Subject: [PATCH] netfilter: add xt_FLOWOFFLOAD target
From: Felix Fietkau <[email-masked]>
Date: Tue, 20 Feb 2018 15:56:02 +0100

Signed-off-by: Felix Fietkau <[email-masked]>
---
 create mode 100644 net/netfilter/xt_OFFLOAD.c

--- a/net/ipv4/netfilter/Kconfig
+++ b/net/ipv4/netfilter/Kconfig
@@ -56,8 +56,6 @@ config NF_TABLES_ARP
 	help
 	  This option enables the ARP support for nf_tables.
 
-endif # NF_TABLES
-
 config NF_FLOW_TABLE_IPV4
 	tristate "Netfilter flow table IPv4 module"
 	depends on NF_FLOW_TABLE
@@ -66,6 +64,8 @@ config NF_FLOW_TABLE_IPV4
 
 	  To compile it as a module, choose M here.
 
+endif # NF_TABLES
+
 config NF_DUP_IPV4
 	tristate "Netfilter IPv4 packet duplication to alternate destination"
 	depends on !NF_CONNTRACK || NF_CONNTRACK
--- a/net/ipv6/netfilter/Kconfig
+++ b/net/ipv6/netfilter/Kconfig
@@ -45,7 +45,6 @@ config NFT_FIB_IPV6
 	  multicast or blackhole.
 
 endif # NF_TABLES_IPV6
-endif # NF_TABLES
 
 config NF_FLOW_TABLE_IPV6
 	tristate "Netfilter flow table IPv6 module"
@@ -55,6 +54,8 @@ config NF_FLOW_TABLE_IPV6
 
 	  To compile it as a module, choose M here.
 
+endif # NF_TABLES
+
 config NF_DUP_IPV6
 	tristate "Netfilter IPv6 packet duplication to alternate destination"
 	depends on !NF_CONNTRACK || NF_CONNTRACK
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -682,8 +682,6 @@ config NFT_FIB_NETDEV
 
 endif # NF_TABLES_NETDEV
 
-endif # NF_TABLES
-
 config NF_FLOW_TABLE_INET
 	tristate "Netfilter flow table mixed IPv4/IPv6 module"
 	depends on NF_FLOW_TABLE
@@ -692,11 +690,12 @@ config NF_FLOW_TABLE_INET
 
 	  To compile it as a module, choose M here.
 
+endif # NF_TABLES
+
 config NF_FLOW_TABLE
 	tristate "Netfilter flow table module"
 	depends on NETFILTER_INGRESS
 	depends on NF_CONNTRACK
-	depends on NF_TABLES
 	help
 	  This option adds the flow table core infrastructure.
 
@@ -976,6 +975,15 @@ config NETFILTER_XT_TARGET_NOTRACK
 	depends on NETFILTER_ADVANCED
 	select NETFILTER_XT_TARGET_CT
 
