![Patrick McHardy](/assets/img/avatar_default.png)
As a last step of preventing DoS by creating lots of expectations, this patch introduces a global maximum and a sysctl to control it. The default is initialized to 4 * the expectation hash table size, which results in 1/64 of the default maxmimum of conntracks. Signed-off-by: Patrick McHardy <kaber@trash.net> Signed-off-by: David S. Miller <davem@davemloft.net>
569 lines
14 KiB
C
569 lines
14 KiB
C
/* Expectation handling for nf_conntrack. */
|
|
|
|
/* (C) 1999-2001 Paul `Rusty' Russell
|
|
* (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
|
|
* (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License version 2 as
|
|
* published by the Free Software Foundation.
|
|
*/
|
|
|
|
#include <linux/types.h>
|
|
#include <linux/netfilter.h>
|
|
#include <linux/skbuff.h>
|
|
#include <linux/proc_fs.h>
|
|
#include <linux/seq_file.h>
|
|
#include <linux/stddef.h>
|
|
#include <linux/slab.h>
|
|
#include <linux/err.h>
|
|
#include <linux/percpu.h>
|
|
#include <linux/kernel.h>
|
|
#include <linux/jhash.h>
|
|
|
|
#include <net/netfilter/nf_conntrack.h>
|
|
#include <net/netfilter/nf_conntrack_core.h>
|
|
#include <net/netfilter/nf_conntrack_expect.h>
|
|
#include <net/netfilter/nf_conntrack_helper.h>
|
|
#include <net/netfilter/nf_conntrack_tuple.h>
|
|
|
|
struct hlist_head *nf_ct_expect_hash __read_mostly;
|
|
EXPORT_SYMBOL_GPL(nf_ct_expect_hash);
|
|
|
|
unsigned int nf_ct_expect_hsize __read_mostly;
|
|
EXPORT_SYMBOL_GPL(nf_ct_expect_hsize);
|
|
|
|
static unsigned int nf_ct_expect_hash_rnd __read_mostly;
|
|
static unsigned int nf_ct_expect_count;
|
|
unsigned int nf_ct_expect_max __read_mostly;
|
|
static int nf_ct_expect_hash_rnd_initted __read_mostly;
|
|
static int nf_ct_expect_vmalloc;
|
|
|
|
static struct kmem_cache *nf_ct_expect_cachep __read_mostly;
|
|
static unsigned int nf_ct_expect_next_id;
|
|
|
|
/* nf_conntrack_expect helper functions */
|
|
void nf_ct_unlink_expect(struct nf_conntrack_expect *exp)
|
|
{
|
|
struct nf_conn_help *master_help = nfct_help(exp->master);
|
|
|
|
NF_CT_ASSERT(master_help);
|
|
NF_CT_ASSERT(!timer_pending(&exp->timeout));
|
|
|
|
hlist_del(&exp->hnode);
|
|
nf_ct_expect_count--;
|
|
|
|
hlist_del(&exp->lnode);
|
|
master_help->expecting--;
|
|
nf_ct_expect_put(exp);
|
|
|
|
NF_CT_STAT_INC(expect_delete);
|
|
}
|
|
EXPORT_SYMBOL_GPL(nf_ct_unlink_expect);
|
|
|
|
static void nf_ct_expectation_timed_out(unsigned long ul_expect)
|
|
{
|
|
struct nf_conntrack_expect *exp = (void *)ul_expect;
|
|
|
|
write_lock_bh(&nf_conntrack_lock);
|
|
nf_ct_unlink_expect(exp);
|
|
write_unlock_bh(&nf_conntrack_lock);
|
|
nf_ct_expect_put(exp);
|
|
}
|
|
|
|
static unsigned int nf_ct_expect_dst_hash(const struct nf_conntrack_tuple *tuple)
|
|
{
