net/sched/act_mirred.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * net/sched/act_mirred.c	packet mirroring and redirect actions
  *
  * Authors:	Jamal Hadi Salim (2002-4)
  *
  * TODO: Add ingress support (and socket redirect support)
  */

 #include <linux/types.h>
 #include <linux/kernel.h>
 #include <linux/string.h>
 #include <linux/errno.h>
 #include <linux/skbuff.h>
 #include <linux/rtnetlink.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/gfp.h>
 #include <linux/if_arp.h>
 #include <net/net_namespace.h>
 #include <net/netlink.h>
 #include <net/dst.h>
 #include <net/pkt_sched.h>
 #include <net/pkt_cls.h>
 #include <linux/tc_act/tc_mirred.h>
 #include <net/tc_act/tc_mirred.h>

 static LIST_HEAD(mirred_list);
 static DEFINE_SPINLOCK(mirred_list_lock);

 #define MIRRED_NEST_LIMIT    4
 static DEFINE_PER_CPU(unsigned int, mirred_nest_level);

 static bool tcf_mirred_is_act_redirect(int action)
 {
 	return action == TCA_EGRESS_REDIR || action == TCA_INGRESS_REDIR;
 }

 static bool tcf_mirred_act_wants_ingress(int action)
 {
 	switch (action) {
 	case TCA_EGRESS_REDIR:
 	case TCA_EGRESS_MIRROR:
 		return false;
 	case TCA_INGRESS_REDIR:
 	case TCA_INGRESS_MIRROR:
 		return true;
 	default:
 		BUG();
 	}
 }

 static bool tcf_mirred_can_reinsert(int action)
 {
 	switch (action) {
 	case TC_ACT_SHOT:
 	case TC_ACT_STOLEN:
 	case TC_ACT_QUEUED:
 	case TC_ACT_TRAP:
 		return true;
 	}
 	return false;
 }

 static struct net_device *tcf_mirred_dev_dereference(struct tcf_mirred *m)
 {
 	return rcu_dereference_protected(m->tcfm_dev,
 					 lockdep_is_held(&m->tcf_lock));
 }

 static void tcf_mirred_release(struct tc_action *a)
 {
 	struct tcf_mirred *m = to_mirred(a);
 	struct net_device *dev;

 	spin_lock(&mirred_list_lock);
 	list_del(&m->tcfm_list);
 	spin_unlock(&mirred_list_lock);

 	/* last reference to action, no need to lock */
 	dev = rcu_dereference_protected(m->tcfm_dev, 1);
 	dev_put(dev);
 }

 static const struct nla_policy mirred_policy[TCA_MIRRED_MAX + 1] = {
 	[TCA_MIRRED_PARMS]	= { .len = sizeof(struct tc_mirred) },
 };

 static unsigned int mirred_net_id;
 static struct tc_action_ops act_mirred_ops;

 static int tcf_mirred_init(struct net *net, struct nlattr *nla,
 			   struct nlattr *est, struct tc_action **a,
 			   struct tcf_proto *tp,
 			   u32 flags, struct netlink_ext_ack *extack)
 {
 	struct tc_action_net *tn = net_generic(net, mirred_net_id);
 	bool bind = flags & TCA_ACT_FLAGS_BIND;
 	struct nlattr *tb[TCA_MIRRED_MAX + 1];
 	struct tcf_chain *goto_ch = NULL;
 	bool mac_header_xmit = false;
 	struct tc_mirred *parm;
 	struct tcf_mirred *m;
 	struct net_device *dev;
 	bool exists = false;
 	int ret, err;
 	u32 index;

 	if (!nla) {
 		NL_SET_ERR_MSG_MOD(extack, "Mirred requires attributes to be passed");
 		return -EINVAL;
 	}
 	ret = nla_parse_nested_deprecated(tb, TCA_MIRRED_MAX, nla,
 					  mirred_policy, extack);
 	if (ret < 0)
 		return ret;
 	if (!tb[TCA_MIRRED_PARMS]) {
 		NL_SET_ERR_MSG_MOD(extack, "Missing required mirred parameters");
 		return -EINVAL;
 	}
 	parm = nla_data(tb[TCA_MIRRED_PARMS]);
 	index = parm->index;
 	err = tcf_idr_check_alloc(tn, &index, a, bind);
 	if (err < 0)
 		return err;
 	exists = err;
 	if (exists && bind)
 		return 0;

