net/bridge/netfilter/ebt_redirect.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  ebt_redirect
   4  *
   5  *      Authors:
   6  *      Bart De Schuymer <bdschuym@pandora.be>
   7  *
   8  *  April, 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_redirect.h>
  18
  19 static unsigned int
  20 ebt_redirect_tg(struct sk_buff *skb, const struct xt_action_param *par)
  21 {
  22         const struct ebt_redirect_info *info = par->targinfo;
  23
  24         if (skb_ensure_writable(skb, 0))
  25                 return EBT_DROP;
  26
  27         if (xt_hooknum(par) != NF_BR_BROUTING)
  28                 /* rcu_read_lock()ed by nf_hook_thresh */
  29                 ether_addr_copy(eth_hdr(skb)->h_dest,
  30                                 br_port_get_rcu(xt_in(par))->br->dev->dev_addr);
  31         else
  32                 ether_addr_copy(eth_hdr(skb)->h_dest, xt_in(par)->dev_addr);
  33         skb->pkt_type = PACKET_HOST;
  34         return info->target;
  35 }
  36
  37 static int ebt_redirect_tg_check(const struct xt_tgchk_param *par)
  38 {
  39         const struct ebt_redirect_info *info = par->targinfo;
  40         unsigned int hook_mask;
  41
  42         if (BASE_CHAIN && info->target == EBT_RETURN)
  43                 return -EINVAL;
  44
  45         hook_mask = par->hook_mask & ~(1 << NF_BR_NUMHOOKS);
  46         if ((strcmp(par->table, "nat") != 0 ||
  47             hook_mask & ~(1 << NF_BR_PRE_ROUTING)) &&
  48             (strcmp(par->table, "broute") != 0 ||
  49             hook_mask & ~(1 << NF_BR_BROUTING)))
  50                 return -EINVAL;
  51         if (ebt_invalid_target(info->target))
  52                 return -EINVAL;
  53         return 0;
  54 }
  55
  56 static struct xt_target ebt_redirect_tg_reg __read_mostly = {
  57         .name           = "redirect",
  58         .revision       = 0,
  59         .family         = NFPROTO_BRIDGE,
  60         .hooks          = (1 << NF_BR_NUMHOOKS) | (1 << NF_BR_PRE_ROUTING) |
  61                           (1 << NF_BR_BROUTING),
  62         .target         = ebt_redirect_tg,
  63         .checkentry     = ebt_redirect_tg_check,
  64         .targetsize     = sizeof(struct ebt_redirect_info),
  65         .me             = THIS_MODULE,
  66 };
  67
  68 static int __init ebt_redirect_init(void)
  69 {
  70         return xt_register_target(&ebt_redirect_tg_reg);
  71 }
  72
  73 static void __exit ebt_redirect_fini(void)
  74 {
  75         xt_unregister_target(&ebt_redirect_tg_reg);
  76 }
  77
  78 module_init(ebt_redirect_init);
  79 module_exit(ebt_redirect_fini);
  80 MODULE_DESCRIPTION("Ebtables: Packet redirection to localhost");
  81 MODULE_LICENSE("GPL");