net/netfilter/xt_connlimit.c

   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
  27 static bool
  28 connlimit_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
  83 static 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
  97         return PTR_ERR_OR_ZERO(info->data);
  98 }
  99
 100 static void connlimit_mt_destroy(const struct xt_mtdtor_param *par)
 101 {
 102         const struct xt_connlimit_info *info = par->matchinfo;
 103
 104         nf_conncount_destroy(par->net, par->family, info->data);
 105 }
 106
 107 static struct xt_match connlimit_mt_reg __read_mostly = {
 108         .name       = "connlimit",
 109         .revision   = 1,
 110         .family     = NFPROTO_UNSPEC,
 111         .checkentry = connlimit_mt_check,
 112         .match      = connlimit_mt,
 113         .matchsize  = sizeof(struct xt_connlimit_info),
 114         .usersize   = offsetof(struct xt_connlimit_info, data),
 115         .destroy    = connlimit_mt_destroy,
 116         .me         = THIS_MODULE,
 117 };
 118
 119 static int __init connlimit_mt_init(void)
 120 {
 121         return xt_register_match(&connlimit_mt_reg);
 122 }
 123
 124 static void __exit connlimit_mt_exit(void)
 125 {
 126         xt_unregister_match(&connlimit_mt_reg);
 127 }
 128
 129 module_init(connlimit_mt_init);
 130 module_exit(connlimit_mt_exit);
 131 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
 132 MODULE_DESCRIPTION("Xtables: Number of connections matching");
 133 MODULE_LICENSE("GPL");
 134 MODULE_ALIAS("ipt_connlimit");
 135 MODULE_ALIAS("ip6t_connlimit");