 	switch (parm->eaction) {
 	case TCA_EGRESS_MIRROR:
 	case TCA_EGRESS_REDIR:
 	case TCA_INGRESS_REDIR:
 	case TCA_INGRESS_MIRROR:
 		break;
 	default:
 		if (exists)
 			tcf_idr_release(*a, bind);
 		else
 			tcf_idr_cleanup(tn, index);
 		NL_SET_ERR_MSG_MOD(extack, "Unknown mirred option");
 		return -EINVAL;
 	}

 	if (!exists) {
 		if (!parm->ifindex) {
 			tcf_idr_cleanup(tn, index);
 			NL_SET_ERR_MSG_MOD(extack, "Specified device does not exist");
 			return -EINVAL;
 		}
 		ret = tcf_idr_create_from_flags(tn, index, est, a,
 						&act_mirred_ops, bind, flags);
 		if (ret) {
 			tcf_idr_cleanup(tn, index);
 			return ret;
 		}
 		ret = ACT_P_CREATED;
 	} else if (!(flags & TCA_ACT_FLAGS_REPLACE)) {
 		tcf_idr_release(*a, bind);
 		return -EEXIST;
 	}

 	m = to_mirred(*a);
 	if (ret == ACT_P_CREATED)
 		INIT_LIST_HEAD(&m->tcfm_list);

 	err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
 	if (err < 0)
 		goto release_idr;

 	spin_lock_bh(&m->tcf_lock);

 	if (parm->ifindex) {
 		dev = dev_get_by_index(net, parm->ifindex);
 		if (!dev) {
 			spin_unlock_bh(&m->tcf_lock);
 			err = -ENODEV;
 			goto put_chain;
 		}
 		mac_header_xmit = dev_is_mac_header_xmit(dev);
 		dev = rcu_replace_pointer(m->tcfm_dev, dev,
 					  lockdep_is_held(&m->tcf_lock));
 		dev_put(dev);
 		m->tcfm_mac_header_xmit = mac_header_xmit;
 	}
 	goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
 	m->tcfm_eaction = parm->eaction;
 	spin_unlock_bh(&m->tcf_lock);
 	if (goto_ch)
 		tcf_chain_put_by_act(goto_ch);

 	if (ret == ACT_P_CREATED) {
 		spin_lock(&mirred_list_lock);
 		list_add(&m->tcfm_list, &mirred_list);
 		spin_unlock(&mirred_list_lock);
 	}

 	return ret;
 put_chain:
 	if (goto_ch)
 		tcf_chain_put_by_act(goto_ch);
 release_idr:
 	tcf_idr_release(*a, bind);
 	return err;
 }

 static bool is_mirred_nested(void)
 {
 	return unlikely(__this_cpu_read(mirred_nest_level) > 1);
 }

 static int tcf_mirred_forward(bool want_ingress, struct sk_buff *skb)
 {
 	int err;

 	if (!want_ingress)
 		err = tcf_dev_queue_xmit(skb, dev_queue_xmit);
 	else if (is_mirred_nested())
 		err = netif_rx(skb);
 	else
 		err = netif_receive_skb(skb);

 	return err;
 }

 static int tcf_mirred_act(struct sk_buff *skb, const struct tc_action *a,
 			  struct tcf_result *res)
 {
 	struct tcf_mirred *m = to_mirred(a);
 	struct sk_buff *skb2 = skb;
 	bool m_mac_header_xmit;
 	struct net_device *dev;
 	unsigned int nest_level;
 	int retval, err = 0;
 	bool use_reinsert;
 	bool want_ingress;
 	bool is_redirect;
 	bool expects_nh;
 	bool at_ingress;
 	int m_eaction;
 	int mac_len;
 	bool at_nh;

 	nest_level = __this_cpu_inc_return(mirred_nest_level);
 	if (unlikely(nest_level > MIRRED_NEST_LIMIT)) {
 		net_warn_ratelimited("Packet exceeded mirred recursion limit on dev %s\n",
 				     netdev_name(skb->dev));
 		__this_cpu_dec(mirred_nest_level);
 		return TC_ACT_SHOT;
 	}

 	tcf_lastuse_update(&m->tcf_tm);
 	tcf_action_update_bstats(&m->common, skb);

 	m_mac_header_xmit = READ_ONCE(m->tcfm_mac_header_xmit);
 	m_eaction = READ_ONCE(m->tcfm_eaction);
 	retval = READ_ONCE(m->tcf_action);
 	dev = rcu_dereference_bh(m->tcfm_dev);
 	if (unlikely(!dev)) {
 		pr_notice_once("tc mirred: target device is gone\n");
 		goto out;
 	}

 	if (unlikely(!(dev->flags & IFF_UP))) {
 		net_notice_ratelimited("tc mirred to Houston: device %s is down\n",
 				       dev->name);
 		goto out;
 	}

