net/bridge/netfilter/ebtable_nat.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  ebtable_nat
   4  *
   5  *      Authors:
   6  *      Bart De Schuymer <bdschuym@pandora.be>
   7  *
   8  *  April, 2002
   9  *
  10  */
  11
  12 #include <linux/netfilter_bridge/ebtables.h>
  13 #include <uapi/linux/netfilter_bridge.h>
  14 #include <linux/module.h>
  15
  16 #define NAT_VALID_HOOKS ((1 << NF_BR_PRE_ROUTING) | (1 << NF_BR_LOCAL_OUT) | \
  17                          (1 << NF_BR_POST_ROUTING))
  18
  19 static struct ebt_entries initial_chains[] = {
  20         {
  21                 .name   = "PREROUTING",
  22                 .policy = EBT_ACCEPT,
  23         },
  24         {
  25                 .name   = "OUTPUT",
  26                 .policy = EBT_ACCEPT,
  27         },
  28         {
  29                 .name   = "POSTROUTING",
  30                 .policy = EBT_ACCEPT,
  31         }
  32 };
  33
  34 static struct ebt_replace_kernel initial_table = {
  35         .name           = "nat",
  36         .valid_hooks    = NAT_VALID_HOOKS,
  37         .entries_size   = 3 * sizeof(struct ebt_entries),
  38         .hook_entry     = {
  39                 [NF_BR_PRE_ROUTING]     = &initial_chains[0],
  40                 [NF_BR_LOCAL_OUT]       = &initial_chains[1],
  41                 [NF_BR_POST_ROUTING]    = &initial_chains[2],
  42         },
  43         .entries        = (char *)initial_chains,
  44 };
  45
  46 static int check(const struct ebt_table_info *info, unsigned int valid_hooks)
  47 {
  48         if (valid_hooks & ~NAT_VALID_HOOKS)
  49                 return -EINVAL;
  50         return 0;
  51 }
  52
  53 static const struct ebt_table frame_nat = {
  54         .name           = "nat",
  55         .table          = &initial_table,
  56         .valid_hooks    = NAT_VALID_HOOKS,
  57         .check          = check,
  58         .me             = THIS_MODULE,
  59 };
  60
  61 static unsigned int ebt_nat_hook(void *priv, struct sk_buff *skb,
  62                                  const struct nf_hook_state *state)
  63 {
  64         return ebt_do_table(skb, state, priv);
  65 }
  66
  67 static const struct nf_hook_ops ebt_ops_nat[] = {
  68         {
  69                 .hook           = ebt_nat_hook,
  70                 .pf             = NFPROTO_BRIDGE,
  71                 .hooknum        = NF_BR_LOCAL_OUT,
  72                 .priority       = NF_BR_PRI_NAT_DST_OTHER,
  73         },
  74         {
  75                 .hook           = ebt_nat_hook,
  76                 .pf             = NFPROTO_BRIDGE,
  77                 .hooknum        = NF_BR_POST_ROUTING,
  78                 .priority       = NF_BR_PRI_NAT_SRC,
  79         },
  80         {
  81                 .hook           = ebt_nat_hook,
  82                 .pf             = NFPROTO_BRIDGE,
  83                 .hooknum        = NF_BR_PRE_ROUTING,
  84                 .priority       = NF_BR_PRI_NAT_DST_BRIDGED,
  85         },
  86 };
  87
  88 static int frame_nat_table_init(struct net *net)
  89 {
  90         return ebt_register_table(net, &frame_nat, ebt_ops_nat);
  91 }
  92
  93 static void __net_exit frame_nat_net_pre_exit(struct net *net)
  94 {
  95         ebt_unregister_table_pre_exit(net, "nat");
  96 }
  97
  98 static void __net_exit frame_nat_net_exit(struct net *net)
  99 {
 100         ebt_unregister_table(net, "nat");
 101 }
 102
 103 static struct pernet_operations frame_nat_net_ops = {
 104         .exit = frame_nat_net_exit,
 105         .pre_exit = frame_nat_net_pre_exit,
 106 };
 107
 108 static int __init ebtable_nat_init(void)
 109 {
 110         int ret = ebt_register_template(&frame_nat, frame_nat_table_init);
 111
 112         if (ret)
 113                 return ret;
 114
 115         ret = register_pernet_subsys(&frame_nat_net_ops);
 116         if (ret) {
 117                 ebt_unregister_template(&frame_nat);
 118                 return ret;
 119         }
 120
 121         return ret;
 122 }
 123
 124 static void __exit ebtable_nat_fini(void)
 125 {
 126         unregister_pernet_subsys(&frame_nat_net_ops);
 127         ebt_unregister_template(&frame_nat);
 128 }
 129
 130 module_init(ebtable_nat_init);
 131 module_exit(ebtable_nat_fini);
 132 MODULE_LICENSE("GPL");