netfilter: nf_tables: prepare for multiple elements in nft_trans_elem structure

Add helpers to release the individual elements contained in the
trans_elem container structure.

No functional change intended.

Followup patch will add 'nelems' member and will turn 'priv' into
a flexible array.

These helpers can then loop over all elements.
Care needs to be taken to handle a mix of new elements and existing
elements that are being updated (e.g. timeout refresh).

Before this patch, NEWSETELEM transaction with update is released
early so nft_trans_set_elem_destroy() won't get called, so we need
to skip elements marked as update.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Author: Florian Westphal

include/net/netfilter/nf_tables.h

@@ -1759,28 +1759,25 @@ enum nft_trans_elem_flags {
 	NFT_TRANS_UPD_EXPIRATION	= (1 << 1),
 };
 
-struct nft_trans_elem {
-	struct nft_trans		nft_trans;
-	struct nft_set			*set;
-	struct nft_elem_priv		*elem_priv;
+struct nft_trans_one_elem {
+	struct nft_elem_priv		*priv;
 	u64				timeout;
 	u64				expiration;
 	u8				update_flags;
+};
+
+struct nft_trans_elem {
+	struct nft_trans		nft_trans;
+	struct nft_set			*set;
 	bool				bound;
+	unsigned int			nelems;
+	struct nft_trans_one_elem	elems[] __counted_by(nelems);
 };
 
 #define nft_trans_container_elem(t)			\
 	container_of(t, struct nft_trans_elem, nft_trans)
 #define nft_trans_elem_set(trans)			\
 	nft_trans_container_elem(trans)->set
-#define nft_trans_elem_priv(trans)			\
-	nft_trans_container_elem(trans)->elem_priv
-#define nft_trans_elem_update_flags(trans)		\
-	nft_trans_container_elem(trans)->update_flags
-#define nft_trans_elem_timeout(trans)			\
-	nft_trans_container_elem(trans)->timeout
-#define nft_trans_elem_expiration(trans)		\
-	nft_trans_container_elem(trans)->expiration
 #define nft_trans_elem_set_bound(trans)			\
 	nft_trans_container_elem(trans)->bound