 	/* we could easily avoid the clone only if called by ingress and clsact;
 	 * since we can't easily detect the clsact caller, skip clone only for
 	 * ingress - that covers the TC S/W datapath.
 	 */
 	is_redirect = tcf_mirred_is_act_redirect(m_eaction);
 	at_ingress = skb_at_tc_ingress(skb);
 	use_reinsert = at_ingress && is_redirect &&
 		       tcf_mirred_can_reinsert(retval);
 	if (!use_reinsert) {
 		skb2 = skb_clone(skb, GFP_ATOMIC);
 		if (!skb2)
 			goto out;
 	}

 	want_ingress = tcf_mirred_act_wants_ingress(m_eaction);

 	/* All mirred/redirected skbs should clear previous ct info */
 	nf_reset_ct(skb2);
 	if (want_ingress && !at_ingress) /* drop dst for egress -> ingress */
 		skb_dst_drop(skb2);

 	expects_nh = want_ingress || !m_mac_header_xmit;
 	at_nh = skb->data == skb_network_header(skb);
 	if (at_nh != expects_nh) {
 		mac_len = skb_at_tc_ingress(skb) ? skb->mac_len :
 			  skb_network_header(skb) - skb_mac_header(skb);
 		if (expects_nh) {
 			/* target device/action expect data at nh */
 			skb_pull_rcsum(skb2, mac_len);
 		} else {
 			/* target device/action expect data at mac */
 			skb_push_rcsum(skb2, mac_len);
 		}
 	}

 	skb2->skb_iif = skb->dev->ifindex;
 	skb2->dev = dev;

 	/* mirror is always swallowed */
 	if (is_redirect) {
 		skb_set_redirected(skb2, skb2->tc_at_ingress);

 		/* let's the caller reinsert the packet, if possible */
 		if (use_reinsert) {
 			res->ingress = want_ingress;
 			err = tcf_mirred_forward(res->ingress, skb);
 			if (err)
 				tcf_action_inc_overlimit_qstats(&m->common);
 			__this_cpu_dec(mirred_nest_level);
 			return TC_ACT_CONSUMED;
 		}
 	}

 	err = tcf_mirred_forward(want_ingress, skb2);
 	if (err) {
 out:
 		tcf_action_inc_overlimit_qstats(&m->common);
 		if (tcf_mirred_is_act_redirect(m_eaction))
 			retval = TC_ACT_SHOT;
 	}
 	__this_cpu_dec(mirred_nest_level);

 	return retval;
 }

 static void tcf_stats_update(struct tc_action *a, u64 bytes, u64 packets,
 			     u64 drops, u64 lastuse, bool hw)
 {
 	struct tcf_mirred *m = to_mirred(a);
 	struct tcf_t *tm = &m->tcf_tm;

 	tcf_action_update_stats(a, bytes, packets, drops, hw);
 	tm->lastuse = max_t(u64, tm->lastuse, lastuse);
 }

 static int tcf_mirred_dump(struct sk_buff *skb, struct tc_action *a, int bind,
 			   int ref)
 {
 	unsigned char *b = skb_tail_pointer(skb);
 	struct tcf_mirred *m = to_mirred(a);
 	struct tc_mirred opt = {
 		.index   = m->tcf_index,
 		.refcnt  = refcount_read(&m->tcf_refcnt) - ref,
 		.bindcnt = atomic_read(&m->tcf_bindcnt) - bind,
 	};
 	struct net_device *dev;
 	struct tcf_t t;

 	spin_lock_bh(&m->tcf_lock);
 	opt.action = m->tcf_action;
 	opt.eaction = m->tcfm_eaction;
 	dev = tcf_mirred_dev_dereference(m);
 	if (dev)
 		opt.ifindex = dev->ifindex;

 	if (nla_put(skb, TCA_MIRRED_PARMS, sizeof(opt), &opt))
 		goto nla_put_failure;

 	tcf_tm_dump(&t, &m->tcf_tm);
 	if (nla_put_64bit(skb, TCA_MIRRED_TM, sizeof(t), &t, TCA_MIRRED_PAD))
 		goto nla_put_failure;
 	spin_unlock_bh(&m->tcf_lock);