|
|
if (unlikely(!nf_ct_expect_hash_rnd_initted)) {
|
|
get_random_bytes(&nf_ct_expect_hash_rnd, 4);
|
|
nf_ct_expect_hash_rnd_initted = 1;
|
|
}
|
|
|
|
return jhash2(tuple->dst.u3.all, ARRAY_SIZE(tuple->dst.u3.all),
|
|
(((tuple->dst.protonum ^ tuple->src.l3num) << 16) |
|
|
tuple->dst.u.all) ^ nf_ct_expect_hash_rnd) %
|
|
nf_ct_expect_hsize;
|
|
}
|
|
|
|
struct nf_conntrack_expect *
|
|
__nf_ct_expect_find(const struct nf_conntrack_tuple *tuple)
|
|
{
|
|
struct nf_conntrack_expect *i;
|
|
struct hlist_node *n;
|
|
unsigned int h;
|
|
|
|
if (!nf_ct_expect_count)
|
|
return NULL;
|
|
|
|
h = nf_ct_expect_dst_hash(tuple);
|
|
hlist_for_each_entry(i, n, &nf_ct_expect_hash[h], hnode) {
|
|
if (nf_ct_tuple_mask_cmp(tuple, &i->tuple, &i->mask))
|
|
return i;
|
|
}
|
|
return NULL;
|
|
}
|
|
EXPORT_SYMBOL_GPL(__nf_ct_expect_find);
|
|
|
|
/* Just find a expectation corresponding to a tuple. */
|
|
struct nf_conntrack_expect *
|
|
nf_ct_expect_find_get(const struct nf_conntrack_tuple *tuple)
|
|
{
|
|
struct nf_conntrack_expect *i;
|
|
|
|
read_lock_bh(&nf_conntrack_lock);
|
|
i = __nf_ct_expect_find(tuple);
|
|
if (i)
|
|
atomic_inc(&i->use);
|
|
read_unlock_bh(&nf_conntrack_lock);
|
|
|
|
return i;
|
|
}
|
|
EXPORT_SYMBOL_GPL(nf_ct_expect_find_get);
|
|
|
|
/* If an expectation for this connection is found, it gets delete from
|
|
* global list then returned. */
|
|
struct nf_conntrack_expect *
|
|
nf_ct_find_expectation(const struct nf_conntrack_tuple *tuple)
|
|
{
|
|
struct nf_conntrack_expect *exp;
|
|
|
|
exp = __nf_ct_expect_find(tuple);
|
|
if (!exp)
|
|
return NULL;
|
|
|
|
/* If master is not in hash table yet (ie. packet hasn't left
|
|
this machine yet), how can other end know about expected?
|
|
Hence these are not the droids you are looking for (if
|
|
master ct never got confirmed, we'd hold a reference to it
|
|
and weird things would happen to future packets). */
|
|
if (!nf_ct_is_confirmed(exp->master))
|
|
return NULL;
|
|
|
|
if (exp->flags & NF_CT_EXPECT_PERMANENT) {
|
|
atomic_inc(&exp->use);
|
|
return exp;
|
|
} else if (del_timer(&exp->timeout)) {
|
|
nf_ct_unlink_expect(exp);
|
|
return exp;
|
|
}
|
|
|
|
return NULL;
|
|
}
|
|
|
|
/* delete all expectations for this conntrack */
|
|
void nf_ct_remove_expectations(struct nf_conn *ct)
|
|
{
|
|
struct nf_conn_help *help = nfct_help(ct);
|
|
struct nf_conntrack_expect *exp;
|
|
struct hlist_node *n, *next;
|
|
|
|
/* Optimization: most connection never expect any others. */
|
|
if (!help || help->expecting == 0)
|
|
return;
|
|
|
|
hlist_for_each_entry_safe(exp, n, next, &help->expectations, lnode) {
|
|
if (del_timer(&exp->timeout)) {
|
|
nf_ct_unlink_expect(exp);
|
|
nf_ct_expect_put(exp);
|
|
}
|
|
}
|
|
}
|
|
EXPORT_SYMBOL_GPL(nf_ct_remove_expectations);
