linux/net/netfilter/xt_cluster.c
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   1/*
   2 * (C) 2008-2009 Pablo Neira Ayuso <pablo@netfilter.org>
   3 *
   4 * This program is free software; you can redistribute it and/or modify
   5 * it under the terms of the GNU General Public License version 2 as
   6 * published by the Free Software Foundation.
   7 */
   8#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   9#include <linux/module.h>
  10#include <linux/skbuff.h>
  11#include <linux/jhash.h>
  12#include <linux/ip.h>
  13#include <net/ipv6.h>
  14
  15#include <linux/netfilter/x_tables.h>
  16#include <net/netfilter/nf_conntrack.h>
  17#include <linux/netfilter/xt_cluster.h>
  18
  19static inline u32 nf_ct_orig_ipv4_src(const struct nf_conn *ct)
  20{
  21        return (__force u32)ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;
  22}
  23
  24static inline const u32 *nf_ct_orig_ipv6_src(const struct nf_conn *ct)
  25{
  26        return (__force u32 *)ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip6;
  27}
  28
  29static inline u_int32_t
  30xt_cluster_hash_ipv4(u_int32_t ip, const struct xt_cluster_match_info *info)
  31{
  32        return jhash_1word(ip, info->hash_seed);
  33}
  34
  35static inline u_int32_t
  36xt_cluster_hash_ipv6(const void *ip, const struct xt_cluster_match_info *info)
  37{
  38        return jhash2(ip, NF_CT_TUPLE_L3SIZE / sizeof(__u32), info->hash_seed);
  39}
  40
  41static inline u_int32_t
  42xt_cluster_hash(const struct nf_conn *ct,
  43                const struct xt_cluster_match_info *info)
  44{
  45        u_int32_t hash = 0;
  46
  47        switch(nf_ct_l3num(ct)) {
  48        case AF_INET:
  49                hash = xt_cluster_hash_ipv4(nf_ct_orig_ipv4_src(ct), info);
  50                break;
  51        case AF_INET6:
  52                hash = xt_cluster_hash_ipv6(nf_ct_orig_ipv6_src(ct), info);
  53                break;
  54        default:
  55                WARN_ON(1);
  56                break;
  57        }
  58        return (((u64)hash * info->total_nodes) >> 32);
  59}
  60
  61static inline bool
  62xt_cluster_ipv6_is_multicast(const struct in6_addr *addr)
  63{
  64        __be32 st = addr->s6_addr32[0];
  65        return ((st & htonl(0xFF000000)) == htonl(0xFF000000));
  66}
  67
  68static inline bool
  69xt_cluster_is_multicast_addr(const struct sk_buff *skb, u_int8_t family)
  70{
  71        bool is_multicast = false;
  72
  73        switch(family) {
  74        case NFPROTO_IPV4:
  75                is_multicast = ipv4_is_multicast(ip_hdr(skb)->daddr);
  76                break;
  77        case NFPROTO_IPV6:
  78                is_multicast =
  79                        xt_cluster_ipv6_is_multicast(&ipv6_hdr(skb)->daddr);
  80                break;
  81        default:
  82                WARN_ON(1);
  83                break;
  84        }
  85        return is_multicast;
  86}
  87
  88static bool
  89xt_cluster_mt(const struct sk_buff *skb, struct xt_action_param *par)
  90{
  91        struct sk_buff *pskb = (struct sk_buff *)skb;
  92        const struct xt_cluster_match_info *info = par->matchinfo;
  93        const struct nf_conn *ct;
  94        enum ip_conntrack_info ctinfo;
  95        unsigned long hash;
  96
  97        /* This match assumes that all nodes see the same packets. This can be
  98         * achieved if the switch that connects the cluster nodes support some
  99         * sort of 'port mirroring'. However, if your switch does not support
 100         * this, your cluster nodes can reply ARP request using a multicast MAC
 101         * address. Thus, your switch will flood the same packets to the
 102         * cluster nodes with the same multicast MAC address. Using a multicast
 103         * link address is a RFC 1812 (section 3.3.2) violation, but this works
 104         * fine in practise.
 105         *
 106         * Unfortunately, if you use the multicast MAC address, the link layer
 107         * sets skbuff's pkt_type to PACKET_MULTICAST, which is not accepted
 108         * by TCP and others for packets coming to this node. For that reason,
 109         * this match mangles skbuff's pkt_type if it detects a packet
 110         * addressed to a unicast address but using PACKET_MULTICAST. Yes, I
 111         * know, matches should not alter packets, but we are doing this here
 112         * because we would need to add a PKTTYPE target for this sole purpose.
 113         */
 114        if (!xt_cluster_is_multicast_addr(skb, par->family) &&
 115            skb->pkt_type == PACKET_MULTICAST) {
 116                pskb->pkt_type = PACKET_HOST;
 117        }
 118
 119        ct = nf_ct_get(skb, &ctinfo);
 120        if (ct == NULL)
 121                return false;
 122
 123        if (nf_ct_is_untracked(ct))
 124                return false;
 125
 126        if (ct->master)
 127                hash = xt_cluster_hash(ct->master, info);
 128        else
 129                hash = xt_cluster_hash(ct, info);
 130
 131        return !!((1 << hash) & info->node_mask) ^
 132               !!(info->flags & XT_CLUSTER_F_INV);
 133}
 134
 135static int xt_cluster_mt_checkentry(const struct xt_mtchk_param *par)
 136{
 137        struct xt_cluster_match_info *info = par->matchinfo;
 138
 139        if (info->total_nodes > XT_CLUSTER_NODES_MAX) {
 140                pr_info("you have exceeded the maximum "
 141                        "number of cluster nodes (%u > %u)\n",
 142                        info->total_nodes, XT_CLUSTER_NODES_MAX);
 143                return -EINVAL;
 144        }
 145        if (info->node_mask >= (1ULL << info->total_nodes)) {
 146                pr_info("this node mask cannot be "
 147                        "higher than the total number of nodes\n");
 148                return -EDOM;
 149        }
 150        return 0;
 151}
 152
 153static struct xt_match xt_cluster_match __read_mostly = {
 154        .name           = "cluster",
 155        .family         = NFPROTO_UNSPEC,
 156        .match          = xt_cluster_mt,
 157        .checkentry     = xt_cluster_mt_checkentry,
 158        .matchsize      = sizeof(struct xt_cluster_match_info),
 159        .me             = THIS_MODULE,
 160};
 161
 162static int __init xt_cluster_mt_init(void)
 163{
 164        return xt_register_match(&xt_cluster_match);
 165}
 166
 167static void __exit xt_cluster_mt_fini(void)
 168{
 169        xt_unregister_match(&xt_cluster_match);
 170}
 171
 172MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
 173MODULE_LICENSE("GPL");
 174MODULE_DESCRIPTION("Xtables: hash-based cluster match");
 175MODULE_ALIAS("ipt_cluster");
 176MODULE_ALIAS("ip6t_cluster");
 177module_init(xt_cluster_mt_init);
 178module_exit(xt_cluster_mt_fini);
 179
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