 	return skb->len;

 nla_put_failure:
 	spin_unlock_bh(&m->tcf_lock);
 	nlmsg_trim(skb, b);
 	return -1;
 }

 static int tcf_mirred_walker(struct net *net, struct sk_buff *skb,
 			     struct netlink_callback *cb, int type,
 			     const struct tc_action_ops *ops,
 			     struct netlink_ext_ack *extack)
 {
 	struct tc_action_net *tn = net_generic(net, mirred_net_id);

 	return tcf_generic_walker(tn, skb, cb, type, ops, extack);
 }

 static int tcf_mirred_search(struct net *net, struct tc_action **a, u32 index)
 {
 	struct tc_action_net *tn = net_generic(net, mirred_net_id);

 	return tcf_idr_search(tn, a, index);
 }

 static int mirred_device_event(struct notifier_block *unused,
 			       unsigned long event, void *ptr)
 {
 	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 	struct tcf_mirred *m;

 	ASSERT_RTNL();
 	if (event == NETDEV_UNREGISTER) {
 		spin_lock(&mirred_list_lock);
 		list_for_each_entry(m, &mirred_list, tcfm_list) {
 			spin_lock_bh(&m->tcf_lock);
 			if (tcf_mirred_dev_dereference(m) == dev) {
 				dev_put(dev);
 				/* Note : no rcu grace period necessary, as
 				 * net_device are already rcu protected.
 				 */
 				RCU_INIT_POINTER(m->tcfm_dev, NULL);
 			}
 			spin_unlock_bh(&m->tcf_lock);
 		}
 		spin_unlock(&mirred_list_lock);
 	}

 	return NOTIFY_DONE;
 }

 static struct notifier_block mirred_device_notifier = {
 	.notifier_call = mirred_device_event,
 };

 static void tcf_mirred_dev_put(void *priv)
 {
 	struct net_device *dev = priv;

 	dev_put(dev);
 }

 static struct net_device *
 tcf_mirred_get_dev(const struct tc_action *a,
 		   tc_action_priv_destructor *destructor)
 {
 	struct tcf_mirred *m = to_mirred(a);
 	struct net_device *dev;

 	rcu_read_lock();
 	dev = rcu_dereference(m->tcfm_dev);
 	if (dev) {
 		dev_hold(dev);
 		*destructor = tcf_mirred_dev_put;
 	}
 	rcu_read_unlock();

 	return dev;
 }

 static size_t tcf_mirred_get_fill_size(const struct tc_action *act)
 {
 	return nla_total_size(sizeof(struct tc_mirred));
 }

 static struct tc_action_ops act_mirred_ops = {
 	.kind		=	"mirred",
 	.id		=	TCA_ID_MIRRED,
 	.owner		=	THIS_MODULE,
 	.act		=	tcf_mirred_act,
 	.stats_update	=	tcf_stats_update,
 	.dump		=	tcf_mirred_dump,
 	.cleanup	=	tcf_mirred_release,
 	.init		=	tcf_mirred_init,
 	.walk		=	tcf_mirred_walker,
 	.lookup		=	tcf_mirred_search,
 	.get_fill_size	=	tcf_mirred_get_fill_size,
 	.size		=	sizeof(struct tcf_mirred),
 	.get_dev	=	tcf_mirred_get_dev,
 };

 static __net_init int mirred_init_net(struct net *net)
 {
 	struct tc_action_net *tn = net_generic(net, mirred_net_id);

 	return tc_action_net_init(net, tn, &act_mirred_ops);
 }

 static void __net_exit mirred_exit_net(struct list_head *net_list)
 {
 	tc_action_net_exit(net_list, mirred_net_id);
 }

 static struct pernet_operations mirred_net_ops = {
 	.init = mirred_init_net,
 	.exit_batch = mirred_exit_net,
 	.id   = &mirred_net_id,
 	.size = sizeof(struct tc_action_net),
 };

