release/src/linux/linux/net/ipv4/netfilter/ipt_MASQUERADE.c

   1 /* Masquerade.  Simple mapping which alters range to a local IP address
   2    (depending on route). */
   3 #include <linux/config.h>
   4 #include <linux/types.h>
   5 #include <linux/ip.h>
   6 #include <linux/timer.h>
   7 #include <linux/module.h>
   8 #include <linux/netfilter.h>
   9 #include <net/protocol.h>
  10 #include <net/checksum.h>
  11 #include <linux/netfilter_ipv4.h>
  12 #include <linux/netfilter_ipv4/ip_nat_rule.h>
  13 #include <linux/netfilter_ipv4/ip_tables.h>
  14
  15 #define DEBUGP(format, args...)
  16
  17 /* Lock protects masq region inside conntrack */
  18 DECLARE_RWLOCK(masq_lock);
  19
  20 static int
  21 masquerade_check(const char *tablename,
  22                  const struct ipt_entry *e,
  23                  void *targinfo,
  24                  unsigned int targinfosize,
  25                  unsigned int hook_mask)
  26 {
  27         const struct ip_nat_multi_range *mr = targinfo;
  28
  29         if (strcmp(tablename, "nat") != 0) {
  30                 DEBUGP("masquerade_check: bad table `%s'.\n", table);
  31                 return 0;
  32         }
  33         if (targinfosize != IPT_ALIGN(sizeof(*mr))) {
  34                 DEBUGP("masquerade_check: size %u != %u.\n",
  35                        targinfosize, sizeof(*mr));
  36                 return 0;
  37         }
  38         if (hook_mask & ~(1 << NF_IP_POST_ROUTING)) {
  39                 DEBUGP("masquerade_check: bad hooks %x.\n", hook_mask);
  40                 return 0;
  41         }
  42         if (mr->range[0].flags & IP_NAT_RANGE_MAP_IPS) {
  43                 DEBUGP("masquerade_check: bad MAP_IPS.\n");
  44                 return 0;
  45         }
  46         if (mr->rangesize != 1) {
  47                 DEBUGP("masquerade_check: bad rangesize %u.\n", mr->rangesize);
  48                 return 0;
  49         }
  50         return 1;
  51 }
  52
  53 static unsigned int
  54 masquerade_target(struct sk_buff **pskb,
  55                   unsigned int hooknum,
  56                   const struct net_device *in,
  57                   const struct net_device *out,
  58                   const void *targinfo,
  59                   void *userinfo)
  60 {
  61         struct ip_conntrack *ct;
  62         enum ip_conntrack_info ctinfo;
  63         const struct ip_nat_multi_range *mr;
  64         struct ip_nat_multi_range newrange;
  65         u_int32_t newsrc;
  66         struct rtable *rt;
  67         struct rt_key key;
  68
  69         IP_NF_ASSERT(hooknum == NF_IP_POST_ROUTING);
  70
  71         if ((*pskb)->sk)
  72                 return NF_ACCEPT;
  73
  74         ct = ip_conntrack_get(*pskb, &ctinfo);
  75         IP_NF_ASSERT(ct && (ctinfo == IP_CT_NEW
  76                                   || ctinfo == IP_CT_RELATED));
  77
  78         mr = targinfo;
  79
  80         key.dst = (*pskb)->nh.iph->daddr;
  81         key.src = 0; /* Unknown: that's what we're trying to establish */
  82         key.tos = RT_TOS((*pskb)->nh.iph->tos)|RTO_CONN;
  83         key.oif = out->ifindex;
  84 #ifdef CONFIG_IP_ROUTE_FWMARK
  85         key.fwmark = (*pskb)->nfmark;
  86 #endif
  87         if (ip_route_output_key(&rt, &key) != 0) {
  88                 /* Shouldn't happen */
  89                 printk("MASQUERADE: No route: Rusty's brain broke!\n");
  90                 return NF_DROP;
  91         }
  92
  93         newsrc = rt->rt_src;
  94         DEBUGP("newsrc = %u.%u.%u.%u\n", NIPQUAD(newsrc));
  95         ip_rt_put(rt);
  96
  97         WRITE_LOCK(&masq_lock);
  98         ct->nat.masq_index = out->ifindex;
  99         WRITE_UNLOCK(&masq_lock);
 100
 101         /* Transfer from original range. */
 102         newrange = ((struct ip_nat_multi_range)
 103                 { 1, { { 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 ip_nat_setup_info(ct, &newrange, hooknum);
 109 }
 110
 111 static inline int
 112 device_cmp(const struct ip_conntrack *i, void *ifindex)
 113 {
 114         int ret;
 115
 116         READ_LOCK(&masq_lock);
 117         ret = (i->nat.masq_index == (int)(long)ifindex);
 118         READ_UNLOCK(&masq_lock);
 119
 120         return ret;
 121 }
 122
 123 static int masq_device_event(struct notifier_block *this,
 124                              unsigned long event,
 125                              void *ptr)
 126 {
 127         struct net_device *dev = ptr;
 128
 129         if (event == NETDEV_DOWN) {
 130                 /* Device was downed.  Search entire table for
 131                    conntracks which were associated with that device,
 132                    and forget them. */
 133                 IP_NF_ASSERT(dev->ifindex != 0);
 134
 135                 ip_ct_selective_cleanup(device_cmp, (void *)(long)dev->ifindex);
 136         }
 137
 138         return NOTIFY_DONE;
 139 }
 140
 141 static int masq_inet_event(struct notifier_block *this,
 142                            unsigned long event,
 143                            void *ptr)
 144 {
 145         struct net_device *dev = ((struct in_ifaddr *)ptr)->ifa_dev->dev;
 146
 147         if (event == NETDEV_DOWN) {
 148                 /* IP address was deleted.  Search entire table for
 149                    conntracks which were associated with that device,
 150                    and forget them. */
 151                 IP_NF_ASSERT(dev->ifindex != 0);
 152
 153                 ip_ct_selective_cleanup(device_cmp, (void *)(long)dev->ifindex);
 154         }
 155
 156         return NOTIFY_DONE;
 157 }
 158
 159 static struct notifier_block masq_dev_notifier = {
 160         masq_device_event,
 161         NULL,
 162         0
 163 };
 164
 165 static struct notifier_block masq_inet_notifier = {
 166         masq_inet_event,
 167         NULL,
 168         0
 169 };
 170
 171 static struct ipt_target masquerade
 172 = { { NULL, NULL }, "MASQUERADE", masquerade_target, masquerade_check, NULL,
 173     THIS_MODULE };
 174
 175 static int __init init(void)
 176 {
 177         int ret;
 178
 179         ret = ipt_register_target(&masquerade);
 180
 181         if (ret == 0) {
 182                 /* Register for device down reports */
 183                 register_netdevice_notifier(&masq_dev_notifier);
 184                 /* Register IP address change reports */
 185                 register_inetaddr_notifier(&masq_inet_notifier);
 186         }
 187
 188         return ret;
 189 }
 190
 191 static void __exit fini(void)
 192 {
 193         ipt_unregister_target(&masquerade);
 194         unregister_netdevice_notifier(&masq_dev_notifier);
 195         unregister_inetaddr_notifier(&masq_inet_notifier);
 196 }
 197
 198 module_init(init);
 199 module_exit(fini);
 200 MODULE_LICENSE("GPL");
 201
 202 EXPORT_SYMBOL(masq_lock);