- 根目录:
- net
- netfilter
- xt_connlimit.c
/*
* 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/rbtree.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>
#define CONNLIMIT_SLOTS 256U
#ifdef CONFIG_LOCKDEP
#define CONNLIMIT_LOCK_SLOTS 8U
#else
#define CONNLIMIT_LOCK_SLOTS 256U
#endif
#define CONNLIMIT_GC_MAX_NODES 8
/* 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_rb {
struct rb_node node;
struct hlist_head hhead; /* connections/hosts in same subnet */
union nf_inet_addr addr; /* search key */
};
static spinlock_t xt_connlimit_locks[CONNLIMIT_LOCK_SLOTS] __cacheline_aligned_in_smp;
struct xt_connlimit_data {
struct rb_root climit_root4[CONNLIMIT_SLOTS];
struct rb_root climit_root6[CONNLIMIT_SLOTS];
};
static u_int32_t connlimit_rnd __read_mostly;
static struct kmem_cache *connlimit_rb_cachep __read_mostly;
static struct kmem_cache *connlimit_conn_cachep __read_mostly;
static inline unsigned int connlimit_iphash(__be32 addr)
{
return jhash_1word((__force __u32)addr,
connlimit_rnd) % CONNLIMIT_SLOTS;
}
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) % CONNLIMIT_SLOTS;
}
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 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 ntohl(addr->ip & mask->ip) -
ntohl(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));
}
}
static bool add_hlist(struct hlist_head *head,
const struct nf_conntrack_tuple *tuple,
const union nf_inet_addr *addr)
{
struct xt_connlimit_conn *conn;
conn = kmem_cache_alloc(connlimit_conn_cachep, GFP_ATOMIC);
if (conn == NULL)
return false;
conn->tuple = *tuple;
conn->addr = *addr;
hlist_add_head(&conn->node, head);
return true;
}
static unsigned int check_hlist(struct net *net,
struct hlist_head *head,
const struct nf_conntrack_tuple *tuple,
u16 zone,
bool *addit)
{
const struct nf_conntrack_tuple_hash *found;
struct xt_connlimit_conn *conn;
struct hlist_node *n;
struct nf_conn *found_ct;
unsigned int length = 0;
*addit = true;
rcu_read_lock();
/* check the saved connections */
hlist_for_each_entry_safe(conn, n, head, node) {
found = nf_conntrack_find_get(net, zone, &conn->tuple);
if (found == NULL) {
hlist_del(&conn->node);
kmem_cache_free(connlimit_conn_cachep, conn);
continue;
}
found_ct = nf_ct_tuplehash_to_ctrack(found);
if (nf_ct_tuple_equal(&conn->tuple, tuple)) {
/*
* 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;
} else 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);
kmem_cache_free(connlimit_conn_cachep, conn);
continue;
}
nf_ct_put(found_ct);
length++;
}
rcu_read_unlock();
return length;
}
static void tree_nodes_free(struct rb_root *root,
struct xt_connlimit_rb *gc_nodes[],
unsigned int gc_count)
{
struct xt_connlimit_rb *rbconn;
while (gc_count) {
rbconn = gc_nodes[--gc_count];
rb_erase(&rbconn->node, root);
kmem_cache_free(connlimit_rb_cachep, rbconn);
}
}
static unsigned int
count_tree(struct net *net, struct rb_root *root,
const struct nf_conntrack_tuple *tuple,
const union nf_inet_addr *addr, const union nf_inet_addr *mask,
u8 family, u16 zone)
{
struct xt_connlimit_rb *gc_nodes[CONNLIMIT_GC_MAX_NODES];
struct rb_node **rbnode, *parent;
struct xt_connlimit_rb *rbconn;
struct xt_connlimit_conn *conn;
unsigned int gc_count;
bool no_gc = false;
restart:
gc_count = 0;
parent = NULL;
rbnode = &(root->rb_node);
while (*rbnode) {
int diff;
bool addit;
rbconn = container_of(*rbnode, struct xt_connlimit_rb, node);
parent = *rbnode;
diff = same_source_net(addr, mask, &rbconn->addr, family);
if (diff < 0) {
rbnode = &((*rbnode)->rb_left);
} else if (diff > 0) {
rbnode = &((*rbnode)->rb_right);
} else {
/* same source network -> be counted! */
unsigned int count;
count = check_hlist(net, &rbconn->hhead, tuple, zone, &addit);
tree_nodes_free(root, gc_nodes, gc_count);
if (!addit)
return count;
if (!add_hlist(&rbconn->hhead, tuple, addr))
return 0; /* hotdrop */
return count + 1;
}
if (no_gc || gc_count >= ARRAY_SIZE(gc_nodes))
continue;
/* only used for GC on hhead, retval and 'addit' ignored */
check_hlist(net, &rbconn->hhead, tuple, zone, &addit);
if (hlist_empty(&rbconn->hhead))
gc_nodes[gc_count++] = rbconn;
}
if (gc_count) {
no_gc = true;
tree_nodes_free(root, gc_nodes, gc_count);
/* tree_node_free before new allocation permits
* allocator to re-use newly free'd object.
