From: Pablo Neira Ayuso <pablo@netfilter.org>
Date: Thu, 11 Jan 2018 16:32:00 +0100
Subject: [PATCH] netfilter: nf_flow_table: add hardware offload support

This patch adds the infrastructure to offload flows to hardware, in case
the nic/switch comes with built-in flow tables capabilities.

If the hardware comes with no hardware flow tables or they have
limitations in terms of features, the existing infrastructure falls back
to the software flow table implementation.

The software flow table garbage collector skips entries that resides in
the hardware, so the hardware will be responsible for releasing this
flow table entry too via flow_offload_dead().

Hardware configuration, either to add or to delete entries, is done from
the hardware offload workqueue, to ensure this is done from user context
given that we may sleep when grabbing the mdio mutex.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 create mode 100644 net/netfilter/nf_flow_table_hw.c

--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -826,6 +826,13 @@ struct xfrmdev_ops {
 };
 #endif
 
+struct flow_offload;
+
+enum flow_offload_type {
+	FLOW_OFFLOAD_ADD	= 0,
+	FLOW_OFFLOAD_DEL,
+};
+
 /*
  * This structure defines the management hooks for network devices.
  * The following hooks can be defined; unless noted otherwise, they are
@@ -1057,6 +1064,10 @@ struct xfrmdev_ops {
  * int (*ndo_bridge_dellink)(struct net_device *dev, struct nlmsghdr *nlh,
  *			     u16 flags);
  *
+ * int (*ndo_flow_offload)(enum flow_offload_type type,
+ *			   struct flow_offload *flow);
+ *	Adds/deletes flow entry to/from net device flowtable.
+ *
  * int (*ndo_change_carrier)(struct net_device *dev, bool new_carrier);
  *	Called to change device carrier. Soft-devices (like dummy, team, etc)
  *	which do not represent real hardware may define this to allow their
@@ -1281,6 +1292,8 @@ struct net_device_ops {
 	int			(*ndo_bridge_dellink)(struct net_device *dev,
 						      struct nlmsghdr *nlh,
 						      u16 flags);
+	int			(*ndo_flow_offload)(enum flow_offload_type type,
+						    struct flow_offload *flow);
 	int			(*ndo_change_carrier)(struct net_device *dev,
 						      bool new_carrier);
 	int			(*ndo_get_phys_port_id)(struct net_device *dev,
--- a/include/net/netfilter/nf_flow_table.h
+++ b/include/net/netfilter/nf_flow_table.h
@@ -20,11 +20,17 @@ struct nf_flowtable_type {
 	struct module			*owner;
 };
 
+enum nf_flowtable_flags {
+	NF_FLOWTABLE_F_HW		= 0x1,
+};
+
 struct nf_flowtable {
 	struct list_head		list;
 	struct rhashtable		rhashtable;
 	const struct nf_flowtable_type	*type;
+	u32				flags;
 	struct delayed_work		gc_work;
+	possible_net_t			ft_net;
 };
 
 enum flow_offload_tuple_dir {
@@ -69,6 +75,7 @@ struct flow_offload_tuple_rhash {
 #define FLOW_OFFLOAD_DNAT	0x2
 #define FLOW_OFFLOAD_DYING	0x4
 #define FLOW_OFFLOAD_TEARDOWN	0x8
+#define FLOW_OFFLOAD_HW		0x10
 
 struct flow_offload {
 	struct flow_offload_tuple_rhash		tuplehash[FLOW_OFFLOAD_DIR_MAX];
@@ -126,6 +133,22 @@ unsigned int nf_flow_offload_ip_hook(voi
 unsigned int nf_flow_offload_ipv6_hook(void *priv, struct sk_buff *skb,
 				       const struct nf_hook_state *state);
 
+void nf_flow_offload_hw_add(struct net *net, struct flow_offload *flow,
+			    struct nf_conn *ct);
+void nf_flow_offload_hw_del(struct net *net, struct flow_offload *flow);
+
+struct nf_flow_table_hw {
+	struct module	*owner;
+	void		(*add)(struct net *net, struct flow_offload *flow,
+			       struct nf_conn *ct);
+	void		(*del)(struct net *net, struct flow_offload *flow);
+};
+
+int nf_flow_table_hw_register(const struct nf_flow_table_hw *offload);
+void nf_flow_table_hw_unregister(const struct nf_flow_table_hw *offload);
+
+extern struct work_struct nf_flow_offload_hw_work;
+
 #define MODULE_ALIAS_NF_FLOWTABLE(family)	\
 	MODULE_ALIAS("nf-flowtable-" __stringify(family))
 
