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01: #ifndef __LINUX_BRIDGE_EBT_AMONG_H
02: #define __LINUX_BRIDGE_EBT_AMONG_H
03: 
04: #include <linux/types.h>
05: 
06: #define EBT_AMONG_DST 0x01
07: #define EBT_AMONG_SRC 0x02
08: 
09: /* Grzegorz Borowiak <grzes@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: 

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