[nf-next,v3,6/7] netfilter: nf_tables: flow offload expression

diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
index 9ba0f4c13de6..528d832fefb4 100644
--- a/include/uapi/linux/netfilter/nf_tables.h
+++ b/include/uapi/linux/netfilter/nf_tables.h
@@ -954,6 +954,17 @@  enum nft_ct_attributes {
 };
 #define NFTA_CT_MAX		(__NFTA_CT_MAX - 1)
 
+/**
+ * enum nft_flow_attributes - ct offload expression attributes
+ * @NFTA_FLOW_TABLE_NAME: flow table name (NLA_STRING)
+ */
+enum nft_offload_attributes {
+	NFTA_FLOW_UNSPEC,
+	NFTA_FLOW_TABLE_NAME,
+	__NFTA_FLOW_MAX,
+};
+#define NFTA_FLOW_MAX		(__NFTA_FLOW_MAX - 1)
+
 enum nft_limit_type {
 	NFT_LIMIT_PKTS,
 	NFT_LIMIT_PKT_BYTES
diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index 0c6256db5a6c..1ada46345f3c 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -497,6 +497,13 @@  config NFT_CT
 	  This option adds the "ct" expression that you can use to match
 	  connection tracking information such as the flow state.
 
+config NFT_FLOW_OFFLOAD
+	depends on NF_CONNTRACK
+	tristate "Netfilter nf_tables hardware flow offload module"
+	help
+	  This option adds the "flow_offload" expression that you can use to
+	  choose what flows are placed into the hardware.
+
 config NFT_SET_RBTREE
 	tristate "Netfilter nf_tables rbtree set module"
 	help
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index 1f7d92bd571a..2c1b8de922f2 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -83,6 +83,7 @@  obj-$(CONFIG_NFT_META)		+= nft_meta.o
 obj-$(CONFIG_NFT_RT)		+= nft_rt.o
 obj-$(CONFIG_NFT_NUMGEN)	+= nft_numgen.o
 obj-$(CONFIG_NFT_CT)		+= nft_ct.o
+obj-$(CONFIG_NFT_FLOW_OFFLOAD)	+= nft_flow_offload.o
 obj-$(CONFIG_NFT_LIMIT)		+= nft_limit.o
 obj-$(CONFIG_NFT_NAT)		+= nft_nat.o
 obj-$(CONFIG_NFT_OBJREF)	+= nft_objref.o
diff --git a/net/netfilter/nft_flow_offload.c b/net/netfilter/nft_flow_offload.c
new file mode 100644
index 000000000000..4f16c37acaa3
--- /dev/null
+++ b/net/netfilter/nft_flow_offload.c
@@ -0,0 +1,268 @@ 
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/netlink.h>
+#include <linux/netfilter.h>
+#include <linux/workqueue.h>
+#include <linux/spinlock.h>
+#include <linux/netfilter/nf_tables.h>
+#include <net/ip.h> /* for ipv4 options. */
+#include <net/netfilter/nf_tables.h>
+#include <net/netfilter/nf_tables_core.h>
+#include <net/netfilter/nf_conntrack_core.h>
+#include <linux/netfilter/nf_conntrack_common.h>
+#include <net/netfilter/nf_flow_table.h>
+
+struct nft_flow_offload {
+	struct nft_flowtable	*flowtable;
+};
+
+static int nft_flow_route(const struct nft_pktinfo *pkt,
+			  const struct nf_conn *ct,
+			  struct nf_flow_route *route,
+			  enum ip_conntrack_dir dir)
+{
+	struct dst_entry *this_dst = skb_dst(pkt->skb);
+	struct dst_entry *other_dst;
+	const struct nf_afinfo *ai;
+	struct flowi fl;
+
+	memset(&fl, 0, sizeof(fl));
+	switch (nft_pf(pkt)) {
