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