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* 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
* Contact: <jengelh@computergmbh.de>
*
* 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(__be32 addr)
{
if (unlikely(!connlimit_rnd_inited)) {
get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd));
connlimit_rnd_inited = true;
}
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;
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((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, unsigned int family)
{
if (family == AF_INET) {
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 xt_connlimit_data *data,
const struct nf_conntrack_tuple *tuple,
const union nf_inet_addr *addr,
const union nf_inet_addr *mask,
const struct xt_match *match)
{
const struct nf_conntrack_tuple_hash *found;
struct xt_connlimit_conn *conn;
struct xt_connlimit_conn *tmp;
const 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)];
rcu_read_lock();
/* check the saved connections */
list_for_each_entry_safe(conn, tmp, hash, list) {
found = __nf_conntrack_find(&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 */
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;
}
rcu_read_unlock();
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_mt(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_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[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));
} else {
const struct iphdr *iph = ip_hdr(skb);
addr.ip = iph->saddr;
}
spin_lock_bh(&info->data->lock);
connections = count_them(info->data, tuple_ptr, &addr,
&info->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_mt_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_mt_destroy(const struct xt_match *match, void *matchinfo)
{
const 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_mt_reg[] __read_mostly = {
{
.name = "connlimit",
.family = AF_INET,
.checkentry = connlimit_mt_check,
.match = connlimit_mt,
.matchsize = sizeof(struct xt_connlimit_info),
.destroy = connlimit_mt_destroy,
.me = THIS_MODULE,
},
{
.name = "connlimit",
.family = AF_INET6,
.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@computergmbh.de>");
MODULE_DESCRIPTION("Xtables: Number of connections matching");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ipt_connlimit");
MODULE_ALIAS("ip6t_connlimit");
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