--- a/include/uapi/linux/netfilter/nf_tables.h
+++ b/include/uapi/linux/netfilter/nf_tables.h
@@ -1341,6 +1341,7 @@ enum nft_object_attributes {
  * @NFTA_FLOWTABLE_HOOK: netfilter hook configuration(NLA_U32)
  * @NFTA_FLOWTABLE_USE: number of references to this flow table (NLA_U32)
  * @NFTA_FLOWTABLE_HANDLE: object handle (NLA_U64)
+ * @NFTA_FLOWTABLE_FLAGS: flags (NLA_U32)
  */
 enum nft_flowtable_attributes {
 	NFTA_FLOWTABLE_UNSPEC,
@@ -1350,6 +1351,7 @@ enum nft_flowtable_attributes {
 	NFTA_FLOWTABLE_USE,
 	NFTA_FLOWTABLE_HANDLE,
 	NFTA_FLOWTABLE_PAD,
+	NFTA_FLOWTABLE_FLAGS,
 	__NFTA_FLOWTABLE_MAX
 };
 #define NFTA_FLOWTABLE_MAX	(__NFTA_FLOWTABLE_MAX - 1)
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -692,6 +692,15 @@ config NF_FLOW_TABLE
 
 	  To compile it as a module, choose M here.
 
+config NF_FLOW_TABLE_HW
+	tristate "Netfilter flow table hardware offload module"
+	depends on NF_FLOW_TABLE
+	help
+	  This option adds hardware offload support for the flow table core
+	  infrastructure.
+
+	  To compile it as a module, choose M here.
+
 config NETFILTER_XTABLES
 	tristate "Netfilter Xtables support (required for ip_tables)"
 	default m if NETFILTER_ADVANCED=n
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -116,6 +116,7 @@ obj-$(CONFIG_NF_FLOW_TABLE)	+= nf_flow_t
 nf_flow_table-objs := nf_flow_table_core.o nf_flow_table_ip.o
 
 obj-$(CONFIG_NF_FLOW_TABLE_INET) += nf_flow_table_inet.o
+obj-$(CONFIG_NF_FLOW_TABLE_HW)	+= nf_flow_table_hw.o
 
 # generic X tables 
 obj-$(CONFIG_NETFILTER_XTABLES) += x_tables.o xt_tcpudp.o
--- a/net/netfilter/nf_flow_table_core.c
+++ b/net/netfilter/nf_flow_table_core.c
@@ -218,10 +218,16 @@ int flow_offload_add(struct nf_flowtable
 }
 EXPORT_SYMBOL_GPL(flow_offload_add);
 
+static inline bool nf_flow_in_hw(const struct flow_offload *flow)
+{
+	return flow->flags & FLOW_OFFLOAD_HW;
+}
+
 static void flow_offload_del(struct nf_flowtable *flow_table,
 			     struct flow_offload *flow)
 {
 	struct flow_offload_entry *e;
+	struct net *net = read_pnet(&flow_table->ft_net);
 
 	rhashtable_remove_fast(&flow_table->rhashtable,
 			       &flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].node,
@@ -236,6 +242,9 @@ static void flow_offload_del(struct nf_f
 	if (!(flow->flags & FLOW_OFFLOAD_TEARDOWN))
 		flow_offload_fixup_ct_state(e->ct);
 
+	if (nf_flow_in_hw(flow))
+		nf_flow_offload_hw_del(net, flow);
+
 	flow_offload_free(flow);
 }
 
@@ -349,6 +358,9 @@ static int nf_flow_offload_gc_step(struc
 		if (!teardown)
 			nf_ct_offload_timeout(flow);
 
+		if (nf_flow_in_hw(flow) && !teardown)
+			continue;
+
 		if (nf_flow_has_expired(flow) || teardown)
 			flow_offload_del(flow_table, flow);
 	}
@@ -484,10 +496,43 @@ int nf_flow_dnat_port(const struct flow_
 }
 EXPORT_SYMBOL_GPL(nf_flow_dnat_port);
 
