Commit e1bf1687 authored by Florian Westphal's avatar Florian Westphal Committed by Pablo Neira Ayuso
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netfilter: nat: Revert "netfilter: nat: convert nat bysrc hash to rhashtable"

This reverts commit 870190a9.

It was not a good idea. The custom hash table was a much better
fit for this purpose.

A fast lookup is not essential, in fact for most cases there is no lookup
at all because original tuple is not taken and can be used as-is.
What needs to be fast is insertion and deletion.

rhlist removal however requires a rhlist walk.
We can have thousands of entries in such a list if source port/addresses
are reused for multiple flows, if this happens removal requests are so
expensive that deletions of a few thousand flows can take several

The advantages that we got from rhashtable are:
1) table auto-sizing
2) multiple locks

1) would be nice to have, but it is not essential as we have at
most one lookup per new flow, so even a million flows in the bysource
table are not a problem compared to current deletion cost.
2) is easy to add to custom hash table.

I tried to add hlist_node to rhlist to speed up rhltable_remove but this
isn't doable without changing semantics.  rhltable_remove_fast will
check that the to-be-deleted object is part of the table and that
requires a list walk that we want to avoid.

Furthermore, using hlist_node increases size of struct rhlist_head, which
in turn increases nf_conn size.


Reported-by: default avatarIvan Babrou <>
Signed-off-by: default avatarFlorian Westphal <>
Signed-off-by: default avatarPablo Neira Ayuso <>
parent a5d7a714
......@@ -17,7 +17,6 @@
#include <linux/bitops.h>
#include <linux/compiler.h>
#include <linux/atomic.h>
#include <linux/rhashtable.h>
#include <linux/netfilter/nf_conntrack_tcp.h>
#include <linux/netfilter/nf_conntrack_dccp.h>
......@@ -77,7 +76,7 @@ struct nf_conn {
possible_net_t ct_net;
struct rhlist_head nat_bysource;
struct hlist_node nat_bysource;
/* all members below initialized via memset */
u8 __nfct_init_offset[0];
#ifndef _NF_NAT_H
#define _NF_NAT_H
#include <linux/rhashtable.h>
#include <linux/netfilter_ipv4.h>
#include <linux/netfilter/nf_nat.h>
#include <net/netfilter/nf_conntrack_tuple.h>
......@@ -30,19 +30,17 @@
#include <net/netfilter/nf_conntrack_zones.h>
#include <linux/netfilter/nf_nat.h>
static DEFINE_SPINLOCK(nf_nat_lock);
static DEFINE_MUTEX(nf_nat_proto_mutex);
static const struct nf_nat_l3proto __rcu *nf_nat_l3protos[NFPROTO_NUMPROTO]
static const struct nf_nat_l4proto __rcu **nf_nat_l4protos[NFPROTO_NUMPROTO]
struct nf_nat_conn_key {
const struct net *net;
const struct nf_conntrack_tuple *tuple;
const struct nf_conntrack_zone *zone;
static struct rhltable nf_nat_bysource_table;
static struct hlist_head *nf_nat_bysource __read_mostly;
static unsigned int nf_nat_htable_size __read_mostly;
static unsigned int nf_nat_hash_rnd __read_mostly;
inline const struct nf_nat_l3proto *
__nf_nat_l3proto_find(u8 family)
......@@ -118,17 +116,19 @@ int nf_xfrm_me_harder(struct net *net, struct sk_buff *skb, unsigned int family)
#endif /* CONFIG_XFRM */
static u32 nf_nat_bysource_hash(const void *data, u32 len, u32 seed)
/* We keep an extra hash for each conntrack, for fast searching. */
static unsigned int
hash_by_src(const struct net *n, const struct nf_conntrack_tuple *tuple)
const struct nf_conntrack_tuple *t;
const struct nf_conn *ct = data;
unsigned int hash;
get_random_once(&nf_nat_hash_rnd, sizeof(nf_nat_hash_rnd));
t = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
/* Original src, to ensure we map it consistently if poss. */
hash = jhash2((u32 *)&tuple->src, sizeof(tuple->src) / sizeof(u32),
tuple->dst.protonum ^ nf_nat_hash_rnd ^ net_hash_mix(n));
seed ^= net_hash_mix(nf_ct_net(ct));
