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
 19static unsigned int
 20ebt_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
 61static 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
 81static 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
 93static int __init ebt_dnat_init(void)
 94{
 95	return xt_register_target(&ebt_dnat_tg_reg);
 96}
 97
 98static void __exit ebt_dnat_fini(void)
 99{
100	xt_unregister_target(&ebt_dnat_tg_reg);
101}
102
103module_init(ebt_dnat_init);
104module_exit(ebt_dnat_fini);
105MODULE_DESCRIPTION("Ebtables: Destination MAC address translation");
106MODULE_LICENSE("GPL");