diff options
Diffstat (limited to 'net/netfilter/xt_connlimit.c')
-rw-r--r-- | net/netfilter/xt_connlimit.c | 317 |
1 files changed, 317 insertions, 0 deletions
diff --git a/net/netfilter/xt_connlimit.c b/net/netfilter/xt_connlimit.c new file mode 100644 index 00000000..c6d5a834 --- /dev/null +++ b/net/netfilter/xt_connlimit.c @@ -0,0 +1,317 @@ +/* + * netfilter module to limit the number of parallel tcp + * connections per IP address. + * (c) 2000 Gerd Knorr <kraxel@bytesex.org> + * Nov 2002: Martin Bene <martin.bene@icomedias.com>: + * only ignore TIME_WAIT or gone connections + * (C) CC Computer Consultants GmbH, 2007 + * + * based on ... + * + * Kernel module to match connection tracking information. + * GPL (C) 1999 Rusty Russell (rusty@rustcorp.com.au). + */ +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt +#include <linux/in.h> +#include <linux/in6.h> +#include <linux/ip.h> +#include <linux/ipv6.h> +#include <linux/jhash.h> +#include <linux/slab.h> +#include <linux/list.h> +#include <linux/module.h> +#include <linux/random.h> +#include <linux/skbuff.h> +#include <linux/spinlock.h> +#include <linux/netfilter/nf_conntrack_tcp.h> +#include <linux/netfilter/x_tables.h> +#include <linux/netfilter/xt_connlimit.h> +#include <net/netfilter/nf_conntrack.h> +#include <net/netfilter/nf_conntrack_core.h> +#include <net/netfilter/nf_conntrack_tuple.h> +#include <net/netfilter/nf_conntrack_zones.h> + +/* we will save the tuples of all connections we care about */ +struct xt_connlimit_conn { + struct hlist_node node; + struct nf_conntrack_tuple tuple; + union nf_inet_addr addr; +}; + +struct xt_connlimit_data { + struct hlist_head iphash[256]; + spinlock_t lock; +}; + +static u_int32_t connlimit_rnd __read_mostly; + +static inline unsigned int connlimit_iphash(__be32 addr) +{ + return jhash_1word((__force __u32)addr, connlimit_rnd) & 0xFF; +} + +static inline unsigned int +connlimit_iphash6(const union nf_inet_addr *addr, + const union nf_inet_addr *mask) +{ + union nf_inet_addr res; + unsigned int i; + + for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) + res.ip6[i] = addr->ip6[i] & mask->ip6[i]; + + return jhash2((u32 *)res.ip6, ARRAY_SIZE(res.ip6), connlimit_rnd) & 0xFF; +} + +static inline bool already_closed(const struct nf_conn *conn) +{ + if (nf_ct_protonum(conn) == IPPROTO_TCP) + return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT || + conn->proto.tcp.state == TCP_CONNTRACK_CLOSE; + else + return 0; +} + +static inline unsigned int +same_source_net(const union nf_inet_addr *addr, + const union nf_inet_addr *mask, + const union nf_inet_addr *u3, u_int8_t family) +{ + if (family == NFPROTO_IPV4) { + return (addr->ip & mask->ip) == (u3->ip & mask->ip); + } else { + union nf_inet_addr lh, rh; + unsigned int i; + + for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) { + lh.ip6[i] = addr->ip6[i] & mask->ip6[i]; + rh.ip6[i] = u3->ip6[i] & mask->ip6[i]; + } + + return memcmp(&lh.ip6, &rh.ip6, sizeof(lh.ip6)) == 0; + } +} + +static int count_them(struct net *net, + struct xt_connlimit_data *data, + const struct nf_conntrack_tuple *tuple, + const union nf_inet_addr *addr, + const union nf_inet_addr *mask, + u_int8_t family) +{ + const struct nf_conntrack_tuple_hash *found; + struct xt_connlimit_conn *conn; + struct hlist_node *pos, *n; + struct nf_conn *found_ct; + struct hlist_head *hash; + bool addit = true; + int matches = 0; + + if (family == NFPROTO_IPV6) + hash = &data->iphash[connlimit_iphash6(addr, mask)]; + else + hash = &data->iphash[connlimit_iphash(addr->ip & mask->ip)]; + + rcu_read_lock(); + + /* check the saved connections */ + hlist_for_each_entry_safe(conn, pos, n, hash, node) { + found = nf_conntrack_find_get(net, NF_CT_DEFAULT_ZONE, + &conn->tuple); + found_ct = NULL; + + if (found != NULL) + found_ct = nf_ct_tuplehash_to_ctrack(found); + + if (found_ct != NULL && + nf_ct_tuple_equal(&conn->tuple, tuple) && + !already_closed(found_ct)) + /* + * Just to be sure we have it only once in the list. + * We should not see tuples twice unless someone hooks + * this into a table without "-p tcp --syn". + */ + addit = false; + + if (found == NULL) { + /* this one is gone */ + hlist_del(&conn->node); + kfree(conn); + continue; + } + + if (already_closed(found_ct)) { + /* + * we do not care about connections