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 43294188aeSJan Engelhardt static u_int32_t connlimit_rnd __read_mostly; 44294188aeSJan Engelhardt static bool connlimit_rnd_inited __read_mostly; 45370786f9SJan Engelhardt 46a34c4589SAl Viro static inline unsigned int connlimit_iphash(__be32 addr) 47370786f9SJan Engelhardt { 48a34c4589SAl Viro return jhash_1word((__force __u32)addr, connlimit_rnd) & 0xFF; 49370786f9SJan Engelhardt } 50370786f9SJan Engelhardt 51370786f9SJan Engelhardt static inline unsigned int 52643a2c15SJan Engelhardt connlimit_iphash6(const union nf_inet_addr *addr, 53643a2c15SJan Engelhardt const union nf_inet_addr *mask) 54370786f9SJan Engelhardt { 55643a2c15SJan Engelhardt union nf_inet_addr res; 56370786f9SJan Engelhardt unsigned int i; 57370786f9SJan Engelhardt 58370786f9SJan Engelhardt for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) 59370786f9SJan Engelhardt res.ip6[i] = addr->ip6[i] & mask->ip6[i]; 60370786f9SJan Engelhardt 61a34c4589SAl Viro return jhash2((u32 *)res.ip6, ARRAY_SIZE(res.ip6), connlimit_rnd) & 0xFF; 62370786f9SJan Engelhardt } 63370786f9SJan Engelhardt 64370786f9SJan Engelhardt static inline bool already_closed(const struct nf_conn *conn) 65370786f9SJan Engelhardt { 665e8fbe2aSPatrick McHardy if (nf_ct_protonum(conn) == IPPROTO_TCP) 67d2ee3f2cSDong Wei return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT || 68d2ee3f2cSDong Wei conn->proto.tcp.state == TCP_CONNTRACK_CLOSE; 69370786f9SJan Engelhardt else 70370786f9SJan Engelhardt return 0; 71370786f9SJan Engelhardt } 72370786f9SJan Engelhardt 73370786f9SJan Engelhardt static inline unsigned int 74643a2c15SJan Engelhardt same_source_net(const union nf_inet_addr *addr, 75643a2c15SJan Engelhardt const union nf_inet_addr *mask, 7676108ceaSJan Engelhardt const union nf_inet_addr *u3, u_int8_t family) 77370786f9SJan Engelhardt { 78ee999d8bSJan Engelhardt if (family == NFPROTO_IPV4) { 79370786f9SJan Engelhardt return (addr->ip & mask->ip) == (u3->ip & mask->ip); 80370786f9SJan Engelhardt } else { 81643a2c15SJan Engelhardt union nf_inet_addr lh, rh; 82370786f9SJan Engelhardt unsigned int i; 83370786f9SJan Engelhardt 84370786f9SJan Engelhardt for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) { 85370786f9SJan Engelhardt lh.ip6[i] = addr->ip6[i] & mask->ip6[i]; 86370786f9SJan Engelhardt rh.ip6[i] = u3->ip6[i] & mask->ip6[i]; 87370786f9SJan Engelhardt } 88370786f9SJan Engelhardt 89370786f9SJan Engelhardt return memcmp(&lh.ip6, &rh.ip6, sizeof(lh.ip6)) == 0; 90370786f9SJan Engelhardt } 91370786f9SJan Engelhardt } 92370786f9SJan Engelhardt 93370786f9SJan Engelhardt static int count_them(struct xt_connlimit_data *data, 94370786f9SJan Engelhardt const struct nf_conntrack_tuple *tuple, 95643a2c15SJan Engelhardt const union nf_inet_addr *addr, 96643a2c15SJan Engelhardt const union nf_inet_addr *mask, 97539054a8SJan Engelhardt u_int8_t family) 98370786f9SJan Engelhardt { 993cf93c96SJan Engelhardt const struct nf_conntrack_tuple_hash *found; 100370786f9SJan Engelhardt struct xt_connlimit_conn *conn; 101370786f9SJan Engelhardt struct xt_connlimit_conn *tmp; 102ea781f19SEric Dumazet struct nf_conn *found_ct; 103370786f9SJan Engelhardt struct list_head *hash; 104370786f9SJan Engelhardt bool addit = true; 105370786f9SJan Engelhardt int matches = 0; 106370786f9SJan Engelhardt 107539054a8SJan Engelhardt if (family == NFPROTO_IPV6) 108370786f9SJan Engelhardt hash = &data->iphash[connlimit_iphash6(addr, mask)]; 109370786f9SJan Engelhardt else 110370786f9SJan Engelhardt hash = &data->iphash[connlimit_iphash(addr->ip & mask->ip)]; 111370786f9SJan Engelhardt 11276507f69SPatrick McHardy rcu_read_lock(); 113370786f9SJan Engelhardt 114370786f9SJan Engelhardt /* check the saved connections */ 115370786f9SJan Engelhardt list_for_each_entry_safe(conn, tmp, hash, list) { 116ea781f19SEric Dumazet found = nf_conntrack_find_get(&init_net, &conn->tuple); 117370786f9SJan Engelhardt found_ct = NULL; 118370786f9SJan Engelhardt 119370786f9SJan Engelhardt if (found != NULL) 120370786f9SJan Engelhardt found_ct = nf_ct_tuplehash_to_ctrack(found); 121370786f9SJan Engelhardt 122370786f9SJan Engelhardt if (found_ct != NULL && 123370786f9SJan Engelhardt nf_ct_tuple_equal(&conn->tuple, tuple) && 124370786f9SJan Engelhardt !already_closed(found_ct)) 125370786f9SJan Engelhardt /* 126370786f9SJan Engelhardt * Just to be sure we have it only once in the list. 127370786f9SJan Engelhardt * We should not see tuples twice unless someone hooks 128370786f9SJan Engelhardt * this into a table without "-p tcp --syn". 129370786f9SJan Engelhardt */ 130370786f9SJan Engelhardt addit = false; 131370786f9SJan Engelhardt 132370786f9SJan Engelhardt if (found == NULL) { 133370786f9SJan Engelhardt /* this one is gone */ 134370786f9SJan Engelhardt list_del(&conn->list); 135370786f9SJan Engelhardt kfree(conn); 136370786f9SJan Engelhardt continue; 137370786f9SJan Engelhardt } 138370786f9SJan Engelhardt 139370786f9SJan Engelhardt if (already_closed(found_ct)) { 140370786f9SJan Engelhardt /* 141370786f9SJan Engelhardt * we do not care about connections which are 142370786f9SJan Engelhardt * closed already -> ditch it 143370786f9SJan Engelhardt */ 144ea781f19SEric Dumazet nf_ct_put(found_ct); 145370786f9SJan Engelhardt list_del(&conn->list); 146370786f9SJan Engelhardt kfree(conn); 147370786f9SJan Engelhardt continue; 148370786f9SJan Engelhardt } 149370786f9SJan Engelhardt 150539054a8SJan Engelhardt if (same_source_net(addr, mask, &conn->tuple.src.u3, family)) 151370786f9SJan Engelhardt /* same source network -> be counted! */ 152370786f9SJan Engelhardt ++matches; 153ea781f19SEric Dumazet nf_ct_put(found_ct); 154370786f9SJan Engelhardt } 155370786f9SJan Engelhardt 15676507f69SPatrick McHardy rcu_read_unlock(); 157370786f9SJan Engelhardt 158370786f9SJan Engelhardt if (addit) { 159370786f9SJan Engelhardt /* save the new connection in our list */ 160370786f9SJan Engelhardt conn = kzalloc(sizeof(*conn), GFP_ATOMIC); 161370786f9SJan Engelhardt if (conn == NULL) 162370786f9SJan Engelhardt return -ENOMEM; 163370786f9SJan Engelhardt conn->tuple = *tuple; 164370786f9SJan Engelhardt list_add(&conn->list, hash); 165370786f9SJan Engelhardt ++matches; 166370786f9SJan Engelhardt } 167370786f9SJan Engelhardt 168370786f9SJan Engelhardt return matches; 169370786f9SJan