = inet_select_addr(out, rt->rt_gateway, RT_SCOPE_UNIVERSE);
  94         if (!newsrc) {
  95                 printk("MASQUERADE: %s ate my IP address\n", out->name);
  96                 return NF_DROP;
  97         }
  98
  99         nat->masq_index = out->ifindex;
 100
 101         /* Transfer from original range. */
 102         newrange = ((struct nf_nat_range)
 103                 { mr->range[0].flags | IP_NAT_RANGE_MAP_IPS,
 104                   newsrc, newsrc,
 105                   mr->range[0].min, mr->range[0].max });
 106
 107         /* Hand modified range to generic setup. */
 108         return nf_nat_setup_info(ct, &newrange, hooknum);
 109 }
 110
 111 static inline int
 112 device_cmp(struct nf_conn *i, void *ifindex)
 113 {
 114         struct nf_conn_nat *nat = nfct_nat(i);
 115
 116         if (!nat)
 117                 return 0;
 118
 119         return nat->masq_index == (int)(long)ifindex;
 120 }
 121
 122 static int masq_device_event(struct notifier_block *this,
 123                              unsigned long event,
 124                              void *ptr)
 125 {
 126         struct net_device *dev = ptr;
 127
 128         if (event == NETDEV_DOWN) {
 129                 /* Device was downed.  Search entire table for
 130                    conntracks which were associated with that device,
 131                    and forget them. */
 132                 NF_CT_ASSERT(dev->ifindex != 0);
 133
 134                 nf_ct_iterate_cleanup(device_cmp, (void *)(long)dev->ifindex);
 135         }
 136
 137         return NOTIFY_DONE;
 138 }
 139
 140 static int masq_inet_event(struct notifier_block *this,
 141                            unsigned long event,
 142                            void *ptr)
 143 {
 144         struct net_device *dev = ((struct in_ifaddr *)ptr)->ifa_dev->dev;
 145         return masq_device_event(this, event, dev);
 146 }
 147
 148 static struct notifier_block masq_dev_notifier = {
 149         .notifier_call  = masq_device_event,
 150 };
 151
 152 static struct notifier_block masq_inet_notifier = {
 153         .notifier_call  = masq_inet_event,
 154 };
 155
 156 static struct xt_target masquerade = {
 157         .name           = "MASQUERADE",
 158         .family         = AF_INET,
 159         .target         = masquerade_target,
 160         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
 161         .table          = "nat",
 162         .hooks          = 1 << NF_IP_POST_ROUTING,
 163         .checkentry     = masquerade_check,
 164         .me             = THIS_MODULE,
 165 };
 166
 167 static int __init ipt_masquerade_init(void)
 168 {
 169         int ret;
 170
 171         ret = xt_register_target(&masquerade);
 172
 173         if (ret == 0) {
 174                 /* Register for device down reports */
 175                 register_netdevice_notifier(&masq_dev_notifier);
 176                 /* Register IP address change reports */
 177                 register_inetaddr_notifier(&masq_inet_notifier);
 178         }
 179
 180         return ret;
 181 }
 182
 183 static void __exit ipt_masquerade_fini(void)
 184 {
 185         xt_unregister_target(&masquerade);
 186         unregister_netdevice_notifier(&masq_dev_notifier);
 187         unregister_inetaddr_notifier(&masq_inet_notifier);
 188 }
 189
 190 module_init(ipt_masquerade_init);
 191 module_exit(ipt_masquerade_fini);