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
12#include <linux/netfilter_bridge/ebtables.h>
13#include <linux/netfilter_bridge/ebt_arp.h>
14#include <linux/if_arp.h>
15#include <linux/if_ether.h>
16#include <linux/module.h>
17
18static int ebt_filter_arp(const struct sk_buff *skb, const struct net_device *in,
19   const struct net_device *out, const void *data, unsigned int datalen)
20{
21	struct ebt_arp_info *info = (struct ebt_arp_info *)data;
22	struct arphdr _arph, *ah;
23
24	ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
25	if (ah == NULL)
26		return EBT_NOMATCH;
27	if (info->bitmask & EBT_ARP_OPCODE && FWINV(info->opcode !=
28	   ah->ar_op, EBT_ARP_OPCODE))
29		return EBT_NOMATCH;
30	if (info->bitmask & EBT_ARP_HTYPE && FWINV(info->htype !=
31	   ah->ar_hrd, EBT_ARP_HTYPE))
32		return EBT_NOMATCH;
33	if (info->bitmask & EBT_ARP_PTYPE && FWINV(info->ptype !=
34	   ah->ar_pro, EBT_ARP_PTYPE))
35		return EBT_NOMATCH;
36
37	if (info->bitmask & (EBT_ARP_SRC_IP | EBT_ARP_DST_IP)) {
38		__be32 saddr, daddr, *sap, *dap;
39
40		if (ah->ar_pln != sizeof(__be32) || ah->ar_pro != htons(ETH_P_IP))
41			return EBT_NOMATCH;
42		sap = skb_header_pointer(skb, sizeof(struct arphdr) +
43					ah->ar_hln, sizeof(saddr),
44					&saddr);
45		if (sap == NULL)
46			return EBT_NOMATCH;
47		dap = skb_header_pointer(skb, sizeof(struct arphdr) +
48					2*ah->ar_hln+sizeof(saddr),
49					sizeof(daddr), &daddr);
50		if (dap == NULL)
51			return EBT_NOMATCH;
52		if (info->bitmask & EBT_ARP_SRC_IP &&
53		    FWINV(info->saddr != (*sap & info->smsk), EBT_ARP_SRC_IP))
54			return EBT_NOMATCH;
55		if (info->bitmask & EBT_ARP_DST_IP &&
56		    FWINV(info->daddr != (*dap & info->dmsk), EBT_ARP_DST_IP))
57			return EBT_NOMATCH;
58		if (info->bitmask & EBT_ARP_GRAT &&
59		    FWINV(*dap != *sap, EBT_ARP_GRAT))
60			return EBT_NOMATCH;
61	}
62
63	if (info->bitmask & (EBT_ARP_SRC_MAC | EBT_ARP_DST_MAC)) {
64		unsigned char _mac[ETH_ALEN], *mp;
65		uint8_t verdict, i;
66
67		if (ah->ar_hln != ETH_ALEN || ah->ar_hrd != htons(ARPHRD_ETHER))
68			return EBT_NOMATCH;
69		if (info->bitmask & EBT_ARP_SRC_MAC) {
70			mp = skb_header_pointer(skb, sizeof(struct arphdr),
71						sizeof(_mac), &_mac);
72			if (mp == NULL)
73				return EBT_NOMATCH;
74			verdict = 0;
75			for (i = 0; i < 6; i++)
76				verdict |= (mp[i] ^ info->smaddr[i]) &
77				       info->smmsk[i];
78			if (FWINV(verdict != 0, EBT_ARP_SRC_MAC))
79				return EBT_NOMATCH;
80		}
81
82		if (info->bitmask & EBT_ARP_DST_MAC) {
83			mp = skb_header_pointer(skb, sizeof(struct arphdr) +
84						ah->ar_hln + ah->ar_pln,
85						sizeof(_mac), &_mac);
86			if (mp == NULL)
87				return EBT_NOMATCH;
88			verdict = 0;
89			for (i = 0; i < 6; i++)
90				verdict |= (mp[i] ^ info->dmaddr[i]) &
91					info->dmmsk[i];
92			if (FWINV(verdict != 0, EBT_ARP_DST_MAC))
93				return EBT_NOMATCH;
94		}
95	}
96
97	return EBT_MATCH;
98}
99
100static int ebt_arp_check(const char *tablename, unsigned int hookmask,
101   const struct ebt_entry *e, void *data, unsigned int datalen)
102{
103	struct ebt_arp_info *info = (struct ebt_arp_info *)data;
104
105	if (datalen != EBT_ALIGN(sizeof(struct ebt_arp_info)))
106		return -EINVAL;
107	if ((e->ethproto != htons(ETH_P_ARP) &&
108	   e->ethproto != htons(ETH_P_RARP)) ||
109	   e->invflags & EBT_IPROTO)
110		return -EINVAL;
111	if (info->bitmask & ~EBT_ARP_MASK || info->invflags & ~EBT_ARP_MASK)
112		return -EINVAL;
113	return 0;
114}
115
116static struct ebt_match filter_arp =
117{
118	.name		= EBT_ARP_MATCH,
119	.match		= ebt_filter_arp,
120	.check		= ebt_arp_check,
121	.me		= THIS_MODULE,
122};
123
124static int __init ebt_arp_init(void)
125{
126	return ebt_register_match(&filter_arp);
127}
128
129static void __exit ebt_arp_fini(void)
130{
131	ebt_unregister_match(&filter_arp);
132}
133
134module_init(ebt_arp_init);
135module_exit(ebt_arp_fini);
136MODULE_LICENSE("GPL");
137