summaryrefslogtreecommitdiffstats
path: root/kernel/linux2.5/net/bridge/netfilter/ebt_arp.c
blob: 35d2608693679cb296d5f5271e61a8ce236b64f1 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
/*
 *  ebt_arp
 *
 *	Authors:
 *	Bart De Schuymer <bdschuym@pandora.be>
 *	Tim Gardner <timg@tpi.com>
 *
 *  April, 2002
 *
 */

#include <linux/netfilter_bridge/ebtables.h>
#include <linux/netfilter_bridge/ebt_arp.h>
#include <linux/if_arp.h>
#include <linux/module.h>

static int ebt_filter_arp(const struct sk_buff *skb, const struct net_device *in,
   const struct net_device *out, const void *data, unsigned int datalen)
{
	struct ebt_arp_info *info = (struct ebt_arp_info *)data;

	if (info->bitmask & EBT_ARP_OPCODE && FWINV(info->opcode !=
	   ((*skb).nh.arph)->ar_op, EBT_ARP_OPCODE))
		return EBT_NOMATCH;
	if (info->bitmask & EBT_ARP_HTYPE && FWINV(info->htype !=
	   ((*skb).nh.arph)->ar_hrd, EBT_ARP_HTYPE))
		return EBT_NOMATCH;
	if (info->bitmask & EBT_ARP_PTYPE && FWINV(info->ptype !=
	   ((*skb).nh.arph)->ar_pro, EBT_ARP_PTYPE))
		return EBT_NOMATCH;

	if (info->bitmask & (EBT_ARP_SRC_IP | EBT_ARP_DST_IP))
	{
		uint32_t arp_len = sizeof(struct arphdr) +
		   (2 * (((*skb).nh.arph)->ar_hln)) +
		   (2 * (((*skb).nh.arph)->ar_pln));
		uint32_t dst;
		uint32_t src;

		/* Make sure the packet is long enough */
		if ((((*skb).nh.raw) + arp_len) > (*skb).tail)
			return EBT_NOMATCH;
		/* IPv4 addresses are always 4 bytes */
		if (((*skb).nh.arph)->ar_pln != sizeof(uint32_t))
			return EBT_NOMATCH;

		if (info->bitmask & EBT_ARP_SRC_IP) {
			memcpy(&src, ((*skb).nh.raw) + sizeof(struct arphdr) +
			   ((*skb).nh.arph)->ar_hln, sizeof(uint32_t));
			if (FWINV(info->saddr != (src & info->smsk),
			   EBT_ARP_SRC_IP))
				return EBT_NOMATCH;
		}

		if (info->bitmask & EBT_ARP_DST_IP) {
			memcpy(&dst, ((*skb).nh.raw)+sizeof(struct arphdr) +
			   (2*(((*skb).nh.arph)->ar_hln)) +
			   (((*skb).nh.arph)->ar_pln), sizeof(uint32_t));
			if (FWINV(info->daddr != (dst & info->dmsk),
			   EBT_ARP_DST_IP))
				return EBT_NOMATCH;
		}
	}
	return EBT_MATCH;
}

static int ebt_arp_check(const char *tablename, unsigned int hookmask,
   const struct ebt_entry *e, void *data, unsigned int datalen)
{
	struct ebt_arp_info *info = (struct ebt_arp_info *)data;

	if (datalen != sizeof(struct ebt_arp_info))
		return -EINVAL;
	if ((e->ethproto != __constant_htons(ETH_P_ARP) &&
	   e->ethproto != __constant_htons(ETH_P_RARP)) ||
	   e->invflags & EBT_IPROTO)
		return -EINVAL;
	if (info->bitmask & ~EBT_ARP_MASK || info->invflags & ~EBT_ARP_MASK)
		return -EINVAL;
	return 0;
}

static struct ebt_match filter_arp =
{
	.name		= EBT_ARP_MATCH,
	.match		= ebt_filter_arp,
	.check		= ebt_arp_check,
	.me		= THIS_MODULE,
};

static int __init init(void)
{
	return ebt_register_match(&filter_arp);
}

static void __exit fini(void)
{
	ebt_unregister_match(&filter_arp);
}

module_init(init);
module_exit(fini);
MODULE_LICENSE("GPL");