net/ipv4/netfilter/iptable_nat.c

   1 /* (C) 1999-2001 Paul `Rusty' Russell
   2  * (C) 2002-2006 Netfilter Core Team <[email protected]>
   3  * (C) 2011 Patrick McHardy <[email protected]>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/netfilter.h>
  12 #include <linux/netfilter_ipv4.h>
  13 #include <linux/netfilter_ipv4/ip_tables.h>
  14 #include <linux/ip.h>
  15 #include <net/ip.h>
  16
  17 #include <net/netfilter/nf_nat.h>
  18
  19 static int __net_init iptable_nat_table_init(struct net *net);
  20
  21 static const struct xt_table nf_nat_ipv4_table = {
  22         .name           = "nat",
  23         .valid_hooks    = (1 << NF_INET_PRE_ROUTING) |
  24                           (1 << NF_INET_POST_ROUTING) |
  25                           (1 << NF_INET_LOCAL_OUT) |
  26                           (1 << NF_INET_LOCAL_IN),
  27         .me             = THIS_MODULE,
  28         .af             = NFPROTO_IPV4,
  29         .table_init     = iptable_nat_table_init,
  30 };
  31
  32 static unsigned int iptable_nat_do_chain(void *priv,
  33                                          struct sk_buff *skb,
  34                                          const struct nf_hook_state *state)
  35 {
  36         return ipt_do_table(skb, state, state->net->ipv4.nat_table);
  37 }
  38
  39 static const struct nf_hook_ops nf_nat_ipv4_ops[] = {
  40         {
  41                 .hook           = iptable_nat_do_chain,
  42                 .pf             = NFPROTO_IPV4,
  43                 .hooknum        = NF_INET_PRE_ROUTING,
  44                 .priority       = NF_IP_PRI_NAT_DST,
  45         },
  46         {
  47                 .hook           = iptable_nat_do_chain,
  48                 .pf             = NFPROTO_IPV4,
  49                 .hooknum        = NF_INET_POST_ROUTING,
  50                 .priority       = NF_IP_PRI_NAT_SRC,
  51         },
  52         {
  53                 .hook           = iptable_nat_do_chain,
  54                 .pf             = NFPROTO_IPV4,
  55                 .hooknum        = NF_INET_LOCAL_OUT,
  56                 .priority       = NF_IP_PRI_NAT_DST,
  57         },
  58         {
  59                 .hook           = iptable_nat_do_chain,
  60                 .pf             = NFPROTO_IPV4,
  61                 .hooknum        = NF_INET_LOCAL_IN,
  62                 .priority       = NF_IP_PRI_NAT_SRC,
  63         },
  64 };
  65
  66 static int ipt_nat_register_lookups(struct net *net)
  67 {
  68         int i, ret;
  69
  70         for (i = 0; i < ARRAY_SIZE(nf_nat_ipv4_ops); i++) {
  71                 ret = nf_nat_ipv4_register_fn(net, &nf_nat_ipv4_ops[i]);
  72                 if (ret) {
  73                         while (i)
  74                                 nf_nat_ipv4_unregister_fn(net, &nf_nat_ipv4_ops[--i]);
  75
  76                         return ret;
  77                 }
  78         }
  79
  80         return 0;
  81 }
  82
  83 static void ipt_nat_unregister_lookups(struct net *net)
  84 {
  85         int i;
  86
  87         for (i = 0; i < ARRAY_SIZE(nf_nat_ipv4_ops); i++)
  88                 nf_nat_ipv4_unregister_fn(net, &nf_nat_ipv4_ops[i]);
  89 }
  90
  91 static int __net_init iptable_nat_table_init(struct net *net)
  92 {
  93         struct ipt_replace *repl;
  94         int ret;
  95
  96         if (net->ipv4.nat_table)
  97                 return 0;
  98
  99         repl = ipt_alloc_initial_table(&nf_nat_ipv4_table);
 100         if (repl == NULL)
 101                 return -ENOMEM;
 102         ret = ipt_register_table(net, &nf_nat_ipv4_table, repl,
 103                                  NULL, &net->ipv4.nat_table);
 104         if (ret < 0) {
 105                 kfree(repl);
 106                 return ret;
 107         }
 108
 109         ret = ipt_nat_register_lookups(net);
 110         if (ret < 0) {
 111                 ipt_unregister_table(net, net->ipv4.nat_table, NULL);
 112                 net->ipv4.nat_table = NULL;
 113         }
 114
 115         kfree(repl);
 116         return ret;
 117 }
 118
 119 static void __net_exit iptable_nat_net_exit(struct net *net)
 120 {
 121         if (!net->ipv4.nat_table)
 122                 return;
 123         ipt_nat_unregister_lookups(net);
 124         ipt_unregister_table(net, net->ipv4.nat_table, NULL);
 125         net->ipv4.nat_table = NULL;
 126 }
 127
 128 static struct pernet_operations iptable_nat_net_ops = {
 129         .exit   = iptable_nat_net_exit,
 130 };
 131
 132 static int __init iptable_nat_init(void)
 133 {
 134         int ret = register_pernet_subsys(&iptable_nat_net_ops);
 135
 136         if (ret)
 137                 return ret;
 138
 139         ret = iptable_nat_table_init(&init_net);
 140         if (ret)
 141                 unregister_pernet_subsys(&iptable_nat_net_ops);
 142         return ret;
 143 }
 144
 145 static void __exit iptable_nat_exit(void)
 146 {
 147         unregister_pernet_subsys(&iptable_nat_net_ops);
 148 }
 149
 150 module_init(iptable_nat_init);
 151 module_exit(iptable_nat_exit);
 152
 153 MODULE_LICENSE("GPL");