diff options
Diffstat (limited to 'net/netfilter/xt_connlimit.c')
-rw-r--r-- | net/netfilter/xt_connlimit.c | 313 |
1 files changed, 313 insertions, 0 deletions
diff --git a/net/netfilter/xt_connlimit.c b/net/netfilter/xt_connlimit.c new file mode 100644 index 000000000000..3335dd5be962 --- /dev/null +++ b/net/netfilter/xt_connlimit.c @@ -0,0 +1,313 @@ +/* + * 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 + * Copyright © Jan Engelhardt <jengelh@gmx.de>, 2007 + * + * based on ... + * + * Kernel module to match connection tracking information. + * GPL (C) 1999 Rusty Russell (rusty@rustcorp.com.au). + */ +#include <linux/in.h> +#include <linux/in6.h> +#include <linux/ip.h> +#include <linux/ipv6.h> +#include <linux/jhash.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> + +/* we will save the tuples of all connections we care about */ +struct xt_connlimit_conn { + struct list_head list; + struct nf_conntrack_tuple tuple; +}; + +struct xt_connlimit_data { + struct list_head iphash[256]; + spinlock_t lock; +}; + +static u_int32_t connlimit_rnd; +static bool connlimit_rnd_inited; + +static inline unsigned int connlimit_iphash(u_int32_t addr) +{ + if (unlikely(!connlimit_rnd_inited)) { + get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd)); + connlimit_rnd_inited = true; + } + return jhash_1word(addr, connlimit_rnd) & 0xFF; +} + +static inline unsigned int +connlimit_iphash6(const union nf_conntrack_address *addr, + const union nf_conntrack_address *mask) +{ + union nf_conntrack_address res; + unsigned int i; + + if (unlikely(!connlimit_rnd_inited)) { + get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd)); + connlimit_rnd_inited = true; + } + + for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) + res.ip6[i] = addr->ip6[i] & mask->ip6[i]; + + return jhash2(res.ip6, ARRAY_SIZE(res.ip6), connlimit_rnd) & 0xFF; +} + +static inline bool already_closed(const struct nf_conn *conn) +{ + u_int16_t proto = conn->tuplehash[0].tuple.dst.protonum; + + if (proto == IPPROTO_TCP) + return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT; + else + return 0; +} + +static inline unsigned int +same_source_net(const union nf_conntrack_address *addr, + const union nf_conntrack_address *mask, + const union nf_conntrack_address *u3, unsigned int family) +{ + if (family == AF_INET) { + return (addr->ip & mask->ip) == (u3->ip & mask->ip); + } else { + union nf_conntrack_address 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 xt_connlimit_data *data, + const struct nf_conntrack_tuple *tuple, + const union nf_conntrack_address *addr, + const union nf_conntrack_address *mask, + const struct xt_match *match) +{ + struct nf_conntrack_tuple_hash *found; + struct xt_connlimit_conn *conn; + struct xt_connlimit_conn *tmp; + struct nf_conn *found_ct; + struct list_head *hash; + bool addit = true; + int matches = 0; + + + if (match->family == AF_INET6) + hash = &data->iphash[connlimit_iphash6(addr, mask)]; + else + hash = &data->iphash[connlimit_iphash(addr->ip & mask->ip)]; + + read_lock_bh(&nf_conntrack_lock); + + /* check the saved connections */ + list_for_each_entry_safe(conn, tmp, hash, list) { + found = __nf_conntrack_find(&conn->tuple, NULL); + 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 */ + list_del(&conn->list); + kfree(conn); + continue; + } + + if (already_closed(found_ct)) { + /* + * we do not care about connections which are + * closed already -> ditch it + */ + list_del(&conn->list); + kfree(conn); + continue; + } + + if (same_source_net(addr, mask, &conn->tuple.src.u3, + match->family)) + /* same source network -> be counted! */ + ++matches; + } + + read_unlock_bh(&nf_conntrack_lock); + + if (addit) { + /* save the new connection in our list */ + conn = kzalloc(sizeof(*conn), GFP_ATOMIC); + if (conn == NULL) + return -ENOMEM; + conn->tuple = *tuple; + list_add(&conn->list, hash); + ++matches; + } + + return matches; +} + +static bool connlimit_match(const struct sk_buff *skb, + const struct net_device *in, + const struct net_device *out, + const struct xt_match *match, + const void *matchinfo, int offset, + unsigned int protoff, bool *hotdrop) +{ + const struct xt_connlimit_info *info = matchinfo; + union nf_conntrack_address addr, mask; + 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[0].tuple; + else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb), + match->family, &tuple)) + goto hotdrop; + + if (match->family == AF_INET6) { + const struct ipv6hdr *iph = ipv6_hdr(skb); + memcpy(&addr.ip6, &iph->saddr, sizeof(iph->saddr)); + memcpy(&mask.ip6, info->v6_mask, sizeof(info->v6_mask)); + } else { + const struct iphdr *iph = ip_hdr(skb); + addr.ip = iph->saddr; + mask.ip = info->v4_mask; + } + + spin_lock_bh(&info->data->lock); + connections = count_them(info->data, tuple_ptr, &addr, &mask, match); + spin_unlock_bh(&info->data->lock); + + if (connections < 0) { + /* kmalloc failed, drop it entirely */ + *hotdrop = true; + return false; + } + + return (connections > info->limit) ^ info->inverse; + + hotdrop: + *hotdrop = true; + return false; +} + +static bool connlimit_check(const char *tablename, const void *ip, + const struct xt_match *match, void *matchinfo, + unsigned int hook_mask) +{ + struct xt_connlimit_info *info = matchinfo; + unsigned int i; + + if (nf_ct_l3proto_try_module_get(match->family) < 0) { + printk(KERN_WARNING "cannot load conntrack support for " + "address family %u\n", match->family); + return false; + } + + /* init private data */ + info->data = kmalloc(sizeof(struct xt_connlimit_data), GFP_KERNEL); + if (info->data == NULL) { + nf_ct_l3proto_module_put(match->family); + return false; + } + + spin_lock_init(&info->data->lock); + for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) + INIT_LIST_HEAD(&info->data->iphash[i]); + + return true; +} + +static void connlimit_destroy(const struct xt_match *match, void *matchinfo) +{ + struct xt_connlimit_info *info = matchinfo; + struct xt_connlimit_conn *conn; + struct xt_connlimit_conn *tmp; + struct list_head *hash = info->data->iphash; + unsigned int i; + + nf_ct_l3proto_module_put(match->family); + + for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) { + list_for_each_entry_safe(conn, tmp, &hash[i], list) { + list_del(&conn->list); + kfree(conn); + } + } + + kfree(info->data); +} + +static struct xt_match connlimit_reg[] __read_mostly = { + { + .name = "connlimit", + .family = AF_INET, + .checkentry = connlimit_check, + .match = connlimit_match, + .matchsize = sizeof(struct xt_connlimit_info), + .destroy = connlimit_destroy, + .me = THIS_MODULE, + }, + { + .name = "connlimit", + .family = AF_INET6, + .checkentry = connlimit_check, + .match = connlimit_match, + .matchsize = sizeof(struct xt_connlimit_info), + .destroy = connlimit_destroy, + .me = THIS_MODULE, + }, +}; + +static int __init xt_connlimit_init(void) +{ + return xt_register_matches(connlimit_reg, ARRAY_SIZE(connlimit_reg)); +} + +static void __exit xt_connlimit_exit(void) +{ + xt_unregister_matches(connlimit_reg, ARRAY_SIZE(connlimit_reg)); +} + +module_init(xt_connlimit_init); +module_exit(xt_connlimit_exit); +MODULE_AUTHOR("Jan Engelhardt <jengelh@gmx.de>"); +MODULE_DESCRIPTION("netfilter xt_connlimit match module"); +MODULE_LICENSE("GPL"); +MODULE_ALIAS("ipt_connlimit"); +MODULE_ALIAS("ip6t_connlimit"); |