net/caif/caif_dev.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * CAIF Interface registration.
  * Copyright (C) ST-Ericsson AB 2010
  * Author:	Sjur Brendeland
  *
  * Borrowed heavily from file: pn_dev.c. Thanks to Remi Denis-Courmont
  *  and Sakari Ailus <sakari.ailus@nokia.com>
  */

 #define pr_fmt(fmt) KBUILD_MODNAME ":%s(): " fmt, __func__

 #include <linux/kernel.h>
 #include <linux/if_arp.h>
 #include <linux/net.h>
 #include <linux/netdevice.h>
 #include <linux/mutex.h>
 #include <linux/module.h>
 #include <linux/spinlock.h>
 #include <net/netns/generic.h>
 #include <net/net_namespace.h>
 #include <net/pkt_sched.h>
 #include <net/caif/caif_device.h>
 #include <net/caif/caif_layer.h>
 #include <net/caif/caif_dev.h>
 #include <net/caif/cfpkt.h>
 #include <net/caif/cfcnfg.h>
 #include <net/caif/cfserl.h>

 MODULE_LICENSE("GPL");

 /* Used for local tracking of the CAIF net devices */
 struct caif_device_entry {
 	struct cflayer layer;
 	struct list_head list;
 	struct net_device *netdev;
 	int __percpu *pcpu_refcnt;
 	spinlock_t flow_lock;
 	struct sk_buff *xoff_skb;
 	void (*xoff_skb_dtor)(struct sk_buff *skb);
 	bool xoff;
 };

 struct caif_device_entry_list {
 	struct list_head list;
 	/* Protects simulanous deletes in list */
 	struct mutex lock;
 };

 struct caif_net {
 	struct cfcnfg *cfg;
 	struct caif_device_entry_list caifdevs;
 };

 static unsigned int caif_net_id;
 static int q_high = 50; /* Percent */

 struct cfcnfg *get_cfcnfg(struct net *net)
 {
 	struct caif_net *caifn;
 	caifn = net_generic(net, caif_net_id);
 	return caifn->cfg;
 }
 EXPORT_SYMBOL(get_cfcnfg);

 static struct caif_device_entry_list *caif_device_list(struct net *net)
 {
 	struct caif_net *caifn;
 	caifn = net_generic(net, caif_net_id);
 	return &caifn->caifdevs;
 }

 static void caifd_put(struct caif_device_entry *e)
 {
 	this_cpu_dec(*e->pcpu_refcnt);
 }

 static void caifd_hold(struct caif_device_entry *e)
 {
 	this_cpu_inc(*e->pcpu_refcnt);
 }

 static int caifd_refcnt_read(struct caif_device_entry *e)
 {
 	int i, refcnt = 0;
 	for_each_possible_cpu(i)
 		refcnt += *per_cpu_ptr(e->pcpu_refcnt, i);
 	return refcnt;
 }

 /* Allocate new CAIF device. */
 static struct caif_device_entry *caif_device_alloc(struct net_device *dev)
 {
 	struct caif_device_entry *caifd;

 	caifd = kzalloc(sizeof(*caifd), GFP_KERNEL);
 	if (!caifd)
 		return NULL;
 	caifd->pcpu_refcnt = alloc_percpu(int);
 	if (!caifd->pcpu_refcnt) {
 		kfree(caifd);
 		return NULL;
 	}
 	caifd->netdev = dev;
 	dev_hold(dev);
 	return caifd;
 }

 static struct caif_device_entry *caif_get(struct net_device *dev)
 {
 	struct caif_device_entry_list *caifdevs =
 	    caif_device_list(dev_net(dev));
 	struct caif_device_entry *caifd;

 	list_for_each_entry_rcu(caifd, &caifdevs->list, list,
 				lockdep_rtnl_is_held()) {
 		if (caifd->netdev == dev)
 			return caifd;
 	}
 	return NULL;
 }

 static void caif_flow_cb(struct sk_buff *skb)
 {
 	struct caif_device_entry *caifd;
 	void (*dtor)(struct sk_buff *skb) = NULL;
 	bool send_xoff;

 	WARN_ON(skb->dev == NULL);

 	rcu_read_lock();
 	caifd = caif_get(skb->dev);

