net/netfilter/xt_cluster.c

   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 #include <linux/module.h>
   9 #include <linux/skbuff.h>
  10 #include <linux/jhash.h>
  11 #include <linux/ip.h>
  12 #include <net/ipv6.h>
  13
  14 #include <linux/netfilter/x_tables.h>
  15 #include <net/netfilter/nf_conntrack.h>
  16 #include <linux/netfilter/xt_cluster.h>
  17
  18 static inline u_int32_t nf_ct_orig_ipv4_src(const struct nf_conn *ct)
  19 {
  20         return ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;
  21 }
  22
  23 static inline const void *nf_ct_orig_ipv6_src(const struct nf_conn *ct)
  24 {
  25         return ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip6;
  26 }
  27
  28 static inline u_int32_t
  29 xt_cluster_hash_ipv4(u_int32_t ip, const struct xt_cluster_match_info *info)
  30 {
  31         return jhash_1word(ip, info->hash_seed);
  32 }
  33
  34 static inline u_int32_t
  35 xt_cluster_hash_ipv6(const void *ip, const struct xt_cluster_match_info *info)
  36 {
  37         return jhash2(ip, NF_CT_TUPLE_L3SIZE / sizeof(__u32), info->hash_seed);
  38 }
  39
  40 static inline u_int32_t
  41 xt_cluster_hash(const struct nf_conn *ct,
  42                 const struct xt_cluster_match_info *info)
  43 {
  44         u_int32_t hash = 0;
  45
  46         switch(nf_ct_l3num(ct)) {
  47         case AF_INET:
  48                 hash = xt_cluster_hash_ipv4(nf_ct_orig_ipv4_src(ct), info);
  49                 break;
  50         case AF_INET6:
  51                 hash = xt_cluster_hash_ipv6(nf_ct_orig_ipv6_src(ct), info);
  52                 break;
  53         default:
  54                 WARN_ON(1);
  55                 break;
  56         }
  57         return (((u64)hash * info->total_nodes) >> 32);
  58 }
  59
  60 static inline bool
  61 xt_cluster_is_multicast_addr(const struct sk_buff *skb, u_int8_t family)
  62 {
  63         bool is_multicast = false;
  64
  65         switch(family) {
  66         case NFPROTO_IPV4:
  67                 is_multicast = ipv4_is_multicast(ip_hdr(skb)->daddr);
  68                 break;
  69         case NFPROTO_IPV6:
  70                 is_multicast = ipv6_addr_type(&ipv6_hdr(skb)->daddr) &
  71                                                 IPV6_ADDR_MULTICAST;
  72                 break;
  73         default:
  74                 WARN_ON(1);
  75                 break;
  76         }
  77         return is_multicast;
  78 }
  79
  80 static bool
  81 xt_cluster_mt(const struct sk_buff *skb, const struct xt_match_param *par)
  82 {
  83         struct sk_buff *pskb = (struct sk_buff *)skb;
  84         const struct xt_cluster_match_info *info = par->matchinfo;
  85         const struct nf_conn *ct;
  86         enum ip_conntrack_info ctinfo;
  87         unsigned long hash;
  88
  89         /* This match assumes that all nodes see the same packets. This can be
  90          * achieved if the switch that connects the cluster nodes support some
  91          * sort of 'port mirroring'. However, if your switch does not support
  92          * this, your cluster nodes can reply ARP request using a multicast MAC
  93          * address. Thus, your switch will flood the same packets to the
  94          * cluster nodes with the same multicast MAC address. Using a multicast
  95          * link address is a RFC 1812 (section 3.3.2) violation, but this works
  96          * fine in practise.
  97          *
  98          * Unfortunately, if you use the multicast MAC address, the link layer
  99          * sets skbuff's pkt_type to PACKET_MULTICAST, which is not accepted
 100          * by TCP and others for packets coming to this node. For that reason,
 101          * this match mangles skbuff's pkt_type if it detects a packet
 102          * addressed to a unicast address but using PACKET_MULTICAST. Yes, I
 103          * know, matches should not alter packets, but we are doing this here
 104          * because we would need to add a PKTTYPE target for this sole purpose.
 105          */
 106         if (!xt_cluster_is_multicast_addr(skb, par->family) &&
 107             skb->pkt_type == PACKET_MULTICAST) {
 108                 pskb->pkt_type = PACKET_HOST;
 109         }
 110
 111         ct = nf_ct_get(skb, &ctinfo);
 112         if (ct == NULL)
 113                 return false;
 114
 115         if (ct == &nf_conntrack_untracked)
 116                 return false;
 117
 118         if (ct->master)
 119                 hash = xt_cluster_hash(ct->master, info);
 120         else
 121                 hash = xt_cluster_hash(ct, info);
 122
 123         return !!((1 << hash) & info->node_mask) ^
 124                !!(info->flags & XT_CLUSTER_F_INV);
 125 }
 126
 127 static bool xt_cluster_mt_checkentry(const struct xt_mtchk_param *par)
 128 {
 129         struct xt_cluster_match_info *info = par->matchinfo;
 130
 131         if (info->node_mask >= (1 << info->total_nodes)) {
 132                 printk(KERN_ERR "xt_cluster: this node mask cannot be "
 133                                 "higher than the total number of nodes\n");
 134                 return false;
 135         }
 136         return true;
 137 }
 138
 139 static struct xt_match xt_cluster_match __read_mostly = {
 140         .name           = "cluster",
 141         .family         = NFPROTO_UNSPEC,
 142         .match          = xt_cluster_mt,
 143         .checkentry     = xt_cluster_mt_checkentry,
 144         .matchsize      = sizeof(struct xt_cluster_match_info),
 145         .me             = THIS_MODULE,
 146 };
 147
 148 static int __init xt_cluster_mt_init(void)
 149 {
 150         return xt_register_match(&xt_cluster_match);
 151 }
 152
 153 static void __exit xt_cluster_mt_fini(void)
 154 {
 155         xt_unregister_match(&xt_cluster_match);
 156 }
 157
 158 MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
 159 MODULE_LICENSE("GPL");
 160 MODULE_DESCRIPTION("Xtables: hash-based cluster match");
 161 MODULE_ALIAS("ipt_cluster");
 162 MODULE_ALIAS("ip6t_cluster");
 163 module_init(xt_cluster_mt_init);
 164 module_exit(xt_cluster_mt_fini);