net/core/drop_monitor.c - third_party/linux - Git at Google

 /*
  * Monitoring code for network dropped packet alerts
  *
  * Copyright (C) 2009 Neil Horman <nhorman@tuxdriver.com>
  */

 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

 #include <linux/netdevice.h>
 #include <linux/etherdevice.h>
 #include <linux/string.h>
 #include <linux/if_arp.h>
 #include <linux/inetdevice.h>
 #include <linux/inet.h>
 #include <linux/interrupt.h>
 #include <linux/netpoll.h>
 #include <linux/sched.h>
 #include <linux/delay.h>
 #include <linux/types.h>
 #include <linux/workqueue.h>
 #include <linux/netlink.h>
 #include <linux/net_dropmon.h>
 #include <linux/percpu.h>
 #include <linux/timer.h>
 #include <linux/bitops.h>
 #include <linux/slab.h>
 #include <linux/module.h>
 #include <net/genetlink.h>
 #include <net/netevent.h>

 #include <trace/events/skb.h>
 #include <trace/events/napi.h>

 #include <asm/unaligned.h>

 #define TRACE_ON 1
 #define TRACE_OFF 0

 /*
  * Globals, our netlink socket pointer
  * and the work handle that will send up
  * netlink alerts
  */
 static int trace_state = TRACE_OFF;
 static DEFINE_MUTEX(trace_state_mutex);

 struct per_cpu_dm_data {
 	spinlock_t		lock;
 	struct sk_buff		*skb;
 	struct work_struct	dm_alert_work;
 	struct timer_list	send_timer;
 };

 struct dm_hw_stat_delta {
 	struct net_device *dev;
 	unsigned long last_rx;
 	struct list_head list;
 	struct rcu_head rcu;
 	unsigned long last_drop_val;
 };

 static struct genl_family net_drop_monitor_family = {
 	.id             = GENL_ID_GENERATE,
 	.hdrsize        = 0,
 	.name           = "NET_DM",
 	.version        = 2,
 };

 static DEFINE_PER_CPU(struct per_cpu_dm_data, dm_cpu_data);

 static int dm_hit_limit = 64;
 static int dm_delay = 1;
 static unsigned long dm_hw_check_delta = 2*HZ;
 static LIST_HEAD(hw_stats_list);

 static struct sk_buff *reset_per_cpu_data(struct per_cpu_dm_data *data)
 {
 	size_t al;
 	struct net_dm_alert_msg *msg;
 	struct nlattr *nla;
 	struct sk_buff *skb;
 	unsigned long flags;

 	al = sizeof(struct net_dm_alert_msg);
 	al += dm_hit_limit * sizeof(struct net_dm_drop_point);
 	al += sizeof(struct nlattr);

 	skb = genlmsg_new(al, GFP_KERNEL);

 	if (skb) {
 		genlmsg_put(skb, 0, 0, &net_drop_monitor_family,
 				0, NET_DM_CMD_ALERT);
 		nla = nla_reserve(skb, NLA_UNSPEC,
 				  sizeof(struct net_dm_alert_msg));
 		msg = nla_data(nla);
 		memset(msg, 0, al);
 	} else {
 		mod_timer(&data->send_timer, jiffies + HZ / 10);
 	}

 	spin_lock_irqsave(&data->lock, flags);
 	swap(data->skb, skb);
 	spin_unlock_irqrestore(&data->lock, flags);

 	return skb;
 }

 static struct genl_multicast_group dropmon_mcgrps[] = {
 	{ .name = "events", },
 };

 static void send_dm_alert(struct work_struct *work)
 {
 	struct sk_buff *skb;
 	struct per_cpu_dm_data *data;

 	data = container_of(work, struct per_cpu_dm_data, dm_alert_work);

 	skb = reset_per_cpu_data(data);

 	if (skb)
 		genlmsg_multicast(&net_drop_monitor_family, skb, 0,
 				  0, GFP_KERNEL);
 }