|
|
|
|
/* Would two expected things clash? */
|
|
static inline int expect_clash(const struct nf_conntrack_expect *a,
|
|
const struct nf_conntrack_expect *b)
|
|
{
|
|
/* Part covered by intersection of masks must be unequal,
|
|
otherwise they clash */
|
|
struct nf_conntrack_tuple_mask intersect_mask;
|
|
int count;
|
|
|
|
intersect_mask.src.u.all = a->mask.src.u.all & b->mask.src.u.all;
|
|
|
|
for (count = 0; count < NF_CT_TUPLE_L3SIZE; count++){
|
|
intersect_mask.src.u3.all[count] =
|
|
a->mask.src.u3.all[count] & b->mask.src.u3.all[count];
|
|
}
|
|
|
|
return nf_ct_tuple_mask_cmp(&a->tuple, &b->tuple, &intersect_mask);
|
|
}
|
|
|
|
static inline int expect_matches(const struct nf_conntrack_expect *a,
|
|
const struct nf_conntrack_expect *b)
|
|
{
|
|
return a->master == b->master
|
|
&& nf_ct_tuple_equal(&a->tuple, &b->tuple)
|
|
&& nf_ct_tuple_mask_equal(&a->mask, &b->mask);
|
|
}
|
|
|
|
/* Generally a bad idea to call this: could have matched already. */
|
|
void nf_ct_unexpect_related(struct nf_conntrack_expect *exp)
|
|
{
|
|
write_lock_bh(&nf_conntrack_lock);
|
|
if (del_timer(&exp->timeout)) {
|
|
nf_ct_unlink_expect(exp);
|
|
nf_ct_expect_put(exp);
|
|
}
|
|
write_unlock_bh(&nf_conntrack_lock);
|
|
}
|
|
EXPORT_SYMBOL_GPL(nf_ct_unexpect_related);
|
|
|
|
/* We don't increase the master conntrack refcount for non-fulfilled
|
|
* conntracks. During the conntrack destruction, the expectations are
|
|
* always killed before the conntrack itself */
|
|
struct nf_conntrack_expect *nf_ct_expect_alloc(struct nf_conn *me)
|
|
{
|
|
struct nf_conntrack_expect *new;
|
|
|
|
new = kmem_cache_alloc(nf_ct_expect_cachep, GFP_ATOMIC);
|
|
if (!new)
|
|
return NULL;
|
|
|
|
new->master = me;
|
|
atomic_set(&new->use, 1);
|
|
return new;
|
|
}
|
|
EXPORT_SYMBOL_GPL(nf_ct_expect_alloc);
|
|
|
|
void nf_ct_expect_init(struct nf_conntrack_expect *exp, int family,
|
|
union nf_conntrack_address *saddr,
|
|
union nf_conntrack_address *daddr,
|
|
u_int8_t proto, __be16 *src, __be16 *dst)
|
|
{
|
|
int len;
|
|
|
|
if (family == AF_INET)
|
|
len = 4;
|
|
else
|
|
len = 16;
|
|
|
|
exp->flags = 0;
|
|
exp->expectfn = NULL;
|
|
exp->helper = NULL;
|
|
exp->tuple.src.l3num = family;
|
|
exp->tuple.dst.protonum = proto;
|
|
|
|
if (saddr) {
|
|
memcpy(&exp->tuple.src.u3, saddr, len);
|
|
if (sizeof(exp->tuple.src.u3) > len)
|
|
/* address needs to be cleared for nf_ct_tuple_equal */
|
|
memset((void *)&exp->tuple.src.u3 + len, 0x00,
|
|
sizeof(exp->tuple.src.u3) - len);
|
|
memset(&exp->mask.src.u3, 0xFF, len);
|
|
if (sizeof(exp->mask.src.u3) > len)
|
|
memset((void *)&exp->mask.src.u3 + len, 0x00,
|
|
sizeof(exp->mask.src.u3) - len);
|
|
} else {
|
|
memset(&exp->tuple.src.u3, 0x00, sizeof(exp->tuple.src.u3));
|
|
