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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 |