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+/*
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+ * (C) 2008-2009 Pablo Neira Ayuso <pablo@netfilter.org>
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+ *
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+ * This program is free software; you can redistribute it and/or modify
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+ * it under the terms of the GNU General Public License version 2 as
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+ * published by the Free Software Foundation.
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+ */
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+#include <linux/module.h>
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+#include <linux/skbuff.h>
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+#include <linux/jhash.h>
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+#include <linux/ip.h>
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+#include <net/ipv6.h>
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+
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+#include <linux/netfilter/x_tables.h>
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+#include <net/netfilter/nf_conntrack.h>
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+#include <linux/netfilter/xt_cluster.h>
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+
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+static inline u_int32_t nf_ct_orig_ipv4_src(const struct nf_conn *ct)
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+{
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+ return ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;
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+}
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+
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+static inline const void *nf_ct_orig_ipv6_src(const struct nf_conn *ct)
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+{
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+ return ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip6;
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+}
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+
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+static inline u_int32_t
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+xt_cluster_hash_ipv4(u_int32_t ip, const struct xt_cluster_match_info *info)
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+{
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+ return jhash_1word(ip, info->hash_seed);
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+}
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+
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+static inline u_int32_t
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+xt_cluster_hash_ipv6(const void *ip, const struct xt_cluster_match_info *info)
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+{
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+ return jhash2(ip, NF_CT_TUPLE_L3SIZE / sizeof(__u32), info->hash_seed);
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+}
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+
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+static inline u_int32_t
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+xt_cluster_hash(const struct nf_conn *ct,
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+ const struct xt_cluster_match_info *info)
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+{
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+ u_int32_t hash = 0;
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+
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+ switch(nf_ct_l3num(ct)) {
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+ case AF_INET:
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+ hash = xt_cluster_hash_ipv4(nf_ct_orig_ipv4_src(ct), info);
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+ break;
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+ case AF_INET6:
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+ hash = xt_cluster_hash_ipv6(nf_ct_orig_ipv6_src(ct), info);
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+ break;
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+ default:
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+ WARN_ON(1);
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+ break;
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+ }
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+ return (((u64)hash * info->total_nodes) >> 32);
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+}
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+
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+static inline bool
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+xt_cluster_is_multicast_addr(const struct sk_buff *skb, u_int8_t family)
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+{
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+ bool is_multicast = false;
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+
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+ switch(family) {
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+ case NFPROTO_IPV4:
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+ is_multicast = ipv4_is_multicast(ip_hdr(skb)->daddr);
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+ break;
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+ case NFPROTO_IPV6:
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+ is_multicast = ipv6_addr_type(&ipv6_hdr(skb)->daddr) &
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+ IPV6_ADDR_MULTICAST;
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+ break;
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+ default:
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+ WARN_ON(1);
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+ break;
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+ }
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+ return is_multicast;
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+}
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+
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+static bool
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+xt_cluster_mt(const struct sk_buff *skb, const struct xt_match_param *par)
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+{
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+ struct sk_buff *pskb = (struct sk_buff *)skb;
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+ const struct xt_cluster_match_info *info = par->matchinfo;
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+ const struct nf_conn *ct;
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+ enum ip_conntrack_info ctinfo;
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+ unsigned long hash;
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+
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+ /* This match assumes that all nodes see the same packets. This can be
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+ * achieved if the switch that connects the cluster nodes support some
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+ * sort of 'port mirroring'. However, if your switch does not support
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+ * this, your cluster nodes can reply ARP request using a multicast MAC
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+ * address. Thus, your switch will flood the same packets to the
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+ * cluster nodes with the same multicast MAC address. Using a multicast
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+ * link address is a RFC 1812 (section 3.3.2) violation, but this works
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+ * fine in practise.
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+ *
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+ * Unfortunately, if you use the multicast MAC address, the link layer
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+ * sets skbuff's pkt_type to PACKET_MULTICAST, which is not accepted
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+ * by TCP and others for packets coming to this node. For that reason,
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+ * this match mangles skbuff's pkt_type if it detects a packet
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+ * addressed to a unicast address but using PACKET_MULTICAST. Yes, I
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+ * know, matches should not alter packets, but we are doing this here
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+ * because we would need to add a PKTTYPE target for this sole purpose.
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+ */
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+ if (!xt_cluster_is_multicast_addr(skb, par->family) &&
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+ skb->pkt_type == PACKET_MULTICAST) {
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+ pskb->pkt_type = PACKET_HOST;
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+ }
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+
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+ ct = nf_ct_get(skb, &ctinfo);
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+ if (ct == NULL)
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+ return false;
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+
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+ if (ct == &nf_conntrack_untracked)
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+ return false;
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+
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+ if (ct->master)
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+ hash = xt_cluster_hash(ct->master, info);
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+ else
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+ hash = xt_cluster_hash(ct, info);
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+
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+ return !!((1 << hash) & info->node_mask) ^
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+ !!(info->flags & XT_CLUSTER_F_INV);
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+}
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+
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+static bool xt_cluster_mt_checkentry(const struct xt_mtchk_param *par)
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+{
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+ struct xt_cluster_match_info *info = par->matchinfo;
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+
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+ if (info->node_mask >= (1 << info->total_nodes)) {
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+ printk(KERN_ERR "xt_cluster: this node mask cannot be "
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+ "higher than the total number of nodes\n");
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+ return false;
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+ }
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+ return true;
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+}
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+
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+static struct xt_match xt_cluster_match __read_mostly = {
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+ .name = "cluster",
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+ .family = NFPROTO_UNSPEC,
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+ .match = xt_cluster_mt,
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+ .checkentry = xt_cluster_mt_checkentry,
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+ .matchsize = sizeof(struct xt_cluster_match_info),
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+ .me = THIS_MODULE,
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+};
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+
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+static int __init xt_cluster_mt_init(void)
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+{
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+ return xt_register_match(&xt_cluster_match);
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+}
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+
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+static void __exit xt_cluster_mt_fini(void)
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+{
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+ xt_unregister_match(&xt_cluster_match);
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+}
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+
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+MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
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+MODULE_LICENSE("GPL");
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+MODULE_DESCRIPTION("Xtables: hash-based cluster match");
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+MODULE_ALIAS("ipt_cluster");
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+MODULE_ALIAS("ip6t_cluster");
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+module_init(xt_cluster_mt_init);
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+module_exit(xt_cluster_mt_fini);
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