 /*
  * This is the timer function to delay the sending of an alert
  * in the event that more drops will arrive during the
  * hysteresis period.
  */
 static void sched_send_work(unsigned long _data)
 {
 	struct per_cpu_dm_data *data = (struct per_cpu_dm_data *)_data;

 	schedule_work(&data->dm_alert_work);
 }

 static void trace_drop_common(struct sk_buff *skb, void *location)
 {
 	struct net_dm_alert_msg *msg;
 	struct nlmsghdr *nlh;
 	struct nlattr *nla;
 	int i;
 	struct sk_buff *dskb;
 	struct per_cpu_dm_data *data;
 	unsigned long flags;

 	local_irq_save(flags);
 	data = &__get_cpu_var(dm_cpu_data);
 	spin_lock(&data->lock);
 	dskb = data->skb;

 	if (!dskb)
 		goto out;

 	nlh = (struct nlmsghdr *)dskb->data;
 	nla = genlmsg_data(nlmsg_data(nlh));
 	msg = nla_data(nla);
 	for (i = 0; i < msg->entries; i++) {
 		if (!memcmp(&location, msg->points[i].pc, sizeof(void *))) {
 			msg->points[i].count++;
 			goto out;
 		}
 	}
 	if (msg->entries == dm_hit_limit)
 		goto out;
 	/*
 	 * We need to create a new entry
 	 */
 	__nla_reserve_nohdr(dskb, sizeof(struct net_dm_drop_point));
 	nla->nla_len += NLA_ALIGN(sizeof(struct net_dm_drop_point));
 	memcpy(msg->points[msg->entries].pc, &location, sizeof(void *));
 	msg->points[msg->entries].count = 1;
 	msg->entries++;

 	if (!timer_pending(&data->send_timer)) {
 		data->send_timer.expires = jiffies + dm_delay * HZ;
 		add_timer(&data->send_timer);
 	}

 out:
 	spin_unlock_irqrestore(&data->lock, flags);
 }

 static void trace_kfree_skb_hit(void *ignore, struct sk_buff *skb, void *location)
 {
 	trace_drop_common(skb, location);
 }

 static void trace_napi_poll_hit(void *ignore, struct napi_struct *napi)
 {
 	struct dm_hw_stat_delta *new_stat;

 	/*
 	 * Don't check napi structures with no associated device
 	 */
 	if (!napi->dev)
 		return;

 	rcu_read_lock();
 	list_for_each_entry_rcu(new_stat, &hw_stats_list, list) {
 		/*
 		 * only add a note to our monitor buffer if:
 		 * 1) this is the dev we received on
 		 * 2) its after the last_rx delta
 		 * 3) our rx_dropped count has gone up
 		 */
 		if ((new_stat->dev == napi->dev)  &&
 		    (time_after(jiffies, new_stat->last_rx + dm_hw_check_delta)) &&
 		    (napi->dev->stats.rx_dropped != new_stat->last_drop_val)) {
 			trace_drop_common(NULL, NULL);
 			new_stat->last_drop_val = napi->dev->stats.rx_dropped;
 			new_stat->last_rx = jiffies;
 			break;
 		}
 	}
 	rcu_read_unlock();
 }

 static int set_all_monitor_traces(int state)
 {
 	int rc = 0;
 	struct dm_hw_stat_delta *new_stat = NULL;
 	struct dm_hw_stat_delta *temp;

 	mutex_lock(&trace_state_mutex);

 	if (state == trace_state) {
 		rc = -EAGAIN;
 		goto out_unlock;
 	}

 	switch (state) {
 	case TRACE_ON:
 		if (!try_module_get(THIS_MODULE)) {
 			rc = -ENODEV;
 			break;
 		}

 		rc |= register_trace_kfree_skb(trace_kfree_skb_hit, NULL);
 		rc |= register_trace_napi_poll(trace_napi_poll_hit, NULL);
 		break;

 	case TRACE_OFF:
 		rc |= unregister_trace_kfree_skb(trace_kfree_skb_hit, NULL);
 		rc |= unregister_trace_napi_poll(trace_napi_poll_hit, NULL);

 		tracepoint_synchronize_unregister();

 		/*
 		 * Clean the device list
 		 */
 		list_for_each_entry_safe(new_stat, temp, &hw_stats_list, list) {
 			if (new_stat->dev == NULL) {
 				list_del_rcu(&new_stat->list);
 				kfree_rcu(new_stat, rcu);
 			}
 		}

 		module_put(THIS_MODULE);

 		break;
 	default:
 		rc = 1;
 		break;
 	}

 	if (!rc)
 		trace_state = state;
 	else
 		rc = -EINPROGRESS;

 out_unlock:
 	mutex_unlock(&trace_state_mutex);

 	return rc;
 }


 static int net_dm_cmd_config(struct sk_buff *skb,
 			struct genl_info *info)
 {
 	return -ENOTSUPP;
 }

