netfilter: nf_tables: add helper functions for expression handling

Add helper functions for initializing, cloning, dumping and destroying
a single expression that is not part of a rule.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 51 insertions, 5 deletions

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index ed0e70ea2bc5..e97bee59fe08 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -1545,6 +1545,23 @@ nla_put_failure:
         return -1;
 };
 
+int nft_expr_dump(struct sk_buff *skb, unsigned int attr,
+                  const struct nft_expr *expr)
+{
+        struct nlattr *nest;
+
+        nest = nla_nest_start(skb, attr);
+        if (!nest)
+                goto nla_put_failure;
+        if (nf_tables_fill_expr_info(skb, expr) < 0)
+                goto nla_put_failure;
+        nla_nest_end(skb, nest);
+        return 0;
+
+nla_put_failure:
+        return -1;
+}
+
 struct nft_expr_info {
         const struct nft_expr_ops       *ops;
         struct nlattr                   *tb[NFT_EXPR_MAXATTR + 1];
@@ -1622,6 +1639,39 @@ static void nf_tables_expr_destroy(const struct nft_ctx *ctx,
         module_put(expr->ops->type->owner);
 }
 
+struct nft_expr *nft_expr_init(const struct nft_ctx *ctx,
+                               const struct nlattr *nla)
+{
+        struct nft_expr_info info;
+        struct nft_expr *expr;
+        int err;
+
+        err = nf_tables_expr_parse(ctx, nla, &info);
+        if (err < 0)
+                goto err1;
+
+        err = -ENOMEM;
+        expr = kzalloc(info.ops->size, GFP_KERNEL);
+        if (expr == NULL)
+                goto err2;
+
+        err = nf_tables_newexpr(ctx, &info, expr);
+        if (err < 0)
+                goto err2;
+
+        return expr;
+err2:
+        module_put(info.ops->type->owner);
+err1:
+        return ERR_PTR(err);
+}
+
+void nft_expr_destroy(const struct nft_ctx *ctx, struct nft_expr *expr)
+{
+        nf_tables_expr_destroy(ctx, expr);
+        kfree(expr);
+}
+
 /*
  * Rules
  */
@@ -1703,12 +1753,8 @@ static int nf_tables_fill_rule_info(struct sk_buff *skb, struct net *net,
         if (list == NULL)
                 goto nla_put_failure;
         nft_rule_for_each_expr(expr, next, rule) {
-                struct nlattr *elem = nla_nest_start(skb, NFTA_LIST_ELEM);
-                if (elem == NULL)
-                        goto nla_put_failure;
-                if (nf_tables_fill_expr_info(skb, expr) < 0)
+                if (nft_expr_dump(skb, NFTA_LIST_ELEM, expr) < 0)
                         goto nla_put_failure;
-                nla_nest_end(skb, elem);
         }
         nla_nest_end(skb, list);