netfilter: nf_tables: shrink memory consumption of set elements

Instead of copying struct nft_set_elem into struct nft_trans_elem, store
the pointer to the opaque set element object in the transaction. Adapt
set backend API (and set backend implementations) to take the pointer to
opaque set element representation whenever required.

This patch deconstifies .remove() and .activate() set backend API since
these modify the set element opaque object. And it also constify
nft_set_elem_ext() this provides access to the nft_set_ext struct
without updating the object.

According to pahole on x86_64, this patch shrinks struct nft_trans_elem
size from 216 to 24 bytes.

This patch also reduces stack memory consumption by removing the
template struct nft_set_elem object, using the opaque set element object
instead such as from the set iterator API, catchall elements and the get
element command.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 7 insertions, 18 deletions

diff --git a/net/netfilter/nft_set_rbtree.c b/net/netfilter/nft_set_rbtree.c
index 475f22568342..25baa9cdb77d 100644
--- a/net/netfilter/nft_set_rbtree.c
+++ b/net/netfilter/nft_set_rbtree.c
@@ -227,12 +227,8 @@ static void nft_rbtree_gc_elem_remove(struct net *net, struct nft_set *set,
 				      struct nft_rbtree *priv,
 				      struct nft_rbtree_elem *rbe)
 {
-	struct nft_set_elem elem = {
-		.priv	= &rbe->priv,
-	};
-
 	lockdep_assert_held_write(&priv->lock);
-	nft_setelem_data_deactivate(net, set, &elem);
+	nft_setelem_data_deactivate(net, set, &rbe->priv);
 	rb_erase(&rbe->node, &priv->root);
 }
 
@@ -521,9 +517,9 @@ static void nft_rbtree_erase(struct nft_rbtree *priv, struct nft_rbtree_elem *rb
 
 static void nft_rbtree_remove(const struct net *net,
 			      const struct nft_set *set,
-			      const struct nft_set_elem *elem)
+			      struct nft_elem_priv *elem_priv)
 {
-	struct nft_rbtree_elem *rbe = nft_elem_priv_cast(elem->priv);
+	struct nft_rbtree_elem *rbe = nft_elem_priv_cast(elem_priv);
 	struct nft_rbtree *priv = nft_set_priv(set);
 
 	nft_rbtree_erase(priv, rbe);
@@ -531,9 +527,9 @@ static void nft_rbtree_remove(const struct net *net,
 
 static void nft_rbtree_activate(const struct net *net,
 				const struct nft_set *set,
-				const struct nft_set_elem *elem)
+				struct nft_elem_priv *elem_priv)
 {
-	struct nft_rbtree_elem *rbe = nft_elem_priv_cast(elem->priv);
+	struct nft_rbtree_elem *rbe = nft_elem_priv_cast(elem_priv);
 
 	nft_set_elem_change_active(net, set, &rbe->ext);
 }
@@ -594,7 +590,6 @@ static void nft_rbtree_walk(const struct nft_ctx *ctx,
 {
 	struct nft_rbtree *priv = nft_set_priv(set);
 	struct nft_rbtree_elem *rbe;
-	struct nft_set_elem elem;
 	struct rb_node *node;
 
 	read_lock_bh(&priv->lock);
@@ -606,9 +601,7 @@ static void nft_rbtree_walk(const struct nft_ctx *ctx,
 		if (!nft_set_elem_active(&rbe->ext, iter->genmask))
 			goto cont;
 
-		elem.priv = &rbe->priv;
-
-		iter->err = iter->fn(ctx, set, iter, &elem);
+		iter->err = iter->fn(ctx, set, iter, &rbe->priv);
 		if (iter->err < 0) {
 			read_unlock_bh(&priv->lock);
 			return;
@@ -623,11 +616,7 @@ static void nft_rbtree_gc_remove(struct net *net, struct nft_set *set,
 				 struct nft_rbtree *priv,
 				 struct nft_rbtree_elem *rbe)
 {
-	struct nft_set_elem elem = {
-		.priv	= rbe,
-	};
-
-	nft_setelem_data_deactivate(net, set, &elem);
+	nft_setelem_data_deactivate(net, set, &rbe->priv);
 	nft_rbtree_erase(priv, rbe);
 }