netfilter: nft_objref: support for stateful object maps

This patch allows us to refer to stateful object dictionaries, the
source register indicates the key data to be used to look up for the
corresponding state object. We can refer to these maps through names or,
alternatively, the map transaction id. This allows us to refer to both
anonymous and named maps.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/uapi/linux/netfilter/nf_tables.h

@@ -1153,11 +1153,17 @@ enum nft_fwd_attributes {
  *
  * @NFTA_OBJREF_IMM_TYPE: object type for immediate reference (NLA_U32: nft_register)
  * @NFTA_OBJREF_IMM_NAME: object name for immediate reference (NLA_STRING)
+ * @NFTA_OBJREF_SET_SREG: source register of the data to look for (NLA_U32: nft_registers)
+ * @NFTA_OBJREF_SET_NAME: name of the set where to look for (NLA_STRING)
+ * @NFTA_OBJREF_SET_ID: id of the set where to look for in this transaction (NLA_U32)
  */
 enum nft_objref_attributes {
 	NFTA_OBJREF_UNSPEC,
 	NFTA_OBJREF_IMM_TYPE,
 	NFTA_OBJREF_IMM_NAME,
+	NFTA_OBJREF_SET_SREG,
+	NFTA_OBJREF_SET_NAME,
+	NFTA_OBJREF_SET_ID,
 	__NFTA_OBJREF_MAX
 };
 #define NFTA_OBJREF_MAX	(__NFTA_OBJREF_MAX - 1)

net/netfilter/nf_tables_api.c

@@ -2504,6 +2504,7 @@ struct nft_set *nf_tables_set_lookup(const struct nft_table *table,
 	}
 	return ERR_PTR(-ENOENT);
 }
+EXPORT_SYMBOL_GPL(nf_tables_set_lookup);
 
 struct nft_set *nf_tables_set_lookup_byid(const struct net *net,
 					  const struct nlattr *nla,
@@ -2522,6 +2523,7 @@ struct nft_set *nf_tables_set_lookup_byid(const struct net *net,
 	}
 	return ERR_PTR(-ENOENT);
 }
+EXPORT_SYMBOL_GPL(nf_tables_set_lookup_byid);
 
 static int nf_tables_set_alloc_name(struct nft_ctx *ctx, struct nft_set *set,
 				    const char *name)
@@ -3124,6 +3126,7 @@ int nf_tables_bind_set(const struct nft_ctx *ctx, struct nft_set *set,
 	list_add_tail_rcu(&binding->list, &set->bindings);
 	return 0;
 }
+EXPORT_SYMBOL_GPL(nf_tables_bind_set);
 
 void nf_tables_unbind_set(const struct nft_ctx *ctx, struct nft_set *set,
 			  struct nft_set_binding *binding)
@@ -3134,6 +3137,7 @@ void nf_tables_unbind_set(const struct nft_ctx *ctx, struct nft_set *set,
 	    nft_is_active(ctx->net, set))
 		nf_tables_set_destroy(ctx, set);
 }
+EXPORT_SYMBOL_GPL(nf_tables_unbind_set);
 
 const struct nft_set_ext_type nft_set_ext_types[] = {
 	[NFT_SET_EXT_KEY]		= {

net/netfilter/nft_objref.c

@@ -81,14 +81,128 @@ static const struct nft_expr_ops nft_objref_ops = {
 	.dump		= nft_objref_dump,
 };
 
