/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ #ifndef __LINUX_BRIDGE_EBT_AMONG_H #define __LINUX_BRIDGE_EBT_AMONG_H #include <linux/types.h> #define EBT_AMONG_DST 0x01 #define EBT_AMONG_SRC 0x02 /* Grzegorz Borowiak <grzes@gnu.univ.gda.pl> 2003 * * Write-once-read-many hash table, used for checking if a given * MAC address belongs to a set or not and possibly for checking * if it is related with a given IPv4 address. * * The hash value of an address is its last byte. * * In real-world ethernet addresses, values of the last byte are * evenly distributed and there is no need to consider other bytes. * It would only slow the routines down. * * For MAC address comparison speedup reasons, we introduce a trick. * MAC address is mapped onto an array of two 32-bit integers. * This pair of integers is compared with MAC addresses in the * hash table, which are stored also in form of pairs of integers * (in `cmp' array). This is quick as it requires only two elementary * number comparisons in worst case. Further, we take advantage of * fact that entropy of 3 last bytes of address is larger than entropy * of 3 first bytes. So first we compare 4 last bytes of addresses and * if they are the same we compare 2 first. * * Yes, it is a memory overhead, but in 2003 AD, who cares? */ struct ebt_mac_wormhash_tuple { __u32 cmp[2]; __be32 ip; }; struct ebt_mac_wormhash { int table[257]; int poolsize; struct ebt_mac_wormhash_tuple pool[0]; }; #define ebt_mac_wormhash_size(x) ((x) ? sizeof(struct ebt_mac_wormhash) \ + (x)->poolsize * sizeof(struct ebt_mac_wormhash_tuple) : 0) struct ebt_among_info { int wh_dst_ofs; int wh_src_ofs; int bitmask; }; #define EBT_AMONG_DST_NEG 0x1 #define EBT_AMONG_SRC_NEG 0x2 #define ebt_among_wh_dst(x) ((x)->wh_dst_ofs ? \ (struct ebt_mac_wormhash*)((char*)(x) + (x)->wh_dst_ofs) : NULL) #define ebt_among_wh_src(x) ((x)->wh_src_ofs ? \ (struct ebt_mac_wormhash*)((char*)(x) + (x)->wh_src_ofs) : NULL) #define EBT_AMONG_MATCH "among" #endif

💾 SAVE CHANGES CANCEL