+	case NFPROTO_IPV4:
+		fl.u.ip4.daddr = ct->tuplehash[!dir].tuple.dst.u3.ip;
+		break;
+	case NFPROTO_IPV6:
+		fl.u.ip6.daddr = ct->tuplehash[!dir].tuple.dst.u3.in6;
+		break;
+	}
+
+	ai = nf_get_afinfo(nft_pf(pkt));
+	if (ai) {
+		ai->route(nft_net(pkt), &other_dst, &fl, false);
+		if (!other_dst)
+			return -ENOENT;
+	}
+
+	route->tuple[dir].dst		= this_dst;
+	route->tuple[dir].ifindex	= nft_in(pkt)->ifindex;
+	route->tuple[!dir].dst		= other_dst;
+	route->tuple[!dir].ifindex	= nft_out(pkt)->ifindex;
+
+	return 0;
+}
+
+static bool nft_flow_offload_skip(struct sk_buff *skb)
+{
+	struct ip_options *opt  = &(IPCB(skb)->opt);
+
+	if (unlikely(opt->optlen))
+		return true;
+	if (skb_sec_path(skb))
+		return true;
+
+	return false;
+}
+
+static void nft_flow_offload_eval(const struct nft_expr *expr,
+				  struct nft_regs *regs,
+				  const struct nft_pktinfo *pkt)
+{
+	struct nft_flow_offload *priv = nft_expr_priv(expr);
+	struct nf_flowtable *flowtable = &priv->flowtable->data;
+	enum ip_conntrack_info ctinfo;
+	struct nf_flow_route route;
+	struct flow_offload *flow;
+	enum ip_conntrack_dir dir;
+	struct nf_conn *ct;
+	int ret;
+
+	if (nft_flow_offload_skip(pkt->skb))
+		goto out;
+
+	ct = nf_ct_get(pkt->skb, &ctinfo);
+	if (!ct)
+		goto out;
+
+	switch (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum) {
+	case IPPROTO_TCP:
+	case IPPROTO_UDP:
+		break;
+	default:
+		goto out;
+	}
+
+	if (test_bit(IPS_HELPER_BIT, &ct->status))
+		goto out;
+
+	if (ctinfo == IP_CT_NEW ||
+	    ctinfo == IP_CT_RELATED)
+		goto out;
+
+	if (test_and_set_bit(IPS_OFFLOAD_BIT, &ct->status))
+		goto out;
+
+	dir = CTINFO2DIR(ctinfo);
+	if (nft_flow_route(pkt, ct, &route, dir) < 0)
+		goto err_flow_route;
+
+	flow = flow_offload_alloc(ct, &route);
+	if (!flow)
+		goto err_flow_alloc;
+
+	ret = flow_offload_add(flowtable, flow);
+	if (ret < 0)
+		goto err_flow_add;
+
+	return;
+
+err_flow_add:
+	flow_offload_free(flow);
+err_flow_alloc:
+	dst_release(route.tuple[!dir].dst);
+err_flow_route:
+	clear_bit(IPS_OFFLOAD_BIT, &ct->status);
+out:
+	regs->verdict.code = NFT_BREAK;
+}
+
+static int nft_flow_offload_validate(const struct nft_ctx *ctx,
+				     const struct nft_expr *expr,
+				     const struct nft_data **data)
+{
+	unsigned int hook_mask = (1 << NF_INET_FORWARD);
+
+	return nft_chain_validate_hooks(ctx->chain, hook_mask);
+}
+
+static int nft_flow_offload_init(const struct nft_ctx *ctx,
+				 const struct nft_expr *expr,
+				 const struct nlattr * const tb[])
+{
+	struct nft_flow_offload *priv = nft_expr_priv(expr);
+	u8 genmask = nft_genmask_next(ctx->net);
+	struct nft_flowtable *flowtable;
+
+	if (!tb[NFTA_FLOW_TABLE_NAME])
+		return -EINVAL;
+
+	flowtable = nf_tables_flowtable_lookup(ctx->table,
+					       tb[NFTA_FLOW_TABLE_NAME],
+					       genmask);
+	if (IS_ERR(flowtable))
+		return PTR_ERR(flowtable);
+
