netfilter: nf_tables: add stateful object reference expression

This new expression allows us to refer to existing stateful objects from
rules.

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

3 files changed, 119 insertions, 0 deletions

diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index def4be06cda6..63729b489c2c 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -551,6 +551,12 @@ config NFT_NAT
 	  This option adds the "nat" expression that you can use to perform
 	  typical Network Address Translation (NAT) packet transformations.
 
+config NFT_OBJREF
+	tristate "Netfilter nf_tables stateful object reference module"
+	help
+	  This option adds the "objref" expression that allows you to refer to
+	  stateful objects, such as counters and quotas.
+
 config NFT_QUEUE
 	depends on NETFILTER_NETLINK_QUEUE
 	tristate "Netfilter nf_tables queue module"
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index e4c8c1d7aaed..ca30d1960f1d 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -88,6 +88,7 @@ obj-$(CONFIG_NFT_NUMGEN)	+= nft_numgen.o
 obj-$(CONFIG_NFT_CT)		+= nft_ct.o
 obj-$(CONFIG_NFT_LIMIT)		+= nft_limit.o
 obj-$(CONFIG_NFT_NAT)		+= nft_nat.o
+obj-$(CONFIG_NFT_OBJREF)	+= nft_objref.o
 obj-$(CONFIG_NFT_QUEUE)		+= nft_queue.o
 obj-$(CONFIG_NFT_QUOTA)		+= nft_quota.o
 obj-$(CONFIG_NFT_REJECT) 	+= nft_reject.o
diff --git a/net/netfilter/nft_objref.c b/net/netfilter/nft_objref.c
new file mode 100644
index 000000000000..23820f796aad
--- /dev/null
+++ b/net/netfilter/nft_objref.c
@@ -0,0 +1,112 @@
+/*
+ * Copyright (c) 2012-2016 Pablo Neira Ayuso <pablo@netfilter.org>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/netlink.h>
+#include <linux/netfilter.h>
+#include <linux/netfilter/nf_tables.h>
+#include <net/netfilter/nf_tables.h>
+
+#define nft_objref_priv(expr)	*((struct nft_object **)nft_expr_priv(expr))
+
+static void nft_objref_eval(const struct nft_expr *expr,
+			    struct nft_regs *regs,
+			    const struct nft_pktinfo *pkt)
+{
+	struct nft_object *obj = nft_objref_priv(expr);
+
+	obj->type->eval(obj, regs, pkt);
+}
+
+static int nft_objref_init(const struct nft_ctx *ctx,
+			   const struct nft_expr *expr,
+			   const struct nlattr * const tb[])
+{
+	struct nft_object *obj = nft_objref_priv(expr);
+	u8 genmask = nft_genmask_next(ctx->net);
+	u32 objtype;
+
+	if (!tb[NFTA_OBJREF_IMM_NAME] ||
+	    !tb[NFTA_OBJREF_IMM_TYPE])
+		return -EINVAL;
+
+	objtype = ntohl(nla_get_be32(tb[NFTA_OBJREF_IMM_TYPE]));
+	obj = nf_tables_obj_lookup(ctx->table, tb[NFTA_OBJREF_IMM_NAME], objtype,
+				   genmask);
+	if (IS_ERR(obj))
+		return -ENOENT;
+
+	nft_objref_priv(expr) = obj;
+	obj->use++;
+
+	return 0;
+}
+
+static int nft_objref_dump(struct sk_buff *skb, const struct nft_expr *expr)
+{
+	const struct nft_object *obj = nft_objref_priv(expr);
+
+	if (nla_put_string(skb, NFTA_OBJREF_IMM_NAME, obj->name) ||
+	    nla_put_be32(skb, NFTA_OBJREF_IMM_TYPE, htonl(obj->type->type)))
+		goto nla_put_failure;
+
+	return 0;
+
+nla_put_failure:
+	return -1;
+}
+
+static void nft_objref_destroy(const struct nft_ctx *ctx,
+			       const struct nft_expr *expr)
+{
+	struct nft_object *obj = nft_objref_priv(expr);
+
+	obj->use--;
+}
+
+static struct nft_expr_type nft_objref_type;
+static const struct nft_expr_ops nft_objref_ops = {
+	.type		= &nft_objref_type,
+	.size		= NFT_EXPR_SIZE(sizeof(struct nft_object *)),
+	.eval		= nft_objref_eval,
+	.init		= nft_objref_init,
+	.destroy	= nft_objref_destroy,
+	.dump		= nft_objref_dump,
+};
+
+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 },
+};
+
+static struct nft_expr_type nft_objref_type __read_mostly = {
+	.name		= "objref",
+	.ops		= &nft_objref_ops,
+	.policy		= nft_objref_policy,
+	.maxattr	= NFTA_OBJREF_MAX,
+	.owner		= THIS_MODULE,
+};
+
+static int __init nft_objref_module_init(void)
+{
+	return nft_register_expr(&nft_objref_type);
+}
+
+static void __exit nft_objref_module_exit(void)
+{
+	nft_unregister_expr(&nft_objref_type);
+}
+
+module_init(nft_objref_module_init);
+module_exit(nft_objref_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
+MODULE_ALIAS_NFT_EXPR("objref");