 	WARN_ON(caifd == NULL);
 	if (!caifd) {
 		rcu_read_unlock();
 		return;
 	}

 	caifd_hold(caifd);
 	rcu_read_unlock();

 	spin_lock_bh(&caifd->flow_lock);
 	send_xoff = caifd->xoff;
 	caifd->xoff = false;
 	dtor = caifd->xoff_skb_dtor;

 	if (WARN_ON(caifd->xoff_skb != skb))
 		skb = NULL;

 	caifd->xoff_skb = NULL;
 	caifd->xoff_skb_dtor = NULL;

 	spin_unlock_bh(&caifd->flow_lock);

 	if (dtor && skb)
 		dtor(skb);

 	if (send_xoff)
 		caifd->layer.up->
 			ctrlcmd(caifd->layer.up,
 				_CAIF_CTRLCMD_PHYIF_FLOW_ON_IND,
 				caifd->layer.id);
 	caifd_put(caifd);
 }

 static int transmit(struct cflayer *layer, struct cfpkt *pkt)
 {
 	int err, high = 0, qlen = 0;
 	struct caif_device_entry *caifd =
 	    container_of(layer, struct caif_device_entry, layer);
 	struct sk_buff *skb;
 	struct netdev_queue *txq;

 	rcu_read_lock_bh();

 	skb = cfpkt_tonative(pkt);
 	skb->dev = caifd->netdev;
 	skb_reset_network_header(skb);
 	skb->protocol = htons(ETH_P_CAIF);

 	/* Check if we need to handle xoff */
 	if (likely(caifd->netdev->priv_flags & IFF_NO_QUEUE))
 		goto noxoff;

 	if (unlikely(caifd->xoff))
 		goto noxoff;

 	if (likely(!netif_queue_stopped(caifd->netdev))) {
 		struct Qdisc *sch;

 		/* If we run with a TX queue, check if the queue is too long*/
 		txq = netdev_get_tx_queue(skb->dev, 0);
 		sch = rcu_dereference_bh(txq->qdisc);
 		if (likely(qdisc_is_empty(sch)))
 			goto noxoff;

 		/* can check for explicit qdisc len value only !NOLOCK,
 		 * always set flow off otherwise
 		 */
 		high = (caifd->netdev->tx_queue_len * q_high) / 100;
 		if (!(sch->flags & TCQ_F_NOLOCK) && likely(sch->q.qlen < high))
 			goto noxoff;
 	}

 	/* Hold lock while accessing xoff */
 	spin_lock_bh(&caifd->flow_lock);
 	if (caifd->xoff) {
 		spin_unlock_bh(&caifd->flow_lock);
 		goto noxoff;
 	}

 	/*
 	 * Handle flow off, we do this by temporary hi-jacking this
 	 * skb's destructor function, and replace it with our own
 	 * flow-on callback. The callback will set flow-on and call
 	 * the original destructor.
 	 */

 	pr_debug("queue has stopped(%d) or is full (%d > %d)\n",
 			netif_queue_stopped(caifd->netdev),
 			qlen, high);
 	caifd->xoff = true;
 	caifd->xoff_skb = skb;
 	caifd->xoff_skb_dtor = skb->destructor;
 	skb->destructor = caif_flow_cb;
 	spin_unlock_bh(&caifd->flow_lock);

 	caifd->layer.up->ctrlcmd(caifd->layer.up,
 					_CAIF_CTRLCMD_PHYIF_FLOW_OFF_IND,
 					caifd->layer.id);
 noxoff:
 	rcu_read_unlock_bh();

 	err = dev_queue_xmit(skb);
 	if (err > 0)
 		err = -EIO;

 	return err;
 }

 /*
  * Stuff received packets into the CAIF stack.
  * On error, returns non-zero and releases the skb.
  */
 static int receive(struct sk_buff *skb, struct net_device *dev,
 		   struct packet_type *pkttype, struct net_device *orig_dev)
 {
 	struct cfpkt *pkt;
 	struct caif_device_entry *caifd;
 	int err;

 	pkt = cfpkt_fromnative(CAIF_DIR_IN, skb);

 	rcu_read_lock();
 	caifd = caif_get(dev);

 	if (!caifd || !caifd->layer.up || !caifd->layer.up->receive ||
 			!netif_oper_up(caifd->netdev)) {
 		rcu_read_unlock();
 		kfree_skb(skb);
 		return NET_RX_DROP;
 	}

 	/* Hold reference to netdevice while using CAIF stack */
 	caifd_hold(caifd);
 	rcu_read_unlock();

 	err = caifd->layer.up->receive(caifd->layer.up, pkt);

 	/* For -EILSEQ the packet is not freed so free it now */
 	if (err == -EILSEQ)
 		cfpkt_destroy(pkt);