*
* This is a rare event; in most cases we will find
* existing node to re-use. (or gc_count is 0).
*/
goto restart;
}
/* no match, need to insert new node */
rbconn = kmem_cache_alloc(connlimit_rb_cachep, GFP_ATOMIC);
if (rbconn == NULL)
return 0;
conn = kmem_cache_alloc(connlimit_conn_cachep, GFP_ATOMIC);
if (conn == NULL) {
kmem_cache_free(connlimit_rb_cachep, rbconn);
return 0;
}
conn->tuple = *tuple;
conn->addr = *addr;
rbconn->addr = *addr;
INIT_HLIST_HEAD(&rbconn->hhead);
hlist_add_head(&conn->node, &rbconn->hhead);
rb_link_node(&rbconn->node, parent, rbnode);
rb_insert_color(&rbconn->node, root);
return 1;
}
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, u16 zone)
{
struct rb_root *root;
int count;
u32 hash;
if (family == NFPROTO_IPV6) {
hash = connlimit_iphash6(addr, mask);
root = &data->climit_root6[hash];
} else {
hash = connlimit_iphash(addr->ip & mask->ip);
root = &data->climit_root4[hash];
}
spin_lock_bh(&xt_connlimit_locks[hash % CONNLIMIT_LOCK_SLOTS]);
count = count_tree(net, root, tuple, addr, mask, family, zone);
spin_unlock_bh(&xt_connlimit_locks[hash % CONNLIMIT_LOCK_SLOTS]);
return count;
}
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;
unsigned int connections;
u16 zone = NF_CT_DEFAULT_ZONE;
ct = nf_ct_get(skb, &ctinfo);
if (ct != NULL) {
tuple_ptr = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
zone = nf_ct_zone(ct);
} 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;
}
connections = count_them(net, info->data, tuple_ptr, &addr,
&info->mask, par->family, zone);
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;
}
for (i = 0; i < ARRAY_SIZE(info->data->climit_root4); ++i)
info->data->climit_root4[i] = RB_ROOT;
for (i = 0; i < ARRAY_SIZE(info->data->climit_root6); ++i)
info->data->climit_root6[i] = RB_ROOT;
return 0;
}
static void destroy_tree(struct rb_root *r)
{
struct xt_connlimit_conn *conn;
struct xt_connlimit_rb *rbconn;
struct hlist_node *n;
struct rb_node *node;
while ((node = rb_first(r)) != NULL) {
rbconn = container_of(node, struct xt_connlimit_rb, node);
rb_erase(node, r);
hlist_for_each_entry_safe(conn, n, &rbconn->hhead, node)
kmem_cache_free(connlimit_conn_cachep, conn);
kmem_cache_free(connlimit_rb_cachep, rbconn);
}
}
static void connlimit_mt_destroy(const struct xt_mtdtor_param *par)
{
const struct xt_connlimit_info *info = par->matchinfo;
unsigned int i;
nf_ct_l3proto_module_put(par->family);
for (i = 0; i < ARRAY_SIZE(info->data->climit_root4); ++i)
destroy_tree(&info->data->climit_root4[i]);
for (i = 0; i < ARRAY_SIZE(info->data->climit_root6); ++i)
destroy_tree(&info->data->climit_root6[i]);
kfree(info->data);
}
static struct xt_match connlimit_mt_reg __read_mostly = {
.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)
{
int ret, i;
BUILD_BUG_ON(CONNLIMIT_LOCK_SLOTS > CONNLIMIT_SLOTS);
BUILD_BUG_ON((CONNLIMIT_SLOTS % CONNLIMIT_LOCK_SLOTS) != 0);
for (i = 0; i < CONNLIMIT_LOCK_SLOTS; ++i)
spin_lock_init(&xt_connlimit_locks[i]);
connlimit_conn_cachep = kmem_cache_create("xt_connlimit_conn",
sizeof(struct xt_connlimit_conn),
0, 0, NULL);
if (!connlimit_conn_cachep)
return -ENOMEM;
connlimit_rb_cachep = kmem_cache_create("xt_connlimit_rb",
sizeof(struct xt_connlimit_rb),
0, 0, NULL);
if (!connlimit_rb_cachep) {
kmem_cache_destroy(connlimit_conn_cachep);
return -ENOMEM;
}
ret = xt_register_match(&connlimit_mt_reg);
if (ret != 0) {
kmem_cache_destroy(connlimit_conn_cachep);
kmem_cache_destroy(connlimit_rb_cachep);
}
return ret;
}
static void __exit connlimit_mt_exit(void)
{
xt_unregister_match(&connlimit_mt_reg);
kmem_cache_destroy(connlimit_conn_cachep);
kmem_cache_destroy(connlimit_rb_cachep);
}
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");