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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
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: default avatarIvan Babrou <ibobrik@gmail.com>
Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent a5d7a714

include/net/netfilter/nf_conntrack.h

+1 −2
Original line number Diff line number Diff line
@@ -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;



#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];

include/net/netfilter/nf_nat.h

+0 −1
Original line number Diff line number Diff line 
#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>

net/netfilter/nf_nat_core.c

+53 −77
Original line number Diff line number Diff line
@@ -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)
@@ -118,17 +116,19 @@ int nf_xfrm_me_harder(struct net *net, struct sk_buff *skb, unsigned int family) 
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 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,
@@ -216,18 +194,14 @@ 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) {

	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;
@@ -235,7 +209,7 @@ find_appropriate_src(struct net *net, 
			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;

		unsigned int srchash;



		err = rhltable_insert_key(&nf_nat_bysource_table,

					  &key,

					  &ct->nat_bysource,

					  nf_nat_bysource_params);

		if (err)

			return NF_DROP;

		srchash = hash_by_src(net,

				      &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);

		spin_lock_bh(&nf_nat_lock);

		hlist_add_head_rcu(&ct->nat_bysource,

				   &nf_nat_bysource[srchash]);

		spin_unlock_bh(&nf_nat_lock);

	}



	/* 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,

			nf_nat_bysource_params);

	spin_lock_bh(&nf_nat_lock);

	hlist_del_rcu(&ct->nat_bysource);

	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.
@@ -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,

				nf_nat_bysource_params);

	if (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 = {
@@ -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) {

		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;

	}
@@ -865,8 +841,8 @@ 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");