memset(&exp->mask.src.u3, 0x00, sizeof(exp->mask.src.u3));
|
|
}
|
|
|
|
if (src) {
|
|
exp->tuple.src.u.all = (__force u16)*src;
|
|
exp->mask.src.u.all = 0xFFFF;
|
|
} else {
|
|
exp->tuple.src.u.all = 0;
|
|
exp->mask.src.u.all = 0;
|
|
}
|
|
|
|
memcpy(&exp->tuple.dst.u3, daddr, len);
|
|
if (sizeof(exp->tuple.dst.u3) > len)
|
|
/* address needs to be cleared for nf_ct_tuple_equal */
|
|
memset((void *)&exp->tuple.dst.u3 + len, 0x00,
|
|
sizeof(exp->tuple.dst.u3) - len);
|
|
|
|
exp->tuple.dst.u.all = (__force u16)*dst;
|
|
}
|
|
EXPORT_SYMBOL_GPL(nf_ct_expect_init);
|
|
|
|
void nf_ct_expect_put(struct nf_conntrack_expect *exp)
|
|
{
|
|
if (atomic_dec_and_test(&exp->use))
|
|
kmem_cache_free(nf_ct_expect_cachep, exp);
|
|
}
|
|
EXPORT_SYMBOL_GPL(nf_ct_expect_put);
|
|
|
|
static void nf_ct_expect_insert(struct nf_conntrack_expect *exp)
|
|
{
|
|
struct nf_conn_help *master_help = nfct_help(exp->master);
|
|
unsigned int h = nf_ct_expect_dst_hash(&exp->tuple);
|
|
|
|
atomic_inc(&exp->use);
|
|
|
|
hlist_add_head(&exp->lnode, &master_help->expectations);
|
|
master_help->expecting++;
|
|
|
|
hlist_add_head(&exp->hnode, &nf_ct_expect_hash[h]);
|
|
nf_ct_expect_count++;
|
|
|
|
setup_timer(&exp->timeout, nf_ct_expectation_timed_out,
|
|
(unsigned long)exp);
|
|
exp->timeout.expires = jiffies + master_help->helper->timeout * HZ;
|
|
add_timer(&exp->timeout);
|
|
|
|
exp->id = ++nf_ct_expect_next_id;
|
|
atomic_inc(&exp->use);
|
|
NF_CT_STAT_INC(expect_create);
|
|
}
|
|
|
|
/* Race with expectations being used means we could have none to find; OK. */
|
|
static void evict_oldest_expect(struct nf_conn *master)
|
|
{
|
|
struct nf_conn_help *master_help = nfct_help(master);
|
|
struct nf_conntrack_expect *exp = NULL;
|
|
struct hlist_node *n;
|
|
|
|
hlist_for_each_entry(exp, n, &master_help->expectations, lnode)
|
|
; /* nothing */
|
|
|
|
if (exp && del_timer(&exp->timeout)) {
|
|
nf_ct_unlink_expect(exp);
|
|
nf_ct_expect_put(exp);
|
|
}
|
|
}
|
|
|
|
static inline int refresh_timer(struct nf_conntrack_expect *i)
|
|
{
|
|
struct nf_conn_help *master_help = nfct_help(i->master);
|
|
|
|
if (!del_timer(&i->timeout))
|
|
return 0;
|
|
|
|
i->timeout.expires = jiffies + master_help->helper->timeout*HZ;
|
|
add_timer(&i->timeout);
|
|
return 1;
|
|
}
|
|
|
|
int nf_ct_expect_related(struct nf_conntrack_expect *expect)
|
|
{
|
|
struct nf_conntrack_expect *i;
|
|
struct nf_conn *master = expect->master;
|
|
struct nf_conn_help *master_help = nfct_help(master);
|
|
struct hlist_node *n;
|
|
unsigned int h;
|
|
int ret;
|
|
|
|
NF_CT_ASSERT(master_help);
|
|
|
|
write_lock_bh(&nf_conntrack_lock);
|
|
if (!master_help->helper) {
|
|
ret = -ESHUTDOWN;
|
|
goto out;
|
|
}
|
|
h = nf_ct_expect_dst_hash(&expect->tuple);
|
|
