1 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
2 #ifndef __LINUX_BRIDGE_EBT_AMONG_H
3 #define __LINUX_BRIDGE_EBT_AMONG_H
4
5 #include <linux/types.h>
6
7 #define EBT_AMONG_DST 0x01
8 #define EBT_AMONG_SRC 0x02
9
10 /* Grzegorz Borowiak <grzes@gnu.univ.gda.pl> 2003
11 *
12 * Write-once-read-many hash table, used for checking if a given
13 * MAC address belongs to a set or not and possibly for checking
14 * if it is related with a given IPv4 address.
15 *
16 * The hash value of an address is its last byte.
17 *
18 * In real-world ethernet addresses, values of the last byte are
19 * evenly distributed and there is no need to consider other bytes.
20 * It would only slow the routines down.
21 *
22 * For MAC address comparison speedup reasons, we introduce a trick.
23 * MAC address is mapped onto an array of two 32-bit integers.
24 * This pair of integers is compared with MAC addresses in the
25 * hash table, which are stored also in form of pairs of integers
26 * (in `cmp' array). This is quick as it requires only two elementary
27 * number comparisons in worst case. Further, we take advantage of
28 * fact that entropy of 3 last bytes of address is larger than entropy
29 * of 3 first bytes. So first we compare 4 last bytes of addresses and
30 * if they are the same we compare 2 first.
31 *
32 * Yes, it is a memory overhead, but in 2003 AD, who cares?
33 */
34
35 struct ebt_mac_wormhash_tuple {
36 __u32 cmp[2];
37 __be32 ip;
38 };
39
40 struct ebt_mac_wormhash {
41 int table[257];
42 int poolsize;
43 struct ebt_mac_wormhash_tuple pool[0];
44 };
45
46 #define ebt_mac_wormhash_size(x) ((x) ? sizeof(struct ebt_mac_wormhash) \
47 + (x)->poolsize * sizeof(struct ebt_mac_wormhash_tuple) : 0)
48
49 struct ebt_among_info {
50 int wh_dst_ofs;
51 int wh_src_ofs;
52 int bitmask;
53 };
54
55 #define EBT_AMONG_DST_NEG 0x1
56 #define EBT_AMONG_SRC_NEG 0x2
57
58 #define ebt_among_wh_dst(x) ((x)->wh_dst_ofs ? \
59 (struct ebt_mac_wormhash*)((char*)(x) + (x)->wh_dst_ofs) : NULL)
60 #define ebt_among_wh_src(x) ((x)->wh_src_ofs ? \
61 (struct ebt_mac_wormhash*)((char*)(x) + (x)->wh_src_ofs) : NULL)
62
63 #define EBT_AMONG_MATCH "among"
64
65 #endif