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");
107