 MODULE_AUTHOR("Jamal Hadi Salim(2002)");
 MODULE_DESCRIPTION("Device Mirror/redirect actions");
 MODULE_LICENSE("GPL");

 static int __init mirred_init_module(void)
 {
 	int err = register_netdevice_notifier(&mirred_device_notifier);
 	if (err)
 		return err;

 	pr_info("Mirror/redirect action on\n");
 	err = tcf_register_action(&act_mirred_ops, &mirred_net_ops);
 	if (err)
 		unregister_netdevice_notifier(&mirred_device_notifier);

 	return err;
 }

 static void __exit mirred_cleanup_module(void)
 {
 	tcf_unregister_action(&act_mirred_ops, &mirred_net_ops);
 	unregister_netdevice_notifier(&mirred_device_notifier);
 }

 module_init(mirred_init_module);
 module_exit(mirred_cleanup_module);
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* net/sched/act_mirred.c packet mirroring and redirect actions
	*
	* Authors: Jamal Hadi Salim (2002-4)
	*
	* TODO: Add ingress support (and socket redirect support)
	*/

	#include <linux/types.h>
	#include <linux/kernel.h>
	#include <linux/string.h>
	#include <linux/errno.h>
	#include <linux/skbuff.h>
	#include <linux/rtnetlink.h>
	#include <linux/module.h>
	#include <linux/init.h>
	#include <linux/gfp.h>
	#include <linux/if_arp.h>
	#include <net/net_namespace.h>
	#include <net/netlink.h>
	#include <net/dst.h>
	#include <net/pkt_sched.h>
	#include <net/pkt_cls.h>
	#include <linux/tc_act/tc_mirred.h>
	#include <net/tc_act/tc_mirred.h>

	static LIST_HEAD(mirred_list);
	static DEFINE_SPINLOCK(mirred_list_lock);

	#define MIRRED_NEST_LIMIT 4
	static DEFINE_PER_CPU(unsigned int, mirred_nest_level);

	static bool tcf_mirred_is_act_redirect(int action)
	{
	return action == TCA_EGRESS_REDIR \|\| action == TCA_INGRESS_REDIR;
	}

	static bool tcf_mirred_act_wants_ingress(int action)
	{
	switch (action) {
	case TCA_EGRESS_REDIR:
	case TCA_EGRESS_MIRROR:
	return false;
	case TCA_INGRESS_REDIR:
	case TCA_INGRESS_MIRROR:
	return true;
	default:
	BUG();
	}
	}

	static bool tcf_mirred_can_reinsert(int action)
	{
	switch (action) {
	case TC_ACT_SHOT:
	case TC_ACT_STOLEN:
	case TC_ACT_QUEUED:
	case TC_ACT_TRAP:
	return true;
	}
	return false;
	}

	static struct net_device tcf_mirred_dev_dereference(struct tcf_mirred m)
	{
	return rcu_dereference_protected(m->tcfm_dev,
	lockdep_is_held(&m->tcf_lock));
	}

	static void tcf_mirred_release(struct tc_action *a)
	{
	struct tcf_mirred *m = to_mirred(a);
	struct net_device *dev;

	spin_lock(&mirred_list_lock);
	list_del(&m->tcfm_list);
	spin_unlock(&mirred_list_lock);

	/* last reference to action, no need to lock */
	dev = rcu_dereference_protected(m->tcfm_dev, 1);
	dev_put(dev);
	}

	static const struct nla_policy mirred_policy[TCA_MIRRED_MAX + 1] = {
	[TCA_MIRRED_PARMS] = { .len = sizeof(struct tc_mirred) },
	};

	static unsigned int mirred_net_id;
	static struct tc_action_ops act_mirred_ops;

	static int tcf_mirred_init(struct net net, struct nlattr nla,
	struct nlattr est, struct tc_action *a,
	struct tcf_proto *tp,
	u32 flags, struct netlink_ext_ack *extack)
	{
	struct tc_action_net *tn = net_generic(net, mirred_net_id);
	bool bind = flags & TCA_ACT_FLAGS_BIND;
	struct nlattr *tb[TCA_MIRRED_MAX + 1];
	struct tcf_chain *goto_ch = NULL;
	bool mac_header_xmit = false;
	struct tc_mirred *parm;
	struct tcf_mirred *m;
	struct net_device *dev;
	bool exists = false;
	int ret, err;
	u32 index;

	if (!nla) {
	NL_SET_ERR_MSG_MOD(extack, "Mirred requires attributes to be passed");
	return -EINVAL;
	}
	ret = nla_parse_nested_deprecated(tb, TCA_MIRRED_MAX, nla,
	mirred_policy, extack);
	if (ret < 0)
	return ret;
	if (!tb[TCA_MIRRED_PARMS]) {
	NL_SET_ERR_MSG_MOD(extack, "Missing required mirred parameters");
	return -EINVAL;
	}
	parm = nla_data(tb[TCA_MIRRED_PARMS]);
	index = parm->index;
	err = tcf_idr_check_alloc(tn, &index, a, bind);
	if (err < 0)
	return err;
	exists = err;
	if (exists && bind)
	return 0;