hlist_for_each_entry(i, n, &nf_ct_expect_hash[h], hnode) {
|
|
if (expect_matches(i, expect)) {
|
|
/* Refresh timer: if it's dying, ignore.. */
|
|
if (refresh_timer(i)) {
|
|
ret = 0;
|
|
goto out;
|
|
}
|
|
} else if (expect_clash(i, expect)) {
|
|
ret = -EBUSY;
|
|
goto out;
|
|
}
|
|
}
|
|
/* Will be over limit? */
|
|
if (master_help->helper->max_expected &&
|
|
master_help->expecting >= master_help->helper->max_expected)
|
|
evict_oldest_expect(master);
|
|
|
|
if (nf_ct_expect_count >= nf_ct_expect_max) {
|
|
if (net_ratelimit())
|
|
printk(KERN_WARNING
|
|
"nf_conntrack: expectation table full");
|
|
ret = -EMFILE;
|
|
goto out;
|
|
}
|
|
|
|
nf_ct_expect_insert(expect);
|
|
nf_ct_expect_event(IPEXP_NEW, expect);
|
|
ret = 0;
|
|
out:
|
|
write_unlock_bh(&nf_conntrack_lock);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(nf_ct_expect_related);
|
|
|
|
#ifdef CONFIG_PROC_FS
|
|
struct ct_expect_iter_state {
|
|
unsigned int bucket;
|
|
};
|
|
|
|
static struct hlist_node *ct_expect_get_first(struct seq_file *seq)
|
|
{
|
|
struct ct_expect_iter_state *st = seq->private;
|
|
|
|
for (st->bucket = 0; st->bucket < nf_ct_expect_hsize; st->bucket++) {
|
|
if (!hlist_empty(&nf_ct_expect_hash[st->bucket]))
|
|
return nf_ct_expect_hash[st->bucket].first;
|
|
}
|
|
return NULL;
|
|
}
|
|
|
|
static struct hlist_node *ct_expect_get_next(struct seq_file *seq,
|
|
struct hlist_node *head)
|
|
{
|
|
struct ct_expect_iter_state *st = seq->private;
|
|
|
|
head = head->next;
|
|
while (head == NULL) {
|
|
if (++st->bucket >= nf_ct_expect_hsize)
|
|
return NULL;
|
|
head = nf_ct_expect_hash[st->bucket].first;
|
|
}
|
|
return head;
|
|
}
|
|
|
|
static struct hlist_node *ct_expect_get_idx(struct seq_file *seq, loff_t pos)
|
|
{
|
|
struct hlist_node *head = ct_expect_get_first(seq);
|
|
|
|
if (head)
|
|
while (pos && (head = ct_expect_get_next(seq, head)))
|
|
pos--;
|
|
return pos ? NULL : head;
|
|
}
|
|
|
|
static void *exp_seq_start(struct seq_file *seq, loff_t *pos)
|
|
{
|
|
read_lock_bh(&nf_conntrack_lock);
|
|
return ct_expect_get_idx(seq, *pos);
|
|
}
|
|
|
|
static void *exp_seq_next(struct seq_file *seq, void *v, loff_t *pos)
|
|
{
|
|
(*pos)++;
|
|
return ct_expect_get_next(seq, v);
|
|
}
|
|
|
|
static void exp_seq_stop(struct seq_file *seq, void *v)
|
|
{
|
|
read_unlock_bh(&nf_conntrack_lock);
|
|
}
|
|
|
|
static int exp_seq_show(struct seq_file *s, void *v)
|
|
{
|
|
struct nf_conntrack_expect *expect;
|
|
struct hlist_node *n = v;
|
|
|
|
expect = hlist_entry(n, struct nf_conntrack_expect, hnode);
|
|
|
|
if (expect->timeout.function)
|
|
seq_printf(s, "%ld ", timer_pending(&expect->timeout)
|
|
? (long)(expect->timeout.expires - jiffies)/HZ : 0);
|
|
else
|
|
seq_printf(s, "- ");
|
|
seq_printf(s, "l3proto = %u proto=%u ",
|
|
