net/bridge/netfilter/ebt_dnat.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  ebt_dnat
   4  *
   5  *      Authors:
   6  *      Bart De Schuymer <[email protected]>
   7  *
   8  *  June, 2002
   9  *
  10  */
  11 #include <linux/module.h>
  12 #include <net/sock.h>
  13 #include "../br_private.h"
  14 #include <linux/netfilter.h>
  15 #include <linux/netfilter/x_tables.h>
  16 #include <linux/netfilter_bridge/ebtables.h>
  17 #include <linux/netfilter_bridge/ebt_nat.h>
  18
  19 static unsigned int
  20 ebt_dnat_tg(struct sk_buff *skb, const struct xt_action_param *par)
  21 {
  22         const struct ebt_nat_info *info = par->targinfo;
  23
  24         if (skb_ensure_writable(skb, 0))
  25                 return EBT_DROP;
  26
  27         ether_addr_copy(eth_hdr(skb)->h_dest, info->mac);
  28
  29         if (is_multicast_ether_addr(info->mac)) {
  30                 if (is_broadcast_ether_addr(info->mac))
  31                         skb->pkt_type = PACKET_BROADCAST;
  32                 else
  33                         skb->pkt_type = PACKET_MULTICAST;
  34         } else {
  35                 const struct net_device *dev;
  36
  37                 switch (xt_hooknum(par)) {
  38                 case NF_BR_BROUTING:
  39                         dev = xt_in(par);
  40                         break;
  41                 case NF_BR_PRE_ROUTING:
  42                         dev = br_port_get_rcu(xt_in(par))->br->dev;
  43                         break;
  44                 default:
  45                         dev = NULL;
  46                         break;
  47                 }
  48
  49                 if (!dev) /* NF_BR_LOCAL_OUT */
  50                         return info->target;
  51
  52                 if (ether_addr_equal(info->mac, dev->dev_addr))
  53                         skb->pkt_type = PACKET_HOST;
  54                 else
  55                         skb->pkt_type = PACKET_OTHERHOST;
  56         }
  57
  58         return info->target;
  59 }
  60
  61 static int ebt_dnat_tg_check(const struct xt_tgchk_param *par)
  62 {
  63         const struct ebt_nat_info *info = par->targinfo;
  64         unsigned int hook_mask;
  65
  66         if (BASE_CHAIN && info->target == EBT_RETURN)
  67                 return -EINVAL;
  68
  69         hook_mask = par->hook_mask & ~(1 << NF_BR_NUMHOOKS);
  70         if ((strcmp(par->table, "nat") != 0 ||
  71             (hook_mask & ~((1 << NF_BR_PRE_ROUTING) |
  72             (1 << NF_BR_LOCAL_OUT)))) &&
  73             (strcmp(par->table, "broute") != 0 ||
  74             hook_mask & ~(1 << NF_BR_BROUTING)))
  75                 return -EINVAL;
  76         if (ebt_invalid_target(info->target))
  77                 return -EINVAL;
  78         return 0;
  79 }
  80
  81 static struct xt_target ebt_dnat_tg_reg __read_mostly = {
  82         .name           = "dnat",
  83         .revision       = 0,
  84         .family         = NFPROTO_BRIDGE,
  85         .hooks          = (1 << NF_BR_NUMHOOKS) | (1 << NF_BR_PRE_ROUTING) |
  86                           (1 << NF_BR_LOCAL_OUT) | (1 << NF_BR_BROUTING),
  87         .target         = ebt_dnat_tg,
  88         .checkentry     = ebt_dnat_tg_check,
  89         .targetsize     = sizeof(struct ebt_nat_info),
  90         .me             = THIS_MODULE,
  91 };
  92
  93 static int __init ebt_dnat_init(void)
  94 {
  95         return xt_register_target(&ebt_dnat_tg_reg);
  96 }
  97
  98 static void __exit ebt_dnat_fini(void)
  99 {
 100         xt_unregister_target(&ebt_dnat_tg_reg);
 101 }
 102
 103 module_init(ebt_dnat_init);
 104 module_exit(ebt_dnat_fini);
 105 MODULE_DESCRIPTION("Ebtables: Destination MAC address translation");
 106 MODULE_LICENSE("GPL");