LXR linux/net/netfilter/xt

   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
  59        return reciprocal_scale(hash, info->total_nodes);
  60}
  61
  62static inline bool
  63xt_cluster_ipv6_is_multicast(const struct in6_addr *addr)
  64{
  65        __be32 st = addr->s6_addr32[0];
  66        return ((st & htonl(0xFF000000)) == htonl(0xFF000000));
  67}
  68
  69static inline bool
  70xt_cluster_is_multicast_addr(const struct sk_buff *skb, u_int8_t family)
  71{
  72        bool is_multicast = false;
  73
  74        switch(family) {
  75        case NFPROTO_IPV4:
  76                is_multicast = ipv4_is_multicast(ip_hdr(skb)->daddr);
  77                break;
  78        case NFPROTO_IPV6:
  79                is_multicast =
  80                        xt_cluster_ipv6_is_multicast(&ipv6_hdr(skb)->daddr);
  81                break;
  82        default:
  83                WARN_ON(1);
  84                break;
  85        }
  86        return is_multicast;
  87}
  88
  89static bool
  90xt_cluster_mt(const struct sk_buff *skb, struct xt_action_param *par)
  91{
  92        struct sk_buff *pskb = (struct sk_buff *)skb;
  93        const struct xt_cluster_match_info *info = par->matchinfo;
  94        const struct nf_conn *ct;
  95        enum ip_conntrack_info ctinfo;
  96        unsigned long hash;
  97
  98        /* This match assumes that all nodes see the same packets. This can be
  99         * achieved if the switch that connects the cluster nodes support some
 100         * sort of 'port mirroring'. However, if your switch does not support
 101         * this, your cluster nodes can reply ARP request using a multicast MAC
 102         * address. Thus, your switch will flood the same packets to the
 103         * cluster nodes with the same multicast MAC address. Using a multicast
 104         * link address is a RFC 1812 (section 3.3.2) violation, but this works
 105         * fine in practise.
 106         *
 107         * Unfortunately, if you use the multicast MAC address, the link layer
 108         * sets skbuff's pkt_type to PACKET_MULTICAST, which is not accepted
 109         * by TCP and others for packets coming to this node. For that reason,
 110         * this match mangles skbuff's pkt_type if it detects a packet
 111         * addressed to a unicast address but using PACKET_MULTICAST. Yes, I
 112         * know, matches should not alter packets, but we are doing this here
 113         * because we would need to add a PKTTYPE target for this sole purpose.
 114         */
 115        if (!xt_cluster_is_multicast_addr(skb, par->family) &&
 116            skb->pkt_type == PACKET_MULTICAST) {
 117                pskb->pkt_type = PACKET_HOST;
 118        }
 119
 120        ct = nf_ct_get(skb, &ctinfo);
 121        if (ct == NULL)
 122                return false;
 123
 124        if (nf_ct_is_untracked(ct))
 125                return false;
 126
 127        if (ct->master)
 128                hash = xt_cluster_hash(ct->master, info);
 129        else
 130                hash = xt_cluster_hash(ct, info);
 131
 132        return !!((1 << hash) & info->node_mask) ^
 133               !!(info->flags & XT_CLUSTER_F_INV);
 134}
 135
 136static int xt_cluster_mt_checkentry(const struct xt_mtchk_param *par)
 137{
 138        struct xt_cluster_match_info *info = par->matchinfo;
 139
 140        if (info->total_nodes > XT_CLUSTER_NODES_MAX) {
 141                pr_info("you have exceeded the maximum "
 142                        "number of cluster nodes (%u > %u)\n",
 143                        info->total_nodes, XT_CLUSTER_NODES_MAX);
 144                return -EINVAL;
 145        }
 146        if (info->node_mask >= (1ULL << info->total_nodes)) {
 147                pr_info("this node mask cannot be "
 148                        "higher than the total number of nodes\n");
 149                return -EDOM;
 150        }
 151        return 0;
 152}
 153
 154static struct xt_match xt_cluster_match __read_mostly = {
 155        .name           = "cluster",
 156        .family         = NFPROTO_UNSPEC,
 157        .match          = xt_cluster_mt,
 158        .checkentry     = xt_cluster_mt_checkentry,
 159        .matchsize      = sizeof(struct xt_cluster_match_info),
 160        .me             = THIS_MODULE,
 161};
 162
 163static int __init xt_cluster_mt_init(void)
 164{
 165        return xt_register_match(&xt_cluster_match);
 166}
 167
 168static void __exit xt_cluster_mt_fini(void)
 169{
 170        xt_unregister_match(&xt_cluster_match);
 171}
 172
 173MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
 174MODULE_LICENSE("GPL");
 175MODULE_DESCRIPTION("Xtables: hash-based cluster match");
 176MODULE_ALIAS("ipt_cluster");
 177MODULE_ALIAS("ip6t_cluster");
 178module_init(xt_cluster_mt_init);
 179module_exit(xt_cluster_mt_fini);
 180