+config NETFILTER_XT_TARGET_FLOWOFFLOAD
+	tristate '"FLOWOFFLOAD" target support'
+	depends on NF_FLOW_TABLE
+	depends on NETFILTER_INGRESS
+	help
+	  This option adds a `FLOWOFFLOAD' target, which uses the nf_flow_offload
+	  module to speed up processing of packets by bypassing the usual
+	  netfilter chains
+
 config NETFILTER_XT_TARGET_RATEEST
 	tristate '"RATEEST" target support'
 	depends on NETFILTER_ADVANCED
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -145,6 +145,7 @@ obj-$(CONFIG_NETFILTER_XT_TARGET_CLASSIF
 obj-$(CONFIG_NETFILTER_XT_TARGET_CONNSECMARK) += xt_CONNSECMARK.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_CT) += xt_CT.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_DSCP) += xt_DSCP.o
+obj-$(CONFIG_NETFILTER_XT_TARGET_FLOWOFFLOAD) += xt_FLOWOFFLOAD.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_HL) += xt_HL.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_HMARK) += xt_HMARK.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_LED) += xt_LED.o
--- /dev/null
+++ b/net/netfilter/xt_FLOWOFFLOAD.c
@@ -0,0 +1,712 @@
+/*
+ * Copyright (C) 2018-2021 Felix Fietkau <[email-masked]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/netfilter.h>
+#include <linux/netfilter/xt_FLOWOFFLOAD.h>
+#include <linux/if_vlan.h>
+#include <linux/if_pppox.h>
+#include <linux/ppp_defs.h>
+#include <net/ip.h>
+#include <net/netfilter/nf_conntrack.h>
+#include <net/netfilter/nf_conntrack_extend.h>
+#include <net/netfilter/nf_conntrack_helper.h>
+#include <net/netfilter/nf_flow_table.h>
+
+struct xt_flowoffload_hook {
+	struct hlist_node list;
+	struct nf_hook_ops ops;
+	struct net *net;
+	bool registered;
+	bool used;
+};
+
+struct xt_flowoffload_table {
+	struct nf_flowtable ft;
+	struct hlist_head hooks;
+	struct delayed_work work;
+};
+
+struct nf_forward_info {
+	const struct net_device *indev;
+	const struct net_device *outdev;
+	const struct net_device *hw_outdev;
+	struct id {
+		__u16	id;
+		__be16	proto;
+	} encap[NF_FLOW_TABLE_ENCAP_MAX];
+	u8 num_encaps;
+	u8 ingress_vlans;
+	u8 h_source[ETH_ALEN];
+	u8 h_dest[ETH_ALEN];
+	enum flow_offload_xmit_type xmit_type;
+};
+
+static DEFINE_SPINLOCK(hooks_lock);
+
+struct xt_flowoffload_table flowtable[2];
+
+static inline __be16 nf_flow_pppoe_proto(const struct sk_buff *skb)
+{
+	__be16 proto;
+
+	proto = *((__be16 *)(skb_mac_header(skb) + ETH_HLEN +
+			     sizeof(struct pppoe_hdr)));
+	switch (proto) {
+	case htons(PPP_IP):
+		return htons(ETH_P_IP);
+	case htons(PPP_IPV6):
+		return htons(ETH_P_IPV6);
+	}
+
+	return 0;
+}
+
+static unsigned int
+xt_flowoffload_net_hook(void *priv, struct sk_buff *skb,
+			const struct nf_hook_state *state)
+{
+	struct vlan_ethhdr *veth;
+	__be16 proto;
+
+	switch (skb->protocol) {
+	case htons(ETH_P_8021Q):
+		veth = (struct vlan_ethhdr *)skb_mac_header(skb);
+		proto = veth->h_vlan_encapsulated_proto;
+		break;
+	case htons(ETH_P_PPP_SES):
+		proto = nf_flow_pppoe_proto(skb);
+		break;
+	default:
+		proto = skb->protocol;
+		break;
+	}
+
+	switch (proto) {
+	case htons(ETH_P_IP):
+		return nf_flow_offload_ip_hook(priv, skb, state);
+	case htons(ETH_P_IPV6):
+		return nf_flow_offload_ipv6_hook(priv, skb, state);
