1/*
2 *  ebt_snat
3 *
4 *	Authors:
5 *	Bart De Schuymer <bdschuym@pandora.be>
6 *
7 *  June, 2002
8 *
9 */
10
11#include <linux/netfilter_bridge/ebtables.h>
12#include <linux/netfilter_bridge/ebt_nat.h>
13#include <linux/module.h>
14#include <net/sock.h>
15#include <linux/if_arp.h>
16#include <net/arp.h>
17
18static int ebt_target_snat(struct sk_buff **pskb, unsigned int hooknr,
19   const struct net_device *in, const struct net_device *out,
20   const void *data, unsigned int datalen)
21{
22	struct ebt_nat_info *info = (struct ebt_nat_info *) data;
23
24	if (skb_shared(*pskb) || skb_cloned(*pskb)) {
25		struct sk_buff *nskb;
26
27		nskb = skb_copy(*pskb, GFP_ATOMIC);
28		if (!nskb)
29			return NF_DROP;
30		if ((*pskb)->sk)
31			skb_set_owner_w(nskb, (*pskb)->sk);
32		kfree_skb(*pskb);
33		*pskb = nskb;
34	}
35	memcpy(eth_hdr(*pskb)->h_source, info->mac, ETH_ALEN);
36	if (!(info->target & NAT_ARP_BIT) &&
37	    eth_hdr(*pskb)->h_proto == htons(ETH_P_ARP)) {
38		struct arphdr _ah, *ap;
39
40		ap = skb_header_pointer(*pskb, 0, sizeof(_ah), &_ah);
41		if (ap == NULL)
42			return EBT_DROP;
43		if (ap->ar_hln != ETH_ALEN)
44			goto out;
45		if (skb_store_bits(*pskb, sizeof(_ah), info->mac,ETH_ALEN))
46			return EBT_DROP;
47	}
48out:
49	return info->target | ~EBT_VERDICT_BITS;
50}
51
52static int ebt_target_snat_check(const char *tablename, unsigned int hookmask,
53   const struct ebt_entry *e, void *data, unsigned int datalen)
54{
55	struct ebt_nat_info *info = (struct ebt_nat_info *) data;
56	int tmp;
57
58	if (datalen != EBT_ALIGN(sizeof(struct ebt_nat_info)))
59		return -EINVAL;
60	tmp = info->target | ~EBT_VERDICT_BITS;
61	if (BASE_CHAIN && tmp == EBT_RETURN)
62		return -EINVAL;
63	CLEAR_BASE_CHAIN_BIT;
64	if (strcmp(tablename, "nat"))
65		return -EINVAL;
66	if (hookmask & ~(1 << NF_BR_POST_ROUTING))
67		return -EINVAL;
68
69	if (tmp < -NUM_STANDARD_TARGETS || tmp >= 0)
70		return -EINVAL;
71	tmp = info->target | EBT_VERDICT_BITS;
72	if ((tmp & ~NAT_ARP_BIT) != ~NAT_ARP_BIT)
73		return -EINVAL;
74	return 0;
75}
76
77static struct ebt_target snat =
78{
79	.name		= EBT_SNAT_TARGET,
80	.target		= ebt_target_snat,
81	.check		= ebt_target_snat_check,
82	.me		= THIS_MODULE,
83};
84
85static int __init ebt_snat_init(void)
86{
87	return ebt_register_target(&snat);
88}
89
90static void __exit ebt_snat_fini(void)
91{
92	ebt_unregister_target(&snat);
93}
94
95module_init(ebt_snat_init);
96module_exit(ebt_snat_fini);
97MODULE_LICENSE("GPL");
98