 	/* Release reference to stack upwards */
 	caifd_put(caifd);

 	if (err != 0)
 		err = NET_RX_DROP;
 	return err;
 }

 static struct packet_type caif_packet_type __read_mostly = {
 	.type = cpu_to_be16(ETH_P_CAIF),
 	.func = receive,
 };

 static void dev_flowctrl(struct net_device *dev, int on)
 {
 	struct caif_device_entry *caifd;

 	rcu_read_lock();

 	caifd = caif_get(dev);
 	if (!caifd || !caifd->layer.up || !caifd->layer.up->ctrlcmd) {
 		rcu_read_unlock();
 		return;
 	}

 	caifd_hold(caifd);
 	rcu_read_unlock();

 	caifd->layer.up->ctrlcmd(caifd->layer.up,
 				 on ?
 				 _CAIF_CTRLCMD_PHYIF_FLOW_ON_IND :
 				 _CAIF_CTRLCMD_PHYIF_FLOW_OFF_IND,
 				 caifd->layer.id);
 	caifd_put(caifd);
 }

 int caif_enroll_dev(struct net_device *dev, struct caif_dev_common *caifdev,
 		     struct cflayer *link_support, int head_room,
 		     struct cflayer **layer,
 		     int (**rcv_func)(struct sk_buff *, struct net_device *,
 				      struct packet_type *,
 				      struct net_device *))
 {
 	struct caif_device_entry *caifd;
 	enum cfcnfg_phy_preference pref;
 	struct cfcnfg *cfg = get_cfcnfg(dev_net(dev));
 	struct caif_device_entry_list *caifdevs;
 	int res;

 	caifdevs = caif_device_list(dev_net(dev));
 	caifd = caif_device_alloc(dev);
 	if (!caifd)
 		return -ENOMEM;
 	*layer = &caifd->layer;
 	spin_lock_init(&caifd->flow_lock);

 	switch (caifdev->link_select) {
 	case CAIF_LINK_HIGH_BANDW:
 		pref = CFPHYPREF_HIGH_BW;
 		break;
 	case CAIF_LINK_LOW_LATENCY:
 		pref = CFPHYPREF_LOW_LAT;
 		break;
 	default:
 		pref = CFPHYPREF_HIGH_BW;
 		break;
 	}
 	mutex_lock(&caifdevs->lock);
 	list_add_rcu(&caifd->list, &caifdevs->list);

 	strscpy(caifd->layer.name, dev->name,
 		sizeof(caifd->layer.name));
 	caifd->layer.transmit = transmit;
 	res = cfcnfg_add_phy_layer(cfg,
 				dev,
 				&caifd->layer,
 				pref,
 				link_support,
 				caifdev->use_fcs,
 				head_room);
 	mutex_unlock(&caifdevs->lock);
 	if (rcv_func)
 		*rcv_func = receive;
 	return res;
 }
 EXPORT_SYMBOL(caif_enroll_dev);

 /* notify Caif of device events */
 static int caif_device_notify(struct notifier_block *me, unsigned long what,
 			      void *ptr)
 {
 	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 	struct caif_device_entry *caifd = NULL;
 	struct caif_dev_common *caifdev;
 	struct cfcnfg *cfg;
 	struct cflayer *layer, *link_support;
 	int head_room = 0;
 	struct caif_device_entry_list *caifdevs;
 	int res;

 	cfg = get_cfcnfg(dev_net(dev));
 	caifdevs = caif_device_list(dev_net(dev));

 	caifd = caif_get(dev);
 	if (caifd == NULL && dev->type != ARPHRD_CAIF)
 		return 0;

 	switch (what) {
 	case NETDEV_REGISTER:
 		if (caifd != NULL)
 			break;

 		caifdev = netdev_priv(dev);

 		link_support = NULL;
 		if (caifdev->use_frag) {
 			head_room = 1;
 			link_support = cfserl_create(dev->ifindex,
 							caifdev->use_stx);
 			if (!link_support) {
 				pr_warn("Out of memory\n");
 				break;
 			}
 		}
 		res = caif_enroll_dev(dev, caifdev, link_support, head_room,
 				&layer, NULL);
 		if (res)
 			cfserl_release(link_support);
 		caifdev->flowctrl = dev_flowctrl;
 		break;

 	case NETDEV_UP:
 		rcu_read_lock();

 		caifd = caif_get(dev);
 		if (caifd == NULL) {
 			rcu_read_unlock();
 			break;
 		}

 		caifd->xoff = false;
 		cfcnfg_set_phy_state(cfg, &caifd->layer, true);
 		rcu_read_unlock();

 		break;

 	case NETDEV_DOWN:
 		rcu_read_lock();

 		caifd = caif_get(dev);
 		if (!caifd || !caifd->layer.up || !caifd->layer.up->ctrlcmd) {
 			rcu_read_unlock();
 			return -EINVAL;
 		}

 		cfcnfg_set_phy_state(cfg, &caifd->layer, false);
 		caifd_hold(caifd);
 		rcu_read_unlock();

 		caifd->layer.up->ctrlcmd(caifd->layer.up,
 					 _CAIF_CTRLCMD_PHYIF_DOWN_IND,
 					 caifd->layer.id);

 		spin_lock_bh(&caifd->flow_lock);

