1/*
2 *  ebt_among
3 *
4 *	Authors:
5 *	Grzegorz Borowiak <grzes@gnu.univ.gda.pl>
6 *
7 *  August, 2003
8 *
9 */
10
11#include <linux/netfilter_bridge/ebtables.h>
12#include <linux/netfilter_bridge/ebt_among.h>
13#include <linux/ip.h>
14#include <linux/if_arp.h>
15#include <linux/module.h>
16
17static int ebt_mac_wormhash_contains(const struct ebt_mac_wormhash *wh,
18				     const char *mac, __be32 ip)
19{
20	/* You may be puzzled as to how this code works.
21	 * Some tricks were used, refer to
22	 * 	include/linux/netfilter_bridge/ebt_among.h
23	 * as there you can find a solution of this mystery.
24	 */
25	const struct ebt_mac_wormhash_tuple *p;
26	int start, limit, i;
27	uint32_t cmp[2] = { 0, 0 };
28	int key = (const unsigned char) mac[5];
29
30	memcpy(((char *) cmp) + 2, mac, 6);
31	start = wh->table[key];
32	limit = wh->table[key + 1];
33	if (ip) {
34		for (i = start; i < limit; i++) {
35			p = &wh->pool[i];
36			if (cmp[1] == p->cmp[1] && cmp[0] == p->cmp[0]) {
37				if (p->ip == 0 || p->ip == ip) {
38					return 1;
39				}
40			}
41		}
42	} else {
43		for (i = start; i < limit; i++) {
44			p = &wh->pool[i];
45			if (cmp[1] == p->cmp[1] && cmp[0] == p->cmp[0]) {
46				if (p->ip == 0) {
47					return 1;
48				}
49			}
50		}
51	}
52	return 0;
53}
54
55static int ebt_mac_wormhash_check_integrity(const struct ebt_mac_wormhash
56					    *wh)
57{
58	int i;
59
60	for (i = 0; i < 256; i++) {
61		if (wh->table[i] > wh->table[i + 1])
62			return -0x100 - i;
63		if (wh->table[i] < 0)
64			return -0x200 - i;
65		if (wh->table[i] > wh->poolsize)
66			return -0x300 - i;
67	}
68	if (wh->table[256] > wh->poolsize)
69		return -0xc00;
70	return 0;
71}
72
73static int get_ip_dst(const struct sk_buff *skb, __be32 *addr)
74{
75	if (eth_hdr(skb)->h_proto == htons(ETH_P_IP)) {
76		struct iphdr _iph, *ih;
77
78		ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
79		if (ih == NULL)
80			return -1;
81		*addr = ih->daddr;
82	} else if (eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) {
83		struct arphdr _arph, *ah;
84		__be32 buf, *bp;
85
86		ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
87		if (ah == NULL ||
88		    ah->ar_pln != sizeof(__be32) ||
89		    ah->ar_hln != ETH_ALEN)
90			return -1;
91		bp = skb_header_pointer(skb, sizeof(struct arphdr) +
92					2 * ETH_ALEN + sizeof(__be32),
93					sizeof(__be32), &buf);
94		if (bp == NULL)
95			return -1;
96		*addr = *bp;
97	}
98	return 0;
99}
100
101static int get_ip_src(const struct sk_buff *skb, __be32 *addr)
102{
103	if (eth_hdr(skb)->h_proto == htons(ETH_P_IP)) {
104		struct iphdr _iph, *ih;
105
106		ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
107		if (ih == NULL)
108			return -1;
109		*addr = ih->saddr;
110	} else if (eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) {
111		struct arphdr _arph, *ah;
112		__be32 buf, *bp;
113
114		ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
115		if (ah == NULL ||
116		    ah->ar_pln != sizeof(__be32) ||
117		    ah->ar_hln != ETH_ALEN)
118			return -1;
119		bp = skb_header_pointer(skb, sizeof(struct arphdr) +
120					ETH_ALEN, sizeof(__be32), &buf);
