net/ipv4/netfilter/iptable_nat.c

   1 /* (C) 1999-2001 Paul `Rusty' Russell
   2  * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
   3  * (C) 2011 Patrick McHardy <kaber@trash.net>
   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 #include <net/netfilter/nf_nat_core.h>
  19 #include <net/netfilter/nf_nat_l3proto.h>
  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 };
  30
  31 static unsigned int iptable_nat_do_chain(const struct nf_hook_ops *ops,
  32                                          struct sk_buff *skb,
  33                                          const struct net_device *in,
  34                                          const struct net_device *out,
  35                                          struct nf_conn *ct)
  36 {
  37         struct net *net = nf_ct_net(ct);
  38
  39         return ipt_do_table(skb, ops->hooknum, in, out, net->ipv4.nat_table);
  40 }
  41
  42 static unsigned int iptable_nat_ipv4_fn(const struct nf_hook_ops *ops,
  43                                         struct sk_buff *skb,
  44                                         const struct nf_hook_state *state)
  45 {
  46         return nf_nat_ipv4_fn(ops, skb, state->in, state->out,
  47                               iptable_nat_do_chain);
  48 }
  49
  50 static unsigned int iptable_nat_ipv4_in(const struct nf_hook_ops *ops,
  51                                         struct sk_buff *skb,
  52                                         const struct nf_hook_state *state)
  53 {
  54         return nf_nat_ipv4_in(ops, skb, state->in, state->out,
  55                               iptable_nat_do_chain);
  56 }
  57
  58 static unsigned int iptable_nat_ipv4_out(const struct nf_hook_ops *ops,
  59                                          struct sk_buff *skb,
  60                                          const struct nf_hook_state *state)
  61 {
  62         return nf_nat_ipv4_out(ops, skb, state->in, state->out,
  63                                iptable_nat_do_chain);
  64 }
  65
  66 static unsigned int iptable_nat_ipv4_local_fn(const struct nf_hook_ops *ops,
  67                                               struct sk_buff *skb,
  68                                               const struct nf_hook_state *state)
  69 {
  70         return nf_nat_ipv4_local_fn(ops, skb, state->in, state->out,
  71                                     iptable_nat_do_chain);
  72 }
  73
  74 static struct nf_hook_ops nf_nat_ipv4_ops[] __read_mostly = {
  75         /* Before packet filtering, change destination */
  76         {
  77                 .hook           = iptable_nat_ipv4_in,
  78                 .owner          = THIS_MODULE,
  79                 .pf             = NFPROTO_IPV4,
  80                 .hooknum        = NF_INET_PRE_ROUTING,
  81                 .priority       = NF_IP_PRI_NAT_DST,
  82         },
  83         /* After packet filtering, change source */
  84         {
  85                 .hook           = iptable_nat_ipv4_out,
  86                 .owner          = THIS_MODULE,
  87                 .pf             = NFPROTO_IPV4,
  88                 .hooknum        = NF_INET_POST_ROUTING,
  89                 .priority       = NF_IP_PRI_NAT_SRC,
  90         },
  91         /* Before packet filtering, change destination */
  92         {
  93                 .hook           = iptable_nat_ipv4_local_fn,
  94                 .owner          = THIS_MODULE,
  95                 .pf             = NFPROTO_IPV4,
  96                 .hooknum        = NF_INET_LOCAL_OUT,
  97                 .priority       = NF_IP_PRI_NAT_DST,
  98         },
  99         /* After packet filtering, change source */
 100         {
 101                 .hook           = iptable_nat_ipv4_fn,
 102                 .owner          = THIS_MODULE,
 103                 .pf             = NFPROTO_IPV4,
 104                 .hooknum        = NF_INET_LOCAL_IN,
 105                 .priority       = NF_IP_PRI_NAT_SRC,
 106         },
 107 };
 108
 109 static int __net_init iptable_nat_net_init(struct net *net)
 110 {
 111         struct ipt_replace *repl;
 112
 113         repl = ipt_alloc_initial_table(&nf_nat_ipv4_table);
 114         if (repl == NULL)
 115                 return -ENOMEM;
 116         net->ipv4.nat_table = ipt_register_table(net, &nf_nat_ipv4_table, repl);
 117         kfree(repl);
 118         return PTR_ERR_OR_ZERO(net->ipv4.nat_table);
 119 }
 120
 121 static void __net_exit iptable_nat_net_exit(struct net *net)
 122 {
 123         ipt_unregister_table(net, net->ipv4.nat_table);
 124 }
 125
 126 static struct pernet_operations iptable_nat_net_ops = {
 127         .init   = iptable_nat_net_init,
 128         .exit   = iptable_nat_net_exit,
 129 };
 130
 131 static int __init iptable_nat_init(void)
 132 {
 133         int err;
 134
 135         err = register_pernet_subsys(&iptable_nat_net_ops);
 136         if (err < 0)
 137                 goto err1;
 138
 139         err = nf_register_hooks(nf_nat_ipv4_ops, ARRAY_SIZE(nf_nat_ipv4_ops));
 140         if (err < 0)
 141                 goto err2;
 142         return 0;
 143
 144 err2:
 145         unregister_pernet_subsys(&iptable_nat_net_ops);
 146 err1:
 147         return err;
 148 }
 149
 150 static void __exit iptable_nat_exit(void)
 151 {
 152         nf_unregister_hooks(nf_nat_ipv4_ops, ARRAY_SIZE(nf_nat_ipv4_ops));
 153         unregister_pernet_subsys(&iptable_nat_net_ops);
 154 }
 155
 156 module_init(iptable_nat_init);
 157 module_exit(iptable_nat_exit);
 158
 159 MODULE_LICENSE("GPL");