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 <linux/netfilter_ipv4.h>
  23 #ifdef CONFIG_NF_NAT_NEEDED
  24 #include <net/netfilter/nf_nat_rule.h>
  25 #else
  26 #include <linux/netfilter_ipv4/ip_nat_rule.h>
  27 #endif
  28 #include <linux/netfilter/x_tables.h>
  29
  30 MODULE_LICENSE("GPL");
  31 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  32 MODULE_DESCRIPTION("iptables MASQUERADE target module");
  33
  34 #if 0
  35 #define DEBUGP printk
  36 #else
  37 #define DEBUGP(format, args...)
  38 #endif
  39
  40 /* Lock protects masq region inside conntrack */
  41 static DEFINE_RWLOCK(masq_lock);
  42
  43 /* FIXME: Multiple targets. --RR */
  44 static int
  45 masquerade_check(const char *tablename,
  46                  const void *e,
  47                  const struct xt_target *target,
  48                  void *targinfo,
  49                  unsigned int hook_mask)
  50 {
  51         const struct ip_nat_multi_range_compat *mr = targinfo;
  52
  53         if (mr->range[0].flags & IP_NAT_RANGE_MAP_IPS) {
  54                 DEBUGP("masquerade_check: bad MAP_IPS.\n");
  55                 return 0;
  56         }
  57         if (mr->rangesize != 1) {
  58                 DEBUGP("masquerade_check: bad rangesize %u.\n", mr->rangesize);
  59                 return 0;
  60         }
  61         return 1;
  62 }
  63
  64 static unsigned int
  65 masquerade_target(struct sk_buff **pskb,
  66                   const struct net_device *in,
  67                   const struct net_device *out,
  68                   unsigned int hooknum,
  69                   const struct xt_target *target,
  70                   const void *targinfo)
  71 {
  72 #ifdef CONFIG_NF_NAT_NEEDED
  73         struct nf_conn_nat *nat;
  74 #endif
  75         struct ip_conntrack *ct;
  76         enum ip_conntrack_info ctinfo;
  77         struct ip_nat_range newrange;
  78         const struct ip_nat_multi_range_compat *mr;
  79         struct rtable *rt;
  80         __be32 newsrc;
  81
  82         IP_NF_ASSERT(hooknum == NF_IP_POST_ROUTING);
  83
  84         ct = ip_conntrack_get(*pskb, &ctinfo);
  85 #ifdef CONFIG_NF_NAT_NEEDED
  86         nat = nfct_nat(ct);
  87 #endif
  88         IP_NF_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED
  89                             || ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY));
  90
  91         /* Source address is 0.0.0.0 - locally generated packet that is
  92          * probably not supposed to be masqueraded.
  93          */
  94 #ifdef CONFIG_NF_NAT_NEEDED
  95         if (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip == 0)
  96 #else
  97         if (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip == 0)
  98 #endif
  99                 return NF_ACCEPT;
 100
 101         mr = targinfo;
 102         rt = (struct rtable *)(*pskb)->dst;
 103         newsrc = inet_select_addr(out, rt->rt_gateway, RT_SCOPE_UNIVERSE);
 104         if (!newsrc) {
 105                 printk("MASQUERADE: %s ate my IP address\n", out->name);
 106                 return NF_DROP;
 107         }
 108
 109         write_lock_bh(&masq_lock);
 110 #ifdef CONFIG_NF_NAT_NEEDED
 111         nat->masq_index = out->ifindex;
 112 #else
 113         ct->nat.masq_index = out->ifindex;
 114 #endif
 115         write_unlock_bh(&masq_lock);
 116
 117         /* Transfer from original range. */
 118         newrange = ((struct ip_nat_range)
 119                 { mr->range[0].flags | IP_NAT_RANGE_MAP_IPS,
 120                   newsrc, newsrc,
 121                   mr->range[0].min, mr->range[0].max });
 122
 123         /* Hand modified range to generic setup. */
 124         return ip_nat_setup_info(ct, &newrange, hooknum);
 125 }
 126
 127 static inline int
 128 device_cmp(struct ip_conntrack *i, void *ifindex)
 129 {
 130         int ret;
 131 #ifdef CONFIG_NF_NAT_NEEDED
 132         struct nf_conn_nat *nat = nfct_nat(i);
 133
 134         if (!nat)
 135                 return 0;
 136 #endif
 137
 138         read_lock_bh(&masq_lock);
 139 #ifdef CONFIG_NF_NAT_NEEDED
 140         ret = (nat->masq_index == (int)(long)ifindex);
 141 #else
 142         ret = (i->nat.masq_index == (int)(long)ifindex);
 143 #endif
 144         read_unlock_bh(&masq_lock);
 145
 146         return ret;
 147 }
 148
 149 static int masq_device_event(struct notifier_block *this,
 150                              unsigned long event,
 151                              void *ptr)
 152 {
 153         struct net_device *dev = ptr;
 154
 155         if (event == NETDEV_DOWN) {
 156                 /* Device was downed.  Search entire table for
 157                    conntracks which were associated with that device,
 158                    and forget them. */
 159                 IP_NF_ASSERT(dev->ifindex != 0);
 160
 161                 ip_ct_iterate_cleanup(device_cmp, (void *)(long)dev->ifindex);
 162         }
 163
 164         return NOTIFY_DONE;
 165 }
 166
 167 static int masq_inet_event(struct notifier_block *this,
 168                            unsigned long event,
 169                            void *ptr)
 170 {
 171         struct net_device *dev = ((struct in_ifaddr *)ptr)->ifa_dev->dev;
 172
 173         if (event == NETDEV_DOWN) {
 174                 /* IP address was deleted.  Search entire table for
 175                    conntracks which were associated with that device,
 176                    and forget them. */
 177                 IP_NF_ASSERT(dev->ifindex != 0);
 178
 179                 ip_ct_iterate_cleanup(device_cmp, (void *)(long)dev->ifindex);
 180         }
 181
 182         return NOTIFY_DONE;
 183 }
 184
 185 static struct notifier_block masq_dev_notifier = {
 186         .notifier_call  = masq_device_event,
 187 };
 188
 189 static struct notifier_block masq_inet_notifier = {
 190         .notifier_call  = masq_inet_event,
 191 };
 192
 193 static struct xt_target masquerade = {
 194         .name           = "MASQUERADE",
 195         .family         = AF_INET,
 196         .target         = masquerade_target,
 197         .targetsize     = sizeof(struct ip_nat_multi_range_compat),
 198         .table          = "nat",
 199         .hooks          = 1 << NF_IP_POST_ROUTING,
 200         .checkentry     = masquerade_check,
 201         .me             = THIS_MODULE,
 202 };
 203
 204 static int __init ipt_masquerade_init(void)
 205 {
 206         int ret;
 207
 208         ret = xt_register_target(&masquerade);
 209
 210         if (ret == 0) {
 211                 /* Register for device down reports */
 212                 register_netdevice_notifier(&masq_dev_notifier);
 213                 /* Register IP address change reports */
 214                 register_inetaddr_notifier(&masq_inet_notifier);
 215         }
 216
 217         return ret;
 218 }
 219
 220 static void __exit ipt_masquerade_fini(void)
 221 {
 222         xt_unregister_target(&masquerade);
 223         unregister_netdevice_notifier(&masq_dev_notifier);
 224         unregister_inetaddr_notifier(&masq_inet_notifier);
 225 }
 226
 227 module_init(ipt_masquerade_init);
 228 module_exit(ipt_masquerade_fini);