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 { 755e8fbe2aSPatrick McHardy if (nf_ct_protonum(conn) == IPPROTO_TCP) 76370786f9SJan Engelhardt return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT; 77370786f9SJan Engelhardt else 78370786f9SJan Engelhardt return 0; 79370786f9SJan Engelhardt } 80370786f9SJan Engelhardt 81370786f9SJan Engelhardt static inline unsigned int 82643a2c15SJan Engelhardt same_source_net(const union nf_inet_addr *addr, 83643a2c15SJan Engelhardt const union nf_inet_addr *mask, 84643a2c15SJan Engelhardt const union nf_inet_addr *u3, unsigned int family) 85370786f9SJan Engelhardt { 86370786f9SJan Engelhardt if (family == AF_INET) { 87370786f9SJan Engelhardt return (addr->ip & mask->ip) == (u3->ip & mask->ip); 88370786f9SJan Engelhardt } else { 89643a2c15SJan Engelhardt union nf_inet_addr lh, rh; 90370786f9SJan Engelhardt unsigned int i; 91370786f9SJan Engelhardt 92370786f9SJan Engelhardt for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) { 93370786f9SJan Engelhardt lh.ip6[i] = addr->ip6[i] & mask->ip6[i]; 94370786f9SJan Engelhardt rh.ip6[i] = u3->ip6[i] & mask->ip6[i]; 95370786f9SJan Engelhardt } 96370786f9SJan Engelhardt 97370786f9SJan Engelhardt return memcmp(&lh.ip6, &rh.ip6, sizeof(lh.ip6)) == 0; 98370786f9SJan Engelhardt } 99370786f9SJan Engelhardt } 100370786f9SJan Engelhardt 101370786f9SJan Engelhardt static int count_them(struct xt_connlimit_data *data, 102370786f9SJan Engelhardt const struct nf_conntrack_tuple *tuple, 103643a2c15SJan Engelhardt const union nf_inet_addr *addr, 104643a2c15SJan Engelhardt const union nf_inet_addr *mask, 105370786f9SJan Engelhardt const struct xt_match *match) 106370786f9SJan Engelhardt { 1073cf93c96SJan Engelhardt const struct nf_conntrack_tuple_hash *found; 108370786f9SJan Engelhardt struct xt_connlimit_conn *conn; 109370786f9SJan Engelhardt struct xt_connlimit_conn *tmp; 1103cf93c96SJan Engelhardt const struct nf_conn *found_ct; 111370786f9SJan Engelhardt struct list_head *hash; 112370786f9SJan Engelhardt bool addit = true; 113370786f9SJan Engelhardt int matches = 0; 114370786f9SJan Engelhardt 115370786f9SJan Engelhardt 116370786f9SJan Engelhardt if (match->family == AF_INET6) 117370786f9SJan Engelhardt hash = &data->iphash[connlimit_iphash6(addr, mask)]; 118370786f9SJan Engelhardt else 119370786f9SJan Engelhardt hash = &data->iphash[connlimit_iphash(addr->ip & mask->ip)]; 120370786f9SJan Engelhardt 12176507f69SPatrick McHardy rcu_read_lock(); 122370786f9SJan Engelhardt 123370786f9SJan Engelhardt /* check the saved connections */ 124370786f9SJan Engelhardt list_for_each_entry_safe(conn, tmp, hash, list) { 125ba419affSPatrick McHardy found = __nf_conntrack_find(&conn->tuple); 126370786f9SJan Engelhardt found_ct = NULL; 127370786f9SJan Engelhardt 128370786f9SJan Engelhardt if (found != NULL) 129370786f9SJan Engelhardt found_ct = nf_ct_tuplehash_to_ctrack(found); 130370786f9SJan Engelhardt 131370786f9SJan Engelhardt if (found_ct != NULL && 132370786f9SJan Engelhardt nf_ct_tuple_equal(&conn->tuple, tuple) && 133370786f9SJan Engelhardt !already_closed(found_ct)) 134370786f9SJan Engelhardt /* 135370786f9SJan Engelhardt * Just to be sure we have it only once in the list. 136370786f9SJan Engelhardt * We should not see tuples twice unless someone hooks 137370786f9SJan Engelhardt * this into a table without "-p tcp --syn". 