1 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ 2 #ifndef __LINUX_BRIDGE_EBT_AMONG_H 3 #define __LINUX_BRIDGE_EBT_AMONG_H 4 5 #include <linux/types.h> 6 7 #define EBT_AMONG_DST 0x01 8 #define EBT_AMONG_SRC 0x02 9 10 /* Grzegorz Borowiak <grzes@gnu.univ.gda.pl> 2003 11 * 12 * Write-once-read-many hash table, used for checking if a given 13 * MAC address belongs to a set or not and possibly for checking 14 * if it is related with a given IPv4 address. 15 * 16 * The hash value of an address is its last byte. 17 * 18 * In real-world ethernet addresses, values of the last byte are 19 * evenly distributed and there is no need to consider other bytes. 20 * It would only slow the routines down. 21 * 22 * For MAC address comparison speedup reasons, we introduce a trick. 23 * MAC address is mapped onto an array of two 32-bit integers. 24 * This pair of integers is compared with MAC addresses in the 25 * hash table, which are stored also in form of pairs of integers 26 * (in `cmp' array). This is quick as it requires only two elementary 27 * number comparisons in worst case. Further, we take advantage of 28 * fact that entropy of 3 last bytes of address is larger than entropy 29 * of 3 first bytes. So first we compare 4 last bytes of addresses and 30 * if they are the same we compare 2 first. 31 * 32 * Yes, it is a memory overhead, but in 2003 AD, who cares? 33 */ 34 35 struct ebt_mac_wormhash_tuple { 36 __u32 cmp[2]; 37 __be32 ip; 38 }; 39 40 struct ebt_mac_wormhash { 41 int table[257]; 42 int poolsize; 43 struct ebt_mac_wormhash_tuple pool[]; 44 }; 45 46 #define ebt_mac_wormhash_size(x) ((x) ? sizeof(struct ebt_mac_wormhash) \ 47 + (x)->poolsize * sizeof(struct ebt_mac_wormhash_tuple) : 0) 48 49 struct ebt_among_info { 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