[PATCH WIP nf-next] netfilter: nf_tables: Introduce stateful object update operation

[Fernando Fernandez Mancera <ffmancera@xxxxxxxxxx>]

This is a WIP patch version. I still having some issues in userspace but I
would like to get feedback about the kernel-side patch. Thanks!

Signed-off-by: Fernando Fernandez Mancera <ffmancera@xxxxxxxxxx>
---
 include/net/netfilter/nf_tables.h |  6 +++
 net/netfilter/nf_tables_api.c     | 73 ++++++++++++++++++++++++++++---
 2 files changed, 72 insertions(+), 7 deletions(-)

diff --git a/include/net/netfilter/nf_tables.h b/include/net/netfilter/nf_tables.h
index dc301e3d6739..dc4e32040ea9 100644
--- a/include/net/netfilter/nf_tables.h
+++ b/include/net/netfilter/nf_tables.h
@@ -1123,6 +1123,9 @@ struct nft_object_ops {
 	int				(*dump)(struct sk_buff *skb,
 						struct nft_object *obj,
 						bool reset);
+	int				(*update)(const struct nft_ctx *ctx,
+						  const struct nlattr *const tb[],
+						  struct nft_object *obj);
 	const struct nft_object_type	*type;
 };
 
@@ -1405,10 +1408,13 @@ struct nft_trans_elem {
 
 struct nft_trans_obj {
 	struct nft_object		*obj;
+	bool				update;
 };
 
 #define nft_trans_obj(trans)	\
 	(((struct nft_trans_obj *)trans->data)->obj)
+#define nft_trans_obj_update(trans)	\
+	(((struct nft_trans_obj *)trans->data)->update)
 
 struct nft_trans_flowtable {
 	struct nft_flowtable		*flowtable;
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index fe3b7b0c6c66..d7b94904599c 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -5122,6 +5122,48 @@ nft_obj_type_get(struct net *net, u32 objtype)
 	return ERR_PTR(-ENOENT);
 }
 
+static int nf_tables_updobj(const struct nft_ctx *ctx,
+			    const struct nft_object_type *type,
+			    const struct nlattr *attr,
+			    struct nft_object *obj)
+{
+	struct nft_trans *trans;
+	struct nlattr **tb;
+	int err = -ENOMEM;
+
+	trans = nft_trans_alloc(ctx, NFT_MSG_NEWOBJ,
+				sizeof(struct nft_trans_obj));
+	if (!trans)
+		return -ENOMEM;
+
+	tb = kmalloc_array(type->maxattr + 1, sizeof(*tb), GFP_KERNEL);
+	if (!tb)
+		goto err;
+
+	if (attr) {
+		err = nla_parse_nested_deprecated(tb, type->maxattr, attr,
+						  type->policy, NULL);
+		if (err < 0)
+			goto err;
+	} else {
+		memset(tb, 0, sizeof(tb[0]) * (type->maxattr + 1));
+	}
+
+	err = obj->ops->update(ctx, (const struct nlattr * const *)tb, obj);
+	if (err < 0)
+		goto err;
+
+	nft_trans_obj_update(trans) = true;
+	list_add_tail(&trans->list, &ctx->net->nft.commit_list);
+
+	kfree(tb);
+	return 0;
+
+err:
+	nft_trans_destroy(trans);
+	return err;
+}
+
 static int nf_tables_newobj(struct net *net, struct sock *nlsk,
 			    struct sk_buff *skb, const struct nlmsghdr *nlh,
 			    const struct nlattr * const nla[],
@@ -5161,7 +5203,13 @@ static int nf_tables_newobj(struct net *net, struct sock *nlsk,
 			NL_SET_BAD_ATTR(extack, nla[NFTA_OBJ_NAME]);
 			return -EEXIST;
 		}
-		return 0;
+		if (nlh->nlmsg_flags & NLM_F_REPLACE)
+			return -EOPNOTSUPP;
+
+		type = nft_obj_type_get(net, objtype);
+		nft_ctx_init(&ctx, net, skb, nlh, family, table, NULL, nla);
+
+		return nf_tables_updobj(&ctx, type, nla[NFTA_OBJ_DATA], obj);
 	}
 
 	nft_ctx_init(&ctx, net, skb, nlh, family, table, NULL, nla);
@@ -6786,10 +6834,17 @@ static int nf_tables_commit(struct net *net, struct sk_buff *skb)
 			te->set->ndeact--;
 			break;
 		case NFT_MSG_NEWOBJ:
-			nft_clear(net, nft_trans_obj(trans));
-			nf_tables_obj_notify(&trans->ctx, nft_trans_obj(trans),
-					     NFT_MSG_NEWOBJ);
-			nft_trans_destroy(trans);
+			if (nft_trans_obj_update(trans)) {
+				nf_tables_obj_notify(&trans->ctx,
+						     nft_trans_obj(trans),
+						     NFT_MSG_NEWOBJ);
+			} else {
+				nft_clear(net, nft_trans_obj(trans));
+				nf_tables_obj_notify(&trans->ctx,
+						     nft_trans_obj(trans),
+						     NFT_MSG_NEWOBJ);
+				nft_trans_destroy(trans);
+			}
 			break;
 		case NFT_MSG_DELOBJ:
 			nft_obj_del(nft_trans_obj(trans));
@@ -6936,8 +6991,12 @@ static int __nf_tables_abort(struct net *net)
 			nft_trans_destroy(trans);
 			break;
 		case NFT_MSG_NEWOBJ:
-			trans->ctx.table->use--;
-			nft_obj_del(nft_trans_obj(trans));
+			if (nft_trans_obj_update(trans)) {
+				nft_trans_destroy(trans);
+			} else {
+				trans->ctx.table->use--;
+				nft_obj_del(nft_trans_obj(trans));
+			}
 			break;
 		case NFT_MSG_DELOBJ:
 			trans->ctx.table->use++;
-- 
2.20.1