net/ipv4/netfilter/iptable_nat.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* (C) 1999-2001 Paul `Rusty' Russell
   3  * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
   4  * (C) 2011 Patrick McHardy <kaber@trash.net>
   5  */
   6
   7 #include <linux/module.h>
   8 #include <linux/netfilter.h>
   9 #include <linux/netfilter_ipv4.h>
  10 #include <linux/netfilter_ipv4/ip_tables.h>
  11 #include <linux/ip.h>
  12 #include <net/ip.h>
  13
  14 #include <net/netfilter/nf_nat.h>
  15
  16 static int __net_init iptable_nat_table_init(struct net *net);
  17
  18 static const struct xt_table nf_nat_ipv4_table = {
  19         .name           = "nat",
  20         .valid_hooks    = (1 << NF_INET_PRE_ROUTING) |
  21                           (1 << NF_INET_POST_ROUTING) |
  22                           (1 << NF_INET_LOCAL_OUT) |
  23                           (1 << NF_INET_LOCAL_IN),
  24         .me             = THIS_MODULE,
  25         .af             = NFPROTO_IPV4,
  26         .table_init     = iptable_nat_table_init,
  27 };
  28
  29 static unsigned int iptable_nat_do_chain(void *priv,
  30                                          struct sk_buff *skb,
  31                                          const struct nf_hook_state *state)
  32 {
  33         return ipt_do_table(skb, state, state->net->ipv4.nat_table);
  34 }
  35
  36 static const struct nf_hook_ops nf_nat_ipv4_ops[] = {
  37         {
  38                 .hook           = iptable_nat_do_chain,
  39                 .pf             = NFPROTO_IPV4,
  40                 .hooknum        = NF_INET_PRE_ROUTING,
  41                 .priority       = NF_IP_PRI_NAT_DST,
  42         },
  43         {
  44                 .hook           = iptable_nat_do_chain,
  45                 .pf             = NFPROTO_IPV4,
  46                 .hooknum        = NF_INET_POST_ROUTING,
  47                 .priority       = NF_IP_PRI_NAT_SRC,
  48         },
  49         {
  50                 .hook           = iptable_nat_do_chain,
  51                 .pf             = NFPROTO_IPV4,
  52                 .hooknum        = NF_INET_LOCAL_OUT,
  53                 .priority       = NF_IP_PRI_NAT_DST,
  54         },
  55         {
  56                 .hook           = iptable_nat_do_chain,
  57                 .pf             = NFPROTO_IPV4,
  58                 .hooknum        = NF_INET_LOCAL_IN,
  59                 .priority       = NF_IP_PRI_NAT_SRC,
  60         },
  61 };
  62
  63 static int ipt_nat_register_lookups(struct net *net)
  64 {
  65         int i, ret;
  66
  67         for (i = 0; i < ARRAY_SIZE(nf_nat_ipv4_ops); i++) {
  68                 ret = nf_nat_ipv4_register_fn(net, &nf_nat_ipv4_ops[i]);
  69                 if (ret) {
  70                         while (i)
  71                                 nf_nat_ipv4_unregister_fn(net, &nf_nat_ipv4_ops[--i]);
  72
  73                         return ret;
  74                 }
  75         }
  76
  77         return 0;
  78 }
  79
  80 static void ipt_nat_unregister_lookups(struct net *net)
  81 {
  82         int i;
  83
  84         for (i = 0; i < ARRAY_SIZE(nf_nat_ipv4_ops); i++)
  85                 nf_nat_ipv4_unregister_fn(net, &nf_nat_ipv4_ops[i]);
  86 }
  87
  88 static int __net_init iptable_nat_table_init(struct net *net)
  89 {
  90         struct ipt_replace *repl;
  91         int ret;
  92
  93         if (net->ipv4.nat_table)
  94                 return 0;
  95
  96         repl = ipt_alloc_initial_table(&nf_nat_ipv4_table);
  97         if (repl == NULL)
  98                 return -ENOMEM;
  99         ret = ipt_register_table(net, &nf_nat_ipv4_table, repl,
 100                                  NULL, &net->ipv4.nat_table);
 101         if (ret < 0) {
 102                 kfree(repl);
 103                 return ret;
 104         }
 105
 106         ret = ipt_nat_register_lookups(net);
 107         if (ret < 0) {
 108                 ipt_unregister_table(net, net->ipv4.nat_table, NULL);
 109                 net->ipv4.nat_table = NULL;
 110         }
 111
 112         kfree(repl);
 113         return ret;
 114 }
 115
 116 static void __net_exit iptable_nat_net_pre_exit(struct net *net)
 117 {
 118         if (net->ipv4.nat_table)
 119                 ipt_nat_unregister_lookups(net);
 120 }
 121
 122 static void __net_exit iptable_nat_net_exit(struct net *net)
 123 {
 124         if (!net->ipv4.nat_table)
 125                 return;
 126         ipt_unregister_table_exit(net, net->ipv4.nat_table);
 127         net->ipv4.nat_table = NULL;
 128 }
 129
 130 static struct pernet_operations iptable_nat_net_ops = {
 131         .pre_exit = iptable_nat_net_pre_exit,
 132         .exit   = iptable_nat_net_exit,
 133 };
 134
 135 static int __init iptable_nat_init(void)
 136 {
 137         int ret = register_pernet_subsys(&iptable_nat_net_ops);
 138
 139         if (ret)
 140                 return ret;
 141
 142         ret = iptable_nat_table_init(&init_net);
 143         if (ret)
 144                 unregister_pernet_subsys(&iptable_nat_net_ops);
 145         return ret;
 146 }
 147
 148 static void __exit iptable_nat_exit(void)
 149 {
 150         unregister_pernet_subsys(&iptable_nat_net_ops);
 151 }
 152
 153 module_init(iptable_nat_init);
 154 module_exit(iptable_nat_exit);
 155
 156 MODULE_LICENSE("GPL");