+	}
+
+	return NF_ACCEPT;
+}
+
+static int
+xt_flowoffload_create_hook(struct xt_flowoffload_table *table,
+			   struct net_device *dev)
+{
+	struct xt_flowoffload_hook *hook;
+	struct nf_hook_ops *ops;
+
+	hook = kzalloc(sizeof(*hook), GFP_ATOMIC);
+	if (!hook)
+		return -ENOMEM;
+
+	ops = &hook->ops;
+	ops->pf = NFPROTO_NETDEV;
+	ops->hooknum = NF_NETDEV_INGRESS;
+	ops->priority = 10;
+	ops->priv = &table->ft;
+	ops->hook = xt_flowoffload_net_hook;
+	ops->dev = dev;
+
+	hlist_add_head(&hook->list, &table->hooks);
+	mod_delayed_work(system_power_efficient_wq, &table->work, 0);
+
+	return 0;
+}
+
+static struct xt_flowoffload_hook *
+flow_offload_lookup_hook(struct xt_flowoffload_table *table,
+			 struct net_device *dev)
+{
+	struct xt_flowoffload_hook *hook;
+
+	hlist_for_each_entry(hook, &table->hooks, list) {
+		if (hook->ops.dev == dev)
+			return hook;
+	}
+
+	return NULL;
+}
+
+static void
+xt_flowoffload_check_device(struct xt_flowoffload_table *table,
+			    struct net_device *dev)
+{
+	struct xt_flowoffload_hook *hook;
+
+	if (!dev)
+		return;
+
+	spin_lock_bh(&hooks_lock);
+	hook = flow_offload_lookup_hook(table, dev);
+	if (hook)
+		hook->used = true;
+	else
+		xt_flowoffload_create_hook(table, dev);
+	spin_unlock_bh(&hooks_lock);
+}
+
+static void
+xt_flowoffload_register_hooks(struct xt_flowoffload_table *table)
+{
+	struct xt_flowoffload_hook *hook;
+
+restart:
+	hlist_for_each_entry(hook, &table->hooks, list) {
+		if (hook->registered)
+			continue;
+
+		hook->registered = true;
+		hook->net = dev_net(hook->ops.dev);
+		spin_unlock_bh(&hooks_lock);
+		nf_register_net_hook(hook->net, &hook->ops);
+		if (table->ft.flags & NF_FLOWTABLE_HW_OFFLOAD)
+			table->ft.type->setup(&table->ft, hook->ops.dev,
+					      FLOW_BLOCK_BIND);
+		spin_lock_bh(&hooks_lock);
+		goto restart;
+	}
+
+}
+
+static bool
+xt_flowoffload_cleanup_hooks(struct xt_flowoffload_table *table)
+{
+	struct xt_flowoffload_hook *hook;
+	bool active = false;
+
+restart:
+	spin_lock_bh(&hooks_lock);
+	hlist_for_each_entry(hook, &table->hooks, list) {
+		if (hook->used || !hook->registered) {
+			active = true;
+			continue;
+		}
+
+		hlist_del(&hook->list);
+		spin_unlock_bh(&hooks_lock);
+		if (table->ft.flags & NF_FLOWTABLE_HW_OFFLOAD)
+			table->ft.type->setup(&table->ft, hook->ops.dev,
+					      FLOW_BLOCK_UNBIND);
+		nf_unregister_net_hook(hook->net, &hook->ops);
+		kfree(hook);
+		goto restart;
+	}
+	spin_unlock_bh(&hooks_lock);
+
+	return active;
+}
+
+static void
+xt_flowoffload_check_hook(struct flow_offload *flow, void *data)
+{
+	struct xt_flowoffload_table *table = data;
+	struct flow_offload_tuple *tuple0 = &flow->tuplehash[0].tuple;
+	struct flow_offload_tuple *tuple1 = &flow->tuplehash[1].tuple;
+	struct xt_flowoffload_hook *hook;
+
+	spin_lock_bh(&hooks_lock);
+	hlist_for_each_entry(hook, &table->hooks, list) {
+		if (hook->ops.dev->ifindex != tuple0->iifidx &&
+		    hook->ops.dev->ifindex != tuple1->iifidx)
+			continue;
+
+		hook->used = true;
+	}
+	spin_unlock_bh(&hooks_lock);
+}
+
+static void
+xt_flowoffload_hook_work(struct work_struct *work)
+{
+	struct xt_flowoffload_table *table;
+	struct xt_flowoffload_hook *hook;
+	int err;
