1370786f9SJan Engelhardt /* 2370786f9SJan Engelhardt * netfilter module to limit the number of parallel tcp 3370786f9SJan Engelhardt * connections per IP address. 4370786f9SJan Engelhardt * (c) 2000 Gerd Knorr <kraxel@bytesex.org> 5370786f9SJan Engelhardt * Nov 2002: Martin Bene <martin.bene@icomedias.com>: 6370786f9SJan Engelhardt * only ignore TIME_WAIT or gone connections 7ba5dc275SJan Engelhardt * (C) CC Computer Consultants GmbH, 2007 8ba5dc275SJan Engelhardt * Contact: <jengelh@computergmbh.de> 9370786f9SJan Engelhardt * 10370786f9SJan Engelhardt * based on ... 11370786f9SJan Engelhardt * 12370786f9SJan Engelhardt * Kernel module to match connection tracking information. 13370786f9SJan Engelhardt * GPL (C) 1999 Rusty Russell (rusty@rustcorp.com.au). 14370786f9SJan Engelhardt */ 15370786f9SJan Engelhardt #include <linux/in.h> 16370786f9SJan Engelhardt #include <linux/in6.h> 17370786f9SJan Engelhardt #include <linux/ip.h> 18370786f9SJan Engelhardt #include <linux/ipv6.h> 19370786f9SJan Engelhardt #include <linux/jhash.h> 20370786f9SJan Engelhardt #include <linux/list.h> 21370786f9SJan Engelhardt #include <linux/module.h> 22370786f9SJan Engelhardt #include <linux/random.h> 23370786f9SJan Engelhardt #include <linux/skbuff.h> 24370786f9SJan Engelhardt #include <linux/spinlock.h> 25370786f9SJan Engelhardt #include <linux/netfilter/nf_conntrack_tcp.h> 26370786f9SJan Engelhardt #include <linux/netfilter/x_tables.h> 27370786f9SJan Engelhardt #include <linux/netfilter/xt_connlimit.h> 28370786f9SJan Engelhardt #include <net/netfilter/nf_conntrack.h> 29370786f9SJan Engelhardt #include <net/netfilter/nf_conntrack_core.h> 30370786f9SJan Engelhardt #include <net/netfilter/nf_conntrack_tuple.h> 315d0aa2ccSPatrick McHardy #include <net/netfilter/nf_conntrack_zones.h> 32370786f9SJan Engelhardt 33370786f9SJan Engelhardt /* we will save the tuples of all connections we care about */ 34370786f9SJan Engelhardt struct xt_connlimit_conn { 35370786f9SJan Engelhardt struct list_head list; 36370786f9SJan Engelhardt struct nf_conntrack_tuple tuple; 37370786f9SJan Engelhardt }; 38370786f9SJan Engelhardt 39370786f9SJan Engelhardt struct xt_connlimit_data { 40370786f9SJan Engelhardt struct list_head iphash[256]; 41370786f9SJan Engelhardt spinlock_t lock; 42370786f9SJan Engelhardt }; 43370786f9SJan Engelhardt 44294188aeSJan Engelhardt static u_int32_t connlimit_rnd __read_mostly; 45294188aeSJan Engelhardt static bool connlimit_rnd_inited __read_mostly; 46370786f9SJan Engelhardt 47a34c4589SAl Viro static inline unsigned int connlimit_iphash(__be32 addr) 48370786f9SJan Engelhardt { 49a34c4589SAl Viro return jhash_1word((__force __u32)addr, connlimit_rnd) & 0xFF; 50370786f9SJan Engelhardt } 51370786f9SJan Engelhardt 52370786f9SJan Engelhardt static inline unsigned int 53643a2c15SJan Engelhardt connlimit_iphash6(const union nf_inet_addr *addr, 54643a2c15SJan Engelhardt const union nf_inet_addr *mask) 55370786f9SJan Engelhardt { 56643a2c15SJan Engelhardt union nf_inet_addr res; 57370786f9SJan