Engelhardt } 170370786f9SJan Engelhardt 171d3c5ee6dSJan Engelhardt static bool 172f7108a20SJan Engelhardt connlimit_mt(const struct sk_buff *skb, const struct xt_match_param *par) 173370786f9SJan Engelhardt { 174f7108a20SJan Engelhardt const struct xt_connlimit_info *info = par->matchinfo; 17522c2d8bcSJan Engelhardt union nf_inet_addr addr; 176370786f9SJan Engelhardt struct nf_conntrack_tuple tuple; 177370786f9SJan Engelhardt const struct nf_conntrack_tuple *tuple_ptr = &tuple; 178370786f9SJan Engelhardt enum ip_conntrack_info ctinfo; 179370786f9SJan Engelhardt const struct nf_conn *ct; 180370786f9SJan Engelhardt int connections; 181370786f9SJan Engelhardt 182370786f9SJan Engelhardt ct = nf_ct_get(skb, &ctinfo); 183370786f9SJan Engelhardt if (ct != NULL) 184370786f9SJan Engelhardt tuple_ptr = &ct->tuplehash[0].tuple; 185370786f9SJan Engelhardt else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb), 18692f3b2b1SJan Engelhardt par->family, &tuple)) 187370786f9SJan Engelhardt goto hotdrop; 188370786f9SJan Engelhardt 18992f3b2b1SJan Engelhardt if (par->family == NFPROTO_IPV6) { 190370786f9SJan Engelhardt const struct ipv6hdr *iph = ipv6_hdr(skb); 191370786f9SJan Engelhardt memcpy(&addr.ip6, &iph->saddr, sizeof(iph->saddr)); 192370786f9SJan Engelhardt } else { 193370786f9SJan Engelhardt const struct iphdr *iph = ip_hdr(skb); 194370786f9SJan Engelhardt addr.ip = iph->saddr; 195370786f9SJan Engelhardt } 196370786f9SJan Engelhardt 197370786f9SJan Engelhardt spin_lock_bh(&info->data->lock); 19822c2d8bcSJan Engelhardt connections = count_them(info->data, tuple_ptr, &addr, 199539054a8SJan Engelhardt &info->mask, par->family); 200370786f9SJan Engelhardt spin_unlock_bh(&info->data->lock); 201370786f9SJan Engelhardt 202370786f9SJan Engelhardt if (connections < 0) { 203370786f9SJan Engelhardt /* kmalloc failed, drop it entirely */ 204f7108a20SJan Engelhardt *par->hotdrop = true; 205370786f9SJan Engelhardt return false; 206370786f9SJan Engelhardt } 207370786f9SJan Engelhardt 208370786f9SJan Engelhardt return (connections > info->limit) ^ info->inverse; 209370786f9SJan Engelhardt 210370786f9SJan Engelhardt hotdrop: 211f7108a20SJan Engelhardt *par->hotdrop = true; 212370786f9SJan Engelhardt return false; 213370786f9SJan Engelhardt } 214370786f9SJan Engelhardt 2159b4fce7aSJan Engelhardt static bool connlimit_mt_check(const struct xt_mtchk_param *par) 216370786f9SJan Engelhardt { 2179b4fce7aSJan Engelhardt struct xt_connlimit_info *info = par->matchinfo; 218370786f9SJan Engelhardt unsigned int i; 219370786f9SJan Engelhardt 220294188aeSJan Engelhardt if (unlikely(!connlimit_rnd_inited)) { 221294188aeSJan Engelhardt get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd)); 222294188aeSJan Engelhardt connlimit_rnd_inited = true; 223294188aeSJan Engelhardt } 22492f3b2b1SJan Engelhardt if (nf_ct_l3proto_try_module_get(par->family) < 0) { 225370786f9SJan Engelhardt printk(KERN_WARNING "cannot load conntrack support for " 22692f3b2b1SJan Engelhardt "address family %u\n", par->family); 227370786f9SJan Engelhardt return false; 228370786f9SJan Engelhardt } 229370786f9SJan Engelhardt 230370786f9SJan Engelhardt /* init