[nf-next,v4,6/6] netfilter: nf_tables: add connlimit support

diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
index 6a3d653d5b27..05cd30063cf4 100644
--- a/include/uapi/linux/netfilter/nf_tables.h
+++ b/include/uapi/linux/netfilter/nf_tables.h
@@ -1010,6 +1010,24 @@  enum nft_limit_attributes {
 };
 #define NFTA_LIMIT_MAX		(__NFTA_LIMIT_MAX - 1)
 
+enum nft_connlimit_flags {
+	NFT_CONNLIMIT_F_INV	= (1 << 0),
+};
+
+/**
+ * enum nft_connlimit_attributes - nf_tables connlimit expression netlink attributes
+ *
+ * @NFTA_CONNLIMIT_COUNT: number of connections (NLA_U32)
+ * @NFTA_CONNLIMIT_FLAGS: flags (NLA_U32: enum nft_connlimit_flags)
+ */
+enum nft_connlimit_attributes {
+	NFTA_CONNLIMIT_UNSPEC,
+	NFTA_CONNLIMIT_COUNT,
+	NFTA_CONNLIMIT_FLAGS,
+	__NFTA_CONNLIMIT_MAX
+};
+#define NFTA_CONNLIMIT_MAX	(__NFTA_CONNLIMIT_MAX - 1)
+
 /**
  * enum nft_counter_attributes - nf_tables counter expression netlink attributes
  *
@@ -1315,7 +1333,8 @@  enum nft_ct_helper_attributes {
 #define NFT_OBJECT_QUOTA	2
 #define NFT_OBJECT_CT_HELPER	3
 #define NFT_OBJECT_LIMIT	4
-#define __NFT_OBJECT_MAX	5
+#define NFT_OBJECT_CONNLIMIT	5
+#define __NFT_OBJECT_MAX	6
 #define NFT_OBJECT_MAX		(__NFT_OBJECT_MAX - 1)
 
 /**
diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index 44d8a55e9721..2847d1f64647 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -536,6 +536,15 @@  config NFT_COUNTER
 	  This option adds the "counter" expression that you can use to
 	  include packet and byte counters in a rule.
 
+config NFT_CONNLIMIT
+	tristate "Netfilter nf_tables connlimit module"
+	depends on NF_CONNTRACK
+	depends on NETFILTER_ADVANCED
+	select NETFILTER_CONNCOUNT
+	help
+	  This option adds the "connlimit" expression that you can use to
+	  ratelimit rule matchings per connections.
+
 config NFT_LOG
 	tristate "Netfilter nf_tables log module"
 	help
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index fd32bd2c9521..b44dfd34b6bf 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -80,6 +80,7 @@  nf_tables-objs := nf_tables_core.o nf_tables_api.o nft_chain_filter.o \
 