Engelhardt unsigned int i; 58370786f9SJan Engelhardt 59370786f9SJan Engelhardt for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) 60370786f9SJan Engelhardt res.ip6[i] = addr->ip6[i] & mask->ip6[i]; 61370786f9SJan Engelhardt 62a34c4589SAl Viro return jhash2((u32 *)res.ip6, ARRAY_SIZE(res.ip6), connlimit_rnd) & 0xFF; 63370786f9SJan Engelhardt } 64370786f9SJan Engelhardt 65370786f9SJan Engelhardt static inline bool already_closed(const struct nf_conn *conn) 66370786f9SJan Engelhardt { 675e8fbe2aSPatrick McHardy if (nf_ct_protonum(conn) == IPPROTO_TCP) 68d2ee3f2cSDong Wei return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT || 69d2ee3f2cSDong Wei conn->proto.tcp.state == TCP_CONNTRACK_CLOSE; 70370786f9SJan Engelhardt else 71370786f9SJan Engelhardt return 0; 72370786f9SJan Engelhardt } 73370786f9SJan Engelhardt 74370786f9SJan Engelhardt static inline unsigned int 75643a2c15SJan Engelhardt same_source_net(const union nf_inet_addr *addr, 76643a2c15SJan Engelhardt const union nf_inet_addr *mask, 7776108ceaSJan Engelhardt const union nf_inet_addr *u3, u_int8_t family) 78370786f9SJan Engelhardt { 79ee999d8bSJan Engelhardt if (family == NFPROTO_IPV4) { 80370786f9SJan Engelhardt return (addr->ip & mask->ip) == (u3->ip & mask->ip); 81370786f9SJan Engelhardt } else { 82643a2c15SJan Engelhardt union nf_inet_addr lh, rh; 83370786f9SJan Engelhardt unsigned int i; 84370786f9SJan Engelhardt 85370786f9SJan Engelhardt for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) { 86370786f9SJan Engelhardt lh.ip6[i] = addr->ip6[i] & mask->ip6[i]; 87370786f9SJan Engelhardt rh.ip6[i] = u3->ip6[i] & mask->ip6[i]; 88370786f9SJan Engelhardt } 89370786f9SJan Engelhardt 90370786f9SJan Engelhardt return memcmp(&lh.ip6, &rh.ip6, sizeof(lh.ip6)) == 0; 91370786f9SJan Engelhardt } 92370786f9SJan Engelhardt } 93370786f9SJan Engelhardt 9483fc8102SAlexey Dobriyan static int count_them(struct net *net, 9583fc8102SAlexey Dobriyan struct xt_connlimit_data *data, 96370786f9SJan Engelhardt const struct nf_conntrack_tuple *tuple, 97643a2c15SJan Engelhardt const union nf_inet_addr *addr, 98643a2c15SJan Engelhardt const union nf_inet_addr *mask, 99539054a8SJan Engelhardt u_int8_t family) 100370786f9SJan Engelhardt { 1013cf93c96SJan Engelhardt const struct nf_conntrack_tuple_hash *found; 102370786f9SJan Engelhardt struct xt_connlimit_conn *conn; 103370786f9SJan Engelhardt struct xt_connlimit_conn *tmp; 104ea781f19SEric Dumazet struct nf_conn *found_ct; 105370786f9SJan Engelhardt struct list_head *hash; 106370786f9SJan Engelhardt bool addit = true; 107370786f9SJan Engelhardt int matches = 0; 108370786f9SJan Engelhardt 109539054a8SJan Engelhardt if (family == NFPROTO_IPV6) 110370786f9SJan Engelhardt hash = &data->iphash[connlimit_iphash6(addr, mask)]; 111370786f9SJan Engelhardt else 112370786f9SJan Engelhardt hash = &data->iphash[connlimit_iphash(addr->ip & mask->ip)]; 113370786f9SJan Engelhardt 11476507f69SPatrick McHardy rcu_read_lock(); 115370786f9SJan Engelhardt 116370786f9SJan Engelhardt /* check the saved connections */ 117370786f9SJan Engelhardt list_for_each_entry_safe(conn, tmp, hash, list) { 1185d0aa2ccSPatrick McHardy found = nf_conntrack_find_get(net, NF_CT_DEFAULT_ZONE, 1195d0aa2ccSPatrick McHardy &conn->tuple); 120370786f9SJan Engelhardt found_ct = NULL; 121370786f9SJan Engelhardt 122370786f9SJan Engelhardt if (found != NULL) 123370786f9SJan Engelhardt found_ct = nf_ct_tuplehash_to_ctrack(found); 124370786f9SJan Engelhardt 125370786f9SJan Engelhardt if (found_ct != NULL && 126370786f9SJan Engelhardt nf_ct_tuple_equal(&conn->tuple, tuple) && 127370786f9SJan Engelhardt !already_closed(found_ct)) 128370786f9SJan Engelhardt /* 129370786f9SJan Engelhardt * Just to be sure we have it only once in the list. 130370786f9SJan Engelhardt * We should not see tuples twice unless someone hooks 131370786f9SJan Engelhardt * this into a table without "-p tcp --syn". 132370786f9SJan Engelhardt */ 133370786f9SJan Engelhardt addit = false; 134370786f9SJan Engelhardt 135370786f9SJan Engelhardt if (found == NULL) { 136370786f9SJan Engelhardt /* this one is gone */ 137370786f9SJan Engelhardt list_del(&conn->list); 138370786f9SJan Engelhardt kfree(conn); 139370786f9SJan Engelhardt continue; 140370786f9SJan Engelhardt } 141370786f9SJan Engelhardt 142370786f9SJan Engelhardt if (already_closed(found_ct)) { 143370786f9SJan Engelhardt /* 144370786f9SJan Engelhardt * we do not care about connections which are 145370786f9SJan Engelhardt * closed already -> ditch it 146370786f9SJan Engelhardt */ 147ea781f19SEric Dumazet nf_ct_put(found_ct); 148370786f9SJan Engelhardt list_del(&conn->list); 149370786f9SJan Engelhardt kfree(conn); 150370786f9SJan Engelhardt continue; 151370786f9SJan Engelhardt } 152370786f9SJan Engelhardt 153539054a8SJan Engelhardt if (same_source_net(addr, mask, &conn->tuple.src.u3, family)) 154370786f9SJan Engelhardt /* same source network -> be counted! */ 155370786f9SJan Engelhardt ++matches; 156ea781f19SEric Dumazet nf_ct_put(found_ct); 157370786f9SJan Engelhardt } 158370786f9SJan Engelhardt 15976507f69SPatrick McHardy rcu_read_unlock(); 160370786f9SJan Engelhardt 161370786f9SJan Engelhardt if (addit) { 162370786f9SJan Engelhardt /* save the new connection in our list */ 163370786f9SJan Engelhardt conn = kzalloc(sizeof(*conn), GFP_ATOMIC); 164370786f9SJan Engelhardt if (conn == NULL) 165370786f9SJan Engelhardt return -ENOMEM; 166370786f9SJan Engelhardt conn->tuple = *tuple; 167370786f9SJan Engelhardt list_add(&conn->list, hash); 168370786f9SJan Engelhardt ++matches; 169370786f9SJan Engelhardt } 170370786f9SJan Engelhardt 171370786f9SJan Engelhardt return matches; 172370786f9SJan Engelhardt } 173370786f9SJan Engelhardt 174d3c5ee6dSJan Engelhardt static bool 175f7108a20SJan Engelhardt connlimit_mt(const struct sk_buff *skb, const struct xt_match_param *par) 176370786f9SJan Engelhardt { 17783fc8102SAlexey Dobriyan struct net *net = dev_net(par->in ? par->in : par->out); 178f7108a20SJan Engelhardt const struct xt_connlimit_info *info = par->matchinfo; 