expect->tuple.src.l3num,
|
|
expect->tuple.dst.protonum);
|
|
print_tuple(s, &expect->tuple,
|
|
__nf_ct_l3proto_find(expect->tuple.src.l3num),
|
|
__nf_ct_l4proto_find(expect->tuple.src.l3num,
|
|
expect->tuple.dst.protonum));
|
|
return seq_putc(s, '\n');
|
|
}
|
|
|
|
static struct seq_operations exp_seq_ops = {
|
|
.start = exp_seq_start,
|
|
.next = exp_seq_next,
|
|
.stop = exp_seq_stop,
|
|
.show = exp_seq_show
|
|
};
|
|
|
|
static int exp_open(struct inode *inode, struct file *file)
|
|
{
|
|
struct seq_file *seq;
|
|
struct ct_expect_iter_state *st;
|
|
int ret;
|
|
|
|
st = kmalloc(sizeof(struct ct_expect_iter_state), GFP_KERNEL);
|
|
if (st == NULL)
|
|
return -ENOMEM;
|
|
ret = seq_open(file, &exp_seq_ops);
|
|
if (ret)
|
|
goto out_free;
|
|
seq = file->private_data;
|
|
seq->private = st;
|
|
memset(st, 0, sizeof(struct ct_expect_iter_state));
|
|
return ret;
|
|
out_free:
|
|
kfree(st);
|
|
return ret;
|
|
}
|
|
|
|
static const struct file_operations exp_file_ops = {
|
|
.owner = THIS_MODULE,
|
|
.open = exp_open,
|
|
.read = seq_read,
|
|
.llseek = seq_lseek,
|
|
.release = seq_release_private,
|
|
};
|
|
#endif /* CONFIG_PROC_FS */
|
|
|
|
static int __init exp_proc_init(void)
|
|
{
|
|
#ifdef CONFIG_PROC_FS
|
|
struct proc_dir_entry *proc;
|
|
|
|
proc = proc_net_fops_create("nf_conntrack_expect", 0440, &exp_file_ops);
|
|
if (!proc)
|
|
return -ENOMEM;
|
|
#endif /* CONFIG_PROC_FS */
|
|
return 0;
|
|
}
|
|
|
|
static void exp_proc_remove(void)
|
|
{
|
|
#ifdef CONFIG_PROC_FS
|
|
proc_net_remove("nf_conntrack_expect");
|
|
#endif /* CONFIG_PROC_FS */
|
|
}
|
|
|
|
module_param_named(expect_hashsize, nf_ct_expect_hsize, uint, 0600);
|
|
|
|
int __init nf_conntrack_expect_init(void)
|
|
{
|
|
int err = -ENOMEM;
|
|
|
|
if (!nf_ct_expect_hsize) {
|
|
nf_ct_expect_hsize = nf_conntrack_htable_size / 256;
|
|
if (!nf_ct_expect_hsize)
|
|
nf_ct_expect_hsize = 1;
|
|
}
|
|
nf_ct_expect_max = nf_ct_expect_hsize * 4;
|
|
|
|
nf_ct_expect_hash = nf_ct_alloc_hashtable(&nf_ct_expect_hsize,
|
|
&nf_ct_expect_vmalloc);
|
|
if (nf_ct_expect_hash == NULL)
|
|
goto err1;
|
|
|
|
nf_ct_expect_cachep = kmem_cache_create("nf_conntrack_expect",
|
|
sizeof(struct nf_conntrack_expect),
|
|
0, 0, NULL, NULL);
|
|
if (!nf_ct_expect_cachep)
|
|
goto err2;
|
|
|
|
err = exp_proc_init();
|
|
if (err < 0)
|
|
goto err3;
|
|
|
|
return 0;
|
|
|
|
err3:
|
|
nf_ct_free_hashtable(nf_ct_expect_hash, nf_ct_expect_vmalloc,
|
|
nf_ct_expect_hsize);
|
|
err2:
|
|
kmem_cache_destroy(nf_ct_expect_cachep);
|
|
err1:
|
|
return err;
|
|
}
|
|
|
|
void nf_conntrack_expect_fini(void)
|
|
{
|
|
exp_proc_remove();
|
|
kmem_cache_destroy(nf_ct_expect_cachep);
|
|
nf_ct_free_hashtable(nf_ct_expect_hash, nf_ct_expect_vmalloc,
|
|
nf_ct_expect_hsize);
|
|
}
|