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 (at) 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 32 struct ebt_mac_wormhash_tuple 33 { 34 uint32_t cmp[2]; 35 __be32 ip; 36 }; 37 38 struct ebt_mac_wormhash 39 { 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 48 struct ebt_among_info 49 { 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 66
