net/netfilter/xt_cluster.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * (C) 2008-2009 Pablo Neira Ayuso <pablo@netfilter.org>
   4  */
   5 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   6 #include <linux/module.h>
   7 #include <linux/skbuff.h>
   8 #include <linux/jhash.h>
   9 #include <linux/ip.h>
  10 #include <net/ipv6.h>
  11
  12 #include <linux/netfilter/x_tables.h>
  13 #include <net/netfilter/nf_conntrack.h>
  14 #include <linux/netfilter/xt_cluster.h>
  15
  16 static inline u32 nf_ct_orig_ipv4_src(const struct nf_conn *ct)
  17 {
  18         return (__force u32)ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;
  19 }
  20
  21 static inline const u32 *nf_ct_orig_ipv6_src(const struct nf_conn *ct)
  22 {
  23         return (__force u32 *)ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip6;
  24 }
  25
  26 static inline u_int32_t
  27 xt_cluster_hash_ipv4(u_int32_t ip, const struct xt_cluster_match_info *info)
  28 {
  29         return jhash_1word(ip, info->hash_seed);
  30 }
  31
  32 static inline u_int32_t
  33 xt_cluster_hash_ipv6(const void *ip, const struct xt_cluster_match_info *info)
  34 {
  35         return jhash2(ip, NF_CT_TUPLE_L3SIZE / sizeof(__u32), info->hash_seed);
  36 }
  37
  38 static inline u_int32_t
  39 xt_cluster_hash(const struct nf_conn *ct,
  40                 const struct xt_cluster_match_info *info)
  41 {
  42         u_int32_t hash = 0;
  43
  44         switch(nf_ct_l3num(ct)) {
  45         case AF_INET:
  46                 hash = xt_cluster_hash_ipv4(nf_ct_orig_ipv4_src(ct), info);
  47                 break;
  48         case AF_INET6:
  49                 hash = xt_cluster_hash_ipv6(nf_ct_orig_ipv6_src(ct), info);
  50                 break;
  51         default:
  52                 WARN_ON(1);
  53                 break;
  54         }
  55
  56         return reciprocal_scale(hash, info->total_nodes);
  57 }
  58
  59 static inline bool
  60 xt_cluster_is_multicast_addr(const struct sk_buff *skb, u_int8_t family)
  61 {
  62         bool is_multicast = false;
  63
  64         switch(family) {
  65         case NFPROTO_IPV4:
  66                 is_multicast = ipv4_is_multicast(ip_hdr(skb)->daddr);
  67                 break;
  68         case NFPROTO_IPV6:
  69                 is_multicast = ipv6_addr_is_multicast(&ipv6_hdr(skb)->daddr);
  70                 break;
  71         default:
  72                 WARN_ON(1);
  73                 break;
  74         }
  75         return is_multicast;
  76 }
  77
  78 static bool
  79 xt_cluster_mt(const struct sk_buff *skb, struct xt_action_param *par)
  80 {
  81         struct sk_buff *pskb = (struct sk_buff *)skb;
  82         const struct xt_cluster_match_info *info = par->matchinfo;
  83         const struct nf_conn *ct;
  84         enum ip_conntrack_info ctinfo;
  85         unsigned long hash;
  86
  87         /* This match assumes that all nodes see the same packets. This can be
  88          * achieved if the switch that connects the cluster nodes support some
  89          * sort of 'port mirroring'. However, if your switch does not support
  90          * this, your cluster nodes can reply ARP request using a multicast MAC
  91          * address. Thus, your switch will flood the same packets to the
  92          * cluster nodes with the same multicast MAC address. Using a multicast
  93          * link address is a RFC 1812 (section 3.3.2) violation, but this works
  94          * fine in practise.
  95          *
  96          * Unfortunately, if you use the multicast MAC address, the link layer
  97          * sets skbuff's pkt_type to PACKET_MULTICAST, which is not accepted
  98          * by TCP and others for packets coming to this node. For that reason,
  99          * this match mangles skbuff's pkt_type if it detects a packet
 100          * addressed to a unicast address but using PACKET_MULTICAST. Yes, I
 101          * know, matches should not alter packets, but we are doing this here
 102          * because we would need to add a PKTTYPE target for this sole purpose.
 103          */
 104         if (!xt_cluster_is_multicast_addr(skb, xt_family(par)) &&
 105             skb->pkt_type == PACKET_MULTICAST) {
 106                 pskb->pkt_type = PACKET_HOST;
 107         }
 108
 109         ct = nf_ct_get(skb, &ctinfo);
 110         if (ct == NULL)
 111                 return false;
 112
 113         if (ct->master)
 114                 hash = xt_cluster_hash(ct->master, info);
 115         else
 116                 hash = xt_cluster_hash(ct, info);
 117
 118         return !!((1 << hash) & info->node_mask) ^
 119                !!(info->flags & XT_CLUSTER_F_INV);
 120 }
 121
 122 static int xt_cluster_mt_checkentry(const struct xt_mtchk_param *par)
 123 {
 124         struct xt_cluster_match_info *info = par->matchinfo;
 125         int ret;
 126
 127         if (info->total_nodes > XT_CLUSTER_NODES_MAX) {
 128                 pr_info_ratelimited("you have exceeded the maximum number of cluster nodes (%u > %u)\n",
 129                                     info->total_nodes, XT_CLUSTER_NODES_MAX);
 130                 return -EINVAL;
 131         }
 132         if (info->node_mask >= (1ULL << info->total_nodes)) {
 133                 pr_info_ratelimited("node mask cannot exceed total number of nodes\n");
 134                 return -EDOM;
 135         }
 136
 137         ret = nf_ct_netns_get(par->net, par->family);
 138         if (ret < 0)
 139                 pr_info_ratelimited("cannot load conntrack support for proto=%u\n",
 140                                     par->family);
 141         return ret;
 142 }
 143
 144 static void xt_cluster_mt_destroy(const struct xt_mtdtor_param *par)
 145 {
 146         nf_ct_netns_put(par->net, par->family);
 147 }
 148
 149 static struct xt_match xt_cluster_match __read_mostly = {
 150         .name           = "cluster",
 151         .family         = NFPROTO_UNSPEC,
 152         .match          = xt_cluster_mt,
 153         .checkentry     = xt_cluster_mt_checkentry,
 154         .matchsize      = sizeof(struct xt_cluster_match_info),
 155         .destroy        = xt_cluster_mt_destroy,
 156         .me             = THIS_MODULE,
 157 };
 158
 159 static int __init xt_cluster_mt_init(void)
 160 {
 161         return xt_register_match(&xt_cluster_match);
 162 }
 163
 164 static void __exit xt_cluster_mt_fini(void)
 165 {
 166         xt_unregister_match(&xt_cluster_match);
 167 }
 168
 169 MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
 170 MODULE_LICENSE("GPL");
 171 MODULE_DESCRIPTION("Xtables: hash-based cluster match");
 172 MODULE_ALIAS("ipt_cluster");
 173 MODULE_ALIAS("ip6t_cluster");
 174 module_init(xt_cluster_mt_init);
 175 module_exit(xt_cluster_mt_fini);