138370786f9SJan Engelhardt */ 139370786f9SJan Engelhardt addit = false; 140370786f9SJan Engelhardt 141370786f9SJan Engelhardt if (found == NULL) { 142370786f9SJan Engelhardt /* this one is gone */ 143370786f9SJan Engelhardt list_del(&conn->list); 144370786f9SJan Engelhardt kfree(conn); 145370786f9SJan Engelhardt continue; 146370786f9SJan Engelhardt } 147370786f9SJan Engelhardt 148370786f9SJan Engelhardt if (already_closed(found_ct)) { 149370786f9SJan Engelhardt /* 150370786f9SJan Engelhardt * we do not care about connections which are 151370786f9SJan Engelhardt * closed already -> ditch it 152370786f9SJan Engelhardt */ 153370786f9SJan Engelhardt list_del(&conn->list); 154370786f9SJan Engelhardt kfree(conn); 155370786f9SJan Engelhardt continue; 156370786f9SJan Engelhardt } 157370786f9SJan Engelhardt 158370786f9SJan Engelhardt if (same_source_net(addr, mask, &conn->tuple.src.u3, 159370786f9SJan Engelhardt match->family)) 160370786f9SJan Engelhardt /* same source network -> be counted! */ 161370786f9SJan Engelhardt ++matches; 162370786f9SJan Engelhardt } 163370786f9SJan Engelhardt 16476507f69SPatrick McHardy rcu_read_unlock(); 165370786f9SJan Engelhardt 166370786f9SJan Engelhardt if (addit) { 167370786f9SJan Engelhardt /* save the new connection in our list */ 168370786f9SJan Engelhardt conn = kzalloc(sizeof(*conn), GFP_ATOMIC); 169370786f9SJan Engelhardt if (conn == NULL) 170370786f9SJan Engelhardt return -ENOMEM; 171370786f9SJan Engelhardt conn->tuple = *tuple; 172370786f9SJan Engelhardt list_add(&conn->list, hash); 173370786f9SJan Engelhardt ++matches; 174370786f9SJan Engelhardt } 175370786f9SJan Engelhardt 176370786f9SJan Engelhardt return matches; 177370786f9SJan Engelhardt } 178370786f9SJan Engelhardt 179d3c5ee6dSJan Engelhardt static bool 180d3c5ee6dSJan Engelhardt connlimit_mt(const struct sk_buff *skb, const struct net_device *in, 181d3c5ee6dSJan Engelhardt const struct net_device *out, const struct xt_match *match, 182d3c5ee6dSJan Engelhardt const void *matchinfo, int offset, unsigned int protoff, 183d3c5ee6dSJan Engelhardt bool *hotdrop) 184370786f9SJan Engelhardt { 185370786f9SJan Engelhardt const struct xt_connlimit_info *info = matchinfo; 18622c2d8bcSJan Engelhardt union nf_inet_addr addr; 187370786f9SJan Engelhardt struct nf_conntrack_tuple tuple; 188370786f9SJan Engelhardt const struct nf_conntrack_tuple *tuple_ptr = &tuple; 189370786f9SJan Engelhardt enum ip_conntrack_info ctinfo; 190370786f9SJan Engelhardt const struct nf_conn *ct; 191370786f9SJan Engelhardt int connections; 192370786f9SJan Engelhardt 193370786f9SJan Engelhardt ct = nf_ct_get(skb, &ctinfo); 194370786f9SJan Engelhardt if (ct != NULL) 