	switch (parm->eaction) {
	case TCA_EGRESS_MIRROR:
	case TCA_EGRESS_REDIR:
	case TCA_INGRESS_REDIR:
	case TCA_INGRESS_MIRROR:
	break;
	default:
	if (exists)
	tcf_idr_release(*a, bind);
	else
	tcf_idr_cleanup(tn, index);
	NL_SET_ERR_MSG_MOD(extack, "Unknown mirred option");
	return -EINVAL;
	}

	if (!exists) {
	if (!parm->ifindex) {
	tcf_idr_cleanup(tn, index);
	NL_SET_ERR_MSG_MOD(extack, "Specified device does not exist");
	return -EINVAL;
	}
	ret = tcf_idr_create_from_flags(tn, index, est, a,
	&act_mirred_ops, bind, flags);
	if (ret) {
	tcf_idr_cleanup(tn, index);
	return ret;
	}
	ret = ACT_P_CREATED;
	} else if (!(flags & TCA_ACT_FLAGS_REPLACE)) {
	tcf_idr_release(*a, bind);
	return -EEXIST;
	}

	m = to_mirred(*a);
	if (ret == ACT_P_CREATED)
	INIT_LIST_HEAD(&m->tcfm_list);

	err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
	if (err < 0)
	goto release_idr;

	spin_lock_bh(&m->tcf_lock);

	if (parm->ifindex) {
	dev = dev_get_by_index(net, parm->ifindex);
	if (!dev) {
	spin_unlock_bh(&m->tcf_lock);
	err = -ENODEV;
	goto put_chain;
	}
	mac_header_xmit = dev_is_mac_header_xmit(dev);
	dev = rcu_replace_pointer(m->tcfm_dev, dev,
	lockdep_is_held(&m->tcf_lock));
	dev_put(dev);
	m->tcfm_mac_header_xmit = mac_header_xmit;
	}
	goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
	m->tcfm_eaction = parm->eaction;
	spin_unlock_bh(&m->tcf_lock);
	if (goto_ch)
	tcf_chain_put_by_act(goto_ch);

	if (ret == ACT_P_CREATED) {
	spin_lock(&mirred_list_lock);
	list_add(&m->tcfm_list, &mirred_list);
	spin_unlock(&mirred_list_lock);
	}

	return ret;
	put_chain:
	if (goto_ch)
	tcf_chain_put_by_act(goto_ch);
	release_idr:
	tcf_idr_release(*a, bind);
	return err;
	}

	static bool is_mirred_nested(void)
	{
	return unlikely(__this_cpu_read(mirred_nest_level) > 1);
	}

	static int tcf_mirred_forward(bool want_ingress, struct sk_buff *skb)
	{
	int err;

	if (!want_ingress)
	err = tcf_dev_queue_xmit(skb, dev_queue_xmit);
	else if (is_mirred_nested())
	err = netif_rx(skb);
	else
	err = netif_receive_skb(skb);

	return err;
	}

	static int tcf_mirred_act(struct sk_buff skb, const struct tc_action a,
	struct tcf_result *res)
	{
	struct tcf_mirred *m = to_mirred(a);
	struct sk_buff *skb2 = skb;
	bool m_mac_header_xmit;
	struct net_device *dev;
	unsigned int nest_level;
	int retval, err = 0;
	bool use_reinsert;
	bool want_ingress;
	bool is_redirect;
	bool expects_nh;
	bool at_ingress;
	int m_eaction;
	int mac_len;
	bool at_nh;

	nest_level = __this_cpu_inc_return(mirred_nest_level);
	if (unlikely(nest_level > MIRRED_NEST_LIMIT)) {
	net_warn_ratelimited("Packet exceeded mirred recursion limit on dev %s\n",
	netdev_name(skb->dev));
	__this_cpu_dec(mirred_nest_level);
	return TC_ACT_SHOT;
	}

	tcf_lastuse_update(&m->tcf_tm);
	tcf_action_update_bstats(&m->common, skb);

	m_mac_header_xmit = READ_ONCE(m->tcfm_mac_header_xmit);
	m_eaction = READ_ONCE(m->tcfm_eaction);
	retval = READ_ONCE(m->tcf_action);
	dev = rcu_dereference_bh(m->tcfm_dev);
	if (unlikely(!dev)) {
	pr_notice_once("tc mirred: target device is gone\n");
	goto out;
	}

	if (unlikely(!(dev->flags & IFF_UP))) {
	net_notice_ratelimited("tc mirred to Houston: device %s is down\n",
	dev->name);
	goto out;
	}

