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> 31370786f9SJan Engelhardt 32370786f9SJan Engelhardt /* we will save the tuples of all connections we care about */ 33370786f9SJan Engelhardt struct xt_connlimit_conn { 34370786f9SJan Engelhardt struct list_head list; 35370786f9SJan Engelhardt struct nf_conntrack_tuple tuple; 36370786f9SJan Engelhardt }; 37370786f9SJan Engelhardt 38370786f9SJan Engelhardt struct xt_connlimit_data { 39370786f9SJan Engelhardt struct list_head iphash[256]; 40370786f9SJan Engelhardt spinlock_t lock; 41370786f9SJan Engelhardt }; 42370786f9SJan Engelhardt 43370786f9SJan Engelhardt static u_int32_t connlimit_rnd; 44370786f9SJan Engelhardt static bool connlimit_rnd_inited; 45370786f9SJan Engelhardt 46a34c4589SAl Viro static inline unsigned int connlimit_iphash(__be32 addr) 47370786f9SJan Engelhardt { 48370786f9SJan Engelhardt if (unlikely(!connlimit_rnd_inited)) { 49370786f9SJan Engelhardt get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd)); 50370786f9SJan Engelhardt connlimit_rnd_inited = true; 51370786f9SJan Engelhardt } 52a34c4589SAl Viro return jhash_1word((__force __u32)addr, connlimit_rnd) & 0xFF; 53370786f9SJan Engelhardt } 54370786f9SJan Engelhardt 55370786f9SJan Engelhardt static inline unsigned int 56643a2c15SJan Engelhardt connlimit_iphash6(const union nf_inet_addr *addr, 57643a2c15SJan Engelhardt const union nf_inet_addr *mask) 58370786f9SJan Engelhardt { 59643a2c15SJan Engelhardt union nf_inet_addr res; 60370786f9SJan Engelhardt unsigned int i; 61370786f9SJan Engelhardt 62370786f9SJan Engelhardt if (unlikely(!connlimit_rnd_inited)) { 63370786f9SJan Engelhardt get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd)); 64370786f9SJan Engelhardt connlimit_rnd_inited = true; 65370786f9SJan Engelhardt } 66370786f9SJan Engelhardt 67370786f9SJan Engelhardt for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) 68370786f9SJan Engelhardt res.ip6[i] = addr->ip6[i] & mask->ip6[i]; 69370786f9SJan Engelhardt 70a34c4589SAl Viro return jhash2((u32 *)res.ip6, ARRAY_SIZE(res.ip6), connlimit_rnd) & 0xFF; 71370786f9SJan Engelhardt } 72370786f9SJan Engelhardt 73370786f9SJan Engelhardt static inline bool already_closed(const struct nf_conn *conn) 74370786f9SJan Engelhardt { 75370786f9SJan Engelhardt u_int16_t proto = conn->tuplehash[0].tuple.dst.protonum; 76370786f9SJan Engelhardt 77370786f9SJan Engelhardt if (proto == IPPROTO_TCP) 78370786f9SJan Engelhardt return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT; 79370786f9SJan Engelhardt else 80370786f9SJan Engelhardt return 0; 81370786f9SJan Engelhardt } 82370786f9SJan Engelhardt 83370786f9SJan Engelhardt static inline unsigned int 84643a2c15SJan Engelhardt same_source_net(const union nf_inet_addr *addr, 85643a2c15SJan Engelhardt const union nf_inet_addr *mask, 86643a2c15SJan Engelhardt const union nf_inet_addr *u3, unsigned int family) 87370786f9SJan Engelhardt { 88370786f9SJan Engelhardt if (family == AF_INET) { 89370786f9SJan Engelhardt return (addr->ip & mask->ip) == (u3->ip & mask->ip); 90370786f9SJan Engelhardt } else { 91643a2c15SJan Engelhardt union nf_inet_addr lh, rh; 92370786f9SJan Engelhardt unsigned int i; 93370786f9SJan Engelhardt 94370786f9SJan Engelhardt for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) { 95370786f9SJan Engelhardt lh.ip6[i] = addr->ip6[i] & mask->ip6[i]; 96370786f9SJan Engelhardt rh.ip6[i] = u3->ip6[i] & mask->ip6[i]; 97370786f9SJan Engelhardt } 98370786f9SJan Engelhardt 99370786f9SJan Engelhardt return memcmp(&lh.ip6, &rh.ip6, sizeof(lh.ip6)) == 0; 100370786f9SJan Engelhardt } 101370786f9SJan