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 | |