+
+	table = container_of(work, struct xt_flowoffload_table, work.work);
+
+	spin_lock_bh(&hooks_lock);
+	xt_flowoffload_register_hooks(table);
+	hlist_for_each_entry(hook, &table->hooks, list)
+		hook->used = false;
+	spin_unlock_bh(&hooks_lock);
+
+	err = nf_flow_table_iterate(&table->ft, xt_flowoffload_check_hook,
+				    table);
+	if (err && err != -EAGAIN)
+		goto out;
+
+	if (!xt_flowoffload_cleanup_hooks(table))
+		return;
+
+out:
+	queue_delayed_work(system_power_efficient_wq, &table->work, HZ);
+}
+
+static bool
+xt_flowoffload_skip(struct sk_buff *skb, int family)
+{
+	if (skb_sec_path(skb))
+		return true;
+
+	if (family == NFPROTO_IPV4) {
+		const struct ip_options *opt = &(IPCB(skb)->opt);
+
+		if (unlikely(opt->optlen))
+			return true;
+	}
+
+	return false;
+}
+
+static enum flow_offload_xmit_type nf_xmit_type(struct dst_entry *dst)
+{
+	if (dst_xfrm(dst))
+		return FLOW_OFFLOAD_XMIT_XFRM;
+
+	return FLOW_OFFLOAD_XMIT_NEIGH;
+}
+
+static void nf_default_forward_path(struct nf_flow_route *route,
+				    struct dst_entry *dst_cache,
+				    enum ip_conntrack_dir dir,
+				    struct net_device **dev)
+{
+	dev[!dir] = dst_cache->dev;
+	route->tuple[!dir].in.ifindex	= dst_cache->dev->ifindex;
+	route->tuple[dir].dst		= dst_cache;
+	route->tuple[dir].xmit_type	= nf_xmit_type(dst_cache);
+}
+
+static bool nf_is_valid_ether_device(const struct net_device *dev)
+{
+	if (!dev || (dev->flags & IFF_LOOPBACK) || dev->type != ARPHRD_ETHER ||
+	    dev->addr_len != ETH_ALEN || !is_valid_ether_addr(dev->dev_addr))
+		return false;
+
+	return true;
+}
+
+static void nf_dev_path_info(const struct net_device_path_stack *stack,
+			     struct nf_forward_info *info,
+			     unsigned char *ha)
+{
+	const struct net_device_path *path;
+	int i;
+
+	memcpy(info->h_dest, ha, ETH_ALEN);
+
+	for (i = 0; i < stack->num_paths; i++) {
+		path = &stack->path[i];
+		switch (path->type) {
+		case DEV_PATH_ETHERNET:
+		case DEV_PATH_DSA:
+		case DEV_PATH_VLAN:
+		case DEV_PATH_PPPOE:
+			info->indev = path->dev;
+			if (is_zero_ether_addr(info->h_source))
+				memcpy(info->h_source, path->dev->dev_addr, ETH_ALEN);
+
+			if (path->type == DEV_PATH_ETHERNET)
+				break;
+			if (path->type == DEV_PATH_DSA) {
+				i = stack->num_paths;
+				break;
+			}
+
+			/* DEV_PATH_VLAN and DEV_PATH_PPPOE */
+			if (info->num_encaps >= NF_FLOW_TABLE_ENCAP_MAX) {
+				info->indev = NULL;
+				break;
+			}
+			if (!info->outdev)
+				info->outdev = path->dev;
+			info->encap[info->num_encaps].id = path->encap.id;
+			info->encap[info->num_encaps].proto = path->encap.proto;
+			info->num_encaps++;
+			if (path->type == DEV_PATH_PPPOE)
+				memcpy(info->h_dest, path->encap.h_dest, ETH_ALEN);
+			break;
+		case DEV_PATH_BRIDGE:
+			if (is_zero_ether_addr(info->h_source))
+				memcpy(info->h_source, path->dev->dev_addr, ETH_ALEN);
+
+			switch (path->bridge.vlan_mode) {
+			case DEV_PATH_BR_VLAN_UNTAG_HW:
+				info->ingress_vlans |= BIT(info->num_encaps - 1);
+				break;
+			case DEV_PATH_BR_VLAN_TAG:
+				info->encap[info->num_encaps].id = path->bridge.vlan_id;
+				info->encap[info->num_encaps].proto = path->bridge.vlan_proto;
+				info->num_encaps++;