Engelhardt } 102370786f9SJan Engelhardt 103370786f9SJan Engelhardt static int count_them(struct xt_connlimit_data *data, 104370786f9SJan Engelhardt const struct nf_conntrack_tuple *tuple, 105643a2c15SJan Engelhardt const union nf_inet_addr *addr, 106643a2c15SJan Engelhardt const union nf_inet_addr *mask, 107370786f9SJan Engelhardt const struct xt_match *match) 108370786f9SJan Engelhardt { 1093cf93c96SJan Engelhardt const struct nf_conntrack_tuple_hash *found; 110370786f9SJan Engelhardt struct xt_connlimit_conn *conn; 111370786f9SJan Engelhardt struct xt_connlimit_conn *tmp; 1123cf93c96SJan Engelhardt const struct nf_conn *found_ct; 113370786f9SJan Engelhardt struct list_head *hash; 114370786f9SJan Engelhardt bool addit = true; 115370786f9SJan Engelhardt int matches = 0; 116370786f9SJan Engelhardt 117370786f9SJan Engelhardt 118370786f9SJan Engelhardt if (match->family == AF_INET6) 119370786f9SJan Engelhardt hash = &data->iphash[connlimit_iphash6(addr, mask)]; 120370786f9SJan Engelhardt else 121370786f9SJan Engelhardt hash = &data->iphash[connlimit_iphash(addr->ip & mask->ip)]; 122370786f9SJan Engelhardt 12376507f69SPatrick McHardy rcu_read_lock(); 124370786f9SJan Engelhardt 125370786f9SJan Engelhardt /* check the saved connections */ 126370786f9SJan Engelhardt list_for_each_entry_safe(conn, tmp, hash, list) { 127ba419affSPatrick McHardy found = __nf_conntrack_find(&conn->tuple); 128370786f9SJan Engelhardt found_ct = NULL; 129370786f9SJan Engelhardt 130370786f9SJan Engelhardt if (found != NULL) 131370786f9SJan Engelhardt found_ct = nf_ct_tuplehash_to_ctrack(found); 132370786f9SJan Engelhardt 133370786f9SJan Engelhardt if (found_ct != NULL && 134370786f9SJan Engelhardt nf_ct_tuple_equal(&conn->tuple, tuple) && 135370786f9SJan Engelhardt !already_closed(found_ct)) 136370786f9SJan Engelhardt /* 137370786f9SJan Engelhardt * Just to be sure we have it only once in the list. 138370786f9SJan Engelhardt * We should not see tuples twice unless someone hooks 139370786f9SJan Engelhardt * this into a table without "-p tcp --syn". 140370786f9SJan Engelhardt */ 141370786f9SJan Engelhardt addit = false; 142370786f9SJan Engelhardt 143370786f9SJan Engelhardt if (found == NULL) { 144370786f9SJan Engelhardt /* this one is gone */ 145370786f9SJan Engelhardt list_del(&conn->list); 146370786f9SJan Engelhardt kfree(conn); 147370786f9SJan Engelhardt continue; 148370786f9SJan Engelhardt } 149370786f9SJan Engelhardt 150370786f9SJan Engelhardt if (already_closed(found_ct)) { 151370786f9SJan Engelhardt /* 152370786f9SJan Engelhardt * we do not care about connections which are 153370786f9SJan Engelhardt * closed already -> ditch it 154370786f9SJan Engelhardt */ 155370786f9SJan Engelhardt list_del(&conn->list); 156370786f9SJan Engelhardt kfree(conn); 157370786f9SJan Engelhardt continue; 158370786f9SJan Engelhardt } 159370786f9SJan Engelhardt 160370786f9SJan Engelhardt if (same_source_net(addr, mask, &conn->tuple.src.u3, 161370786f9SJan Engelhardt match->family)) 162370786f9SJan Engelhardt /* same source network -> be counted! */ 163370786f9SJan Engelhardt ++matches; 164370786f9SJan Engelhardt } 165370786f9SJan Engelhardt 16676507f69SPatrick McHardy rcu_read_unlock(); 167370786f9SJan Engelhardt 168370786f9SJan Engelhardt if (addit) { 169370786f9SJan Engelhardt /* save the new connection in our list */ 170370786f9SJan Engelhardt conn = kzalloc(sizeof(*conn), GFP_ATOMIC); 171370786f9SJan Engelhardt if (conn == NULL) 172370786f9SJan Engelhardt return -ENOMEM; 173370786f9SJan Engelhardt conn->tuple = *tuple; 174370786f9SJan Engelhardt