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 29 static bool 30 connlimit_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 66 key[0] = (info->flags & XT_CONNLIMIT_DADDR) ? 67 (__force __u32)iph->daddr : (__force __u32)iph->saddr; 68 key[0] &= (__force __u32)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 85 static 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 } 101 102 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