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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 423 | giacomo | 1 | #ifndef __LINUX_BRIDGE_EBT_AMONG_H |
| 2 | #define __LINUX_BRIDGE_EBT_AMONG_H |
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| 3 | |||
| 4 | #define EBT_AMONG_DST 0x01 |
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| 5 | #define EBT_AMONG_SRC 0x02 |
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| 6 | |||
| 7 | /* Grzegorz Borowiak <grzes@gnu.univ.gda.pl> 2003 |
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| 8 | * |
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| 9 | * Write-once-read-many hash table, used for checking if a given |
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| 10 | * MAC address belongs to a set or not and possibly for checking |
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| 11 | * if it is related with a given IPv4 address. |
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| 12 | * |
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| 13 | * The hash value of an address is its last byte. |
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| 14 | * |
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| 15 | * In real-world ethernet addresses, values of the last byte are |
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| 16 | * evenly distributed and there is no need to consider other bytes. |
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| 17 | * It would only slow the routines down. |
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| 18 | * |
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| 19 | * For MAC address comparison speedup reasons, we introduce a trick. |
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| 20 | * MAC address is mapped onto an array of two 32-bit integers. |
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| 21 | * This pair of integers is compared with MAC addresses in the |
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| 22 | * hash table, which are stored also in form of pairs of integers |
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| 23 | * (in `cmp' array). This is quick as it requires only two elementary |
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| 24 | * number comparisons in worst case. Further, we take advantage of |
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| 25 | * fact that entropy of 3 last bytes of address is larger than entropy |
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| 26 | * of 3 first bytes. So first we compare 4 last bytes of addresses and |
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| 27 | * if they are the same we compare 2 first. |
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| 28 | * |
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| 29 | * Yes, it is a memory overhead, but in 2003 AD, who cares? |
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| 30 | */ |
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| 31 | |||
| 32 | struct ebt_mac_wormhash_tuple |
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| 33 | { |
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| 34 | uint32_t cmp[2]; |
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| 35 | uint32_t ip; |
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| 36 | }; |
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| 37 | |||
| 38 | struct ebt_mac_wormhash |
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| 39 | { |
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| 40 | int table[257]; |
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| 41 | int poolsize; |
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| 42 | struct ebt_mac_wormhash_tuple pool[0]; |
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| 43 | }; |
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| 44 | |||
| 45 | #define ebt_mac_wormhash_size(x) ((x) ? sizeof(struct ebt_mac_wormhash) \ |
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| 46 | + (x)->poolsize * sizeof(struct ebt_mac_wormhash_tuple) : 0) |
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| 47 | |||
| 48 | struct ebt_among_info |
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| 49 | { |
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| 50 | int wh_dst_ofs; |
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| 51 | int wh_src_ofs; |
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| 52 | int bitmask; |
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| 53 | }; |
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| 54 | |||
| 55 | #define EBT_AMONG_DST_NEG 0x1 |
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| 56 | #define EBT_AMONG_SRC_NEG 0x2 |
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| 57 | |||
| 58 | #define ebt_among_wh_dst(x) ((x)->wh_dst_ofs ? \ |
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| 59 | (struct ebt_mac_wormhash*)((char*)(x) + (x)->wh_dst_ofs) : NULL) |
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| 60 | #define ebt_among_wh_src(x) ((x)->wh_src_ofs ? \ |
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| 61 | (struct ebt_mac_wormhash*)((char*)(x) + (x)->wh_src_ofs) : NULL) |
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| 62 | |||
| 63 | #define EBT_AMONG_MATCH "among" |
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| 64 | |||
| 65 | #endif |