195370786f9SJan Engelhardt tuple_ptr = &ct->tuplehash[0].tuple; 196370786f9SJan Engelhardt else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb), 197370786f9SJan Engelhardt match->family, &tuple)) 198370786f9SJan Engelhardt goto hotdrop; 199370786f9SJan Engelhardt 200370786f9SJan Engelhardt if (match->family == AF_INET6) { 201370786f9SJan Engelhardt const struct ipv6hdr *iph = ipv6_hdr(skb); 202370786f9SJan Engelhardt memcpy(&addr.ip6, &iph->saddr, sizeof(iph->saddr)); 203370786f9SJan Engelhardt } else { 204370786f9SJan Engelhardt const struct iphdr *iph = ip_hdr(skb); 205370786f9SJan Engelhardt addr.ip = iph->saddr; 206370786f9SJan Engelhardt } 207370786f9SJan Engelhardt 208370786f9SJan Engelhardt spin_lock_bh(&info->data->lock); 20922c2d8bcSJan Engelhardt connections = count_them(info->data, tuple_ptr, &addr, 21022c2d8bcSJan Engelhardt &info->mask, match); 211370786f9SJan Engelhardt spin_unlock_bh(&info->data->lock); 212370786f9SJan Engelhardt 213370786f9SJan Engelhardt if (connections < 0) { 214370786f9SJan Engelhardt /* kmalloc failed, drop it entirely */ 215370786f9SJan Engelhardt *hotdrop = true; 216370786f9SJan Engelhardt return false; 217370786f9SJan Engelhardt } 218370786f9SJan Engelhardt 219370786f9SJan Engelhardt return (connections > info->limit) ^ info->inverse; 220370786f9SJan Engelhardt 221370786f9SJan Engelhardt hotdrop: 222370786f9SJan Engelhardt *hotdrop = true; 223370786f9SJan Engelhardt return false; 224370786f9SJan Engelhardt } 225370786f9SJan Engelhardt 226d3c5ee6dSJan Engelhardt static bool 227d3c5ee6dSJan Engelhardt connlimit_mt_check(const char *tablename, const void *ip, 228370786f9SJan Engelhardt const struct xt_match *match, void *matchinfo, 229370786f9SJan Engelhardt unsigned int hook_mask) 230370786f9SJan Engelhardt { 231370786f9SJan Engelhardt struct xt_connlimit_info *info = matchinfo; 232370786f9SJan Engelhardt unsigned int i; 233370786f9SJan Engelhardt 234370786f9SJan Engelhardt if (nf_ct_l3proto_try_module_get(match->family) < 0) { 235370786f9SJan Engelhardt printk(KERN_WARNING "cannot load conntrack support for " 236370786f9SJan Engelhardt "address family %u\n", match->family); 237370786f9SJan Engelhardt return false; 238370786f9SJan Engelhardt } 239370786f9SJan Engelhardt 240370786f9SJan Engelhardt /* init private data */ 241370786f9SJan Engelhardt info->data = kmalloc(sizeof(struct xt_connlimit_data), GFP_KERNEL); 242370786f9SJan Engelhardt if (info->data == NULL) { 243370786f9SJan Engelhardt nf_ct_l3proto_module_put(match->family); 244370786f9SJan Engelhardt return false; 245370786f9SJan Engelhardt } 246370786f9SJan Engelhardt 247370786f9SJan Engelhardt spin_lock_init(&info->data->lock); 248370786f9SJan Engelhardt for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) 249370786f9SJan Engelhardt INIT_LIST_HEAD(&info->data->iphash[i]); 250370786f9SJan Engelhardt 251370786f9SJan Engelhardt return true; 252370786f9SJan Engelhardt } 253370786f9SJan Engelhardt 254d3c5ee6dSJan Engelhardt static void 255d3c5ee6dSJan Engelhardt