+	priv->flowtable = flowtable;
+	flowtable->use++;
+
+	return nf_ct_netns_get(ctx->net, ctx->afi->family);
+}
+
+static void nft_flow_offload_destroy(const struct nft_ctx *ctx,
+				     const struct nft_expr *expr)
+{
+	struct nft_flow_offload *priv = nft_expr_priv(expr);
+
+	priv->flowtable->use--;
+	nf_ct_netns_put(ctx->net, ctx->afi->family);
+}
+
+static int nft_flow_offload_dump(struct sk_buff *skb, const struct nft_expr *expr)
+{
+	struct nft_flow_offload *priv = nft_expr_priv(expr);
+
+	if (nla_put_string(skb, NFTA_FLOW_TABLE_NAME, priv->flowtable->name))
+		goto nla_put_failure;
+
+	return 0;
+
+nla_put_failure:
+	return -1;
+}
+
+struct nft_expr_type nft_flow_offload_type;
+static const struct nft_expr_ops nft_flow_offload_ops = {
+	.type		= &nft_flow_offload_type,
+	.size		= NFT_EXPR_SIZE(sizeof(struct nft_flow_offload)),
+	.eval		= nft_flow_offload_eval,
+	.init		= nft_flow_offload_init,
+	.destroy	= nft_flow_offload_destroy,
+	.validate	= nft_flow_offload_validate,
+	.dump		= nft_flow_offload_dump,
+};
+
+struct nft_expr_type nft_flow_offload_type __read_mostly = {
+	.name		= "flow_offload",
+	.ops		= &nft_flow_offload_ops,
+	.maxattr	= NFTA_FLOW_MAX,
+	.owner		= THIS_MODULE,
+};
+
+static void flow_offload_iterate_cleanup(struct flow_offload *flow, void *data)
+{
+	struct net_device *dev = data;
+
+	if (dev && flow->tuplehash[0].tuple.iifidx != dev->ifindex)
+		return;
+
+	flow_offload_dead(flow);
+}
+
+static void nft_flow_offload_iterate_cleanup(struct nf_flowtable *flowtable,
+					     void *data)
+{
+	nf_flow_table_iterate(flowtable, flow_offload_iterate_cleanup, data);
+}
+
+static int flow_offload_netdev_event(struct notifier_block *this,
+				     unsigned long event, void *ptr)
+{
+	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+
+	if (event != NETDEV_DOWN)
+		return NOTIFY_DONE;
+
+	nft_flow_table_iterate(dev_net(dev), nft_flow_offload_iterate_cleanup, dev);
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block flow_offload_netdev_notifier = {
+	.notifier_call	= flow_offload_netdev_event,
+};
+
+static int __init nft_flow_offload_module_init(void)
+{
+	int err;
+
+	register_netdevice_notifier(&flow_offload_netdev_notifier);
+
+	err = nft_register_expr(&nft_flow_offload_type);
+	if (err < 0)
+		goto register_expr;
+
+	return 0;
+
+register_expr:
+	unregister_netdevice_notifier(&flow_offload_netdev_notifier);
+	return err;
+}
+
+static void __exit nft_flow_offload_module_exit(void)
+{
+	struct net *net;
+
+	nft_unregister_expr(&nft_flow_offload_type);
+	unregister_netdevice_notifier(&flow_offload_netdev_notifier);
+	rtnl_lock();
+	for_each_net(net)
+		nft_flow_table_iterate(net, nft_flow_offload_iterate_cleanup, NULL);
+	rtnl_unlock();
+}
+
+module_init(nft_flow_offload_module_init);
+module_exit(nft_flow_offload_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
+MODULE_ALIAS_NFT_EXPR("flow_offload");