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Subject[PATCH 4.9 85/87] netfilter: nat: Revert "netfilter: nat: convert nat bysrc hash to rhashtable"
Date
4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Florian Westphal <fw@strlen.de>

commit e1bf1687740ce1a3598a1c5e452b852ff2190682 upstream.

This reverts commit 870190a9ec9075205c0fa795a09fa931694a3ff1.

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
seconds(!).

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.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=196821
Reported-by: Ivan Babrou <ibobrik@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>


---
include/net/netfilter/nf_conntrack.h | 3
include/net/netfilter/nf_nat.h | 1
net/netfilter/nf_nat_core.c | 131 ++++++++++++++---------------------
3 files changed, 56 insertions(+), 79 deletions(-)

--- a/include/net/netfilter/nf_conntrack.h
+++ b/include/net/netfilter/nf_conntrack.h
@@ -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>
@@ -101,7 +100,7 @@ struct nf_conn {
possible_net_t ct_net;

#if IS_ENABLED(CONFIG_NF_NAT)
- struct rhlist_head nat_bysource;
+ struct hlist_node nat_bysource;
#endif
/* all members below initialized via memset */
u8 __nfct_init_offset[0];
--- a/include/net/netfilter/nf_nat.h
+++ b/include/net/netfilter/nf_nat.h
@@ -1,6 +1,5 @@
#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>
--- a/net/netfilter/nf_nat_core.c
+++ b/net/netfilter/nf_nat_core.c
@@ -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]
__read_mostly;
static const struct nf_nat_l4proto __rcu **nf_nat_l4protos[NFPROTO_NUMPROTO]
__read_mostly;

-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)
@@ -121,17 +119,19 @@ int nf_xfrm_me_harder(struct net *net, s
EXPORT_SYMBOL(nf_xfrm_me_harder);
#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 inline 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) */
@@ -187,28 +187,6 @@ 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,
@@ -219,26 +197,22 @@ 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,
- nf_nat_bysource_params);

- rhl_for_each_entry_rcu(ct, h, hl, nat_bysource) {
- nf_ct_invert_tuplepr(result,
- &ct->tuplehash[IP_CT_DIR_REPLY].tuple);
- result->dst = tuple->dst;
+ 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. */
+ nf_ct_invert_tuplepr(result,
+ &ct->tuplehash[IP_CT_DIR_REPLY].tuple);
+ result->dst = tuple->dst;

- if (in_range(l3proto, l4proto, result, range))
- return 1;
+ if (in_range(l3proto, l4proto, result, range))
+ return 1;
+ }
}
-
return 0;
}

@@ -411,6 +385,7 @@ 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;
struct nf_conn_nat *nat;

@@ -452,19 +427,16 @@ 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,
- &key,
- &ct->nat_bysource,
- nf_nat_bysource_params);
- if (err)
- return NF_DROP;
+ unsigned int srchash;
+
+ srchash = hash_by_src(net,
+ &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
+ spin_lock_bh(&nf_nat_lock);
+ /* nf_conntrack_alter_reply might re-allocate extension aera */
+ nat = nfct_nat(ct);
+ hlist_add_head_rcu(&ct->nat_bysource,
+ &nf_nat_bysource[srchash]);
+ spin_unlock_bh(&nf_nat_lock);
}

/* It's done. */
@@ -578,9 +550,10 @@ static int nf_nat_proto_clean(struct nf_
* Else, when the conntrack is destoyed, nf_nat_cleanup_conntrack()
* will delete entry from already-freed table.
*/
+ spin_lock_bh(&nf_nat_lock);
+ hlist_del_rcu(&ct->nat_bysource);
ct->status &= ~IPS_NAT_DONE_MASK;
- rhltable_remove(&nf_nat_bysource_table, &ct->nat_bysource,
- nf_nat_bysource_params);
+ spin_unlock_bh(&nf_nat_lock);

/* don't delete conntrack. Although that would make things a lot
* simpler, we'd end up flushing all conntracks on nat rmmod.
@@ -710,8 +683,11 @@ static void nf_nat_cleanup_conntrack(str
if (!nat)
return;

- rhltable_remove(&nf_nat_bysource_table, &ct->nat_bysource,
- nf_nat_bysource_params);
+ NF_CT_ASSERT(ct->status & IPS_SRC_NAT_DONE);
+
+ spin_lock_bh(&nf_nat_lock);
+ hlist_del_rcu(&ct->nat_bysource);
+ spin_unlock_bh(&nf_nat_lock);
}

static struct nf_ct_ext_type nat_extend __read_mostly = {
@@ -846,13 +822,16 @@ 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) {
- rhltable_destroy(&nf_nat_bysource_table);
+ nf_ct_free_hashtable(nf_nat_bysource, nf_nat_htable_size);
printk(KERN_ERR "nf_nat_core: Unable to register extension\n");
return ret;
}
@@ -876,7 +855,7 @@ static int __init nf_nat_init(void)
return 0;

cleanup_extend:
- rhltable_destroy(&nf_nat_bysource_table);
+ nf_ct_free_hashtable(nf_nat_bysource, nf_nat_htable_size);
nf_ct_extend_unregister(&nat_extend);
return ret;
}
@@ -896,8 +875,8 @@ static void __exit nf_nat_cleanup(void)

for (i = 0; i < NFPROTO_NUMPROTO; i++)
kfree(nf_nat_l4protos[i]);
-
- rhltable_destroy(&nf_nat_bysource_table);
+ synchronize_net();
+ nf_ct_free_hashtable(nf_nat_bysource, nf_nat_htable_size);
}

MODULE_LICENSE("GPL");

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