netfilter: nft_dynset: support for element deletion

This patch implements the delete operation from the ruleset.

It implements a new delete() function in nft_set_rhash. It is simpler
to use than the already existing remove(), because it only takes the set
and the key as arguments, whereas remove() expects a full
nft_set_elem structure.

Signed-off-by: Ander Juaristi <a@juaristi.eus>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Author: juaristi

include/net/netfilter/nf_tables.h

@@ -302,17 +302,23 @@ struct nft_expr;
  *	struct nft_set_ops - nf_tables set operations
  *
  *	@lookup: look up an element within the set
+ *	@update: update an element if exists, add it if doesn't exist
+ *	@delete: delete an element
  *	@insert: insert new element into set
  *	@activate: activate new element in the next generation
  *	@deactivate: lookup for element and deactivate it in the next generation
  *	@flush: deactivate element in the next generation
  *	@remove: remove element from set
- *	@walk: iterate over all set elemeennts
+ *	@walk: iterate over all set elements
  *	@get: get set elements
  *	@privsize: function to return size of set private data
  *	@init: initialize private data of new set instance
  *	@destroy: destroy private data of set instance
  *	@elemsize: element private size
+ *
+ *	Operations lookup, update and delete have simpler interfaces, are faster
+ *	and currently only used in the packet path. All the rest are slower,
+ *	control plane functions.
  */
 struct nft_set_ops {
 	bool				(*lookup)(const struct net *net,
@@ -327,6 +333,8 @@ struct nft_set_ops {
 						  const struct nft_expr *expr,
 						  struct nft_regs *regs,
 						  const struct nft_set_ext **ext);
+	bool				(*delete)(const struct nft_set *set,
+						  const u32 *key);
 
 	int				(*insert)(const struct net *net,
 						  const struct nft_set *set,

include/uapi/linux/netfilter/nf_tables.h

@@ -636,6 +636,7 @@ enum nft_lookup_attributes {
 enum nft_dynset_ops {
 	NFT_DYNSET_OP_ADD,
 	NFT_DYNSET_OP_UPDATE,
+	NFT_DYNSET_OP_DELETE,
 };
 
 enum nft_dynset_flags {

net/netfilter/nft_dynset.c

@@ -84,6 +84,11 @@ void nft_dynset_eval(const struct nft_expr *expr,
 	const struct nft_expr *sexpr;
 	u64 timeout;
 
+	if (priv->op == NFT_DYNSET_OP_DELETE) {
+		set->ops->delete(set, &regs->data[priv->sreg_key]);
+		return;
+	}
+
 	if (set->ops->update(set, &regs->data[priv->sreg_key], nft_dynset_new,
 			     expr, regs, &ext)) {
 		sexpr = NULL;
@@ -161,6 +166,7 @@ static int nft_dynset_init(const struct nft_ctx *ctx,
 	priv->op = ntohl(nla_get_be32(tb[NFTA_DYNSET_OP]));
 	switch (priv->op) {
 	case NFT_DYNSET_OP_ADD:
+	case NFT_DYNSET_OP_DELETE:
 		break;
 	case NFT_DYNSET_OP_UPDATE:
 		if (!(set->flags & NFT_SET_TIMEOUT))

net/netfilter/nft_set_hash.c

@@ -234,6 +234,24 @@ static void nft_rhash_remove(const struct net *net,
 	rhashtable_remove_fast(&priv->ht, &he->node, nft_rhash_params);
 }
 
+static bool nft_rhash_delete(const struct nft_set *set,
+			     const u32 *key)
+{
+	struct nft_rhash *priv = nft_set_priv(set);
+	struct nft_rhash_cmp_arg arg = {
+		.genmask = NFT_GENMASK_ANY,
+		.set = set,
+		.key = key,
+	};
+	struct nft_rhash_elem *he;
+
+	he = rhashtable_lookup(&priv->ht, &arg, nft_rhash_params);
+	if (he == NULL)
+		return false;
+
+	return rhashtable_remove_fast(&priv->ht, &he->node, nft_rhash_params) == 0;
+}
+
 static void nft_rhash_walk(const struct nft_ctx *ctx, struct nft_set *set,
 			   struct nft_set_iter *iter)
 {
@@ -662,6 +680,7 @@ struct nft_set_type nft_set_rhash_type __read_mostly = {
 		.remove		= nft_rhash_remove,
 		.lookup		= nft_rhash_lookup,
 		.update		= nft_rhash_update,
+		.delete		= nft_rhash_delete,
 		.walk		= nft_rhash_walk,
 		.get		= nft_rhash_get,
 	},