1#ifndef __LINUX_BRIDGE_EBT_AMONG_H
2#define __LINUX_BRIDGE_EBT_AMONG_H
3
4#include <linux/types.h>
5
6#define EBT_AMONG_DST 0x01
7#define EBT_AMONG_SRC 0x02
8
9/* Grzegorz Borowiak <grzes@gnu.univ.gda.pl> 2003
10 *
11 * Write-once-read-many hash table, used for checking if a given
12 * MAC address belongs to a set or not and possibly for checking
13 * if it is related with a given IPv4 address.
14 *
15 * The hash value of an address is its last byte.
16 *
17 * In real-world ethernet addresses, values of the last byte are
18 * evenly distributed and there is no need to consider other bytes.
19 * It would only slow the routines down.
20 *
21 * For MAC address comparison speedup reasons, we introduce a trick.
22 * MAC address is mapped onto an array of two 32-bit integers.
23 * This pair of integers is compared with MAC addresses in the
24 * hash table, which are stored also in form of pairs of integers
25 * (in `cmp' array). This is quick as it requires only two elementary
26 * number comparisons in worst case. Further, we take advantage of
27 * fact that entropy of 3 last bytes of address is larger than entropy
28 * of 3 first bytes. So first we compare 4 last bytes of addresses and
29 * if they are the same we compare 2 first.
30 *
31 * Yes, it is a memory overhead, but in 2003 AD, who cares?
32 */
33
34struct ebt_mac_wormhash_tuple {
35	__u32 cmp[2];
36	__be32 ip;
37};
38
39struct ebt_mac_wormhash {
40	int table[257];
41	int poolsize;
42	struct ebt_mac_wormhash_tuple pool[0];
43};
44
45#define ebt_mac_wormhash_size(x) ((x) ? sizeof(struct ebt_mac_wormhash) \
46		+ (x)->poolsize * sizeof(struct ebt_mac_wormhash_tuple) : 0)
47
48struct ebt_among_info {
49	int wh_dst_ofs;
50	int wh_src_ofs;
51	int bitmask;
52};
53
54#define EBT_AMONG_DST_NEG 0x1
55#define EBT_AMONG_SRC_NEG 0x2
56
57#define ebt_among_wh_dst(x) ((x)->wh_dst_ofs ? \
58	(struct ebt_mac_wormhash*)((char*)(x) + (x)->wh_dst_ofs) : NULL)
59#define ebt_among_wh_src(x) ((x)->wh_src_ofs ? \
60	(struct ebt_mac_wormhash*)((char*)(x) + (x)->wh_src_ofs) : NULL)
61
62#define EBT_AMONG_MATCH "among"
63
64#endif
65