Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc-2.6
[linux-2.6.git] / net / bridge / netfilter / ebt_among.c
1 /*
2  *  ebt_among
3  *
4  *      Authors:
5  *      Grzegorz Borowiak <grzes@gnu.univ.gda.pl>
6  *
7  *  August, 2003
8  *
9  */
10 #include <linux/ip.h>
11 #include <linux/if_arp.h>
12 #include <linux/module.h>
13 #include <linux/netfilter/x_tables.h>
14 #include <linux/netfilter_bridge/ebtables.h>
15 #include <linux/netfilter_bridge/ebt_among.h>
16
17 static bool 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 true;
39                 }
40         } else {
41                 for (i = start; i < limit; i++) {
42                         p = &wh->pool[i];
43                         if (cmp[1] == p->cmp[1] && cmp[0] == p->cmp[0])
44                                 if (p->ip == 0)
45                                         return true;
46                 }
47         }
48         return false;
49 }
50
51 static int ebt_mac_wormhash_check_integrity(const struct ebt_mac_wormhash
52                                             *wh)
53 {
54         int i;
55
56         for (i = 0; i < 256; i++) {
57                 if (wh->table[i] > wh->table[i + 1])
58                         return -0x100 - i;
59                 if (wh->table[i] < 0)
60                         return -0x200 - i;
61                 if (wh->table[i] > wh->poolsize)
62                         return -0x300 - i;
63         }
64         if (wh->table[256] > wh->poolsize)
65                 return -0xc00;
66         return 0;
67 }
68
69 static int get_ip_dst(const struct sk_buff *skb, __be32 *addr)
70 {
71         if (eth_hdr(skb)->h_proto == htons(ETH_P_IP)) {
72                 const struct iphdr *ih;
73                 struct iphdr _iph;
74
75                 ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
76                 if (ih == NULL)
77                         return -1;
78                 *addr = ih->daddr;
79         } else if (eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) {
80                 const struct arphdr *ah;
81                 struct arphdr _arph;
82                 const __be32 *bp;
83                 __be32 buf;
84
85                 ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
86                 if (ah == NULL ||
87                     ah->ar_pln != sizeof(__be32) ||
88                     ah->ar_hln != ETH_ALEN)
89                         return -1;
90                 bp = skb_header_pointer(skb, sizeof(struct arphdr) +
91                                         2 * ETH_ALEN + sizeof(__be32),
92                                         sizeof(__be32), &buf);
93                 if (bp == NULL)
94                         return -1;
95                 *addr = *bp;
96         }
97         return 0;
98 }
99
100 static int get_ip_src(const struct sk_buff *skb, __be32 *addr)
101 {
102         if (eth_hdr(skb)->h_proto == htons(ETH_P_IP)) {
103                 const struct iphdr *ih;
104                 struct iphdr _iph;
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                 const struct arphdr *ah;
112                 struct arphdr _arph;
113                 const __be32 *bp;
114                 __be32 buf;
115
116                 ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
117                 if (ah == NULL ||
118                     ah->ar_pln != sizeof(__be32) ||
119                     ah->ar_hln != ETH_ALEN)
120                         return -1;
121                 bp = skb_header_pointer(skb, sizeof(struct arphdr) +
122                                         ETH_ALEN, sizeof(__be32), &buf);
123                 if (bp == NULL)
124                         return -1;
125                 *addr = *bp;
126         }
127         return 0;
128 }
129
130 static bool
131 ebt_among_mt(const struct sk_buff *skb, const struct xt_match_param *par)
132 {
133         const struct ebt_among_info *info = par->matchinfo;
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 false;
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 false;
149                 } else {
150                         /* we match only if it DOES NOT contain */
151                         if (ebt_mac_wormhash_contains(wh_src, smac, sip))
152                                 return false;
153                 }
154         }
155
156         if (wh_dst) {
157                 dmac = eth_hdr(skb)->h_dest;
158                 if (get_ip_dst(skb, &dip))
159                         return false;
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 false;
164                 } else {
165                         /* we match only if it DOES NOT contain */
166                         if (ebt_mac_wormhash_contains(wh_dst, dmac, dip))
167                                 return false;
168                 }
169         }
170
171         return true;
172 }
173
174 static bool ebt_among_mt_check(const struct xt_mtchk_param *par)
175 {
176         const struct ebt_among_info *info = par->matchinfo;
177         const struct ebt_entry_match *em =
178                 container_of(par->matchinfo, const struct ebt_entry_match, 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 (em->match_size != EBT_ALIGN(expected_length)) {
189                 printk(KERN_WARNING
190                        "ebtables: among: wrong size: %d "
191                        "against expected %d, rounded to %Zd\n",
192                        em->match_size, expected_length,
193                        EBT_ALIGN(expected_length));
194                 return false;
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 false;
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 false;
205         }
206         return true;
207 }
208
209 static struct xt_match ebt_among_mt_reg __read_mostly = {
210         .name           = "among",
211         .revision       = 0,
212         .family         = NFPROTO_BRIDGE,
213         .match          = ebt_among_mt,
214         .checkentry     = ebt_among_mt_check,
215         .matchsize      = -1, /* special case */
216         .me             = THIS_MODULE,
217 };
218
219 static int __init ebt_among_init(void)
220 {
221         return xt_register_match(&ebt_among_mt_reg);
222 }
223
224 static void __exit ebt_among_fini(void)
225 {
226         xt_unregister_match(&ebt_among_mt_reg);
227 }
228
229 module_init(ebt_among_init);
230 module_exit(ebt_among_fini);
231 MODULE_DESCRIPTION("Ebtables: Combined MAC/IP address list matching");
232 MODULE_LICENSE("GPL");