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 <bdschuym@pandora.be>
   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         struct net_device *dev;
  24
  25         if (!skb_make_writable(skb, 0))
  26                 return EBT_DROP;
  27
  28         ether_addr_copy(eth_hdr(skb)->h_dest, info->mac);
  29
  30         if (is_multicast_ether_addr(info->mac)) {
  31                 if (is_broadcast_ether_addr(info->mac))
  32                         skb->pkt_type = PACKET_BROADCAST;
  33                 else
  34                         skb->pkt_type = PACKET_MULTICAST;
  35         } else {
  36                 if (xt_hooknum(par) != NF_BR_BROUTING)
  37                         dev = br_port_get_rcu(xt_in(par))->br->dev;
  38                 else
  39                         dev = xt_in(par);
  40
  41                 if (ether_addr_equal(info->mac, dev->dev_addr))
  42                         skb->pkt_type = PACKET_HOST;
  43                 else
  44                         skb->pkt_type = PACKET_OTHERHOST;
  45         }
  46
  47         return info->target;
  48 }
  49
  50 static int ebt_dnat_tg_check(const struct xt_tgchk_param *par)
  51 {
  52         const struct ebt_nat_info *info = par->targinfo;
  53         unsigned int hook_mask;
  54
  55         if (BASE_CHAIN && info->target == EBT_RETURN)
  56                 return -EINVAL;
  57
  58         hook_mask = par->hook_mask & ~(1 << NF_BR_NUMHOOKS);
  59         if ((strcmp(par->table, "nat") != 0 ||
  60             (hook_mask & ~((1 << NF_BR_PRE_ROUTING) |
  61             (1 << NF_BR_LOCAL_OUT)))) &&
  62             (strcmp(par->table, "broute") != 0 ||
  63             hook_mask & ~(1 << NF_BR_BROUTING)))
  64                 return -EINVAL;
  65         if (ebt_invalid_target(info->target))
  66                 return -EINVAL;
  67         return 0;
  68 }
  69
  70 static struct xt_target ebt_dnat_tg_reg __read_mostly = {
  71         .name           = "dnat",
  72         .revision       = 0,
  73         .family         = NFPROTO_BRIDGE,
  74         .hooks          = (1 << NF_BR_NUMHOOKS) | (1 << NF_BR_PRE_ROUTING) |
  75                           (1 << NF_BR_LOCAL_OUT) | (1 << NF_BR_BROUTING),
  76         .target         = ebt_dnat_tg,
  77         .checkentry     = ebt_dnat_tg_check,
  78         .targetsize     = sizeof(struct ebt_nat_info),
  79         .me             = THIS_MODULE,
  80 };
  81
  82 static int __init ebt_dnat_init(void)
  83 {
  84         return xt_register_target(&ebt_dnat_tg_reg);
  85 }
  86
  87 static void __exit ebt_dnat_fini(void)
  88 {
  89         xt_unregister_target(&ebt_dnat_tg_reg);
  90 }
  91
  92 module_init(ebt_dnat_init);
  93 module_exit(ebt_dnat_fini);
  94 MODULE_DESCRIPTION("Ebtables: Destination MAC address translation");
  95 MODULE_LICENSE("GPL");