/* 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 … #define EBT_AMONG_SRC … /* Grzegorz Borowiak <[email protected]> 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 { … }; struct ebt_mac_wormhash { … }; #define ebt_mac_wormhash_size(x) … struct ebt_among_info { … }; #define EBT_AMONG_DST_NEG … #define EBT_AMONG_SRC_NEG … #define ebt_among_wh_dst(x) … #define ebt_among_wh_src(x) … #define EBT_AMONG_MATCH … #endif
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