 		/*
 		 * Replace our xoff-destructor with original destructor.
 		 * We trust that skb->destructor *always* is called before
 		 * the skb reference is invalid. The hijacked SKB destructor
 		 * takes the flow_lock so manipulating the skb->destructor here
 		 * should be safe.
 		*/
 		if (caifd->xoff_skb_dtor != NULL && caifd->xoff_skb != NULL)
 			caifd->xoff_skb->destructor = caifd->xoff_skb_dtor;

 		caifd->xoff = false;
 		caifd->xoff_skb_dtor = NULL;
 		caifd->xoff_skb = NULL;

 		spin_unlock_bh(&caifd->flow_lock);
 		caifd_put(caifd);
 		break;

 	case NETDEV_UNREGISTER:
 		mutex_lock(&caifdevs->lock);

 		caifd = caif_get(dev);
 		if (caifd == NULL) {
 			mutex_unlock(&caifdevs->lock);
 			break;
 		}
 		list_del_rcu(&caifd->list);

 		/*
 		 * NETDEV_UNREGISTER is called repeatedly until all reference
 		 * counts for the net-device are released. If references to
 		 * caifd is taken, simply ignore NETDEV_UNREGISTER and wait for
 		 * the next call to NETDEV_UNREGISTER.
 		 *
 		 * If any packets are in flight down the CAIF Stack,
 		 * cfcnfg_del_phy_layer will return nonzero.
 		 * If no packets are in flight, the CAIF Stack associated
 		 * with the net-device un-registering is freed.
 		 */

 		if (caifd_refcnt_read(caifd) != 0 ||
 			cfcnfg_del_phy_layer(cfg, &caifd->layer) != 0) {

 			pr_info("Wait for device inuse\n");
 			/* Enrole device if CAIF Stack is still in use */
 			list_add_rcu(&caifd->list, &caifdevs->list);
 			mutex_unlock(&caifdevs->lock);
 			break;
 		}

 		synchronize_rcu();
 		dev_put(caifd->netdev);
 		free_percpu(caifd->pcpu_refcnt);
 		kfree(caifd);

 		mutex_unlock(&caifdevs->lock);
 		break;
 	}
 	return 0;
 }

 static struct notifier_block caif_device_notifier = {
 	.notifier_call = caif_device_notify,
 	.priority = 0,
 };

 /* Per-namespace Caif devices handling */
 static int caif_init_net(struct net *net)
 {
 	struct caif_net *caifn = net_generic(net, caif_net_id);
 	INIT_LIST_HEAD(&caifn->caifdevs.list);
 	mutex_init(&caifn->caifdevs.lock);

 	caifn->cfg = cfcnfg_create();
 	if (!caifn->cfg)
 		return -ENOMEM;

 	return 0;
 }

 static void caif_exit_net(struct net *net)
 {
 	struct caif_device_entry *caifd, *tmp;
 	struct caif_device_entry_list *caifdevs =
 	    caif_device_list(net);
 	struct cfcnfg *cfg =  get_cfcnfg(net);

 	rtnl_lock();
 	mutex_lock(&caifdevs->lock);

 	list_for_each_entry_safe(caifd, tmp, &caifdevs->list, list) {
 		int i = 0;
 		list_del_rcu(&caifd->list);
 		cfcnfg_set_phy_state(cfg, &caifd->layer, false);

 		while (i < 10 &&
 			(caifd_refcnt_read(caifd) != 0 ||
 			cfcnfg_del_phy_layer(cfg, &caifd->layer) != 0)) {

 			pr_info("Wait for device inuse\n");
 			msleep(250);
 			i++;
 		}
 		synchronize_rcu();
 		dev_put(caifd->netdev);
 		free_percpu(caifd->pcpu_refcnt);
 		kfree(caifd);
 	}
 	cfcnfg_remove(cfg);

 	mutex_unlock(&caifdevs->lock);
 	rtnl_unlock();
 }

 static struct pernet_operations caif_net_ops = {
 	.init = caif_init_net,
 	.exit = caif_exit_net,
 	.id   = &caif_net_id,
 	.size = sizeof(struct caif_net),
 };

