1/*
2 *  ebt_snat
3 *
4 *	Authors:
5 *	Bart De Schuymer <bdschuym@pandora.be>
6 *
7 *  June, 2002
8 *
9 */
10#include <linux/module.h>
11#include <net/sock.h>
12#include <linux/if_arp.h>
13#include <net/arp.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_snat_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_make_writable(skb, 0))
25		return EBT_DROP;
26
27	ether_addr_copy(eth_hdr(skb)->h_source, info->mac);
28	if (!(info->target & NAT_ARP_BIT) &&
29	    eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) {
30		const struct arphdr *ap;
31		struct arphdr _ah;
32
33		ap = skb_header_pointer(skb, 0, sizeof(_ah), &_ah);
34		if (ap == NULL)
35			return EBT_DROP;
36		if (ap->ar_hln != ETH_ALEN)
37			goto out;
38		if (skb_store_bits(skb, sizeof(_ah), info->mac, ETH_ALEN))
39			return EBT_DROP;
40	}
41out:
42	return info->target | ~EBT_VERDICT_BITS;
43}
44
45static int ebt_snat_tg_check(const struct xt_tgchk_param *par)
46{
47	const struct ebt_nat_info *info = par->targinfo;
48	int tmp;
49
50	tmp = info->target | ~EBT_VERDICT_BITS;
51	if (BASE_CHAIN && tmp == EBT_RETURN)
52		return -EINVAL;
53
54	if (tmp < -NUM_STANDARD_TARGETS || tmp >= 0)
55		return -EINVAL;
56	tmp = info->target | EBT_VERDICT_BITS;
57	if ((tmp & ~NAT_ARP_BIT) != ~NAT_ARP_BIT)
58		return -EINVAL;
59	return 0;
60}
61
62static struct xt_target ebt_snat_tg_reg __read_mostly = {
63	.name		= "snat",
64	.revision	= 0,
65	.family		= NFPROTO_BRIDGE,
66	.table		= "nat",
67	.hooks		= (1 << NF_BR_NUMHOOKS) | (1 << NF_BR_POST_ROUTING),
68	.target		= ebt_snat_tg,
69	.checkentry	= ebt_snat_tg_check,
70	.targetsize	= sizeof(struct ebt_nat_info),
71	.me		= THIS_MODULE,
72};
73
74static int __init ebt_snat_init(void)
75{
76	return xt_register_target(&ebt_snat_tg_reg);
77}
78
79static void __exit ebt_snat_fini(void)
80{
81	xt_unregister_target(&ebt_snat_tg_reg);
82}
83
84module_init(ebt_snat_init);
85module_exit(ebt_snat_fini);
86MODULE_DESCRIPTION("Ebtables: Source MAC address translation");
87MODULE_LICENSE("GPL");
88