aboutsummaryrefslogtreecommitdiffstats
path: root/net/bridge/netfilter/ebt_arp.c
blob: a073dffe7a11e1993eeade9d6f65acc87e3960f2 (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
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
/*
 *  ebt_arp
 *
 *	Authors:
 *	Bart De Schuymer <bdschuym@pandora.be>
 *	Tim Gardner <timg@tpi.com>
 *
 *  April, 2002
 *
 */
#include <linux/if_arp.h>
#include <linux/if_ether.h>
#include <linux/module.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_bridge/ebtables.h>
#include <linux/netfilter_bridge/ebt_arp.h>

static bool
ebt_arp_mt(const struct sk_buff *skb, const struct net_device *in,
	   const struct net_device *out, const struct xt_match *match,
	   const void *data, int offset, unsigned int protoff, bool *hotdrop)
{
	const struct ebt_arp_info *info = data;
	const struct arphdr *ah;
	struct arphdr _arph;

	ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
	if (ah == NULL)
		return false;
	if (info->bitmask & EBT_ARP_OPCODE && FWINV(info->opcode !=
	   ah->ar_op, EBT_ARP_OPCODE))
		return false;
	if (info->bitmask & EBT_ARP_HTYPE && FWINV(info->htype !=
	   ah->ar_hrd, EBT_ARP_HTYPE))
		return false;
	if (info->bitmask & EBT_ARP_PTYPE && FWINV(info->ptype !=
	   ah->ar_pro, EBT_ARP_PTYPE))
		return false;

	if (info->bitmask & (EBT_ARP_SRC_IP | EBT_ARP_DST_IP | EBT_ARP_GRAT)) {
		const __be32 *sap, *dap;
		__be32 saddr, daddr;

		if (ah->ar_pln != sizeof(__be32) || ah->ar_pro != htons(ETH_P_IP))
			return false;
		sap = skb_header_pointer(skb, sizeof(struct arphdr) +
					ah->ar_hln, sizeof(saddr),
					&saddr);
		if (sap == NULL)
			return false;
		dap = skb_header_pointer(skb, sizeof(struct arphdr) +
					2*ah->ar_hln+sizeof(saddr),
					sizeof(daddr), &daddr);
		if (dap == NULL)
			return false;
		if (info->bitmask & EBT_ARP_SRC_IP &&
		    FWINV(info->saddr != (*sap & info->smsk), EBT_ARP_SRC_IP))
			return false;
		if (info->bitmask & EBT_ARP_DST_IP &&
		    FWINV(info->daddr != (*dap & info->dmsk), EBT_ARP_DST_IP))
			return false;
		if (info->bitmask & EBT_ARP_GRAT &&
		    FWINV(*dap != *sap, EBT_ARP_GRAT))
			return false;
	}

	if (info->bitmask & (EBT_ARP_SRC_MAC | EBT_ARP_DST_MAC)) {
		const unsigned char *mp;
		unsigned char _mac[ETH_ALEN];
		uint8_t verdict, i;

		if (ah->ar_hln != ETH_ALEN || ah->ar_hrd != htons(ARPHRD_ETHER))
			return false;
		if (info->bitmask & EBT_ARP_SRC_MAC) {
			mp = skb_header_pointer(skb, sizeof(struct arphdr),
						sizeof(_mac), &_mac);
			if (mp == NULL)
				return false;
			verdict = 0;
			for (i = 0; i < 6; i++)
				verdict |= (mp[i] ^ info->smaddr[i]) &
				       info->smmsk[i];
			if (FWINV(verdict != 0, EBT_ARP_SRC_MAC))
				return false;
		}

		if (info->bitmask & EBT_ARP_DST_MAC) {
			mp = skb_header_pointer(skb, sizeof(struct arphdr) +
						ah->ar_hln + ah->ar_pln,
						sizeof(_mac), &_mac);
			if (mp == NULL)
				return false;
			verdict = 0;
			for (i = 0; i < 6; i++)
				verdict |= (mp[i] ^ info->dmaddr[i]) &
					info->dmmsk[i];
			if (FWINV(verdict != 0, EBT_ARP_DST_MAC))
				return false;
		}
	}

	return true;
}

static bool
ebt_arp_mt_check(const char *table, const void *entry,
		 const struct xt_match *match, void *data,
		 unsigned int hook_mask)
{
	const struct ebt_arp_info *info = data;
	const struct ebt_entry *e = entry;

	if ((e->ethproto != htons(ETH_P_ARP) &&
	   e->ethproto != htons(ETH_P_RARP)) ||
	   e->invflags & EBT_IPROTO)
		return false;
	if (info->bitmask & ~EBT_ARP_MASK || info->invflags & ~EBT_ARP_MASK)
		return false;
	return true;
}

static struct xt_match ebt_arp_mt_reg __read_mostly = {
	.name		= "arp",
	.revision	= 0,
	.family		= NFPROTO_BRIDGE,
	.match		= ebt_arp_mt,
	.checkentry	= ebt_arp_mt_check,
	.matchsize	= XT_ALIGN(sizeof(struct ebt_arp_info)),
	.me		= THIS_MODULE,
};

static int __init ebt_arp_init(void)
{
	return xt_register_match(&ebt_arp_mt_reg);
}

static void __exit ebt_arp_fini(void)
{
	xt_unregister_match(&ebt_arp_mt_reg);
}

module_init(ebt_arp_init);
module_exit(ebt_arp_fini);
MODULE_DESCRIPTION("Ebtables: ARP protocol packet match");
MODULE_LICENSE("GPL");

Privacy Policy