1/*
2 *  ebt_arpreply
3 *
4 *	Authors:
5 *	Grzegorz Borowiak <grzes@gnu.univ.gda.pl>
6 *	Bart De Schuymer <bdschuym@pandora.be>
7 *
8 *  August, 2003
9 *
10 */
11
12#include <linux/netfilter_bridge/ebtables.h>
13#include <linux/netfilter_bridge/ebt_arpreply.h>
14#include <linux/if_arp.h>
15#include <net/arp.h>
16#include <linux/module.h>
17
18static int ebt_target_reply(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_arpreply_info *info = (struct ebt_arpreply_info *)data;
23	__be32 _sip, *siptr, _dip, *diptr;
24	struct arphdr _ah, *ap;
25	unsigned char _sha[ETH_ALEN], *shp;
26	struct sk_buff *skb = *pskb;
27
28	ap = skb_header_pointer(skb, 0, sizeof(_ah), &_ah);
29	if (ap == NULL)
30		return EBT_DROP;
31
32	if (ap->ar_op != htons(ARPOP_REQUEST) ||
33	    ap->ar_hln != ETH_ALEN ||
34	    ap->ar_pro != htons(ETH_P_IP) ||
35	    ap->ar_pln != 4)
36		return EBT_CONTINUE;
37
38	shp = skb_header_pointer(skb, sizeof(_ah), ETH_ALEN, &_sha);
39	if (shp == NULL)
40		return EBT_DROP;
41
42	siptr = skb_header_pointer(skb, sizeof(_ah) + ETH_ALEN,
43				   sizeof(_sip), &_sip);
44	if (siptr == NULL)
45		return EBT_DROP;
46
47	diptr = skb_header_pointer(skb,
48				   sizeof(_ah) + 2 * ETH_ALEN + sizeof(_sip),
49				   sizeof(_dip), &_dip);
50	if (diptr == NULL)
51		return EBT_DROP;
52
53	arp_send(ARPOP_REPLY, ETH_P_ARP, *siptr, (struct net_device *)in,
54		 *diptr, shp, info->mac, shp);
55
56	return info->target;
57}
58
59static int ebt_target_reply_check(const char *tablename, unsigned int hookmask,
60   const struct ebt_entry *e, void *data, unsigned int datalen)
61{
62	struct ebt_arpreply_info *info = (struct ebt_arpreply_info *)data;
63
64	if (datalen != EBT_ALIGN(sizeof(struct ebt_arpreply_info)))
65		return -EINVAL;
66	if (BASE_CHAIN && info->target == EBT_RETURN)
67		return -EINVAL;
68	if (e->ethproto != htons(ETH_P_ARP) ||
69	    e->invflags & EBT_IPROTO)
70		return -EINVAL;
71	CLEAR_BASE_CHAIN_BIT;
72	if (strcmp(tablename, "nat") || hookmask & ~(1 << NF_BR_PRE_ROUTING))
73		return -EINVAL;
74	return 0;
75}
76
77static struct ebt_target reply_target =
78{
79	.name		= EBT_ARPREPLY_TARGET,
80	.target		= ebt_target_reply,
81	.check		= ebt_target_reply_check,
82	.me		= THIS_MODULE,
83};
84
85static int __init ebt_arpreply_init(void)
86{
87	return ebt_register_target(&reply_target);
88}
89
90static void __exit ebt_arpreply_fini(void)
91{
92	ebt_unregister_target(&reply_target);
93}
94
95module_init(ebt_arpreply_init);
96module_exit(ebt_arpreply_fini);
97MODULE_LICENSE("GPL");
98