--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/include/linux/netfilter_bridge/ebt_among.h	Sun Jan 11 20:20:11 2009 +0100
@@ -0,0 +1,65 @@
+#ifndef __LINUX_BRIDGE_EBT_AMONG_H
+#define __LINUX_BRIDGE_EBT_AMONG_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
+{
+	uint32_t 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