+struct nft_objref_map {
+	struct nft_set		*set;
+	enum nft_registers	sreg:8;
+	struct nft_set_binding	binding;
+};
+
+static void nft_objref_map_eval(const struct nft_expr *expr,
+				struct nft_regs *regs,
+				const struct nft_pktinfo *pkt)
+{
+	struct nft_objref_map *priv = nft_expr_priv(expr);
+	const struct nft_set *set = priv->set;
+	const struct nft_set_ext *ext;
+	struct nft_object *obj;
+	bool found;
+
+	found = set->ops->lookup(nft_net(pkt), set, &regs->data[priv->sreg],
+				 &ext);
+	if (!found) {
+		regs->verdict.code = NFT_BREAK;
+		return;
+	}
+	obj = *nft_set_ext_obj(ext);
+	obj->type->eval(obj, regs, pkt);
+}
+
+static int nft_objref_map_init(const struct nft_ctx *ctx,
+			       const struct nft_expr *expr,
+			       const struct nlattr * const tb[])
+{
+	struct nft_objref_map *priv = nft_expr_priv(expr);
+	u8 genmask = nft_genmask_next(ctx->net);
+	struct nft_set *set;
+	int err;
+
+	set = nf_tables_set_lookup(ctx->table, tb[NFTA_OBJREF_SET_NAME], genmask);
+	if (IS_ERR(set)) {
+		if (tb[NFTA_OBJREF_SET_ID]) {
+			set = nf_tables_set_lookup_byid(ctx->net,
+							tb[NFTA_OBJREF_SET_ID],
+							genmask);
+		}
+		if (IS_ERR(set))
+			return PTR_ERR(set);
+	}
+
+	if (!(set->flags & NFT_SET_OBJECT))
+		return -EINVAL;
+
+	priv->sreg = nft_parse_register(tb[NFTA_OBJREF_SET_SREG]);
+	err = nft_validate_register_load(priv->sreg, set->klen);
+	if (err < 0)
+		return err;
+
+	priv->binding.flags = set->flags & NFT_SET_OBJECT;
+
+	err = nf_tables_bind_set(ctx, set, &priv->binding);
+	if (err < 0)
+		return err;
+
+	priv->set = set;
+	return 0;
+}
+
+static int nft_objref_map_dump(struct sk_buff *skb, const struct nft_expr *expr)
+{
+	const struct nft_objref_map *priv = nft_expr_priv(expr);
+
+	if (nft_dump_register(skb, NFTA_OBJREF_SET_SREG, priv->sreg) ||
+	    nla_put_string(skb, NFTA_OBJREF_SET_NAME, priv->set->name))
+		goto nla_put_failure;
+
+	return 0;
+
+nla_put_failure:
+	return -1;
+}
+
+static void nft_objref_map_destroy(const struct nft_ctx *ctx,
+				   const struct nft_expr *expr)
+{
+	struct nft_objref_map *priv = nft_expr_priv(expr);
+
+	nf_tables_unbind_set(ctx, priv->set, &priv->binding);
+}
+
+static struct nft_expr_type nft_objref_type;
+static const struct nft_expr_ops nft_objref_map_ops = {
+	.type		= &nft_objref_type,
+	.size		= NFT_EXPR_SIZE(sizeof(struct nft_objref_map)),
+	.eval		= nft_objref_map_eval,
+	.init		= nft_objref_map_init,
+	.destroy	= nft_objref_map_destroy,
+	.dump		= nft_objref_map_dump,
+};
+
+static const struct nft_expr_ops *
+nft_objref_select_ops(const struct nft_ctx *ctx,
+                      const struct nlattr * const tb[])
+{
+	if (tb[NFTA_OBJREF_SET_SREG] &&
+	    (tb[NFTA_OBJREF_SET_NAME] ||
+	     tb[NFTA_OBJREF_SET_ID]))
+		return &nft_objref_map_ops;
+	else if (tb[NFTA_OBJREF_IMM_NAME] &&
+		 tb[NFTA_OBJREF_IMM_TYPE])
+		return &nft_objref_ops;
+
+	return ERR_PTR(-EOPNOTSUPP);
+}
+
 static const struct nla_policy nft_objref_policy[NFTA_OBJREF_MAX + 1] = {
 	[NFTA_OBJREF_IMM_NAME]	= { .type = NLA_STRING },
 	[NFTA_OBJREF_IMM_TYPE]	= { .type = NLA_U32 },
+	[NFTA_OBJREF_SET_SREG]	= { .type = NLA_U32 },
+	[NFTA_OBJREF_SET_NAME]	= { .type = NLA_STRING },
+	[NFTA_OBJREF_SET_ID]	= { .type = NLA_U32 },
 };
 
 static struct nft_expr_type nft_objref_type __read_mostly = {
 	.name		= "objref",
-	.ops		= &nft_objref_ops,
+	.select_ops	= nft_objref_select_ops,
 	.policy		= nft_objref_policy,
 	.maxattr	= NFTA_OBJREF_MAX,
 	.owner		= THIS_MODULE,