which are + * closed already -> ditch it + */ + nf_ct_put(found_ct); + hlist_del(&conn->node); + kfree(conn); + continue; + } + + if (same_source_net(addr, mask, &conn->addr, family)) + /* same source network -> be counted! */ + ++matches; + nf_ct_put(found_ct); + } + + rcu_read_unlock(); + + if (addit) { + /* save the new connection in our list */ + conn = kmalloc(sizeof(*conn), GFP_ATOMIC); + if (conn == NULL) + return -ENOMEM; + conn->tuple = *tuple; + conn->addr = *addr; + hlist_add_head(&conn->node, hash); + ++matches; + } + + return matches; +} + +static bool +connlimit_mt(const struct sk_buff *skb, struct xt_action_param *par) +{ + struct net *net = dev_net(par->in ? par->in : par->out); + const struct xt_connlimit_info *info = par->matchinfo; + union nf_inet_addr addr; + struct nf_conntrack_tuple tuple; + const struct nf_conntrack_tuple *tuple_ptr = &tuple; + enum ip_conntrack_info ctinfo; + const struct nf_conn *ct; + int connections; + + ct = nf_ct_get(skb, &ctinfo); + if (ct != NULL) + tuple_ptr = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple; + else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb), + par->family, &tuple)) + goto hotdrop; + + if (par->family == NFPROTO_IPV6) { + const struct ipv6hdr *iph = ipv6_hdr(skb); + memcpy(&addr.ip6, (info->flags & XT_CONNLIMIT_DADDR) ? + &iph->daddr : &iph->saddr, sizeof(addr.ip6)); + } else { + const struct iphdr *iph = ip_hdr(skb); + addr.ip = (info->flags & XT_CONNLIMIT_DADDR) ? + iph->daddr : iph->saddr; + } + + spin_lock_bh(&info->data->lock); + connections = count_them(net, info->data, tuple_ptr, &addr, + &info->mask, par->family); + spin_unlock_bh(&info->data->lock); + + if (connections < 0) + /* kmalloc failed, drop it entirely */ + goto hotdrop; + + return (connections > info->limit) ^ + !!(info->flags & XT_CONNLIMIT_INVERT); + + hotdrop: + par->hotdrop = true; + return false; +} + +static int connlimit_mt_check(const struct xt_mtchk_param *par) +{ + struct xt_connlimit_info *info = par->matchinfo; + unsigned int i; + int ret; + + if (unlikely(!connlimit_rnd)) { + u_int32_t rand; + + do { + get_random_bytes(&rand, sizeof(rand)); + } while (!rand); + cmpxchg(&connlimit_rnd, 0, rand); + } + ret = nf_ct_l3proto_try_module_get(par->family); + if (ret < 0) { + pr_info("cannot load conntrack support for " + "address family %u\n", par->family); + return ret; + } + + /* init private data */ + info->data = kmalloc(sizeof(struct xt_connlimit_data), GFP_KERNEL); + if (info->data == NULL) { + nf_ct_l3proto_module_put(par->family); + return -ENOMEM; + } + + spin_lock_init(&info->data->lock); + for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) + INIT_HLIST_HEAD(&info->data->iphash[i]); + + return 0; +} + +static void connlimit_mt_destroy(const struct xt_mtdtor_param *par) +{ + const struct xt_connlimit_info *info = par->matchinfo; + struct xt_connlimit_conn *conn; + struct hlist_node *pos, *n; + struct hlist_head *hash = info->data->iphash; + unsigned int i; + + nf_ct_l3proto_module_put(par->family); + + for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) { + hlist_for_each_entry_safe(conn, pos, n, &hash[i], node) { + hlist_del(&conn->node); + kfree(conn); + } + } + + kfree(info->data); +} + +static struct xt_match connlimit_mt_reg[] __read_mostly = { + { + .name = "connlimit", + .revision = 0, + .family = NFPROTO_UNSPEC, + .checkentry = connlimit_mt_check, + .match = connlimit_mt, + .matchsize = sizeof(struct xt_connlimit_info), + .destroy = connlimit_mt_destroy, + .me = THIS_MODULE, + }, + { + .name = "connlimit", + .revision = 1, + .family = NFPROTO_UNSPEC, + .checkentry = connlimit_mt_check, + .match = connlimit_mt, + .matchsize = sizeof(struct xt_connlimit_info), + .destroy = connlimit_mt_destroy, + .me = THIS_MODULE, + }, +}; + +static int __init connlimit_mt_init(void) +{ + return xt_register_matches(connlimit_mt_reg, + ARRAY_SIZE(connlimit_mt_reg)); +} + +static void __exit connlimit_mt_exit(void) +{ + xt_unregister_matches(connlimit_mt_reg, ARRAY_SIZE(connlimit_mt_reg)); +} + +module_init(connlimit_mt_init); +module_exit(connlimit_mt_exit); +MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>"); +MODULE_DESCRIPTION("Xtables: Number of connections matching"); +MODULE_LICENSE("GPL"); +MODULE_ALIAS("ipt_connlimit"); +MODULE_ALIAS("ip6t_connlimit"); |