 /* Initialize Caif devices list */
 static int __init caif_device_init(void)
 {
 	int result;

 	result = register_pernet_subsys(&caif_net_ops);

 	if (result)
 		return result;

 	register_netdevice_notifier(&caif_device_notifier);
 	dev_add_pack(&caif_packet_type);

 	return result;
 }

 static void __exit caif_device_exit(void)
 {
 	unregister_netdevice_notifier(&caif_device_notifier);
 	dev_remove_pack(&caif_packet_type);
 	unregister_pernet_subsys(&caif_net_ops);
 }

 module_init(caif_device_init);
 module_exit(caif_device_exit);
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* CAIF Interface registration.
	* Copyright (C) ST-Ericsson AB 2010
	* Author: Sjur Brendeland
	*
	* Borrowed heavily from file: pn_dev.c. Thanks to Remi Denis-Courmont
	* and Sakari Ailus <sakari.ailus@nokia.com>
	*/

	#define pr_fmt(fmt) KBUILD_MODNAME ":%s(): " fmt, __func__

	#include <linux/kernel.h>
	#include <linux/if_arp.h>
	#include <linux/net.h>
	#include <linux/netdevice.h>
	#include <linux/mutex.h>
	#include <linux/module.h>
	#include <linux/spinlock.h>
	#include <net/netns/generic.h>
	#include <net/net_namespace.h>
	#include <net/pkt_sched.h>
	#include <net/caif/caif_device.h>
	#include <net/caif/caif_layer.h>
	#include <net/caif/caif_dev.h>
	#include <net/caif/cfpkt.h>
	#include <net/caif/cfcnfg.h>
	#include <net/caif/cfserl.h>

	MODULE_LICENSE("GPL");

	/* Used for local tracking of the CAIF net devices */
	struct caif_device_entry {
	struct cflayer layer;
	struct list_head list;
	struct net_device *netdev;
	int __percpu *pcpu_refcnt;
	spinlock_t flow_lock;
	struct sk_buff *xoff_skb;
	void (xoff_skb_dtor)(struct sk_buff skb);
	bool xoff;
	};

	struct caif_device_entry_list {
	struct list_head list;
	/* Protects simulanous deletes in list */
	struct mutex lock;
	};

	struct caif_net {
	struct cfcnfg *cfg;
	struct caif_device_entry_list caifdevs;
	};

	static unsigned int caif_net_id;
	static int q_high = 50; /* Percent */

	struct cfcnfg get_cfcnfg(struct net net)
	{
	struct caif_net *caifn;
	caifn = net_generic(net, caif_net_id);
	return caifn->cfg;
	}
	EXPORT_SYMBOL(get_cfcnfg);

	static struct caif_device_entry_list caif_device_list(struct net net)
	{
	struct caif_net *caifn;
	caifn = net_generic(net, caif_net_id);
	return &caifn->caifdevs;
	}

	static void caifd_put(struct caif_device_entry *e)
	{
	this_cpu_dec(*e->pcpu_refcnt);
	}

	static void caifd_hold(struct caif_device_entry *e)
	{
	this_cpu_inc(*e->pcpu_refcnt);
	}

	static int caifd_refcnt_read(struct caif_device_entry *e)
	{
	int i, refcnt = 0;
	for_each_possible_cpu(i)
	refcnt += *per_cpu_ptr(e->pcpu_refcnt, i);
	return refcnt;
	}

	/* Allocate new CAIF device. */
	static struct caif_device_entry caif_device_alloc(struct net_device dev)
	{
	struct caif_device_entry *caifd;

	caifd = kzalloc(sizeof(*caifd), GFP_KERNEL);
	if (!caifd)
	return NULL;
	caifd->pcpu_refcnt = alloc_percpu(int);
	if (!caifd->pcpu_refcnt) {
	kfree(caifd);
	return NULL;
	}
	caifd->netdev = dev;
	dev_hold(dev);
	return caifd;
	}

	static struct caif_device_entry caif_get(struct net_device dev)
	{
	struct caif_device_entry_list *caifdevs =
	caif_device_list(dev_net(dev));
	struct caif_device_entry *caifd;

	list_for_each_entry_rcu(caifd, &caifdevs->list, list,
	lockdep_rtnl_is_held()) {
	if (caifd->netdev == dev)
	return caifd;
	}
	return NULL;
	}

	static void caif_flow_cb(struct sk_buff *skb)
	{
	struct caif_device_entry *caifd;
	void (dtor)(struct sk_buff skb) = NULL;
	bool send_xoff;

	WARN_ON(skb->dev == NULL);

	rcu_read_lock();
	caifd = caif_get(skb->dev);