121		if (bp == NULL)
122			return -1;
123		*addr = *bp;
124	}
125	return 0;
126}
127
128static int ebt_filter_among(const struct sk_buff *skb,
129			    const struct net_device *in,
130			    const struct net_device *out, const void *data,
131			    unsigned int datalen)
132{
133	struct ebt_among_info *info = (struct ebt_among_info *) data;
134	const char *dmac, *smac;
135	const struct ebt_mac_wormhash *wh_dst, *wh_src;
136	__be32 dip = 0, sip = 0;
137
138	wh_dst = ebt_among_wh_dst(info);
139	wh_src = ebt_among_wh_src(info);
140
141	if (wh_src) {
142		smac = eth_hdr(skb)->h_source;
143		if (get_ip_src(skb, &sip))
144			return EBT_NOMATCH;
145		if (!(info->bitmask & EBT_AMONG_SRC_NEG)) {
146			/* we match only if it contains */
147			if (!ebt_mac_wormhash_contains(wh_src, smac, sip))
148				return EBT_NOMATCH;
149		} else {
150			/* we match only if it DOES NOT contain */
151			if (ebt_mac_wormhash_contains(wh_src, smac, sip))
152				return EBT_NOMATCH;
153		}
154	}
155
156	if (wh_dst) {
157		dmac = eth_hdr(skb)->h_dest;
158		if (get_ip_dst(skb, &dip))
159			return EBT_NOMATCH;
160		if (!(info->bitmask & EBT_AMONG_DST_NEG)) {
161			/* we match only if it contains */
162			if (!ebt_mac_wormhash_contains(wh_dst, dmac, dip))
163				return EBT_NOMATCH;
164		} else {
165			/* we match only if it DOES NOT contain */
166			if (ebt_mac_wormhash_contains(wh_dst, dmac, dip))
167				return EBT_NOMATCH;
168		}
169	}
170
171	return EBT_MATCH;
172}
173
174static int ebt_among_check(const char *tablename, unsigned int hookmask,
175			   const struct ebt_entry *e, void *data,
176			   unsigned int datalen)
177{
178	struct ebt_among_info *info = (struct ebt_among_info *) data;
179	int expected_length = sizeof(struct ebt_among_info);
180	const struct ebt_mac_wormhash *wh_dst, *wh_src;
181	int err;
182
183	wh_dst = ebt_among_wh_dst(info);
184	wh_src = ebt_among_wh_src(info);
185	expected_length += ebt_mac_wormhash_size(wh_dst);
186	expected_length += ebt_mac_wormhash_size(wh_src);
187
188	if (datalen != EBT_ALIGN(expected_length)) {
189		printk(KERN_WARNING
190		       "ebtables: among: wrong size: %d"
191		       "against expected %d, rounded to %Zd\n",
192		       datalen, expected_length,
193		       EBT_ALIGN(expected_length));
194		return -EINVAL;
195	}
196	if (wh_dst && (err = ebt_mac_wormhash_check_integrity(wh_dst))) {
197		printk(KERN_WARNING
198		       "ebtables: among: dst integrity fail: %x\n", -err);
199		return -EINVAL;
200	}
201	if (wh_src && (err = ebt_mac_wormhash_check_integrity(wh_src))) {
202		printk(KERN_WARNING
203		       "ebtables: among: src integrity fail: %x\n", -err);
204		return -EINVAL;
205	}
206	return 0;
207}
208
209static struct ebt_match filter_among = {
210	.name		= EBT_AMONG_MATCH,
211	.match		= ebt_filter_among,
212	.check		= ebt_among_check,
213	.me		= THIS_MODULE,
214};
215
216static int __init ebt_among_init(void)
217{
218	return ebt_register_match(&filter_among);
219}
220
221static void __exit ebt_among_fini(void)
222{
223	ebt_unregister_match(&filter_among);
224}
225
226module_init(ebt_among_init);
227module_exit(ebt_among_fini);
228MODULE_LICENSE("GPL");
229