+				break;
+			case DEV_PATH_BR_VLAN_UNTAG:
+				info->num_encaps--;
+				break;
+			case DEV_PATH_BR_VLAN_KEEP:
+				break;
+			}
+			break;
+		default:
+			info->indev = NULL;
+			break;
+		}
+	}
+	if (!info->outdev)
+		info->outdev = info->indev;
+
+	info->hw_outdev = info->indev;
+
+	if (nf_is_valid_ether_device(info->indev))
+		info->xmit_type = FLOW_OFFLOAD_XMIT_DIRECT;
+}
+
+static int nf_dev_fill_forward_path(const struct nf_flow_route *route,
+				     const struct dst_entry *dst_cache,
+				     const struct nf_conn *ct,
+				     enum ip_conntrack_dir dir, u8 *ha,
+				     struct net_device_path_stack *stack)
+{
+	const void *daddr = &ct->tuplehash[!dir].tuple.src.u3;
+	struct net_device *dev = dst_cache->dev;
+	struct neighbour *n;
+	u8 nud_state;
+
+	if (!nf_is_valid_ether_device(dev))
+		goto out;
+
+	n = dst_neigh_lookup(dst_cache, daddr);
+	if (!n)
+		return -1;
+
+	read_lock_bh(&n->lock);
+	nud_state = n->nud_state;
+	ether_addr_copy(ha, n->ha);
+	read_unlock_bh(&n->lock);
+	neigh_release(n);
+
+	if (!(nud_state & NUD_VALID))
+		return -1;
+
+out:
+	return dev_fill_forward_path(dev, ha, stack);
+}
+
+static void nf_dev_forward_path(struct nf_flow_route *route,
+				const struct nf_conn *ct,
+				enum ip_conntrack_dir dir,
+				struct net_device **devs)
+{
+	const struct dst_entry *dst = route->tuple[dir].dst;
+	struct net_device_path_stack stack;
+	struct nf_forward_info info = {};
+	unsigned char ha[ETH_ALEN];
+	int i;
+
+	if (nf_dev_fill_forward_path(route, dst, ct, dir, ha, &stack) >= 0)
+		nf_dev_path_info(&stack, &info, ha);
+
+	devs[!dir] = (struct net_device *)info.indev;
+	if (!info.indev)
+		return;
+
+	route->tuple[!dir].in.ifindex = info.indev->ifindex;
+	for (i = 0; i < info.num_encaps; i++) {
+		route->tuple[!dir].in.encap[i].id = info.encap[i].id;
+		route->tuple[!dir].in.encap[i].proto = info.encap[i].proto;
+	}
+	route->tuple[!dir].in.num_encaps = info.num_encaps;
+	route->tuple[!dir].in.ingress_vlans = info.ingress_vlans;
+
+	if (info.xmit_type == FLOW_OFFLOAD_XMIT_DIRECT) {
+		memcpy(route->tuple[dir].out.h_source, info.h_source, ETH_ALEN);
+		memcpy(route->tuple[dir].out.h_dest, info.h_dest, ETH_ALEN);
+		route->tuple[dir].out.ifindex = info.outdev->ifindex;
+		route->tuple[dir].out.hw_ifindex = info.hw_outdev->ifindex;
+		route->tuple[dir].xmit_type = info.xmit_type;
+	}
+}
+
+static int
+xt_flowoffload_route(struct sk_buff *skb, const struct nf_conn *ct,
+		     const struct xt_action_param *par,
+		     struct nf_flow_route *route, enum ip_conntrack_dir dir,
+		     struct net_device **devs)
+{
+	struct dst_entry *this_dst = skb_dst(skb);
+	struct dst_entry *other_dst = NULL;
+	struct flowi fl;
+
+	memset(&fl, 0, sizeof(fl));
+	switch (xt_family(par)) {
+	case NFPROTO_IPV4:
+		fl.u.ip4.daddr = ct->tuplehash[dir].tuple.src.u3.ip;
+		fl.u.ip4.flowi4_oif = xt_in(par)->ifindex;
+		break;
+	case NFPROTO_IPV6:
+		fl.u.ip6.saddr = ct->tuplehash[!dir].tuple.dst.u3.in6;
+		fl.u.ip6.daddr = ct->tuplehash[dir].tuple.src.u3.in6;
+		fl.u.ip6.flowi6_oif = xt_in(par)->ifindex;
+		break;
+	}
+
+	nf_route(xt_net(par), &other_dst, &fl, false, xt_family(par));
+	if (!other_dst)
+		return -ENOENT;
+