+static const struct nf_flow_table_hw __rcu *nf_flow_table_hw_hook __read_mostly;
+
+static int nf_flow_offload_hw_init(struct nf_flowtable *flow_table)
+{
+	const struct nf_flow_table_hw *offload;
+
+	if (!rcu_access_pointer(nf_flow_table_hw_hook))
+		request_module("nf-flow-table-hw");
+
+	rcu_read_lock();
+	offload = rcu_dereference(nf_flow_table_hw_hook);
+	if (!offload)
+		goto err_no_hw_offload;
+
+	if (!try_module_get(offload->owner))
+		goto err_no_hw_offload;
+
+	rcu_read_unlock();
+
+	return 0;
+
+err_no_hw_offload:
+	rcu_read_unlock();
+
+	return -EOPNOTSUPP;
+}
+
 int nf_flow_table_init(struct nf_flowtable *flowtable)
 {
 	int err;
 
+	if (flowtable->flags & NF_FLOWTABLE_F_HW) {
+		err = nf_flow_offload_hw_init(flowtable);
+		if (err)
+			return err;
+	}
+
 	INIT_DEFERRABLE_WORK(&flowtable->gc_work, nf_flow_offload_work_gc);
 
 	err = rhashtable_init(&flowtable->rhashtable,
@@ -525,6 +570,8 @@ static void nf_flow_table_iterate_cleanu
 {
 	nf_flow_table_iterate(flowtable, nf_flow_table_do_cleanup, dev);
 	flush_delayed_work(&flowtable->gc_work);
+	if (flowtable->flags & NF_FLOWTABLE_F_HW)
+		flush_work(&nf_flow_offload_hw_work);
 }
 
 void nf_flow_table_cleanup(struct net *net, struct net_device *dev)
@@ -538,6 +585,26 @@ void nf_flow_table_cleanup(struct net *n
 }
 EXPORT_SYMBOL_GPL(nf_flow_table_cleanup);
 
+struct work_struct nf_flow_offload_hw_work;
+EXPORT_SYMBOL_GPL(nf_flow_offload_hw_work);
+
+/* Give the hardware workqueue the chance to remove entries from hardware.*/
+static void nf_flow_offload_hw_free(struct nf_flowtable *flowtable)
+{
+	const struct nf_flow_table_hw *offload;
+
+	flush_work(&nf_flow_offload_hw_work);
+
+	rcu_read_lock();
+	offload = rcu_dereference(nf_flow_table_hw_hook);
+	if (!offload) {
+		rcu_read_unlock();
+		return;
+	}
+	module_put(offload->owner);
+	rcu_read_unlock();
+}
+
 void nf_flow_table_free(struct nf_flowtable *flow_table)
 {
 	mutex_lock(&flowtable_lock);
@@ -547,9 +614,58 @@ void nf_flow_table_free(struct nf_flowta
 	nf_flow_table_iterate(flow_table, nf_flow_table_do_cleanup, NULL);
 	WARN_ON(!nf_flow_offload_gc_step(flow_table));
 	rhashtable_destroy(&flow_table->rhashtable);
+	if (flow_table->flags & NF_FLOWTABLE_F_HW)
+		nf_flow_offload_hw_free(flow_table);
 }
 EXPORT_SYMBOL_GPL(nf_flow_table_free);
 
