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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /include/linux/netfilter_bridge/ebt_among.h
downloadlinux-dev-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.xz
linux-dev-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.zip
Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
Diffstat (limited to 'include/linux/netfilter_bridge/ebt_among.h')
-rw-r--r--include/linux/netfilter_bridge/ebt_among.h65
1 files changed, 65 insertions, 0 deletions
diff --git a/include/linux/netfilter_bridge/ebt_among.h b/include/linux/netfilter_bridge/ebt_among.h
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+++ b/include/linux/netfilter_bridge/ebt_among.h
@@ -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];
+ uint32_t 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