17922c2d8bcSJan Engelhardt union nf_inet_addr addr; 180370786f9SJan Engelhardt struct nf_conntrack_tuple tuple; 181370786f9SJan Engelhardt const struct nf_conntrack_tuple *tuple_ptr = &tuple; 182370786f9SJan Engelhardt enum ip_conntrack_info ctinfo; 183370786f9SJan Engelhardt const struct nf_conn *ct; 184370786f9SJan Engelhardt int connections; 185370786f9SJan Engelhardt 186370786f9SJan Engelhardt ct = nf_ct_get(skb, &ctinfo); 187370786f9SJan Engelhardt if (ct != NULL) 188370786f9SJan Engelhardt tuple_ptr = &ct->tuplehash[0].tuple; 189370786f9SJan Engelhardt else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb), 19092f3b2b1SJan Engelhardt par->family, &tuple)) 191370786f9SJan Engelhardt goto hotdrop; 192370786f9SJan Engelhardt 19392f3b2b1SJan Engelhardt if (par->family == NFPROTO_IPV6) { 194370786f9SJan Engelhardt const struct ipv6hdr *iph = ipv6_hdr(skb); 195370786f9SJan Engelhardt memcpy(&addr.ip6, &iph->saddr, sizeof(iph->saddr)); 196370786f9SJan Engelhardt } else { 197370786f9SJan Engelhardt const struct iphdr *iph = ip_hdr(skb); 198370786f9SJan Engelhardt addr.ip = iph->saddr; 199370786f9SJan Engelhardt } 200370786f9SJan Engelhardt 201370786f9SJan Engelhardt spin_lock_bh(&info->data->lock); 20283fc8102SAlexey Dobriyan connections = count_them(net, info->data, tuple_ptr, &addr, 203539054a8SJan Engelhardt &info->mask, par->family); 204370786f9SJan Engelhardt spin_unlock_bh(&info->data->lock); 205370786f9SJan Engelhardt 206370786f9SJan Engelhardt if (connections < 0) { 207370786f9SJan Engelhardt /* kmalloc failed, drop it entirely */ 208f7108a20SJan Engelhardt *par->hotdrop = true; 209370786f9SJan Engelhardt return false; 210370786f9SJan Engelhardt } 211370786f9SJan Engelhardt 212370786f9SJan Engelhardt return (connections > info->limit) ^ info->inverse; 213370786f9SJan Engelhardt 214370786f9SJan Engelhardt hotdrop: 215f7108a20SJan Engelhardt *par->hotdrop = true; 216370786f9SJan Engelhardt return false; 217370786f9SJan Engelhardt } 218370786f9SJan Engelhardt 2199b4fce7aSJan Engelhardt static bool connlimit_mt_check(const struct xt_mtchk_param *par) 220370786f9SJan Engelhardt { 2219b4fce7aSJan Engelhardt struct xt_connlimit_info *info = par->matchinfo; 222370786f9SJan Engelhardt unsigned int i; 223370786f9SJan Engelhardt 224294188aeSJan Engelhardt if (unlikely(!connlimit_rnd_inited)) { 225294188aeSJan Engelhardt get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd)); 226294188aeSJan Engelhardt connlimit_rnd_inited = true; 227294188aeSJan Engelhardt } 22892f3b2b1SJan Engelhardt if (nf_ct_l3proto_try_module_get(par->family) < 0) { 229370786f9SJan Engelhardt printk(KERN_WARNING "cannot load conntrack support for " 23092f3b2b1SJan Engelhardt "address family %u\n", par->family); 231370786f9SJan Engelhardt return false; 232370786f9SJan Engelhardt } 233370786f9SJan Engelhardt 234370786f9SJan Engelhardt /* init private data */ 235370786f9SJan Engelhardt info->data = kmalloc(sizeof(struct xt_connlimit_data), GFP_KERNEL); 236370786f9SJan Engelhardt if (info->data == NULL) { 23792f3b2b1SJan Engelhardt nf_ct_l3proto_module_put(par->family); 238370786f9SJan Engelhardt return false; 239370786f9SJan Engelhardt } 240370786f9SJan Engelhardt 241370786f9SJan Engelhardt spin_lock_init(&info->data->lock); 242370786f9SJan Engelhardt for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) 243370786f9SJan Engelhardt INIT_LIST_HEAD(&info->data->iphash[i]); 244370786f9SJan Engelhardt 245370786f9SJan Engelhardt return true; 246370786f9SJan Engelhardt } 247370786f9SJan Engelhardt 2486be3d859SJan Engelhardt static void connlimit_mt_destroy(const struct xt_mtdtor_param *par) 249370786f9SJan Engelhardt { 2506be3d859SJan Engelhardt const struct xt_connlimit_info *info = par->matchinfo; 251370786f9SJan Engelhardt struct xt_connlimit_conn *conn; 252370786f9SJan Engelhardt struct xt_connlimit_conn *tmp; 253370786f9SJan Engelhardt struct list_head *hash = info->data->iphash; 254370786f9SJan Engelhardt unsigned int i; 255370786f9SJan Engelhardt 25692f3b2b1SJan Engelhardt nf_ct_l3proto_module_put(par->family); 257370786f9SJan Engelhardt 258370786f9SJan Engelhardt for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) { 259370786f9SJan Engelhardt list_for_each_entry_safe(conn, tmp, &hash[i], list) { 260370786f9SJan Engelhardt list_del(&conn->list); 261370786f9SJan Engelhardt kfree(conn); 262370786f9SJan Engelhardt } 263370786f9SJan Engelhardt } 264370786f9SJan Engelhardt 265370786f9SJan Engelhardt kfree(info->data); 266370786f9SJan Engelhardt } 267370786f9SJan Engelhardt 26892f3b2b1SJan Engelhardt static struct xt_match connlimit_mt_reg __read_mostly = { 269370786f9SJan Engelhardt .name = "connlimit", 27092f3b2b1SJan Engelhardt .revision = 0, 27192f3b2b1SJan Engelhardt .family = NFPROTO_UNSPEC, 272d3c5ee6dSJan Engelhardt .checkentry = connlimit_mt_check, 273d3c5ee6dSJan Engelhardt .match = connlimit_mt, 274370786f9SJan Engelhardt .matchsize = sizeof(struct xt_connlimit_info), 275d3c5ee6dSJan Engelhardt .destroy = connlimit_mt_destroy, 276370786f9SJan Engelhardt .me = THIS_MODULE, 277370786f9SJan Engelhardt }; 278370786f9SJan Engelhardt 279d3c5ee6dSJan Engelhardt static int __init connlimit_mt_init(void) 280370786f9SJan Engelhardt { 28192f3b2b1SJan Engelhardt return xt_register_match(&connlimit_mt_reg); 282370786f9SJan Engelhardt } 283370786f9SJan Engelhardt 284d3c5ee6dSJan Engelhardt static void __exit connlimit_mt_exit(void) 285370786f9SJan Engelhardt { 28692f3b2b1SJan Engelhardt xt_unregister_match(&connlimit_mt_reg); 287370786f9SJan Engelhardt } 288370786f9SJan Engelhardt 289d3c5ee6dSJan Engelhardt module_init(connlimit_mt_init); 290d3c5ee6dSJan Engelhardt module_exit(connlimit_mt_exit); 29192f3b2b1SJan Engelhardt MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>"); 2922ae15b64SJan Engelhardt MODULE_DESCRIPTION("Xtables: Number of connections matching"); 293370786f9SJan Engelhardt MODULE_LICENSE("GPL"); 294370786f9SJan Engelhardt MODULE_ALIAS("ipt_connlimit"); 295370786f9SJan Engelhardt MODULE_ALIAS("ip6t_connlimit"); 296