Current File : //usr/include/linux/netfilter_bridge/ebt_among.h
/* 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[];
};
#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
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