LXR linux/net/netfilter/xt

   1/*
   2 * netfilter module to limit the number of parallel tcp
   3 * connections per IP address.
   4 *   (c) 2000 Gerd Knorr <kraxel@bytesex.org>
   5 *   Nov 2002: Martin Bene <martin.bene@icomedias.com>:
   6 *              only ignore TIME_WAIT or gone connections
   7 *   (C) CC Computer Consultants GmbH, 2007
   8 *
   9 * based on ...
  10 *
  11 * Kernel module to match connection tracking information.
  12 * GPL (C) 1999  Rusty Russell (rusty@rustcorp.com.au).
  13 */
  14#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  15
  16#include <linux/module.h>
  17#include <linux/skbuff.h>
  18#include <linux/netfilter/x_tables.h>
  19#include <linux/netfilter/xt_connlimit.h>
  20
  21#include <net/netfilter/nf_conntrack.h>
  22#include <net/netfilter/nf_conntrack_core.h>
  23#include <net/netfilter/nf_conntrack_tuple.h>
  24#include <net/netfilter/nf_conntrack_zones.h>
  25#include <net/netfilter/nf_conntrack_count.h>
  26
  27static bool
  28connlimit_mt(const struct sk_buff *skb, struct xt_action_param *par)
  29{
  30        struct net *net = xt_net(par);
  31        const struct xt_connlimit_info *info = par->matchinfo;
  32        struct nf_conntrack_tuple tuple;
  33        const struct nf_conntrack_tuple *tuple_ptr = &tuple;
  34        const struct nf_conntrack_zone *zone = &nf_ct_zone_dflt;
  35        enum ip_conntrack_info ctinfo;
  36        const struct nf_conn *ct;
  37        unsigned int connections;
  38        u32 key[5];
  39
  40        ct = nf_ct_get(skb, &ctinfo);
  41        if (ct != NULL) {
  42                tuple_ptr = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
  43                zone = nf_ct_zone(ct);
  44        } else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb),
  45                                      xt_family(par), net, &tuple)) {
  46                goto hotdrop;
  47        }
  48
  49        if (xt_family(par) == NFPROTO_IPV6) {
  50                const struct ipv6hdr *iph = ipv6_hdr(skb);
  51                union nf_inet_addr addr;
  52                unsigned int i;
  53
  54                memcpy(&addr.ip6, (info->flags & XT_CONNLIMIT_DADDR) ?
  55                       &iph->daddr : &iph->saddr, sizeof(addr.ip6));
  56
  57                for (i = 0; i < ARRAY_SIZE(addr.ip6); ++i)
  58                        addr.ip6[i] &= info->mask.ip6[i];
  59                memcpy(key, &addr, sizeof(addr.ip6));
  60                key[4] = zone->id;
  61        } else {
  62                const struct iphdr *iph = ip_hdr(skb);
  63                key[0] = (info->flags & XT_CONNLIMIT_DADDR) ?
  64                          iph->daddr : iph->saddr;
  65
  66                key[0] &= info->mask.ip;
  67                key[1] = zone->id;
  68        }
  69
  70        connections = nf_conncount_count(net, info->data, key, tuple_ptr,
  71                                         zone);
  72        if (connections == 0)
  73                /* kmalloc failed, drop it entirely */
  74                goto hotdrop;
  75
  76        return (connections > info->limit) ^ !!(info->flags & XT_CONNLIMIT_INVERT);
  77
  78 hotdrop:
  79        par->hotdrop = true;
  80        return false;
  81}
  82
  83static int connlimit_mt_check(const struct xt_mtchk_param *par)
  84{
  85        struct xt_connlimit_info *info = par->matchinfo;
  86        unsigned int keylen;
  87
  88        keylen = sizeof(u32);
  89        if (par->family == NFPROTO_IPV6)
  90                keylen += sizeof(struct in6_addr);
  91        else
  92                keylen += sizeof(struct in_addr);
  93
  94        /* init private data */
  95        info->data = nf_conncount_init(par->net, par->family, keylen);
  96        if (IS_ERR(info->data))
  97                return PTR_ERR(info->data);
  98
  99        return 0;
 100}
 101
 102static void connlimit_mt_destroy(const struct xt_mtdtor_param *par)
 103{
 104        const struct xt_connlimit_info *info = par->matchinfo;
 105
 106        nf_conncount_destroy(par->net, par->family, info->data);
 107}
 108
 109static struct xt_match connlimit_mt_reg __read_mostly = {
 110        .name       = "connlimit",
 111        .revision   = 1,
 112        .family     = NFPROTO_UNSPEC,
 113        .checkentry = connlimit_mt_check,
 114        .match      = connlimit_mt,
 115        .matchsize  = sizeof(struct xt_connlimit_info),
 116        .usersize   = offsetof(struct xt_connlimit_info, data),
 117        .destroy    = connlimit_mt_destroy,
 118        .me         = THIS_MODULE,
 119};
 120
 121static int __init connlimit_mt_init(void)
 122{
 123        return xt_register_match(&connlimit_mt_reg);
 124}
 125
 126static void __exit connlimit_mt_exit(void)
 127{
 128        xt_unregister_match(&connlimit_mt_reg);
 129}
 130
 131module_init(connlimit_mt_init);
 132module_exit(connlimit_mt_exit);
 133MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
 134MODULE_DESCRIPTION("Xtables: Number of connections matching");
 135MODULE_LICENSE("GPL");
 136MODULE_ALIAS("ipt_connlimit");
 137MODULE_ALIAS("ip6t_connlimit");
 138