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[NETFILTER]: nf_conntrack: use hashtable for expectations

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Currently all expectations are kept on a global list that

- needs to be searched for every new conncetion
- needs to be walked for evicting expectations when a master connection
  has reached its limit
- needs to be walked on connection destruction for connections that
  have open expectations

This is obviously not good, especially when considering helpers like
H.323 that register *lots* of expectations and can set up permanent
expectations, but it also allows for an easy DoS against firewalls
using connection tracking helpers.

Use a hashtable for expectations to avoid incurring the search overhead
for every new connection. The default hash size is 1/256 of the conntrack
hash table size, this can be overriden using a module parameter.

This patch only introduces the hash table for expectation lookups and
keeps other users to reduce the noise, the following patches will get
rid of it completely.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Patrick McHardy
2007-07-07 22:33:47 -07:00
committed by David S. Miller
parent e9c1b084e1
commit a71c085562
3 changed files with 71 additions and 7 deletions
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1
include/net/netfilter/nf_conntrack_core.h
View File

@@ -84,7 +84,6 @@ print_tuple(struct seq_file *s, const struct nf_conntrack_tuple *tuple,
struct nf_conntrack_l4proto *proto);
extern struct hlist_head *nf_conntrack_hash;
extern struct list_head nf_ct_expect_list;
extern rwlock_t nf_conntrack_lock ;
extern struct hlist_head unconfirmed;

5
include/net/netfilter/nf_conntrack_expect.h
View File

@@ -7,12 +7,17 @@
#include <net/netfilter/nf_conntrack.h>
extern struct list_head nf_ct_expect_list;
extern struct hlist_head *nf_ct_expect_hash;
extern unsigned int nf_ct_expect_hsize;
struct nf_conntrack_expect
{
/* Internal linked list (global expectation list) */
struct list_head list;
/* Hash member */
struct hlist_node hnode;
/* We expect this tuple, with the following mask */
struct nf_conntrack_tuple tuple;
struct nf_conntrack_tuple_mask mask;