	/* we could easily avoid the clone only if called by ingress and clsact;
	* since we can't easily detect the clsact caller, skip clone only for
	* ingress - that covers the TC S/W datapath.
	*/
	is_redirect = tcf_mirred_is_act_redirect(m_eaction);
	at_ingress = skb_at_tc_ingress(skb);
	use_reinsert = at_ingress && is_redirect &&
	tcf_mirred_can_reinsert(retval);
	if (!use_reinsert) {
	skb2 = skb_clone(skb, GFP_ATOMIC);
	if (!skb2)
	goto out;
	}

	want_ingress = tcf_mirred_act_wants_ingress(m_eaction);

	/* All mirred/redirected skbs should clear previous ct info */
	nf_reset_ct(skb2);
	if (want_ingress && !at_ingress) /* drop dst for egress -> ingress */
	skb_dst_drop(skb2);

	expects_nh = want_ingress \|\| !m_mac_header_xmit;
	at_nh = skb->data == skb_network_header(skb);
	if (at_nh != expects_nh) {
	mac_len = skb_at_tc_ingress(skb) ? skb->mac_len :
	skb_network_header(skb) - skb_mac_header(skb);
	if (expects_nh) {
	/* target device/action expect data at nh */
	skb_pull_rcsum(skb2, mac_len);
	} else {
	/* target device/action expect data at mac */
	skb_push_rcsum(skb2, mac_len);
	}
	}

	skb2->skb_iif = skb->dev->ifindex;
	skb2->dev = dev;

	/* mirror is always swallowed */
	if (is_redirect) {
	skb_set_redirected(skb2, skb2->tc_at_ingress);

	/* let's the caller reinsert the packet, if possible */
	if (use_reinsert) {
	res->ingress = want_ingress;
	err = tcf_mirred_forward(res->ingress, skb);
	if (err)
	tcf_action_inc_overlimit_qstats(&m->common);
	__this_cpu_dec(mirred_nest_level);
	return TC_ACT_CONSUMED;
	}
	}

	err = tcf_mirred_forward(want_ingress, skb2);
	if (err) {
	out:
	tcf_action_inc_overlimit_qstats(&m->common);
	if (tcf_mirred_is_act_redirect(m_eaction))
	retval = TC_ACT_SHOT;
	}
	__this_cpu_dec(mirred_nest_level);

	return retval;
	}

	static void tcf_stats_update(struct tc_action *a, u64 bytes, u64 packets,
	u64 drops, u64 lastuse, bool hw)
	{
	struct tcf_mirred *m = to_mirred(a);
	struct tcf_t *tm = &m->tcf_tm;

	tcf_action_update_stats(a, bytes, packets, drops, hw);
	tm->lastuse = max_t(u64, tm->lastuse, lastuse);
	}

	static int tcf_mirred_dump(struct sk_buff skb, struct tc_action a, int bind,
	int ref)
	{
	unsigned char *b = skb_tail_pointer(skb);
	struct tcf_mirred *m = to_mirred(a);
	struct tc_mirred opt = {
	.index = m->tcf_index,
	.refcnt = refcount_read(&m->tcf_refcnt) - ref,
	.bindcnt = atomic_read(&m->tcf_bindcnt) - bind,
	};
	struct net_device *dev;
	struct tcf_t t;

	spin_lock_bh(&m->tcf_lock);
	opt.action = m->tcf_action;
	opt.eaction = m->tcfm_eaction;
	dev = tcf_mirred_dev_dereference(m);
	if (dev)
	opt.ifindex = dev->ifindex;

	if (nla_put(skb, TCA_MIRRED_PARMS, sizeof(opt), &opt))
	goto nla_put_failure;

	tcf_tm_dump(&t, &m->tcf_tm);
	if (nla_put_64bit(skb, TCA_MIRRED_TM, sizeof(t), &t, TCA_MIRRED_PAD))
	goto nla_put_failure;
	spin_unlock_bh(&m->tcf_lock);

	return skb->len;