private data */ 231370786f9SJan Engelhardt info->data = kmalloc(sizeof(struct xt_connlimit_data), GFP_KERNEL); 232370786f9SJan Engelhardt if (info->data == NULL) { 23392f3b2b1SJan Engelhardt nf_ct_l3proto_module_put(par->family); 234370786f9SJan Engelhardt return false; 235370786f9SJan Engelhardt } 236370786f9SJan Engelhardt 237370786f9SJan Engelhardt spin_lock_init(&info->data->lock); 238370786f9SJan Engelhardt for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) 239370786f9SJan Engelhardt INIT_LIST_HEAD(&info->data->iphash[i]); 240370786f9SJan Engelhardt 241370786f9SJan Engelhardt return true; 242370786f9SJan Engelhardt } 243370786f9SJan Engelhardt 2446be3d859SJan Engelhardt static void connlimit_mt_destroy(const struct xt_mtdtor_param *par) 245370786f9SJan Engelhardt { 2466be3d859SJan Engelhardt const struct xt_connlimit_info *info = par->matchinfo; 247370786f9SJan Engelhardt struct xt_connlimit_conn *conn; 248370786f9SJan Engelhardt struct xt_connlimit_conn *tmp; 249370786f9SJan Engelhardt struct list_head *hash = info->data->iphash; 250370786f9SJan Engelhardt unsigned int i; 251370786f9SJan Engelhardt 25292f3b2b1SJan Engelhardt nf_ct_l3proto_module_put(par->family); 253370786f9SJan Engelhardt 254370786f9SJan Engelhardt for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) { 255370786f9SJan Engelhardt list_for_each_entry_safe(conn, tmp, &hash[i], list) { 256370786f9SJan Engelhardt list_del(&conn->list); 257370786f9SJan Engelhardt kfree(conn); 258370786f9SJan Engelhardt } 259370786f9SJan Engelhardt } 260370786f9SJan Engelhardt 261370786f9SJan Engelhardt kfree(info->data); 262370786f9SJan Engelhardt } 263370786f9SJan Engelhardt 26492f3b2b1SJan Engelhardt static struct xt_match connlimit_mt_reg __read_mostly = { 265370786f9SJan Engelhardt .name = "connlimit", 26692f3b2b1SJan Engelhardt .revision = 0, 26792f3b2b1SJan Engelhardt .family = NFPROTO_UNSPEC, 268d3c5ee6dSJan Engelhardt .checkentry = connlimit_mt_check, 269d3c5ee6dSJan Engelhardt .match = connlimit_mt, 270370786f9SJan Engelhardt .matchsize = sizeof(struct xt_connlimit_info), 271d3c5ee6dSJan Engelhardt .destroy = connlimit_mt_destroy, 272370786f9SJan Engelhardt .me = THIS_MODULE, 273370786f9SJan Engelhardt }; 274370786f9SJan Engelhardt 275d3c5ee6dSJan Engelhardt static int __init connlimit_mt_init(void) 276370786f9SJan Engelhardt { 27792f3b2b1SJan Engelhardt return xt_register_match(&connlimit_mt_reg); 278370786f9SJan Engelhardt } 279370786f9SJan Engelhardt 280d3c5ee6dSJan Engelhardt static void __exit connlimit_mt_exit(void) 281370786f9SJan Engelhardt { 28292f3b2b1SJan Engelhardt xt_unregister_match(&connlimit_mt_reg); 283370786f9SJan Engelhardt } 284370786f9SJan Engelhardt 285d3c5ee6dSJan Engelhardt module_init(connlimit_mt_init); 286d3c5ee6dSJan Engelhardt module_exit(connlimit_mt_exit); 28792f3b2b1SJan Engelhardt MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>"); 2882ae15b64SJan Engelhardt MODULE_DESCRIPTION("Xtables: Number of connections matching"); 289370786f9SJan Engelhardt MODULE_LICENSE("GPL"); 290370786f9SJan Engelhardt MODULE_ALIAS("ipt_connlimit"); 291370786f9SJan Engelhardt MODULE_ALIAS("ip6t_connlimit"); 292