+/* Must be called from user context. */
+void nf_flow_offload_hw_add(struct net *net, struct flow_offload *flow,
+			    struct nf_conn *ct)
+{
+	const struct nf_flow_table_hw *offload;
+
+	rcu_read_lock();
+	offload = rcu_dereference(nf_flow_table_hw_hook);
+	if (offload)
+		offload->add(net, flow, ct);
+	rcu_read_unlock();
+}
+EXPORT_SYMBOL_GPL(nf_flow_offload_hw_add);
+
+/* Must be called from user context. */
+void nf_flow_offload_hw_del(struct net *net, struct flow_offload *flow)
+{
+	const struct nf_flow_table_hw *offload;
+
+	rcu_read_lock();
+	offload = rcu_dereference(nf_flow_table_hw_hook);
+	if (offload)
+		offload->del(net, flow);
+	rcu_read_unlock();
+}
+EXPORT_SYMBOL_GPL(nf_flow_offload_hw_del);
+
+int nf_flow_table_hw_register(const struct nf_flow_table_hw *offload)
+{
+	if (rcu_access_pointer(nf_flow_table_hw_hook))
+		return -EBUSY;
+
+	rcu_assign_pointer(nf_flow_table_hw_hook, offload);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(nf_flow_table_hw_register);
+
+void nf_flow_table_hw_unregister(const struct nf_flow_table_hw *offload)
+{
+	WARN_ON(rcu_access_pointer(nf_flow_table_hw_hook) != offload);
+	rcu_assign_pointer(nf_flow_table_hw_hook, NULL);
+
+	synchronize_rcu();
+}
+EXPORT_SYMBOL_GPL(nf_flow_table_hw_unregister);
+
 static int nf_flow_table_netdev_event(struct notifier_block *this,
 				      unsigned long event, void *ptr)
 {
--- /dev/null
+++ b/net/netfilter/nf_flow_table_hw.c
@@ -0,0 +1,169 @@
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/netfilter.h>
+#include <linux/rhashtable.h>
+#include <linux/netdevice.h>
+#include <net/netfilter/nf_flow_table.h>
+#include <net/netfilter/nf_conntrack.h>
+#include <net/netfilter/nf_conntrack_core.h>
+#include <net/netfilter/nf_conntrack_tuple.h>
+
+static DEFINE_SPINLOCK(flow_offload_hw_pending_list_lock);
+static LIST_HEAD(flow_offload_hw_pending_list);
+
+static DEFINE_MUTEX(nf_flow_offload_hw_mutex);
+
+struct flow_offload_hw {
+	struct list_head	list;
+	enum flow_offload_type	type;
+	struct flow_offload	*flow;
+	struct nf_conn		*ct;
+	possible_net_t		flow_hw_net;
+};
+
+static int do_flow_offload_hw(struct net *net, struct flow_offload *flow,
+			      int type)
+{
+	struct net_device *indev;
+	int ret, ifindex;
+
+	ifindex = flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.iifidx;
+	indev = dev_get_by_index(net, ifindex);
+	if (WARN_ON(!indev))
+		return 0;
+
+	mutex_lock(&nf_flow_offload_hw_mutex);
+	ret = indev->netdev_ops->ndo_flow_offload(type, flow);
+	mutex_unlock(&nf_flow_offload_hw_mutex);
+
+	dev_put(indev);
+
+	return ret;
+}
+
+static void flow_offload_hw_work_add(struct flow_offload_hw *offload)
+{
+	struct net *net;
+	int ret;
+
+	if (nf_ct_is_dying(offload->ct))
+		return;
+
+	net = read_pnet(&offload->flow_hw_net);
+	ret = do_flow_offload_hw(net, offload->flow, FLOW_OFFLOAD_ADD);
+	if (ret >= 0)
+		offload->flow->flags |= FLOW_OFFLOAD_HW;
+}
+
+static void flow_offload_hw_work_del(struct flow_offload_hw *offload)
+{
+	struct net *net = read_pnet(&offload->flow_hw_net);
+
+	do_flow_offload_hw(net, offload->flow, FLOW_OFFLOAD_DEL);
+}
+
+static void flow_offload_hw_work(struct work_struct *work)
+{
+	struct flow_offload_hw *offload, *next;
+	LIST_HEAD(hw_offload_pending);
+
+	spin_lock_bh(&flow_offload_hw_pending_list_lock);
+	list_replace_init(&flow_offload_hw_pending_list, &hw_offload_pending);
+	spin_unlock_bh(&flow_offload_hw_pending_list_lock);
+
+	list_for_each_entry_safe(offload, next, &hw_offload_pending, list) {
+		switch (offload->type) {
+		case FLOW_OFFLOAD_ADD:
+			flow_offload_hw_work_add(offload);
+			break;
+		case FLOW_OFFLOAD_DEL:
+			flow_offload_hw_work_del(offload);
+			break;
+		}
+		if (offload->ct)
+			nf_conntrack_put(&offload->ct->ct_general);
+		list_del(&offload->list);
+		kfree(offload);
+	}
+}
+
+static void flow_offload_queue_work(struct flow_offload_hw *offload)
+{
+	spin_lock_bh(&flow_offload_hw_pending_list_lock);
+	list_add_tail(&offload->list, &flow_offload_hw_pending_list);
+	spin_unlock_bh(&flow_offload_hw_pending_list_lock);
+
+	schedule_work(&nf_flow_offload_hw_work);
+}
+
+static void flow_offload_hw_add(struct net *net, struct flow_offload *flow,
+				struct nf_conn *ct)
+{
+	struct flow_offload_hw *offload;
+
+	offload = kmalloc(sizeof(struct flow_offload_hw), GFP_ATOMIC);
+	if (!offload)
+		return;
+
+	nf_conntrack_get(&ct->ct_general);
+	offload->type = FLOW_OFFLOAD_ADD;
+	offload->ct = ct;
+	offload->flow = flow;
+	write_pnet(&offload->flow_hw_net, net);
+
+	flow_offload_queue_work(offload);
+}
+
+static void flow_offload_hw_del(struct net *net, struct flow_offload *flow)
+{
+	struct flow_offload_hw *offload;
+
+	offload = kmalloc(sizeof(struct flow_offload_hw), GFP_ATOMIC);
+	if (!offload)
+		return;
+
+	offload->type = FLOW_OFFLOAD_DEL;
+	offload->ct = NULL;
+	offload->flow = flow;
+	write_pnet(&offload->flow_hw_net, net);
+
+	flow_offload_queue_work(offload);
+}
+
+static const struct nf_flow_table_hw flow_offload_hw = {
+	.add	= flow_offload_hw_add,
+	.del	= flow_offload_hw_del,
+	.owner	= THIS_MODULE,
+};
+
+static int __init nf_flow_table_hw_module_init(void)
+{
+	INIT_WORK(&nf_flow_offload_hw_work, flow_offload_hw_work);
+	nf_flow_table_hw_register(&flow_offload_hw);
+
+	return 0;
+}
+
+static void __exit nf_flow_table_hw_module_exit(void)
+{
+	struct flow_offload_hw *offload, *next;
+	LIST_HEAD(hw_offload_pending);
+
+	nf_flow_table_hw_unregister(&flow_offload_hw);
+	cancel_work_sync(&nf_flow_offload_hw_work);
+
+	list_for_each_entry_safe(offload, next, &hw_offload_pending, list) {
+		if (offload->ct)
+			nf_conntrack_put(&offload->ct->ct_general);
+		list_del(&offload->list);
+		kfree(offload);
+	}
+}
+
+module_init(nf_flow_table_hw_module_init);
+module_exit(nf_flow_table_hw_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
+MODULE_ALIAS("nf-flow-table-hw");
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -4962,6 +4962,14 @@ static int nf_tables_flowtable_parse_hoo
 	if (err < 0)
 		goto err1;
 