 static int net_dm_cmd_trace(struct sk_buff *skb,
 			struct genl_info *info)
 {
 	switch (info->genlhdr->cmd) {
 	case NET_DM_CMD_START:
 		return set_all_monitor_traces(TRACE_ON);
 		break;
 	case NET_DM_CMD_STOP:
 		return set_all_monitor_traces(TRACE_OFF);
 		break;
 	}

 	return -ENOTSUPP;
 }

 static int dropmon_net_event(struct notifier_block *ev_block,
 			     unsigned long event, void *ptr)
 {
 	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 	struct dm_hw_stat_delta *new_stat = NULL;
 	struct dm_hw_stat_delta *tmp;

 	switch (event) {
 	case NETDEV_REGISTER:
 		new_stat = kzalloc(sizeof(struct dm_hw_stat_delta), GFP_KERNEL);

 		if (!new_stat)
 			goto out;

 		new_stat->dev = dev;
 		new_stat->last_rx = jiffies;
 		mutex_lock(&trace_state_mutex);
 		list_add_rcu(&new_stat->list, &hw_stats_list);
 		mutex_unlock(&trace_state_mutex);
 		break;
 	case NETDEV_UNREGISTER:
 		mutex_lock(&trace_state_mutex);
 		list_for_each_entry_safe(new_stat, tmp, &hw_stats_list, list) {
 			if (new_stat->dev == dev) {
 				new_stat->dev = NULL;
 				if (trace_state == TRACE_OFF) {
 					list_del_rcu(&new_stat->list);
 					kfree_rcu(new_stat, rcu);
 					break;
 				}
 			}
 		}
 		mutex_unlock(&trace_state_mutex);
 		break;
 	}
 out:
 	return NOTIFY_DONE;
 }

 static const struct genl_ops dropmon_ops[] = {
 	{
 		.cmd = NET_DM_CMD_CONFIG,
 		.doit = net_dm_cmd_config,
 	},
 	{
 		.cmd = NET_DM_CMD_START,
 		.doit = net_dm_cmd_trace,
 	},
 	{
 		.cmd = NET_DM_CMD_STOP,
 		.doit = net_dm_cmd_trace,
 	},
 };

 static struct notifier_block dropmon_net_notifier = {
 	.notifier_call = dropmon_net_event
 };

 static int __init init_net_drop_monitor(void)
 {
 	struct per_cpu_dm_data *data;
 	int cpu, rc;

 	pr_info("Initializing network drop monitor service\n");

 	if (sizeof(void *) > 8) {
 		pr_err("Unable to store program counters on this arch, Drop monitor failed\n");
 		return -ENOSPC;
 	}

 	rc = genl_register_family_with_ops_groups(&net_drop_monitor_family,
 						  dropmon_ops, dropmon_mcgrps);
 	if (rc) {
 		pr_err("Could not create drop monitor netlink family\n");
 		return rc;
 	}
 	WARN_ON(net_drop_monitor_family.mcgrp_offset != NET_DM_GRP_ALERT);

 	rc = register_netdevice_notifier(&dropmon_net_notifier);
 	if (rc < 0) {
 		pr_crit("Failed to register netdevice notifier\n");
 		goto out_unreg;
 	}

 	rc = 0;

 	for_each_possible_cpu(cpu) {
 		data = &per_cpu(dm_cpu_data, cpu);
 		INIT_WORK(&data->dm_alert_work, send_dm_alert);
 		init_timer(&data->send_timer);
 		data->send_timer.data = (unsigned long)data;
 		data->send_timer.function = sched_send_work;
 		spin_lock_init(&data->lock);
 		reset_per_cpu_data(data);
 	}


 	goto out;

 out_unreg:
 	genl_unregister_family(&net_drop_monitor_family);
 out:
 	return rc;
 }

 static void exit_net_drop_monitor(void)
 {
 	struct per_cpu_dm_data *data;
 	int cpu;

 	BUG_ON(unregister_netdevice_notifier(&dropmon_net_notifier));

 	/*
 	 * Because of the module_get/put we do in the trace state change path
 	 * we are guarnateed not to have any current users when we get here
 	 * all we need to do is make sure that we don't have any running timers
 	 * or pending schedule calls
 	 */

 	for_each_possible_cpu(cpu) {
 		data = &per_cpu(dm_cpu_data, cpu);
 		del_timer_sync(&data->send_timer);
 		cancel_work_sync(&data->dm_alert_work);
 		/*
 		 * At this point, we should have exclusive access
 		 * to this struct and can free the skb inside it
 		 */
 		kfree_skb(data->skb);
 	}