	WARN_ON(caifd == NULL);
	if (!caifd) {
	rcu_read_unlock();
	return;
	}

	caifd_hold(caifd);
	rcu_read_unlock();

	spin_lock_bh(&caifd->flow_lock);
	send_xoff = caifd->xoff;
	caifd->xoff = false;
	dtor = caifd->xoff_skb_dtor;

	if (WARN_ON(caifd->xoff_skb != skb))
	skb = NULL;

	caifd->xoff_skb = NULL;
	caifd->xoff_skb_dtor = NULL;

	spin_unlock_bh(&caifd->flow_lock);

	if (dtor && skb)
	dtor(skb);

	if (send_xoff)
	caifd->layer.up->
	ctrlcmd(caifd->layer.up,
	_CAIF_CTRLCMD_PHYIF_FLOW_ON_IND,
	caifd->layer.id);
	caifd_put(caifd);
	}

	static int transmit(struct cflayer layer, struct cfpkt pkt)
	{
	int err, high = 0, qlen = 0;
	struct caif_device_entry *caifd =
	container_of(layer, struct caif_device_entry, layer);
	struct sk_buff *skb;
	struct netdev_queue *txq;

	rcu_read_lock_bh();

	skb = cfpkt_tonative(pkt);
	skb->dev = caifd->netdev;
	skb_reset_network_header(skb);
	skb->protocol = htons(ETH_P_CAIF);

	/* Check if we need to handle xoff */
	if (likely(caifd->netdev->priv_flags & IFF_NO_QUEUE))
	goto noxoff;

	if (unlikely(caifd->xoff))
	goto noxoff;

	if (likely(!netif_queue_stopped(caifd->netdev))) {
	struct Qdisc *sch;

	/* If we run with a TX queue, check if the queue is too long*/
	txq = netdev_get_tx_queue(skb->dev, 0);
	sch = rcu_dereference_bh(txq->qdisc);
	if (likely(qdisc_is_empty(sch)))
	goto noxoff;

	/* can check for explicit qdisc len value only !NOLOCK,
	* always set flow off otherwise
	*/
	high = (caifd->netdev->tx_queue_len * q_high) / 100;
	if (!(sch->flags & TCQ_F_NOLOCK) && likely(sch->q.qlen < high))
	goto noxoff;
	}

	/* Hold lock while accessing xoff */
	spin_lock_bh(&caifd->flow_lock);
	if (caifd->xoff) {
	spin_unlock_bh(&caifd->flow_lock);
	goto noxoff;
	}

	/*
	* Handle flow off, we do this by temporary hi-jacking this
	* skb's destructor function, and replace it with our own
	* flow-on callback. The callback will set flow-on and call
	* the original destructor.
	*/

	pr_debug("queue has stopped(%d) or is full (%d > %d)\n",
	netif_queue_stopped(caifd->netdev),
	qlen, high);
	caifd->xoff = true;
	caifd->xoff_skb = skb;
	caifd->xoff_skb_dtor = skb->destructor;
	skb->destructor = caif_flow_cb;
	spin_unlock_bh(&caifd->flow_lock);

	caifd->layer.up->ctrlcmd(caifd->layer.up,
	_CAIF_CTRLCMD_PHYIF_FLOW_OFF_IND,
	caifd->layer.id);
	noxoff:
	rcu_read_unlock_bh();

	err = dev_queue_xmit(skb);
	if (err > 0)
	err = -EIO;

	return err;
	}

	/*
	* Stuff received packets into the CAIF stack.
	* On error, returns non-zero and releases the skb.
	*/
	static int receive(struct sk_buff skb, struct net_device dev,
	struct packet_type pkttype, struct net_device orig_dev)
	{
	struct cfpkt *pkt;
	struct caif_device_entry *caifd;
	int err;

	pkt = cfpkt_fromnative(CAIF_DIR_IN, skb);

	rcu_read_lock();
	caifd = caif_get(dev);

	if (!caifd \|\| !caifd->layer.up \|\| !caifd->layer.up->receive \|\|
	!netif_oper_up(caifd->netdev)) {
	rcu_read_unlock();
	kfree_skb(skb);
	return NET_RX_DROP;
	}

	/* Hold reference to netdevice while using CAIF stack */
	caifd_hold(caifd);
	rcu_read_unlock();

	err = caifd->layer.up->receive(caifd->layer.up, pkt);

	/* For -EILSEQ the packet is not freed so free it now */
	if (err == -EILSEQ)
	cfpkt_destroy(pkt);

