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Linux/net/netfilter/xt_connlimit.c

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  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         if (IS_ERR(info->data))
 97                 return PTR_ERR(info->data);
 98 
 99         return 0;
100 }
101 
102 static 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 
109 static 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 
121 static int __init connlimit_mt_init(void)
122 {
123         return xt_register_match(&connlimit_mt_reg);
124 }
125 
126 static void __exit connlimit_mt_exit(void)
127 {
128         xt_unregister_match(&connlimit_mt_reg);
129 }
130 
131 module_init(connlimit_mt_init);
132 module_exit(connlimit_mt_exit);
133 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
134 MODULE_DESCRIPTION("Xtables: Number of connections matching");
135 MODULE_LICENSE("GPL");
136 MODULE_ALIAS("ipt_connlimit");
137 MODULE_ALIAS("ip6t_connlimit");
138 

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