+	for (i = 0; i < n; i++) {
+		if (flowtable->data.flags & NF_FLOWTABLE_F_HW &&
+		    !dev_array[i]->netdev_ops->ndo_flow_offload) {
+			err = -EOPNOTSUPP;
+			goto err1;
+		}
+	}
+
 	ops = kzalloc(sizeof(struct nf_hook_ops) * n, GFP_KERNEL);
 	if (!ops) {
 		err = -ENOMEM;
@@ -5092,10 +5100,19 @@ static int nf_tables_newflowtable(struct
 	}
 
 	flowtable->data.type = type;
+	write_pnet(&flowtable->data.ft_net, net);
+
 	err = type->init(&flowtable->data);
 	if (err < 0)
 		goto err3;
 
+	if (nla[NFTA_FLOWTABLE_FLAGS]) {
+		flowtable->data.flags =
+			ntohl(nla_get_be32(nla[NFTA_FLOWTABLE_FLAGS]));
+		if (flowtable->data.flags & ~NF_FLOWTABLE_F_HW)
+			goto err4;
+	}
+
 	err = nf_tables_flowtable_parse_hook(&ctx, nla[NFTA_FLOWTABLE_HOOK],
 					     flowtable);
 	if (err < 0)
@@ -5193,7 +5210,8 @@ static int nf_tables_fill_flowtable_info
 	    nla_put_string(skb, NFTA_FLOWTABLE_NAME, flowtable->name) ||
 	    nla_put_be32(skb, NFTA_FLOWTABLE_USE, htonl(flowtable->use)) ||
 	    nla_put_be64(skb, NFTA_FLOWTABLE_HANDLE, cpu_to_be64(flowtable->handle),
-			 NFTA_FLOWTABLE_PAD))
+			 NFTA_FLOWTABLE_PAD) ||
+	    nla_put_be32(skb, NFTA_FLOWTABLE_FLAGS, htonl(flowtable->data.flags)))
 		goto nla_put_failure;
 
 	nest = nla_nest_start(skb, NFTA_FLOWTABLE_HOOK);
--- a/net/netfilter/nft_flow_offload.c
+++ b/net/netfilter/nft_flow_offload.c
@@ -121,6 +121,9 @@ static void nft_flow_offload_eval(const
 	if (ret < 0)
 		goto err_flow_add;
 
+	if (flowtable->flags & NF_FLOWTABLE_F_HW)
+		nf_flow_offload_hw_add(nft_net(pkt), flow, ct);
+
 	return;
 
 err_flow_add:
