[NETFILTER]: xt_hashlimit match, revision 1

Introduces the xt_hashlimit match revision 1. It adds support for
kernel-level inversion and grouping source and/or destination IP
addresses, allowing to limit on a per-subnet basis. While this would
technically obsolete xt_limit, xt_hashlimit is a more expensive due
to the hashbucketing.

Kernel-level inversion: Previously you had to do user-level inversion:

	iptables -N foo
	iptables -A foo -m hashlimit --hashlimit(-upto) 5/s -j RETURN
	iptables -A foo -j DROP
	iptables -A INPUT -j foo

now it is simpler:

	iptables -A INPUT -m hashlimit --hashlimit-over 5/s -j DROP
Signed-off-by: Jan Engelhardt <jengelh@computergmbh.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netfilter/xt_hashlimit.h

@@ -9,13 +9,16 @@
 /* details of this structure hidden by the implementation */
 struct xt_hashlimit_htable;
 
-#define XT_HASHLIMIT_HASH_DIP	0x0001
-#define XT_HASHLIMIT_HASH_DPT	0x0002
-#define XT_HASHLIMIT_HASH_SIP	0x0004
-#define XT_HASHLIMIT_HASH_SPT	0x0008
+enum {
+	XT_HASHLIMIT_HASH_DIP = 1 << 0,
+	XT_HASHLIMIT_HASH_DPT = 1 << 1,
+	XT_HASHLIMIT_HASH_SIP = 1 << 2,
+	XT_HASHLIMIT_HASH_SPT = 1 << 3,
+	XT_HASHLIMIT_INVERT   = 1 << 4,
+};
 
 struct hashlimit_cfg {
-	u_int32_t mode;	  /* bitmask of IPT_HASHLIMIT_HASH_* */
+	u_int32_t mode;	  /* bitmask of XT_HASHLIMIT_HASH_* */
 	u_int32_t avg;    /* Average secs between packets * scale */
 	u_int32_t burst;  /* Period multiplier for upper limit. */
 
@@ -37,4 +40,28 @@ struct xt_hashlimit_info {
 		struct xt_hashlimit_info *master;
 	} u;
 };
+
+struct hashlimit_cfg1 {
+	u_int32_t mode;	  /* bitmask of XT_HASHLIMIT_HASH_* */
+	u_int32_t avg;    /* Average secs between packets * scale */
+	u_int32_t burst;  /* Period multiplier for upper limit. */
+
+	/* user specified */
+	u_int32_t size;		/* how many buckets */
+	u_int32_t max;		/* max number of entries */
+	u_int32_t gc_interval;	/* gc interval */
+	u_int32_t expire;	/* when do entries expire? */
+
+	u_int8_t srcmask, dstmask;
+};
+
+struct xt_hashlimit_mtinfo1 {
+	char name[IFNAMSIZ];
+	struct hashlimit_cfg1 cfg;
+
+	/* Used internally by the kernel */
+	struct xt_hashlimit_htable *hinfo __attribute__((aligned(8)));
+	struct xt_hashlimit_mtinfo1 *master __attribute__((aligned(8)));
+};
+
 #endif /*_XT_HASHLIMIT_H*/