connlimit_mt_destroy(const struct xt_match *match, void *matchinfo) 256370786f9SJan Engelhardt { 2573cf93c96SJan Engelhardt const struct xt_connlimit_info *info = matchinfo; 258370786f9SJan Engelhardt struct xt_connlimit_conn *conn; 259370786f9SJan Engelhardt struct xt_connlimit_conn *tmp; 260370786f9SJan Engelhardt struct list_head *hash = info->data->iphash; 261370786f9SJan Engelhardt unsigned int i; 262370786f9SJan Engelhardt 263370786f9SJan Engelhardt nf_ct_l3proto_module_put(match->family); 264370786f9SJan Engelhardt 265370786f9SJan Engelhardt for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) { 266370786f9SJan Engelhardt list_for_each_entry_safe(conn, tmp, &hash[i], list) { 267370786f9SJan Engelhardt list_del(&conn->list); 268370786f9SJan Engelhardt kfree(conn); 269370786f9SJan Engelhardt } 270370786f9SJan Engelhardt } 271370786f9SJan Engelhardt 272370786f9SJan Engelhardt kfree(info->data); 273370786f9SJan Engelhardt } 274370786f9SJan Engelhardt 275d3c5ee6dSJan Engelhardt static struct xt_match connlimit_mt_reg[] __read_mostly = { 276370786f9SJan Engelhardt { 277370786f9SJan Engelhardt .name = "connlimit", 278370786f9SJan Engelhardt .family = AF_INET, 279d3c5ee6dSJan Engelhardt .checkentry = connlimit_mt_check, 280d3c5ee6dSJan Engelhardt .match = connlimit_mt, 281370786f9SJan Engelhardt .matchsize = sizeof(struct xt_connlimit_info), 282d3c5ee6dSJan Engelhardt .destroy = connlimit_mt_destroy, 283370786f9SJan Engelhardt .me = THIS_MODULE, 284370786f9SJan Engelhardt }, 285370786f9SJan Engelhardt { 286370786f9SJan Engelhardt .name = "connlimit", 287370786f9SJan Engelhardt .family = AF_INET6, 288d3c5ee6dSJan Engelhardt .checkentry = connlimit_mt_check, 289d3c5ee6dSJan Engelhardt .match = connlimit_mt, 290370786f9SJan Engelhardt .matchsize = sizeof(struct xt_connlimit_info), 291d3c5ee6dSJan Engelhardt .destroy = connlimit_mt_destroy, 292370786f9SJan Engelhardt .me = THIS_MODULE, 293370786f9SJan Engelhardt }, 294370786f9SJan Engelhardt }; 295370786f9SJan Engelhardt 296d3c5ee6dSJan Engelhardt static int __init connlimit_mt_init(void) 297370786f9SJan Engelhardt { 298d3c5ee6dSJan Engelhardt return xt_register_matches(connlimit_mt_reg, 299d3c5ee6dSJan Engelhardt ARRAY_SIZE(connlimit_mt_reg)); 300370786f9SJan Engelhardt } 301370786f9SJan Engelhardt 302d3c5ee6dSJan Engelhardt static void __exit connlimit_mt_exit(void) 303370786f9SJan Engelhardt { 304d3c5ee6dSJan Engelhardt xt_unregister_matches(connlimit_mt_reg, ARRAY_SIZE(connlimit_mt_reg)); 305370786f9SJan Engelhardt } 306370786f9SJan Engelhardt 307d3c5ee6dSJan Engelhardt module_init(connlimit_mt_init); 308d3c5ee6dSJan Engelhardt module_exit(connlimit_mt_exit); 309ba5dc275SJan Engelhardt MODULE_AUTHOR("Jan Engelhardt <jengelh@computergmbh.de>"); 3102ae15b64SJan Engelhardt MODULE_DESCRIPTION("Xtables: Number of connections matching"); 311370786f9SJan Engelhardt MODULE_LICENSE("GPL"); 312370786f9SJan Engelhardt MODULE_ALIAS("ipt_connlimit"); 313370786f9SJan Engelhardt MODULE_ALIAS("ip6t_connlimit"); 314