 obj-$(CONFIG_NF_TABLES)		+= nf_tables.o
 obj-$(CONFIG_NFT_COMPAT)	+= nft_compat.o
+obj-$(CONFIG_NFT_CONNLIMIT)	+= nft_connlimit.o
 obj-$(CONFIG_NFT_EXTHDR)	+= nft_exthdr.o
 obj-$(CONFIG_NFT_META)		+= nft_meta.o
 obj-$(CONFIG_NFT_RT)		+= nft_rt.o
diff --git a/net/netfilter/nft_connlimit.c b/net/netfilter/nft_connlimit.c
new file mode 100644
index 000000000000..50c068d660e5
--- /dev/null
+++ b/net/netfilter/nft_connlimit.c
@@ -0,0 +1,297 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/spinlock.h>
+#include <linux/netlink.h>
+#include <linux/netfilter.h>
+#include <linux/netfilter/nf_tables.h>
+#include <net/netfilter/nf_tables.h>
+#include <net/netfilter/nf_conntrack.h>
+#include <net/netfilter/nf_conntrack_count.h>
+#include <net/netfilter/nf_conntrack_core.h>
+#include <net/netfilter/nf_conntrack_tuple.h>
+#include <net/netfilter/nf_conntrack_zones.h>
+
+struct nft_connlimit {
+	spinlock_t		lock;
+	struct hlist_head	hhead;
+	u32			limit;
+	bool			invert;
+};
+
+static inline void nft_connlimit_do_eval(struct nft_connlimit *priv,
+					 struct nft_regs *regs,
+					 const struct nft_pktinfo *pkt,
+					 const struct nft_set_ext *ext)
+{
+	const struct nf_conntrack_zone *zone = &nf_ct_zone_dflt;
+	const struct nf_conntrack_tuple *tuple_ptr;
+	struct nf_conntrack_tuple tuple;
+	enum ip_conntrack_info ctinfo;
+	const struct nf_conn *ct;
+	unsigned int count;
+	bool addit;
+
+	tuple_ptr = &tuple;
+
+	ct = nf_ct_get(pkt->skb, &ctinfo);
+	if (ct != NULL) {
+		tuple_ptr = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
+		zone = nf_ct_zone(ct);
+	} else if (!nf_ct_get_tuplepr(pkt->skb, skb_network_offset(pkt->skb),
+				      nft_pf(pkt), nft_net(pkt), &tuple)) {
+		regs->verdict.code = NF_DROP;
+		return;
+	}
+
+	spin_lock_bh(&priv->lock);
+	count = nf_conncount_lookup(nft_net(pkt), &priv->hhead, tuple_ptr, zone,
+				    &addit);
+
+	if (!addit)
+		goto out;
+
+	if (!nf_conncount_add(&priv->hhead, tuple_ptr)) {
+		regs->verdict.code = NF_DROP;
+		spin_unlock_bh(&priv->lock);
+		return;
+	}
+	count++;
+out:
+	spin_unlock_bh(&priv->lock);
+
+	if ((count > priv->limit) ^ priv->invert) {
+		regs->verdict.code = NFT_BREAK;
+		return;
+	}
+}
+
+static int nft_connlimit_do_init(const struct nft_ctx *ctx,
+				 const struct nlattr * const tb[],
+				 struct nft_connlimit *priv)
+{
+	bool invert = false;
+	u32 flags, limit;
+
+	if (!tb[NFTA_CONNLIMIT_COUNT])
+		return -EINVAL;
+
+	limit = ntohl(nla_get_be32(tb[NFTA_CONNLIMIT_COUNT]));
+
+	if (tb[NFTA_CONNLIMIT_FLAGS]) {
+		flags = ntohl(nla_get_be32(tb[NFTA_CONNLIMIT_FLAGS]));
+		if (flags & ~NFT_CONNLIMIT_F_INV)
+			return -EOPNOTSUPP;
+		if (flags & NFT_CONNLIMIT_F_INV)
+			invert = true;
+	}
+
+	spin_lock_init(&priv->lock);
+	INIT_HLIST_HEAD(&priv->hhead);
+	priv->limit	= limit;
+	priv->invert	= invert;
+
+	return nf_ct_netns_get(ctx->net, ctx->family);
+}
+
+static void nft_connlimit_do_destroy(const struct nft_ctx *ctx,
+				     struct nft_connlimit *priv)
+{
+	nf_ct_netns_put(ctx->net, ctx->family);
+	nf_conncount_cache_free(&priv->hhead);
+}
+
+static int nft_connlimit_do_dump(struct sk_buff *skb,
+				 struct nft_connlimit *priv)
+{
+	if (nla_put_be32(skb, NFTA_CONNLIMIT_COUNT, htonl(priv->limit)))
+		goto nla_put_failure;
+	if (priv->invert &&
+	    nla_put_be32(skb, NFTA_CONNLIMIT_FLAGS, htonl(NFT_CONNLIMIT_F_INV)))
+		goto nla_put_failure;
+
+	return 0;
+
+nla_put_failure:
+	return -1;
+}
+
+static inline void nft_connlimit_obj_eval(struct nft_object *obj,
+					struct nft_regs *regs,
+					const struct nft_pktinfo *pkt)
+{
+	struct nft_connlimit *priv = nft_obj_data(obj);
+
+	nft_connlimit_do_eval(priv, regs, pkt, NULL);
+}
+
+static int nft_connlimit_obj_init(const struct nft_ctx *ctx,
+				const struct nlattr * const tb[],
+				struct nft_object *obj)
+{
+	struct nft_connlimit *priv = nft_obj_data(obj);
+
+	return nft_connlimit_do_init(ctx, tb, priv);
+}
+
+static void nft_connlimit_obj_destroy(const struct nft_ctx *ctx,
+				      struct nft_object *obj)
+{
+	struct nft_connlimit *priv = nft_obj_data(obj);
+
+	nft_connlimit_do_destroy(ctx, priv);
+}
+
+static int nft_connlimit_obj_dump(struct sk_buff *skb,
