[NETFILTER]: Add iptables CLUSTERIP target, seq_file version

This enables you to build a static load sharing cluster between multiple
nodes - without the requirement to have a load balancer.  It uses a
series of [evil] tricks like replying with linklayer multicast addresses
to ARP requests, and using CONNMARK for stateful blocking all traffic
not intended for the local node.
Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netfilter_ipv4/ipt_CLUSTERIP.h

+#ifndef _IPT_CLUSTERIP_H_target
+#define _IPT_CLUSTERIP_H_target
+
+enum clusterip_hashmode {
+    CLUSTERIP_HASHMODE_SIP = 0,
+    CLUSTERIP_HASHMODE_SIP_SPT,
+    CLUSTERIP_HASHMODE_SIP_SPT_DPT,
+};
+
+#define CLUSTERIP_HASHMODE_MAX CLUSTERIP_HASHMODE_SIP_SPT_DPT
+
+#define CLUSTERIP_MAX_NODES 16
+
+#define CLUSTERIP_FLAG_NEW 0x00000001
+
+struct clusterip_config;
+
+struct ipt_clusterip_tgt_info {
+
+	u_int32_t flags;
+	struct clusterip_config *config;
+	
+	/* only relevant for new ones */
+	u_int8_t clustermac[6];
+	u_int16_t num_total_nodes;
+	u_int16_t num_local_nodes;
+	u_int16_t local_nodes[CLUSTERIP_MAX_NODES];
+	enum clusterip_hashmode hash_mode;
+	u_int32_t hash_initval;
+};
+
+#endif /*_IPT_CLUSTERIP_H_target*/

net/ipv4/netfilter/Kconfig

@@ -642,6 +642,16 @@ config IP_NF_TARGET_CONNMARK
 	  Documentation/modules.txt.  The module will be called
 	  ipt_CONNMARK.o.  If unsure, say `N'.
 
+config IP_NF_TARGET_CLUSTERIP
+	tristate "CLUSTERIP target support (EXPERIMENTAL)"
+	depends on IP_NF_CONNTRACK_MARK && IP_NF_IPTABLES && EXPERIMENTAL
+	help
+	  The CLUSTERIP target allows you to build load-balancing clusters of
+	  network servers without having a dedicated load-balancing
+	  router/server/switch.
+	
+	  To compile it as a module, choose M here.  If unsure, say N.
+
 # raw + specific targets
 config IP_NF_RAW
 	tristate  'raw table support (required for NOTRACK/TRACE)'

net/ipv4/netfilter/Makefile

@@ -87,6 +87,7 @@ obj-$(CONFIG_IP_NF_TARGET_CONNMARK) += ipt_CONNMARK.o
 obj-$(CONFIG_IP_NF_TARGET_ULOG) += ipt_ULOG.o
 obj-$(CONFIG_IP_NF_TARGET_TCPMSS) += ipt_TCPMSS.o
 obj-$(CONFIG_IP_NF_TARGET_NOTRACK) += ipt_NOTRACK.o
+obj-$(CONFIG_IP_NF_TARGET_CLUSTERIP) += ipt_CLUSTERIP.o
 
 # generic ARP tables
 obj-$(CONFIG_IP_NF_ARPTABLES) += arp_tables.o