+	nf_default_forward_path(route, this_dst, dir, devs);
+	nf_default_forward_path(route, other_dst, !dir, devs);
+
+	if (route->tuple[dir].xmit_type	== FLOW_OFFLOAD_XMIT_NEIGH &&
+	    route->tuple[!dir].xmit_type == FLOW_OFFLOAD_XMIT_NEIGH) {
+		nf_dev_forward_path(route, ct, dir, devs);
+		nf_dev_forward_path(route, ct, !dir, devs);
+	}
+
+	return 0;
+}
+
+static unsigned int
+flowoffload_tg(struct sk_buff *skb, const struct xt_action_param *par)
+{
+	struct xt_flowoffload_table *table;
+	const struct xt_flowoffload_target_info *info = par->targinfo;
+	struct tcphdr _tcph, *tcph = NULL;
+	enum ip_conntrack_info ctinfo;
+	enum ip_conntrack_dir dir;
+	struct nf_flow_route route = {};
+	struct flow_offload *flow = NULL;
+	struct net_device *devs[2] = {};
+	struct nf_conn *ct;
+	struct net *net;
+
+	if (xt_flowoffload_skip(skb, xt_family(par)))
+		return XT_CONTINUE;
+
+	ct = nf_ct_get(skb, &ctinfo);
+	if (ct == NULL)
+		return XT_CONTINUE;
+
+	switch (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum) {
+	case IPPROTO_TCP:
+		if (ct->proto.tcp.state != TCP_CONNTRACK_ESTABLISHED)
+			return XT_CONTINUE;
+
+		tcph = skb_header_pointer(skb, par->thoff,
+					  sizeof(_tcph), &_tcph);
+		if (unlikely(!tcph || tcph->fin || tcph->rst))
+			return XT_CONTINUE;
+		break;
+	case IPPROTO_UDP:
+		break;
+	default:
+		return XT_CONTINUE;
+	}
+
+	if (nf_ct_ext_exist(ct, NF_CT_EXT_HELPER) ||
+	    ct->status & (IPS_SEQ_ADJUST | IPS_NAT_CLASH))
+		return XT_CONTINUE;
+
+	if (!nf_ct_is_confirmed(ct))
+		return XT_CONTINUE;
+
+	devs[dir] = xt_out(par);
+	devs[!dir] = xt_in(par);
+
+	if (!devs[dir] || !devs[!dir])
+		return XT_CONTINUE;
+
+	if (test_and_set_bit(IPS_OFFLOAD_BIT, &ct->status))
+		return XT_CONTINUE;
+
+	dir = CTINFO2DIR(ctinfo);
+
+	if (xt_flowoffload_route(skb, ct, par, &route, dir, devs) < 0)
+		goto err_flow_route;
+
+	flow = flow_offload_alloc(ct);
+	if (!flow)
+		goto err_flow_alloc;
+
+	if (flow_offload_route_init(flow, &route) < 0)
+		goto err_flow_add;
+
+	if (tcph) {
+		ct->proto.tcp.seen[0].flags |= IP_CT_TCP_FLAG_BE_LIBERAL;
+		ct->proto.tcp.seen[1].flags |= IP_CT_TCP_FLAG_BE_LIBERAL;
+	}
+
+	table = &flowtable[!!(info->flags & XT_FLOWOFFLOAD_HW)];
+
+	net = read_pnet(&table->ft.net);
+	if (!net)
+		write_pnet(&table->ft.net, xt_net(par));
+
+	if (flow_offload_add(&table->ft, flow) < 0)
+		goto err_flow_add;
+
+	xt_flowoffload_check_device(table, devs[0]);
+	xt_flowoffload_check_device(table, devs[1]);
+
+	dst_release(route.tuple[!dir].dst);
+
+	return XT_CONTINUE;
+
+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);
+
+	return XT_CONTINUE;
+}
+
+static int flowoffload_chk(const struct xt_tgchk_param *par)
+{
+	struct xt_flowoffload_target_info *info = par->targinfo;
+
+	if (info->flags & ~XT_FLOWOFFLOAD_MASK)
+		return -EINVAL;
+
+	return 0;
+}
+
+static struct xt_target offload_tg_reg __read_mostly = {
+	.family		= NFPROTO_UNSPEC,
+	.name		= "FLOWOFFLOAD",
+	.revision	= 0,
+	.targetsize	= sizeof(struct xt_flowoffload_target_info),
+	.usersize	= sizeof(struct xt_flowoffload_target_info),
+	.checkentry	= flowoffload_chk,
+	.target		= flowoffload_tg,
+	.me		= THIS_MODULE,
+};
+
+static int flow_offload_netdev_event(struct notifier_block *this,