+				  struct nft_object *obj, bool reset)
+{
+	struct nft_connlimit *priv = nft_obj_data(obj);
+
+	return nft_connlimit_do_dump(skb, priv);
+}
+
+static const struct nla_policy nft_connlimit_policy[NFTA_CONNLIMIT_MAX + 1] = {
+	[NFTA_CONNLIMIT_COUNT]	= { .type = NLA_U32 },
+	[NFTA_CONNLIMIT_FLAGS]	= { .type = NLA_U32 },
+};
+
+static struct nft_object_type nft_connlimit_obj_type;
+static const struct nft_object_ops nft_connlimit_obj_ops = {
+	.type		= &nft_connlimit_obj_type,
+	.size		= sizeof(struct nft_connlimit),
+	.eval		= nft_connlimit_obj_eval,
+	.init		= nft_connlimit_obj_init,
+	.destroy	= nft_connlimit_obj_destroy,
+	.dump		= nft_connlimit_obj_dump,
+};
+
+static struct nft_object_type nft_connlimit_obj_type __read_mostly = {
+	.type		= NFT_OBJECT_CONNLIMIT,
+	.ops		= &nft_connlimit_obj_ops,
+	.maxattr	= NFTA_CONNLIMIT_MAX,
+	.policy		= nft_connlimit_policy,
+	.owner		= THIS_MODULE,
+};
+
+static void nft_connlimit_eval(const struct nft_expr *expr,
+			       struct nft_regs *regs,
+			       const struct nft_pktinfo *pkt)
+{
+	struct nft_connlimit *priv = nft_expr_priv(expr);
+
+	nft_connlimit_do_eval(priv, regs, pkt, NULL);
+}
+
+static int nft_connlimit_dump(struct sk_buff *skb, const struct nft_expr *expr)
+{
+	struct nft_connlimit *priv = nft_expr_priv(expr);
+
+	return nft_connlimit_do_dump(skb, priv);
+}
+
+static int nft_connlimit_init(const struct nft_ctx *ctx,
+			      const struct nft_expr *expr,
+			      const struct nlattr * const tb[])
+{
+	struct nft_connlimit *priv = nft_expr_priv(expr);
+
+	return nft_connlimit_do_init(ctx, tb, priv);
+}
+
+static void nft_connlimit_destroy(const struct nft_ctx *ctx,
+				const struct nft_expr *expr)
+{
+	struct nft_connlimit *priv = nft_expr_priv(expr);
+
+	nft_connlimit_do_destroy(ctx, priv);
+}
+
+static int nft_connlimit_clone(struct nft_expr *dst, const struct nft_expr *src)
+{
+	struct nft_connlimit *priv_dst = nft_expr_priv(dst);
+	struct nft_connlimit *priv_src = nft_expr_priv(src);
+
+	spin_lock_init(&priv_dst->lock);
+	INIT_HLIST_HEAD(&priv_dst->hhead);
+	priv_dst->limit	 = priv_src->limit;
+	priv_dst->invert = priv_src->invert;
+
+	return 0;
+}
+
+static void nft_connlimit_destroy_clone(const struct nft_ctx *ctx,
+					const struct nft_expr *expr)
+{
+	struct nft_connlimit *priv = nft_expr_priv(expr);
+
+	nf_conncount_cache_free(&priv->hhead);
+}
+
+static bool nft_connlimit_gc(struct net *net, const struct nft_expr *expr)
+{
+	struct nft_connlimit *priv = nft_expr_priv(expr);
+	bool addit, ret;
+
+	spin_lock_bh(&priv->lock);
+	nf_conncount_lookup(net, &priv->hhead, NULL, &nf_ct_zone_dflt, &addit);
+
+	ret = hlist_empty(&priv->hhead);
+	spin_unlock_bh(&priv->lock);
+
+	return ret;
+}
+
+static struct nft_expr_type nft_connlimit_type;
+static const struct nft_expr_ops nft_connlimit_ops = {
+	.type		= &nft_connlimit_type,
+	.size		= NFT_EXPR_SIZE(sizeof(struct nft_connlimit)),
+	.eval		= nft_connlimit_eval,
+	.init		= nft_connlimit_init,
+	.destroy	= nft_connlimit_destroy,
+	.clone		= nft_connlimit_clone,
+	.destroy_clone	= nft_connlimit_destroy_clone,
+	.dump		= nft_connlimit_dump,
+	.gc		= nft_connlimit_gc,
+};
+
+static struct nft_expr_type nft_connlimit_type __read_mostly = {
+	.name		= "connlimit",
+	.ops		= &nft_connlimit_ops,
+	.policy		= nft_connlimit_policy,
+	.maxattr	= NFTA_CONNLIMIT_MAX,
+	.flags		= NFT_EXPR_STATEFUL | NFT_EXPR_GC,
+	.owner		= THIS_MODULE,
+};
+
+static int __init nft_connlimit_module_init(void)
+{
+	int err;
+
+	err = nft_register_obj(&nft_connlimit_obj_type);
+	if (err < 0)
+		return err;
+
+	err = nft_register_expr(&nft_connlimit_type);
+	if (err < 0)
+		goto err1;
+
+	return 0;
+err1:
+	nft_unregister_obj(&nft_connlimit_obj_type);
+	return err;
+}
+
+static void __exit nft_connlimit_module_exit(void)
+{
+	nft_unregister_expr(&nft_connlimit_type);
+	nft_unregister_obj(&nft_connlimit_obj_type);
+}
+
+module_init(nft_connlimit_module_init);
+module_exit(nft_connlimit_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Pablo Neira Ayuso");
+MODULE_ALIAS_NFT_EXPR("connlimit");
+MODULE_ALIAS_NFT_OBJ(NFT_OBJECT_CONNLIMIT);