5 * Grzegorz Borowiak <grzes@gnu.univ.gda.pl>
11 #include <linux/netfilter_bridge/ebtables.h>
12 #include <linux/netfilter_bridge/ebt_among.h>
14 #include <linux/if_arp.h>
15 #include <linux/module.h>
17 static int ebt_mac_wormhash_contains(const struct ebt_mac_wormhash *wh,
18 const char *mac, __be32 ip)
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.
25 const struct ebt_mac_wormhash_tuple *p;
27 uint32_t cmp[2] = { 0, 0 };
28 int key = ((const unsigned char *)mac)[5];
30 memcpy(((char *) cmp) + 2, mac, 6);
31 start = wh->table[key];
32 limit = wh->table[key + 1];
34 for (i = start; i < limit; i++) {
36 if (cmp[1] == p->cmp[1] && cmp[0] == p->cmp[0]) {
37 if (p->ip == 0 || p->ip == ip) {
43 for (i = start; i < limit; i++) {
45 if (cmp[1] == p->cmp[1] && cmp[0] == p->cmp[0]) {
55 static int ebt_mac_wormhash_check_integrity(const struct ebt_mac_wormhash
60 for (i = 0; i < 256; i++) {
61 if (wh->table[i] > wh->table[i + 1])
65 if (wh->table[i] > wh->poolsize)
68 if (wh->table[256] > wh->poolsize)
73 static int get_ip_dst(const struct sk_buff *skb, __be32 *addr)
75 if (eth_hdr(skb)->h_proto == htons(ETH_P_IP)) {
76 const struct iphdr *ih;
79 ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
83 } else if (eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) {
84 const struct arphdr *ah;
89 ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
91 ah->ar_pln != sizeof(__be32) ||
92 ah->ar_hln != ETH_ALEN)
94 bp = skb_header_pointer(skb, sizeof(struct arphdr) +
95 2 * ETH_ALEN + sizeof(__be32),
96 sizeof(__be32), &buf);
104 static int get_ip_src(const struct sk_buff *skb, __be32 *addr)
106 if (eth_hdr(skb)->h_proto == htons(ETH_P_IP)) {
107 const struct iphdr *ih;
110 ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
114 } else if (eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) {
115 const struct arphdr *ah;
120 ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
122 ah->ar_pln != sizeof(__be32) ||
123 ah->ar_hln != ETH_ALEN)
125 bp = skb_header_pointer(skb, sizeof(struct arphdr) +
126 ETH_ALEN, sizeof(__be32), &buf);
134 static int ebt_filter_among(const struct sk_buff *skb,
135 const struct net_device *in,
136 const struct net_device *out, const void *data,
137 unsigned int datalen)
139 const struct ebt_among_info *info = data;
140 const char *dmac, *smac;
141 const struct ebt_mac_wormhash *wh_dst, *wh_src;
142 __be32 dip = 0, sip = 0;
144 wh_dst = ebt_among_wh_dst(info);
145 wh_src = ebt_among_wh_src(info);
148 smac = eth_hdr(skb)->h_source;
149 if (get_ip_src(skb, &sip))
151 if (!(info->bitmask & EBT_AMONG_SRC_NEG)) {
152 /* we match only if it contains */
153 if (!ebt_mac_wormhash_contains(wh_src, smac, sip))
156 /* we match only if it DOES NOT contain */
157 if (ebt_mac_wormhash_contains(wh_src, smac, sip))
163 dmac = eth_hdr(skb)->h_dest;
164 if (get_ip_dst(skb, &dip))
166 if (!(info->bitmask & EBT_AMONG_DST_NEG)) {
167 /* we match only if it contains */
168 if (!ebt_mac_wormhash_contains(wh_dst, dmac, dip))
171 /* we match only if it DOES NOT contain */
172 if (ebt_mac_wormhash_contains(wh_dst, dmac, dip))
180 static int ebt_among_check(const char *tablename, unsigned int hookmask,
181 const struct ebt_entry *e, void *data,
182 unsigned int datalen)
184 const struct ebt_among_info *info = data;
185 int expected_length = sizeof(struct ebt_among_info);
186 const struct ebt_mac_wormhash *wh_dst, *wh_src;
189 wh_dst = ebt_among_wh_dst(info);
190 wh_src = ebt_among_wh_src(info);
191 expected_length += ebt_mac_wormhash_size(wh_dst);
192 expected_length += ebt_mac_wormhash_size(wh_src);
194 if (datalen != EBT_ALIGN(expected_length)) {
196 "ebtables: among: wrong size: %d "
197 "against expected %d, rounded to %Zd\n",
198 datalen, expected_length,
199 EBT_ALIGN(expected_length));
202 if (wh_dst && (err = ebt_mac_wormhash_check_integrity(wh_dst))) {
204 "ebtables: among: dst integrity fail: %x\n", -err);
207 if (wh_src && (err = ebt_mac_wormhash_check_integrity(wh_src))) {
209 "ebtables: among: src integrity fail: %x\n", -err);
215 static struct ebt_match filter_among __read_mostly = {
216 .name = EBT_AMONG_MATCH,
217 .match = ebt_filter_among,
218 .check = ebt_among_check,
222 static int __init ebt_among_init(void)
224 return ebt_register_match(&filter_among);
227 static void __exit ebt_among_fini(void)
229 ebt_unregister_match(&filter_among);
232 module_init(ebt_among_init);
233 module_exit(ebt_among_fini);
234 MODULE_DESCRIPTION("Ebtables: Combined MAC/IP address list matching");
235 MODULE_LICENSE("GPL");