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1da177e4 LT |
1 | #ifndef __LINUX_BRIDGE_EBT_AMONG_H |
2 | #define __LINUX_BRIDGE_EBT_AMONG_H | |
3 | ||
4 | #define EBT_AMONG_DST 0x01 | |
5 | #define EBT_AMONG_SRC 0x02 | |
6 | ||
7 | /* Grzegorz Borowiak <grzes@gnu.univ.gda.pl> 2003 | |
8 | * | |
9 | * Write-once-read-many hash table, used for checking if a given | |
10 | * MAC address belongs to a set or not and possibly for checking | |
11 | * if it is related with a given IPv4 address. | |
12 | * | |
13 | * The hash value of an address is its last byte. | |
14 | * | |
15 | * In real-world ethernet addresses, values of the last byte are | |
16 | * evenly distributed and there is no need to consider other bytes. | |
17 | * It would only slow the routines down. | |
18 | * | |
19 | * For MAC address comparison speedup reasons, we introduce a trick. | |
20 | * MAC address is mapped onto an array of two 32-bit integers. | |
21 | * This pair of integers is compared with MAC addresses in the | |
22 | * hash table, which are stored also in form of pairs of integers | |
23 | * (in `cmp' array). This is quick as it requires only two elementary | |
24 | * number comparisons in worst case. Further, we take advantage of | |
25 | * fact that entropy of 3 last bytes of address is larger than entropy | |
26 | * of 3 first bytes. So first we compare 4 last bytes of addresses and | |
27 | * if they are the same we compare 2 first. | |
28 | * | |
29 | * Yes, it is a memory overhead, but in 2003 AD, who cares? | |
30 | */ | |
31 | ||
d94d9fee | 32 | struct ebt_mac_wormhash_tuple { |
1da177e4 | 33 | uint32_t cmp[2]; |
47c183fa | 34 | __be32 ip; |
1da177e4 LT |
35 | }; |
36 | ||
d94d9fee | 37 | struct ebt_mac_wormhash { |
1da177e4 LT |
38 | int table[257]; |
39 | int poolsize; | |
40 | struct ebt_mac_wormhash_tuple pool[0]; | |
41 | }; | |
42 | ||
43 | #define ebt_mac_wormhash_size(x) ((x) ? sizeof(struct ebt_mac_wormhash) \ | |
44 | + (x)->poolsize * sizeof(struct ebt_mac_wormhash_tuple) : 0) | |
45 | ||
d94d9fee | 46 | struct ebt_among_info { |
1da177e4 LT |
47 | int wh_dst_ofs; |
48 | int wh_src_ofs; | |
49 | int bitmask; | |
50 | }; | |
51 | ||
52 | #define EBT_AMONG_DST_NEG 0x1 | |
53 | #define EBT_AMONG_SRC_NEG 0x2 | |
54 | ||
55 | #define ebt_among_wh_dst(x) ((x)->wh_dst_ofs ? \ | |
56 | (struct ebt_mac_wormhash*)((char*)(x) + (x)->wh_dst_ofs) : NULL) | |
57 | #define ebt_among_wh_src(x) ((x)->wh_src_ofs ? \ | |
58 | (struct ebt_mac_wormhash*)((char*)(x) + (x)->wh_src_ofs) : NULL) | |
59 | ||
60 | #define EBT_AMONG_MATCH "among" | |
61 | ||
62 | #endif |