return jhash2((const u32 *)&t->src, sizeof(t->src) / sizeof(u32),
t->dst.protonum ^ seed);
return reciprocal_scale(hash, nf_nat_htable_size);
/* Is this tuple already taken? (not by us) */
......@@ -184,28 +184,6 @@ same_src(const struct nf_conn *ct,
t->src.u.all == tuple->src.u.all);
static int nf_nat_bysource_cmp(struct rhashtable_compare_arg *arg,
const void *obj)
const struct nf_nat_conn_key *key = arg->key;
const struct nf_conn *ct = obj;
if (!same_src(ct, key->tuple) ||
!net_eq(nf_ct_net(ct), key->net) ||
!nf_ct_zone_equal(ct, key->zone, IP_CT_DIR_ORIGINAL))
return 1;
return 0;
static struct rhashtable_params nf_nat_bysource_params = {
.head_offset = offsetof(struct nf_conn, nat_bysource),
.obj_hashfn = nf_nat_bysource_hash,
.obj_cmpfn = nf_nat_bysource_cmp,
.nelem_hint = 256,
.min_size = 1024,
/* Only called for SRC manip */
static int
find_appropriate_src(struct net *net,
......@@ -216,26 +194,22 @@ find_appropriate_src(struct net *net,
struct nf_conntrack_tuple *result,
const struct nf_nat_range *range)
unsigned int h = hash_by_src(net, tuple);
const struct nf_conn *ct;
struct nf_nat_conn_key key = {
.net = net,
.tuple = tuple,
.zone = zone
struct rhlist_head *hl, *h;
hl = rhltable_lookup(&nf_nat_bysource_table, &key,
rhl_for_each_entry_rcu(ct, h, hl, nat_bysource) {
result->dst = tuple->dst;
if (in_range(l3proto, l4proto, result, range))
return 1;
hlist_for_each_entry_rcu(ct, &nf_nat_bysource[h], nat_bysource) {
if (same_src(ct, tuple) &&
net_eq(net, nf_ct_net(ct)) &&
nf_ct_zone_equal(ct, zone, IP_CT_DIR_ORIGINAL)) {
/* Copy source part from reply tuple. */
result->dst = tuple->dst;
if (in_range(l3proto, l4proto, result, range))
return 1;
return 0;
......@@ -408,6 +382,7 @@ nf_nat_setup_info(struct nf_conn *ct,
const struct nf_nat_range *range,
enum nf_nat_manip_type maniptype)
struct net *net = nf_ct_net(ct);
struct nf_conntrack_tuple curr_tuple, new_tuple;
/* Can't setup nat info for confirmed ct. */
......@@ -449,19 +424,14 @@ nf_nat_setup_info(struct nf_conn *ct,
if (maniptype == NF_NAT_MANIP_SRC) {
struct nf_nat_conn_key key = {
.net = nf_ct_net(ct),
.tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple,
.zone = nf_ct_zone(ct),
int err;
err = rhltable_insert_key(&nf_nat_bysource_table,
if (err)
return NF_DROP;
unsigned int srchash;
srchash = hash_by_src(net,
/* It's done. */
......@@ -570,8 +540,9 @@ static int nf_nat_proto_clean(struct nf_conn *ct, void *data)
* will delete entry from already-freed table.
clear_bit(IPS_SRC_NAT_DONE_BIT, &ct->status);
rhltable_remove(&nf_nat_bysource_table, &ct->nat_bysource,
/* don't delete conntrack. Although that would make things a lot
* simpler, we'd end up flushing all conntracks on nat rmmod.
......@@ -699,9 +670,11 @@ EXPORT_SYMBOL_GPL(nf_nat_l3proto_unregister);
/* No one using conntrack by the time this called. */
static void nf_nat_cleanup_conntrack(struct nf_conn *ct)
if (ct->status & IPS_SRC_NAT_DONE)
rhltable_remove(&nf_nat_bysource_table, &ct->nat_bysource,
if (ct->status & IPS_SRC_NAT_DONE) {
static struct nf_ct_ext_type nat_extend __read_mostly = {
......@@ -825,13 +798,16 @@ static int __init nf_nat_init(void)
int ret;
ret = rhltable_init(&nf_nat_bysource_table, &nf_nat_bysource_params);
if (ret)
return ret;
/* Leave them the same for the moment. */
nf_nat_htable_size = nf_conntrack_htable_size;
nf_nat_bysource = nf_ct_alloc_hashtable(&nf_nat_htable_size, 0);
if (!nf_nat_bysource)
return -ENOMEM;
ret = nf_ct_extend_register(&nat_extend);
if (ret < 0) {
nf_ct_free_hashtable(nf_nat_bysource, nf_nat_htable_size);
printk(KERN_ERR "nf_nat_core: Unable to register extension\n");
return ret;
......@@ -865,8 +841,8 @@ static void __exit nf_nat_cleanup(void)
for (i = 0; i < NFPROTO_NUMPROTO; i++)
nf_ct_free_hashtable(nf_nat_bysource, nf_nat_htable_size);
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