1/*
2 *  ebt_arp
3 *
4 *	Authors:
5 *	Bart De Schuymer <bdschuym@pandora.be>
6 *	Tim Gardner <timg@tpi.com>
7 *
8 *  April, 2002
9 *
10 */
11#include <linux/if_arp.h>
12#include <linux/if_ether.h>
13#include <linux/module.h>
14#include <linux/netfilter/x_tables.h>
15#include <linux/netfilter_bridge/ebtables.h>
16#include <linux/netfilter_bridge/ebt_arp.h>
17
18static bool
19ebt_arp_mt(const struct sk_buff *skb, struct xt_action_param *par)
20{
21	const struct ebt_arp_info *info = par->matchinfo;
22	const struct arphdr *ah;
23	struct arphdr _arph;
24
25	ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
26	if (ah == NULL)
27		return false;
28	if (info->bitmask & EBT_ARP_OPCODE && FWINV(info->opcode !=
29	   ah->ar_op, EBT_ARP_OPCODE))
30		return false;
31	if (info->bitmask & EBT_ARP_HTYPE && FWINV(info->htype !=
32	   ah->ar_hrd, EBT_ARP_HTYPE))
33		return false;
34	if (info->bitmask & EBT_ARP_PTYPE && FWINV(info->ptype !=
35	   ah->ar_pro, EBT_ARP_PTYPE))
36		return false;
37
38	if (info->bitmask & (EBT_ARP_SRC_IP | EBT_ARP_DST_IP | EBT_ARP_GRAT)) {
39		const __be32 *sap, *dap;
40		__be32 saddr, daddr;
41
42		if (ah->ar_pln != sizeof(__be32) || ah->ar_pro != htons(ETH_P_IP))
43			return false;
44		sap = skb_header_pointer(skb, sizeof(struct arphdr) +
45					ah->ar_hln, sizeof(saddr),
46					&saddr);
47		if (sap == NULL)
48			return false;
49		dap = skb_header_pointer(skb, sizeof(struct arphdr) +
50					2*ah->ar_hln+sizeof(saddr),
51					sizeof(daddr), &daddr);
52		if (dap == NULL)
53			return false;
54		if (info->bitmask & EBT_ARP_SRC_IP &&
55		    FWINV(info->saddr != (*sap & info->smsk), EBT_ARP_SRC_IP))
56			return false;
57		if (info->bitmask & EBT_ARP_DST_IP &&
58		    FWINV(info->daddr != (*dap & info->dmsk), EBT_ARP_DST_IP))
59			return false;
60		if (info->bitmask & EBT_ARP_GRAT &&
61		    FWINV(*dap != *sap, EBT_ARP_GRAT))
62			return false;
63	}
64
65	if (info->bitmask & (EBT_ARP_SRC_MAC | EBT_ARP_DST_MAC)) {
66		const unsigned char *mp;
67		unsigned char _mac[ETH_ALEN];
68		uint8_t verdict, i;
69
70		if (ah->ar_hln != ETH_ALEN || ah->ar_hrd != htons(ARPHRD_ETHER))
71			return false;
72		if (info->bitmask & EBT_ARP_SRC_MAC) {
73			mp = skb_header_pointer(skb, sizeof(struct arphdr),
74						sizeof(_mac), &_mac);
75			if (mp == NULL)
76				return false;
77			verdict = 0;
78			for (i = 0; i < 6; i++)
79				verdict |= (mp[i] ^ info->smaddr[i]) &
80				       info->smmsk[i];
81			if (FWINV(verdict != 0, EBT_ARP_SRC_MAC))
82				return false;
83		}
84
85		if (info->bitmask & EBT_ARP_DST_MAC) {
86			mp = skb_header_pointer(skb, sizeof(struct arphdr) +
87						ah->ar_hln + ah->ar_pln,
88						sizeof(_mac), &_mac);
89			if (mp == NULL)
90				return false;
91			verdict = 0;
92			for (i = 0; i < 6; i++)
93				verdict |= (mp[i] ^ info->dmaddr[i]) &
94					info->dmmsk[i];
95			if (FWINV(verdict != 0, EBT_ARP_DST_MAC))
96				return false;
97		}
98	}
99
100	return true;
101}
102
103static int ebt_arp_mt_check(const struct xt_mtchk_param *par)
104{
105	const struct ebt_arp_info *info = par->matchinfo;
106	const struct ebt_entry *e = par->entryinfo;
107
108	if ((e->ethproto != htons(ETH_P_ARP) &&
109	   e->ethproto != htons(ETH_P_RARP)) ||
110	   e->invflags & EBT_IPROTO)
111		return -EINVAL;
112	if (info->bitmask & ~EBT_ARP_MASK || info->invflags & ~EBT_ARP_MASK)
113		return -EINVAL;
114	return 0;
115}
116
117static struct xt_match ebt_arp_mt_reg __read_mostly = {
118	.name		= "arp",
119	.revision	= 0,
120	.family		= NFPROTO_BRIDGE,
121	.match		= ebt_arp_mt,
122	.checkentry	= ebt_arp_mt_check,
123	.matchsize	= sizeof(struct ebt_arp_info),
124	.me		= THIS_MODULE,
125};
126
127static int __init ebt_arp_init(void)
128{
129	return xt_register_match(&ebt_arp_mt_reg);
130}
131
132static void __exit ebt_arp_fini(void)
133{
134	xt_unregister_match(&ebt_arp_mt_reg);
135}
136
137module_init(ebt_arp_init);
138module_exit(ebt_arp_fini);
139MODULE_DESCRIPTION("Ebtables: ARP protocol packet match");
140MODULE_LICENSE("GPL");
141