+				     unsigned long event, void *ptr)
+{
+	struct xt_flowoffload_hook *hook0, *hook1;
+	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+
+	if (event != NETDEV_UNREGISTER)
+		return NOTIFY_DONE;
+
+	spin_lock_bh(&hooks_lock);
+	hook0 = flow_offload_lookup_hook(&flowtable[0], dev);
+	if (hook0)
+		hlist_del(&hook0->list);
+
+	hook1 = flow_offload_lookup_hook(&flowtable[1], dev);
+	if (hook1)
+		hlist_del(&hook1->list);
+	spin_unlock_bh(&hooks_lock);
+
+	if (hook0) {
+		nf_unregister_net_hook(hook0->net, &hook0->ops);
+		kfree(hook0);
+	}
+
+	if (hook1) {
+		nf_unregister_net_hook(hook1->net, &hook1->ops);
+		kfree(hook1);
+	}
+
+	nf_flow_table_cleanup(dev);
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block flow_offload_netdev_notifier = {
+	.notifier_call	= flow_offload_netdev_event,
+};
+
+static int nf_flow_rule_route_inet(struct net *net,
+				   const struct flow_offload *flow,
+				   enum flow_offload_tuple_dir dir,
+				   struct nf_flow_rule *flow_rule)
+{
+	const struct flow_offload_tuple *flow_tuple = &flow->tuplehash[dir].tuple;
+	int err;
+
+	switch (flow_tuple->l3proto) {
+	case NFPROTO_IPV4:
+		err = nf_flow_rule_route_ipv4(net, flow, dir, flow_rule);
+		break;
+	case NFPROTO_IPV6:
+		err = nf_flow_rule_route_ipv6(net, flow, dir, flow_rule);
+		break;
+	default:
+		err = -1;
+		break;
+	}
+
+	return err;
+}
+
+static struct nf_flowtable_type flowtable_inet = {
+	.family		= NFPROTO_INET,
+	.init		= nf_flow_table_init,
+	.setup		= nf_flow_table_offload_setup,
+	.action		= nf_flow_rule_route_inet,
+	.free		= nf_flow_table_free,
+	.hook		= xt_flowoffload_net_hook,
+	.owner		= THIS_MODULE,
+};
+
+static int init_flowtable(struct xt_flowoffload_table *tbl)
+{
+	INIT_DELAYED_WORK(&tbl->work, xt_flowoffload_hook_work);
+	tbl->ft.type = &flowtable_inet;
+
+	return nf_flow_table_init(&tbl->ft);
+}
+
+static int __init xt_flowoffload_tg_init(void)
+{
+	int ret;
+
+	register_netdevice_notifier(&flow_offload_netdev_notifier);
+
+	ret = init_flowtable(&flowtable[0]);
+	if (ret)
+		return ret;
+
+	ret = init_flowtable(&flowtable[1]);
+	if (ret)
+		goto cleanup;
+
+	flowtable[1].ft.flags = NF_FLOWTABLE_HW_OFFLOAD;
+
+	ret = xt_register_target(&offload_tg_reg);
+	if (ret)
+		goto cleanup2;
+
+	return 0;
+
+cleanup2:
+	nf_flow_table_free(&flowtable[1].ft);
+cleanup:
+	nf_flow_table_free(&flowtable[0].ft);
+	return ret;
+}
+
+static void __exit xt_flowoffload_tg_exit(void)
+{
+	xt_unregister_target(&offload_tg_reg);
+	unregister_netdevice_notifier(&flow_offload_netdev_notifier);
+	nf_flow_table_free(&flowtable[0].ft);
+	nf_flow_table_free(&flowtable[1].ft);
+}
+
+MODULE_LICENSE("GPL");
+module_init(xt_flowoffload_tg_init);
+module_exit(xt_flowoffload_tg_exit);
--- a/net/netfilter/nf_flow_table_core.c
+++ b/net/netfilter/nf_flow_table_core.c
@@ -7,7 +7,6 @@
 #include <linux/netdevice.h>
 #include <net/ip.h>
 #include <net/ip6_route.h>
-#include <net/netfilter/nf_tables.h>
 #include <net/netfilter/nf_flow_table.h>
 #include <net/netfilter/nf_conntrack.h>
 #include <net/netfilter/nf_conntrack_core.h>
@@ -380,8 +379,7 @@ flow_offload_lookup(struct nf_flowtable
 }
 EXPORT_SYMBOL_GPL(flow_offload_lookup);
 