	/* Release reference to stack upwards */
	caifd_put(caifd);

	if (err != 0)
	err = NET_RX_DROP;
	return err;
	}

	static struct packet_type caif_packet_type __read_mostly = {
	.type = cpu_to_be16(ETH_P_CAIF),
	.func = receive,
	};

	static void dev_flowctrl(struct net_device *dev, int on)
	{
	struct caif_device_entry *caifd;

	rcu_read_lock();

	caifd = caif_get(dev);
	if (!caifd \|\| !caifd->layer.up \|\| !caifd->layer.up->ctrlcmd) {
	rcu_read_unlock();
	return;
	}

	caifd_hold(caifd);
	rcu_read_unlock();

	caifd->layer.up->ctrlcmd(caifd->layer.up,
	on ?
	_CAIF_CTRLCMD_PHYIF_FLOW_ON_IND :
	_CAIF_CTRLCMD_PHYIF_FLOW_OFF_IND,
	caifd->layer.id);
	caifd_put(caifd);
	}

	int caif_enroll_dev(struct net_device dev, struct caif_dev_common caifdev,
	struct cflayer *link_support, int head_room,
	struct cflayer **layer,
	int (*rcv_func)(struct sk_buff , struct net_device *,
	struct packet_type *,
	struct net_device *))
	{
	struct caif_device_entry *caifd;
	enum cfcnfg_phy_preference pref;
	struct cfcnfg *cfg = get_cfcnfg(dev_net(dev));
	struct caif_device_entry_list *caifdevs;
	int res;

	caifdevs = caif_device_list(dev_net(dev));
	caifd = caif_device_alloc(dev);
	if (!caifd)
	return -ENOMEM;
	*layer = &caifd->layer;
	spin_lock_init(&caifd->flow_lock);

	switch (caifdev->link_select) {
	case CAIF_LINK_HIGH_BANDW:
	pref = CFPHYPREF_HIGH_BW;
	break;
	case CAIF_LINK_LOW_LATENCY:
	pref = CFPHYPREF_LOW_LAT;
	break;
	default:
	pref = CFPHYPREF_HIGH_BW;
	break;
	}
	mutex_lock(&caifdevs->lock);
	list_add_rcu(&caifd->list, &caifdevs->list);

	strscpy(caifd->layer.name, dev->name,
	sizeof(caifd->layer.name));
	caifd->layer.transmit = transmit;
	res = cfcnfg_add_phy_layer(cfg,
	dev,
	&caifd->layer,
	pref,
	link_support,
	caifdev->use_fcs,
	head_room);
	mutex_unlock(&caifdevs->lock);
	if (rcv_func)
	*rcv_func = receive;
	return res;
	}
	EXPORT_SYMBOL(caif_enroll_dev);

	/* notify Caif of device events */
	static int caif_device_notify(struct notifier_block *me, unsigned long what,
	void *ptr)
	{
	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
	struct caif_device_entry *caifd = NULL;
	struct caif_dev_common *caifdev;
	struct cfcnfg *cfg;
	struct cflayer layer, link_support;
	int head_room = 0;
	struct caif_device_entry_list *caifdevs;
	int res;

	cfg = get_cfcnfg(dev_net(dev));
	caifdevs = caif_device_list(dev_net(dev));

	caifd = caif_get(dev);
	if (caifd == NULL && dev->type != ARPHRD_CAIF)
	return 0;

	switch (what) {
	case NETDEV_REGISTER:
	if (caifd != NULL)
	break;

	caifdev = netdev_priv(dev);

	link_support = NULL;
	if (caifdev->use_frag) {
	head_room = 1;
	link_support = cfserl_create(dev->ifindex,
	caifdev->use_stx);
	if (!link_support) {
	pr_warn("Out of memory\n");
	break;
	}
	}
	res = caif_enroll_dev(dev, caifdev, link_support, head_room,
	&layer, NULL);
	if (res)
	cfserl_release(link_support);
	caifdev->flowctrl = dev_flowctrl;
	break;

	case NETDEV_UP:
	rcu_read_lock();

	caifd = caif_get(dev);
	if (caifd == NULL) {
	rcu_read_unlock();
	break;
	}

	caifd->xoff = false;
	cfcnfg_set_phy_state(cfg, &caifd->layer, true);
	rcu_read_unlock();

	break;

	case NETDEV_DOWN:
	rcu_read_lock();

	caifd = caif_get(dev);
	if (!caifd \|\| !caifd->layer.up \|\| !caifd->layer.up->ctrlcmd) {
	rcu_read_unlock();
	return -EINVAL;
	}

	cfcnfg_set_phy_state(cfg, &caifd->layer, false);
	caifd_hold(caifd);
	rcu_read_unlock();

	caifd->layer.up->ctrlcmd(caifd->layer.up,
	_CAIF_CTRLCMD_PHYIF_DOWN_IND,
	caifd->layer.id);

	spin_lock_bh(&caifd->flow_lock);