list_add(&conn->list, hash); 175370786f9SJan Engelhardt ++matches; 176370786f9SJan Engelhardt } 177370786f9SJan Engelhardt 178370786f9SJan Engelhardt return matches; 179370786f9SJan Engelhardt } 180370786f9SJan Engelhardt 181d3c5ee6dSJan Engelhardt static bool 182d3c5ee6dSJan Engelhardt connlimit_mt(const struct sk_buff *skb, const struct net_device *in, 183d3c5ee6dSJan Engelhardt const struct net_device *out, const struct xt_match *match, 184d3c5ee6dSJan Engelhardt const void *matchinfo, int offset, unsigned int protoff, 185d3c5ee6dSJan Engelhardt bool *hotdrop) 186370786f9SJan Engelhardt { 187370786f9SJan Engelhardt const struct xt_connlimit_info *info = matchinfo; 18822c2d8bcSJan Engelhardt union nf_inet_addr addr; 189370786f9SJan Engelhardt struct nf_conntrack_tuple tuple; 190370786f9SJan Engelhardt const struct nf_conntrack_tuple *tuple_ptr = &tuple; 191370786f9SJan Engelhardt enum ip_conntrack_info ctinfo; 192370786f9SJan Engelhardt const struct nf_conn *ct; 193370786f9SJan Engelhardt int connections; 194370786f9SJan Engelhardt 195370786f9SJan Engelhardt ct = nf_ct_get(skb, &ctinfo); 196370786f9SJan Engelhardt if (ct != NULL) 197370786f9SJan Engelhardt tuple_ptr = &ct->tuplehash[0].tuple; 198370786f9SJan Engelhardt else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb), 199370786f9SJan Engelhardt match->family, &tuple)) 200370786f9SJan Engelhardt goto hotdrop; 201370786f9SJan Engelhardt 202370786f9SJan Engelhardt if (match->family == AF_INET6) { 203370786f9SJan Engelhardt const struct ipv6hdr *iph = ipv6_hdr(skb); 204370786f9SJan Engelhardt memcpy(&addr.ip6, &iph->saddr, sizeof(iph->saddr)); 205370786f9SJan Engelhardt } else { 206370786f9SJan Engelhardt const struct iphdr *iph = ip_hdr(skb); 207370786f9SJan Engelhardt addr.ip = iph->saddr; 208370786f9SJan Engelhardt } 209370786f9SJan Engelhardt 210370786f9SJan Engelhardt spin_lock_bh(&info->data->lock); 21122c2d8bcSJan Engelhardt connections = count_them(info->data, tuple_ptr, &addr, 21222c2d8bcSJan Engelhardt &info->mask, match); 213370786f9SJan Engelhardt spin_unlock_bh(&info->data->lock); 214370786f9SJan Engelhardt 215370786f9SJan Engelhardt if (connections < 0) { 216370786f9SJan Engelhardt /* kmalloc failed, drop it entirely */ 217370786f9SJan Engelhardt *hotdrop = true; 218370786f9SJan Engelhardt return false; 219370786f9SJan Engelhardt } 220370786f9SJan Engelhardt 221370786f9SJan Engelhardt return (connections > info->limit) ^ info->inverse; 222370786f9SJan Engelhardt 223370786f9SJan Engelhardt hotdrop: 224370786f9SJan Engelhardt *hotdrop = true; 225370786f9SJan Engelhardt return false; 226370786f9SJan Engelhardt } 227370786f9SJan Engelhardt 228d3c5ee6dSJan Engelhardt static bool 229d3c5ee6dSJan Engelhardt connlimit_mt_check(const char *tablename, const void *ip, 230370786f9SJan Engelhardt const struct xt_match *match, void *matchinfo, 231370786f9SJan Engelhardt unsigned int hook_mask) 232370786f9SJan Engelhardt { 233370786f9SJan Engelhardt struct xt_connlimit_info *info = matchinfo; 234370786f9SJan Engelhardt unsigned int i; 235370786f9SJan Engelhardt 236370786f9SJan Engelhardt if (nf_ct_l3proto_try_module_get(match->family) < 0) { 237370786f9SJan Engelhardt printk(KERN_WARNING "cannot load conntrack support for " 238370786f9SJan Engelhardt "address family %u\n", match->family); 239370786f9SJan Engelhardt return false; 240370786f9SJan Engelhardt } 241370786f9SJan Engelhardt 242370786f9SJan Engelhardt /* init private data */ 243370786f9SJan Engelhardt info->data = kmalloc(sizeof(struct xt_connlimit_data), GFP_KERNEL); 244370786f9SJan Engelhardt if (info->data == NULL) { 245370786f9SJan Engelhardt nf_ct_l3proto_module_put(match->family); 246370786f9SJan Engelhardt return false; 247370786f9SJan Engelhardt } 248370786f9SJan Engelhardt 249370786f9SJan Engelhardt spin_lock_init(&info->data->lock); 250370786f9SJan Engelhardt for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) 251370786f9SJan Engelhardt INIT_LIST_HEAD(&info->data->iphash[i]); 252370786f9SJan Engelhardt 253370786f9SJan Engelhardt return true; 254370786f9SJan Engelhardt } 255370786f9SJan Engelhardt 256d3c5ee6dSJan Engelhardt static void 257d3c5ee6dSJan Engelhardt connlimit_mt_destroy(const struct xt_match *match, void *matchinfo) 258370786f9SJan Engelhardt { 2593cf93c96SJan Engelhardt const struct xt_connlimit_info *info = matchinfo; 260370786f9SJan Engelhardt struct xt_connlimit_conn *conn; 261370786f9SJan Engelhardt struct xt_connlimit_conn *tmp; 262370786f9SJan Engelhardt struct list_head *hash = info->data->iphash; 263370786f9SJan Engelhardt unsigned int i; 264370786f9SJan Engelhardt 265370786f9SJan Engelhardt nf_ct_l3proto_module_put(match->family); 266370786f9SJan Engelhardt 267370786f9SJan Engelhardt for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) { 268370786f9SJan Engelhardt list_for_each_entry_safe(conn, tmp, &hash[i], list) { 269370786f9SJan Engelhardt list_del(&conn->list); 270370786f9SJan Engelhardt kfree(conn); 271370786f9SJan Engelhardt } 272370786f9SJan Engelhardt } 273370786f9SJan Engelhardt 274370786f9SJan Engelhardt kfree(info->data); 275370786f9SJan Engelhardt } 276370786f9SJan Engelhardt 277d3c5ee6dSJan Engelhardt static struct xt_match connlimit_mt_reg[] __read_mostly = { 278370786f9SJan Engelhardt { 279370786f9SJan Engelhardt .name = "connlimit", 280370786f9SJan Engelhardt .family = AF_INET, 281d3c5ee6dSJan Engelhardt .checkentry = connlimit_mt_check, 282d3c5ee6dSJan Engelhardt .match = connlimit_mt, 283370786f9SJan Engelhardt .matchsize = sizeof(struct xt_connlimit_info), 284d3c5ee6dSJan Engelhardt .destroy = connlimit_mt_destroy, 285370786f9SJan Engelhardt .me = THIS_MODULE, 286370786f9SJan Engelhardt }, 287370786f9SJan Engelhardt { 288370786f9SJan Engelhardt .name = "connlimit", 289370786f9SJan Engelhardt .family = AF_INET6, 290d3c5ee6dSJan Engelhardt .checkentry = connlimit_mt_check, 291d3c5ee6dSJan Engelhardt .match = connlimit_mt, 292370786f9SJan Engelhardt .matchsize = sizeof(struct xt_connlimit_info), 293d3c5ee6dSJan Engelhardt .destroy = connlimit_mt_destroy, 294370786f9SJan Engelhardt .me = THIS_MODULE, 295370786f9SJan Engelhardt }, 296370786f9SJan Engelhardt }; 297370786f9SJan Engelhardt 298d3c5ee6dSJan Engelhardt static int __init connlimit_mt_init(void) 299370786f9SJan Engelhardt { 300d3c5ee6dSJan Engelhardt return xt_register_matches(connlimit_mt_reg, 301d3c5ee6dSJan Engelhardt ARRAY_SIZE(connlimit_mt_reg)); 302370786f9SJan Engelhardt } 303370786f9SJan Engelhardt 304d3c5ee6dSJan Engelhardt static void __exit connlimit_mt_exit(void) 305370786f9SJan Engelhardt { 306d3c5ee6dSJan Engelhardt xt_unregister_matches(connlimit_mt_reg, ARRAY_SIZE(connlimit_mt_reg)); 307370786f9SJan Engelhardt } 308370786f9SJan Engelhardt 309d3c5ee6dSJan Engelhardt module_init(connlimit_mt_init); 310d3c5ee6dSJan Engelhardt module_exit(connlimit_mt_exit); 311ba5dc275SJan Engelhardt MODULE_AUTHOR("Jan Engelhardt <jengelh@computergmbh.de>"); 3122ae15b64SJan Engelhardt MODULE_DESCRIPTION("Xtables: Number of connections matching"); 313370786f9SJan Engelhardt MODULE_LICENSE("GPL"); 314370786f9SJan Engelhardt MODULE_ALIAS("ipt_connlimit"); 315370786f9SJan Engelhardt MODULE_ALIAS("ip6t_connlimit"); 316