	nla_put_failure:
	spin_unlock_bh(&m->tcf_lock);
	nlmsg_trim(skb, b);
	return -1;
	}

	static int tcf_mirred_walker(struct net net, struct sk_buff skb,
	struct netlink_callback *cb, int type,
	const struct tc_action_ops *ops,
	struct netlink_ext_ack *extack)
	{
	struct tc_action_net *tn = net_generic(net, mirred_net_id);

	return tcf_generic_walker(tn, skb, cb, type, ops, extack);
	}

	static int tcf_mirred_search(struct net net, struct tc_action *a, u32 index)
	{
	struct tc_action_net *tn = net_generic(net, mirred_net_id);

	return tcf_idr_search(tn, a, index);
	}

	static int mirred_device_event(struct notifier_block *unused,
	unsigned long event, void *ptr)
	{
	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
	struct tcf_mirred *m;

	ASSERT_RTNL();
	if (event == NETDEV_UNREGISTER) {
	spin_lock(&mirred_list_lock);
	list_for_each_entry(m, &mirred_list, tcfm_list) {
	spin_lock_bh(&m->tcf_lock);
	if (tcf_mirred_dev_dereference(m) == dev) {
	dev_put(dev);
	/* Note : no rcu grace period necessary, as
	* net_device are already rcu protected.
	*/
	RCU_INIT_POINTER(m->tcfm_dev, NULL);
	}
	spin_unlock_bh(&m->tcf_lock);
	}
	spin_unlock(&mirred_list_lock);
	}

	return NOTIFY_DONE;
	}

	static struct notifier_block mirred_device_notifier = {
	.notifier_call = mirred_device_event,
	};

	static void tcf_mirred_dev_put(void *priv)
	{
	struct net_device *dev = priv;

	dev_put(dev);
	}

	static struct net_device *
	tcf_mirred_get_dev(const struct tc_action *a,
	tc_action_priv_destructor *destructor)
	{
	struct tcf_mirred *m = to_mirred(a);
	struct net_device *dev;

	rcu_read_lock();
	dev = rcu_dereference(m->tcfm_dev);
	if (dev) {
	dev_hold(dev);
	*destructor = tcf_mirred_dev_put;
	}
	rcu_read_unlock();

	return dev;
	}

	static size_t tcf_mirred_get_fill_size(const struct tc_action *act)
	{
	return nla_total_size(sizeof(struct tc_mirred));
	}

	static struct tc_action_ops act_mirred_ops = {
	.kind = "mirred",
	.id = TCA_ID_MIRRED,
	.owner = THIS_MODULE,
	.act = tcf_mirred_act,
	.stats_update = tcf_stats_update,
	.dump = tcf_mirred_dump,
	.cleanup = tcf_mirred_release,
	.init = tcf_mirred_init,
	.walk = tcf_mirred_walker,
	.lookup = tcf_mirred_search,
	.get_fill_size = tcf_mirred_get_fill_size,
	.size = sizeof(struct tcf_mirred),
	.get_dev = tcf_mirred_get_dev,
	};

	static __net_init int mirred_init_net(struct net *net)
	{
	struct tc_action_net *tn = net_generic(net, mirred_net_id);

	return tc_action_net_init(net, tn, &act_mirred_ops);
	}

	static void __net_exit mirred_exit_net(struct list_head *net_list)
	{
	tc_action_net_exit(net_list, mirred_net_id);
	}

	static struct pernet_operations mirred_net_ops = {
	.init = mirred_init_net,
	.exit_batch = mirred_exit_net,
	.id = &mirred_net_id,
	.size = sizeof(struct tc_action_net),
	};

	MODULE_AUTHOR("Jamal Hadi Salim(2002)");
	MODULE_DESCRIPTION("Device Mirror/redirect actions");
	MODULE_LICENSE("GPL");

	static int __init mirred_init_module(void)
	{
	int err = register_netdevice_notifier(&mirred_device_notifier);
	if (err)
	return err;

	pr_info("Mirror/redirect action on\n");
	err = tcf_register_action(&act_mirred_ops, &mirred_net_ops);
	if (err)
	unregister_netdevice_notifier(&mirred_device_notifier);

	return err;
	}

	static void __exit mirred_cleanup_module(void)
	{
	tcf_unregister_action(&act_mirred_ops, &mirred_net_ops);
	unregister_netdevice_notifier(&mirred_device_notifier);
	}

	module_init(mirred_init_module);
	module_exit(mirred_cleanup_module);