	/*
	* Replace our xoff-destructor with original destructor.
	* We trust that skb->destructor always is called before
	* the skb reference is invalid. The hijacked SKB destructor
	* takes the flow_lock so manipulating the skb->destructor here
	* should be safe.
	*/
	if (caifd->xoff_skb_dtor != NULL && caifd->xoff_skb != NULL)
	caifd->xoff_skb->destructor = caifd->xoff_skb_dtor;

	caifd->xoff = false;
	caifd->xoff_skb_dtor = NULL;
	caifd->xoff_skb = NULL;

	spin_unlock_bh(&caifd->flow_lock);
	caifd_put(caifd);
	break;

	case NETDEV_UNREGISTER:
	mutex_lock(&caifdevs->lock);

	caifd = caif_get(dev);
	if (caifd == NULL) {
	mutex_unlock(&caifdevs->lock);
	break;
	}
	list_del_rcu(&caifd->list);

	/*
	* NETDEV_UNREGISTER is called repeatedly until all reference
	* counts for the net-device are released. If references to
	* caifd is taken, simply ignore NETDEV_UNREGISTER and wait for
	* the next call to NETDEV_UNREGISTER.
	*
	* If any packets are in flight down the CAIF Stack,
	* cfcnfg_del_phy_layer will return nonzero.
	* If no packets are in flight, the CAIF Stack associated
	* with the net-device un-registering is freed.
	*/

	if (caifd_refcnt_read(caifd) != 0 \|\|
	cfcnfg_del_phy_layer(cfg, &caifd->layer) != 0) {

	pr_info("Wait for device inuse\n");
	/* Enrole device if CAIF Stack is still in use */
	list_add_rcu(&caifd->list, &caifdevs->list);
	mutex_unlock(&caifdevs->lock);
	break;
	}

	synchronize_rcu();
	dev_put(caifd->netdev);
	free_percpu(caifd->pcpu_refcnt);
	kfree(caifd);

	mutex_unlock(&caifdevs->lock);
	break;
	}
	return 0;
	}

	static struct notifier_block caif_device_notifier = {
	.notifier_call = caif_device_notify,
	.priority = 0,
	};

	/* Per-namespace Caif devices handling */
	static int caif_init_net(struct net *net)
	{
	struct caif_net *caifn = net_generic(net, caif_net_id);
	INIT_LIST_HEAD(&caifn->caifdevs.list);
	mutex_init(&caifn->caifdevs.lock);

	caifn->cfg = cfcnfg_create();
	if (!caifn->cfg)
	return -ENOMEM;

	return 0;
	}

	static void caif_exit_net(struct net *net)
	{
	struct caif_device_entry caifd, tmp;
	struct caif_device_entry_list *caifdevs =
	caif_device_list(net);
	struct cfcnfg *cfg = get_cfcnfg(net);

	rtnl_lock();
	mutex_lock(&caifdevs->lock);

	list_for_each_entry_safe(caifd, tmp, &caifdevs->list, list) {
	int i = 0;
	list_del_rcu(&caifd->list);
	cfcnfg_set_phy_state(cfg, &caifd->layer, false);

	while (i < 10 &&
	(caifd_refcnt_read(caifd) != 0 \|\|
	cfcnfg_del_phy_layer(cfg, &caifd->layer) != 0)) {

	pr_info("Wait for device inuse\n");
	msleep(250);
	i++;
	}
	synchronize_rcu();
	dev_put(caifd->netdev);
	free_percpu(caifd->pcpu_refcnt);
	kfree(caifd);
	}
	cfcnfg_remove(cfg);

	mutex_unlock(&caifdevs->lock);
	rtnl_unlock();
	}

	static struct pernet_operations caif_net_ops = {
	.init = caif_init_net,
	.exit = caif_exit_net,
	.id = &caif_net_id,
	.size = sizeof(struct caif_net),
	};

	/* Initialize Caif devices list */
	static int __init caif_device_init(void)
	{
	int result;

	result = register_pernet_subsys(&caif_net_ops);

	if (result)
	return result;

	register_netdevice_notifier(&caif_device_notifier);
	dev_add_pack(&caif_packet_type);

	return result;
	}

	static void __exit caif_device_exit(void)
	{
	unregister_netdevice_notifier(&caif_device_notifier);
	dev_remove_pack(&caif_packet_type);
	unregister_pernet_subsys(&caif_net_ops);
	}

	module_init(caif_device_init);
	module_exit(caif_device_exit);