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/ip.h>
  17#include <linux/ipv6.h>
  18#include <linux/module.h>
  19#include <linux/skbuff.h>
  20#include <linux/netfilter/x_tables.h>
  21#include <linux/netfilter/xt_connlimit.h>
  22
  23#include <net/netfilter/nf_conntrack.h>
  24#include <net/netfilter/nf_conntrack_core.h>
  25#include <net/netfilter/nf_conntrack_tuple.h>
  26#include <net/netfilter/nf_conntrack_zones.h>
  27#include <net/netfilter/nf_conntrack_count.h>
  28
  29static bool
  30connlimit_mt(const struct sk_buff *skb, struct xt_action_param *par)
  31{
  32        struct net *net = xt_net(par);
  33        const struct xt_connlimit_info *info = par->matchinfo;
  34        struct nf_conntrack_tuple tuple;
  35        const struct nf_conntrack_tuple *tuple_ptr = &tuple;
  36        const struct nf_conntrack_zone *zone = &nf_ct_zone_dflt;
  37        enum ip_conntrack_info ctinfo;
  38        const struct nf_conn *ct;
  39        unsigned int connections;
  40        u32 key[5];
  41
  42        ct = nf_ct_get(skb, &ctinfo);
  43        if (ct != NULL) {
  44                tuple_ptr = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
  45                zone = nf_ct_zone(ct);
  46        } else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb),
  47                                      xt_family(par), net, &tuple)) {
  48                goto hotdrop;
  49        }
  50
  51        if (xt_family(par) == NFPROTO_IPV6) {
  52                const struct ipv6hdr *iph = ipv6_hdr(skb);
  53                union nf_inet_addr addr;
  54                unsigned int i;
  55
  56                memcpy(&addr.ip6, (info->flags & XT_CONNLIMIT_DADDR) ?
  57                       &iph->daddr : &iph->saddr, sizeof(addr.ip6));
  58
  59                for (i = 0; i < ARRAY_SIZE(addr.ip6); ++i)
  60                        addr.ip6[i] &= info->mask.ip6[i];
  61                memcpy(key, &addr, sizeof(addr.ip6));
  62                key[4] = zone->id;
  63        } else {
  64                const struct iphdr *iph = ip_hdr(skb);
  65                key[0] = (info->flags & XT_CONNLIMIT_DADDR) ?
  66                          iph->daddr : iph->saddr;
  67
  68                key[0] &= info->mask.ip;
  69                key[1] = zone->id;
  70        }
  71
  72        connections = nf_conncount_count(net, info->data, key, tuple_ptr,
  73                                         zone);
  74        if (connections == 0)
  75                /* kmalloc failed, drop it entirely */
  76                goto hotdrop;
  77
  78        return (connections > info->limit) ^ !!(info->flags & XT_CONNLIMIT_INVERT);
  79
  80 hotdrop:
  81        par->hotdrop = true;
  82        return false;
  83}
  84
  85static int connlimit_mt_check(const struct xt_mtchk_param *par)
  86{
  87        struct xt_connlimit_info *info = par->matchinfo;
  88        unsigned int keylen;
  89
  90        keylen = sizeof(u32);
  91        if (par->family == NFPROTO_IPV6)
  92                keylen += sizeof(struct in6_addr);
  93        else
  94                keylen += sizeof(struct in_addr);
  95
  96        /* init private data */
  97        info->data = nf_conncount_init(par->net, par->family, keylen);
  98
  99        return PTR_ERR_OR_ZERO(info->data);
 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