netfilter: nf_tables: add stateful objects

This patch augments nf_tables to support stateful objects. This new
infrastructure allows you to create, dump and delete stateful objects,
that are identified by a user-defined name.

This patch adds the generic infrastructure, follow up patches add
support for two stateful objects: counters and quotas.

This patch provides a native infrastructure for nf_tables to replace
nfacct, the extended accounting infrastructure for iptables.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/netfilter/nf_tables.h

@@ -875,6 +875,7 @@ unsigned int nft_do_chain(struct nft_pktinfo *pkt, void *priv);
  *	@list: used internally
  *	@chains: chains in the table
  *	@sets: sets in the table
+ *	@objects: stateful objects in the table
  *	@hgenerator: handle generator state
  *	@use: number of chain references to this table
  *	@flags: table flag (see enum nft_table_flags)
@@ -885,6 +886,7 @@ struct nft_table {
 	struct list_head		list;
 	struct list_head		chains;
 	struct list_head		sets;
+	struct list_head		objects;
 	u64				hgenerator;
 	u32				use;
 	u16				flags:14,
@@ -934,6 +936,73 @@ void nft_unregister_expr(struct nft_expr_type *);
 int nft_verdict_dump(struct sk_buff *skb, int type,
 		     const struct nft_verdict *v);
 
+/**
+ *	struct nft_object - nf_tables stateful object
+ *
+ *	@list: table stateful object list node
+ *	@type: pointer to object type
+ *	@data: pointer to object data
+ *	@name: name of this stateful object
+ *	@genmask: generation mask
+ *	@use: number of references to this stateful object
+ * 	@data: object data, layout depends on type
+ */
+struct nft_object {
+	struct list_head		list;
+	char				name[NFT_OBJ_MAXNAMELEN];
+	u32				genmask:2,
+					use:30;
+	/* runtime data below here */
+	const struct nft_object_type	*type ____cacheline_aligned;
+	unsigned char			data[]
+		__attribute__((aligned(__alignof__(u64))));
+};
+
+static inline void *nft_obj_data(const struct nft_object *obj)
+{
+	return (void *)obj->data;
+}
+
+#define nft_expr_obj(expr)	*((struct nft_object **)nft_expr_priv(expr))
+
+struct nft_object *nf_tables_obj_lookup(const struct nft_table *table,
+					const struct nlattr *nla, u32 objtype,
+					u8 genmask);
+
+/**
+ *	struct nft_object_type - stateful object type
+ *
+ *	@eval: stateful object evaluation function
+ *	@list: list node in list of object types
+ *	@type: stateful object numeric type
+ *	@size: stateful object size
+ *	@owner: module owner
+ *	@maxattr: maximum netlink attribute
+ *	@policy: netlink attribute policy
+ *	@init: initialize object from netlink attributes
+ *	@destroy: release existing stateful object
+ *	@dump: netlink dump stateful object
+ */
+struct nft_object_type {
+	void				(*eval)(struct nft_object *obj,
+						struct nft_regs *regs,
+						const struct nft_pktinfo *pkt);
+	struct list_head		list;
+	u32				type;
+	unsigned int			size;
+	unsigned int			maxattr;
+	struct module			*owner;
+	const struct nla_policy		*policy;
+	int				(*init)(const struct nlattr * const tb[],
+						struct nft_object *obj);
+	void				(*destroy)(struct nft_object *obj);
+	int				(*dump)(struct sk_buff *skb,
+						const struct nft_object *obj);
+};
+
+int nft_register_obj(struct nft_object_type *obj_type);
+void nft_unregister_obj(struct nft_object_type *obj_type);
+
 /**
  *	struct nft_traceinfo - nft tracing information and state
  *
@@ -981,6 +1050,9 @@ void nft_trace_notify(struct nft_traceinfo *info);
 #define MODULE_ALIAS_NFT_SET() \
 	MODULE_ALIAS("nft-set")
 
+#define MODULE_ALIAS_NFT_OBJ(type) \
+	MODULE_ALIAS("nft-obj-" __stringify(type))
+
 /*
  * The gencursor defines two generations, the currently active and the
  * next one. Objects contain a bitmask of 2 bits specifying the generations
@@ -1157,4 +1229,11 @@ struct nft_trans_elem {
 #define nft_trans_elem(trans)	\
 	(((struct nft_trans_elem *)trans->data)->elem)
 
+struct nft_trans_obj {
+	struct nft_object		*obj;
+};
+
+#define nft_trans_obj(trans)	\
+	(((struct nft_trans_obj *)trans->data)->obj)
+
 #endif /* _NET_NF_TABLES_H */

include/uapi/linux/netfilter/nf_tables.h

@@ -4,6 +4,7 @@
 #define NFT_TABLE_MAXNAMELEN	32
 #define NFT_CHAIN_MAXNAMELEN	32
 #define NFT_SET_MAXNAMELEN	32
+#define NFT_OBJ_MAXNAMELEN	32
 #define NFT_USERDATA_MAXLEN	256
 
 /**
@@ -85,6 +86,9 @@ enum nft_verdicts {
  * @NFT_MSG_NEWGEN: announce a new generation, only for events (enum nft_gen_attributes)
  * @NFT_MSG_GETGEN: get the rule-set generation (enum nft_gen_attributes)
  * @NFT_MSG_TRACE: trace event (enum nft_trace_attributes)
+ * @NFT_MSG_NEWOBJ: create a stateful object (enum nft_obj_attributes)
+ * @NFT_MSG_GETOBJ: get a stateful object (enum nft_obj_attributes)
+ * @NFT_MSG_DELOBJ: delete a stateful object (enum nft_obj_attributes)
  */
 enum nf_tables_msg_types {
 	NFT_MSG_NEWTABLE,
@@ -105,6 +109,9 @@ enum nf_tables_msg_types {
 	NFT_MSG_NEWGEN,
 	NFT_MSG_GETGEN,
 	NFT_MSG_TRACE,
+	NFT_MSG_NEWOBJ,
+	NFT_MSG_GETOBJ,
+	NFT_MSG_DELOBJ,
 	NFT_MSG_MAX,
 };
 
@@ -1178,6 +1185,28 @@ enum nft_fib_flags {
 	NFTA_FIB_F_OIF		= 1 << 4,	/* restrict to oif */
 };
 
+#define NFT_OBJECT_UNSPEC	0
+
+/**
+ * enum nft_object_attributes - nf_tables stateful object netlink attributes
+ *
+ * @NFTA_OBJ_TABLE: name of the table containing the expression (NLA_STRING)
+ * @NFTA_OBJ_NAME: name of this expression type (NLA_STRING)
+ * @NFTA_OBJ_TYPE: stateful object type (NLA_U32)
+ * @NFTA_OBJ_DATA: stateful object data (NLA_NESTED)
+ * @NFTA_OBJ_USE: number of references to this expression (NLA_U32)
+ */
+enum nft_object_attributes {
+	NFTA_OBJ_UNSPEC,
+	NFTA_OBJ_TABLE,
+	NFTA_OBJ_NAME,
+	NFTA_OBJ_TYPE,
+	NFTA_OBJ_DATA,
+	NFTA_OBJ_USE,
+	__NFTA_OBJ_MAX
+};
+#define NFTA_OBJ_MAX		(__NFTA_OBJ_MAX - 1)
+
 /**
  * enum nft_trace_attributes - nf_tables trace netlink attributes
  *