netfilter: nf_tables: bogus EBUSY when deleting flowtable after flush

The deletion of a flowtable after a flush in the same transaction
results in EBUSY. This patch adds an activation and deactivation of
flowtables in order to update the _use_ counter.
Signed-off-by: Laura Garcia Liebana <nevola@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/netfilter/nf_tables.h

@@ -1183,6 +1183,10 @@ struct nft_flowtable *nft_flowtable_lookup(const struct nft_table *table,
 					   const struct nlattr *nla,
 					   u8 genmask);
 
+void nf_tables_deactivate_flowtable(const struct nft_ctx *ctx,
+				    struct nft_flowtable *flowtable,
+				    enum nft_trans_phase phase);
+
 void nft_register_flowtable_type(struct nf_flowtable_type *type);
 void nft_unregister_flowtable_type(struct nf_flowtable_type *type);
 

net/netfilter/nf_tables_api.c

@@ -5598,6 +5598,22 @@ struct nft_flowtable *nft_flowtable_lookup(const struct nft_table *table,
 }
 EXPORT_SYMBOL_GPL(nft_flowtable_lookup);
 
+void nf_tables_deactivate_flowtable(const struct nft_ctx *ctx,
+				    struct nft_flowtable *flowtable,
+				    enum nft_trans_phase phase)
+{
+	switch (phase) {
+	case NFT_TRANS_PREPARE:
+	case NFT_TRANS_ABORT:
+	case NFT_TRANS_RELEASE:
+		flowtable->use--;
+		/* fall through */
+	default:
+		return;
+	}
+}
+EXPORT_SYMBOL_GPL(nf_tables_deactivate_flowtable);
+
 static struct nft_flowtable *
 nft_flowtable_lookup_byhandle(const struct nft_table *table,
 			      const struct nlattr *nla, u8 genmask)

net/netfilter/nft_flow_offload.c

@@ -177,6 +177,23 @@ static int nft_flow_offload_init(const struct nft_ctx *ctx,
 	return nf_ct_netns_get(ctx->net, ctx->family);
 }
 
+static void nft_flow_offload_deactivate(const struct nft_ctx *ctx,
+					const struct nft_expr *expr,
+					enum nft_trans_phase phase)
+{
+	struct nft_flow_offload *priv = nft_expr_priv(expr);
+
+	nf_tables_deactivate_flowtable(ctx, priv->flowtable, phase);
+}
+
+static void nft_flow_offload_activate(const struct nft_ctx *ctx,
+				      const struct nft_expr *expr)
+{
+	struct nft_flow_offload *priv = nft_expr_priv(expr);
+
+	priv->flowtable->use++;
+}
+
 static void nft_flow_offload_destroy(const struct nft_ctx *ctx,
 				     const struct nft_expr *expr)
 {
@@ -205,6 +222,8 @@ static const struct nft_expr_ops nft_flow_offload_ops = {
 	.size		= NFT_EXPR_SIZE(sizeof(struct nft_flow_offload)),
 	.eval		= nft_flow_offload_eval,
 	.init		= nft_flow_offload_init,
+	.activate	= nft_flow_offload_activate,
+	.deactivate	= nft_flow_offload_deactivate,
 	.destroy	= nft_flow_offload_destroy,
 	.validate	= nft_flow_offload_validate,
 	.dump		= nft_flow_offload_dump,