LXR linux/net/netfilter/xt

   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
  16static 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
  21static 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
  26static inline u_int32_t
  27xt_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
  32static inline u_int32_t
  33xt_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
  38static inline u_int32_t
  39xt_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
  59static inline bool
  60xt_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
  78static bool
  79xt_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
 122static 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
 144static void xt_cluster_mt_destroy(const struct xt_mtdtor_param *par)
 145{
 146        nf_ct_netns_put(par->net, par->family);
 147}
 148
 149static 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
 159static int __init xt_cluster_mt_init(void)
 160{
 161        return xt_register_match(&xt_cluster_match);
 162}
 163
 164static void __exit xt_cluster_mt_fini(void)
 165{
 166        xt_unregister_match(&xt_cluster_match);
 167}
 168
 169MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
 170MODULE_LICENSE("GPL");
 171MODULE_DESCRIPTION("Xtables: hash-based cluster match");
 172MODULE_ALIAS("ipt_cluster");
 173MODULE_ALIAS("ip6t_cluster");
 174module_init(xt_cluster_mt_init);
 175module_exit(xt_cluster_mt_fini);
 176