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Commit 7c966435 authored by Florian Westphal's avatar Florian Westphal Committed by Pablo Neira Ayuso
Browse files

netfilter: move nat hlist_head to nf_conn 



The nat extension structure is 32bytes in size on x86_64:

struct nf_conn_nat {
        struct hlist_node          bysource;             /*     0    16 */
        struct nf_conn *           ct;                   /*    16     8 */
        union nf_conntrack_nat_help help;                /*    24     4 */
        int                        masq_index;           /*    28     4 */
        /* size: 32, cachelines: 1, members: 4 */
        /* last cacheline: 32 bytes */
};

The hlist is needed to quickly check for possible tuple collisions
when installing a new nat binding. Storing this in the extension
area has two drawbacks:

1. We need ct backpointer to get the conntrack struct from the extension.
2. When reallocation of extension area occurs we need to fixup the bysource
   hash head via hlist_replace_rcu.

We can avoid both by placing the hlist_head in nf_conn and place nf_conn in
the bysource hash rather than the extenstion.

We can also remove the ->move support; no other extension needs it.

Moving the entire nat extension into nf_conn would be possible as well but
then we have to add yet another callback for deletion from the bysource
hash table rather than just using nat extension ->destroy hook for this.

nf_conn size doesn't increase due to aligment, followup patch replaces
hlist_node with single pointer.

Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 242922a0

include/net/netfilter/nf_conntrack.h

+3 −0
Original line number Diff line number Diff line
@@ -117,6 +117,9 @@ struct nf_conn { 
	/* Extensions */

	struct nf_ct_ext *ext;



#if IS_ENABLED(CONFIG_NF_NAT)

	struct hlist_node	nat_bysource;

#endif

	/* Storage reserved for other modules, must be the last member */

	union nf_conntrack_proto proto;

};

include/net/netfilter/nf_conntrack_extend.h

+0 −3
Original line number Diff line number Diff line
@@ -99,9 +99,6 @@ void *__nf_ct_ext_add_length(struct nf_conn *ct, enum nf_ct_ext_id id, 
struct nf_ct_ext_type {

	/* Destroys relationships (can be NULL). */

	void (*destroy)(struct nf_conn *ct);

	/* Called when realloacted (can be NULL).

	   Contents has already been moved. */

	void (*move)(void *new, void *old);



	enum nf_ct_ext_id id;

include/net/netfilter/nf_nat.h

+0 −2
Original line number Diff line number Diff line
@@ -29,8 +29,6 @@ struct nf_conn; 


/* The structure embedded in the conntrack structure. */

struct nf_conn_nat {

	struct hlist_node bysource;

	struct nf_conn *ct;

	union nf_conntrack_nat_help help;

#if IS_ENABLED(CONFIG_NF_NAT_MASQUERADE_IPV4) || \

    IS_ENABLED(CONFIG_NF_NAT_MASQUERADE_IPV6)

net/netfilter/nf_conntrack_extend.c

+2 −13
Original line number Diff line number Diff line
@@ -73,7 +73,7 @@ void *__nf_ct_ext_add_length(struct nf_conn *ct, enum nf_ct_ext_id id, 
			     size_t var_alloc_len, gfp_t gfp)

{

	struct nf_ct_ext *old, *new;

	int i, newlen, newoff;

	int newlen, newoff;

	struct nf_ct_ext_type *t;



	/* Conntrack must not be confirmed to avoid races on reallocation. */
@@ -99,19 +99,8 @@ void *__nf_ct_ext_add_length(struct nf_conn *ct, enum nf_ct_ext_id id, 
		return NULL;



	if (new != old) {

		for (i = 0; i < NF_CT_EXT_NUM; i++) {

			if (!__nf_ct_ext_exist(old, i))

				continue;



			rcu_read_lock();

			t = rcu_dereference(nf_ct_ext_types[i]);

			if (t && t->move)

				t->move((void *)new + new->offset[i],

					(void *)old + old->offset[i]);

			rcu_read_unlock();

		}

		kfree_rcu(old, rcu);

		ct->ext = new;

		rcu_assign_pointer(ct->ext, new);

	}



	new->offset[id] = newoff;

net/netfilter/nf_nat_core.c

+7 −26
Original line number Diff line number Diff line
@@ -198,11 +198,9 @@ find_appropriate_src(struct net *net, 
		     const struct nf_nat_range *range)

{

	unsigned int h = hash_by_src(net, tuple);

	const struct nf_conn_nat *nat;

	const struct nf_conn *ct;



	hlist_for_each_entry_rcu(nat, &nf_nat_bysource[h], bysource) {

		ct = nat->ct;

	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)) {
@@ -435,8 +433,7 @@ nf_nat_setup_info(struct nf_conn *ct, 
		spin_lock_bh(&nf_nat_lock);

		/* nf_conntrack_alter_reply might re-allocate extension aera */

		nat = nfct_nat(ct);

		nat->ct = ct;

		hlist_add_head_rcu(&nat->bysource,

		hlist_add_head_rcu(&ct->nat_bysource,

				   &nf_nat_bysource[srchash]);

		spin_unlock_bh(&nf_nat_lock);

	}
@@ -543,7 +540,7 @@ static int nf_nat_proto_clean(struct nf_conn *ct, void *data) 
	if (nf_nat_proto_remove(ct, data))

		return 1;



	if (!nat || !nat->ct)

	if (!nat)

		return 0;



	/* This netns is being destroyed, and conntrack has nat null binding.
@@ -556,9 +553,8 @@ static int nf_nat_proto_clean(struct nf_conn *ct, void *data) 
		return 1;



	spin_lock_bh(&nf_nat_lock);

	hlist_del_rcu(&nat->bysource);

	hlist_del_rcu(&ct->nat_bysource);

	ct->status &= ~IPS_NAT_DONE_MASK;

	nat->ct = NULL;

	spin_unlock_bh(&nf_nat_lock);



	add_timer(&ct->timeout);
@@ -688,27 +684,13 @@ static void nf_nat_cleanup_conntrack(struct nf_conn *ct) 
{

	struct nf_conn_nat *nat = nf_ct_ext_find(ct, NF_CT_EXT_NAT);



	if (nat == NULL || nat->ct == NULL)

	if (!nat)

		return;



	NF_CT_ASSERT(nat->ct->status & IPS_SRC_NAT_DONE);



	spin_lock_bh(&nf_nat_lock);

	hlist_del_rcu(&nat->bysource);

	spin_unlock_bh(&nf_nat_lock);

}



static void nf_nat_move_storage(void *new, void *old)

{

	struct nf_conn_nat *new_nat = new;

	struct nf_conn_nat *old_nat = old;

	struct nf_conn *ct = old_nat->ct;



	if (!ct || !(ct->status & IPS_SRC_NAT_DONE))

		return;

	NF_CT_ASSERT(ct->status & IPS_SRC_NAT_DONE);



	spin_lock_bh(&nf_nat_lock);

	hlist_replace_rcu(&old_nat->bysource, &new_nat->bysource);

	hlist_del_rcu(&ct->nat_bysource);

	spin_unlock_bh(&nf_nat_lock);

}
@@ -716,7 +698,6 @@ static struct nf_ct_ext_type nat_extend __read_mostly = { 
	.len		= sizeof(struct nf_conn_nat),

	.align		= __alignof__(struct nf_conn_nat),

	.destroy	= nf_nat_cleanup_conntrack,

	.move		= nf_nat_move_storage,

	.id		= NF_CT_EXT_NAT,

	.flags		= NF_CT_EXT_F_PREALLOC,

};