-static int
-nf_flow_table_iterate(struct nf_flowtable *flow_table,
+int nf_flow_table_iterate(struct nf_flowtable *flow_table,
 		      void (*iter)(struct flow_offload *flow, void *data),
 		      void *data)
 {
@@ -413,6 +411,7 @@ nf_flow_table_iterate(struct nf_flowtabl
 
 	return err;
 }
+EXPORT_SYMBOL_GPL(nf_flow_table_iterate);
 
 static void nf_flow_offload_gc_step(struct flow_offload *flow, void *data)
 {
--- /dev/null
+++ b/include/uapi/linux/netfilter/xt_FLOWOFFLOAD.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _XT_FLOWOFFLOAD_H
+#define _XT_FLOWOFFLOAD_H
+
+#include <linux/types.h>
+
+enum {
+	XT_FLOWOFFLOAD_HW	= 1 << 0,
+
+	XT_FLOWOFFLOAD_MASK	= XT_FLOWOFFLOAD_HW
+};
+
+struct xt_flowoffload_target_info {
+	__u32 flags;
+};
+
+#endif /* _XT_FLOWOFFLOAD_H */
--- a/include/net/netfilter/nf_flow_table.h
+++ b/include/net/netfilter/nf_flow_table.h
@@ -271,6 +271,10 @@ void nf_flow_table_free(struct nf_flowta
 
 void flow_offload_teardown(struct flow_offload *flow);
 
+int nf_flow_table_iterate(struct nf_flowtable *flow_table,
+			  void (*iter)(struct flow_offload *flow, void *data),
+			  void *data);
+
 void nf_flow_snat_port(const struct flow_offload *flow,
 		       struct sk_buff *skb, unsigned int thoff,
 		       u8 protocol, enum flow_offload_tuple_dir dir);