 	BUG_ON(genl_unregister_family(&net_drop_monitor_family));
 }

 module_init(init_net_drop_monitor);
 module_exit(exit_net_drop_monitor);

 MODULE_LICENSE("GPL v2");
 MODULE_AUTHOR("Neil Horman <nhorman@tuxdriver.com>");
 MODULE_ALIAS_GENL_FAMILY("NET_DM");
	/*
	* Monitoring code for network dropped packet alerts
	*
	* Copyright (C) 2009 Neil Horman <nhorman@tuxdriver.com>
	*/

	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

	#include <linux/netdevice.h>
	#include <linux/etherdevice.h>
	#include <linux/string.h>
	#include <linux/if_arp.h>
	#include <linux/inetdevice.h>
	#include <linux/inet.h>
	#include <linux/interrupt.h>
	#include <linux/netpoll.h>
	#include <linux/sched.h>
	#include <linux/delay.h>
	#include <linux/types.h>
	#include <linux/workqueue.h>
	#include <linux/netlink.h>
	#include <linux/net_dropmon.h>
	#include <linux/percpu.h>
	#include <linux/timer.h>
	#include <linux/bitops.h>
	#include <linux/slab.h>
	#include <linux/module.h>
	#include <net/genetlink.h>
	#include <net/netevent.h>

	#include <trace/events/skb.h>
	#include <trace/events/napi.h>

	#include <asm/unaligned.h>

	#define TRACE_ON 1
	#define TRACE_OFF 0

	/*
	* Globals, our netlink socket pointer
	* and the work handle that will send up
	* netlink alerts
	*/
	static int trace_state = TRACE_OFF;
	static DEFINE_MUTEX(trace_state_mutex);

	struct per_cpu_dm_data {
	spinlock_t lock;
	struct sk_buff *skb;
	struct work_struct dm_alert_work;
	struct timer_list send_timer;
	};

	struct dm_hw_stat_delta {
	struct net_device *dev;
	unsigned long last_rx;
	struct list_head list;
	struct rcu_head rcu;
	unsigned long last_drop_val;
	};

	static struct genl_family net_drop_monitor_family = {
	.id = GENL_ID_GENERATE,
	.hdrsize = 0,
	.name = "NET_DM",
	.version = 2,
	};

	static DEFINE_PER_CPU(struct per_cpu_dm_data, dm_cpu_data);

	static int dm_hit_limit = 64;
	static int dm_delay = 1;
	static unsigned long dm_hw_check_delta = 2*HZ;
	static LIST_HEAD(hw_stats_list);

	static struct sk_buff reset_per_cpu_data(struct per_cpu_dm_data data)
	{
	size_t al;
	struct net_dm_alert_msg *msg;
	struct nlattr *nla;
	struct sk_buff *skb;
	unsigned long flags;

	al = sizeof(struct net_dm_alert_msg);
	al += dm_hit_limit * sizeof(struct net_dm_drop_point);
	al += sizeof(struct nlattr);

	skb = genlmsg_new(al, GFP_KERNEL);

	if (skb) {
	genlmsg_put(skb, 0, 0, &net_drop_monitor_family,
	0, NET_DM_CMD_ALERT);
	nla = nla_reserve(skb, NLA_UNSPEC,
	sizeof(struct net_dm_alert_msg));
	msg = nla_data(nla);
	memset(msg, 0, al);
	} else {
	mod_timer(&data->send_timer, jiffies + HZ / 10);
	}

	spin_lock_irqsave(&data->lock, flags);
	swap(data->skb, skb);
	spin_unlock_irqrestore(&data->lock, flags);

	return skb;
	}

	static struct genl_multicast_group dropmon_mcgrps[] = {
	{ .name = "events", },
	};

	static void send_dm_alert(struct work_struct *work)
	{
	struct sk_buff *skb;
	struct per_cpu_dm_data *data;

	data = container_of(work, struct per_cpu_dm_data, dm_alert_work);

	skb = reset_per_cpu_data(data);

	if (skb)
	genlmsg_multicast(&net_drop_monitor_family, skb, 0,
	0, GFP_KERNEL);
	}

	/*
	* This is the timer function to delay the sending of an alert
	* in the event that more drops will arrive during the
	* hysteresis period.
	*/
	static void sched_send_work(unsigned long _data)
	{
	struct per_cpu_dm_data data = (struct per_cpu_dm_data )_data;

	schedule_work(&data->dm_alert_work);
	}

	static void trace_drop_common(struct sk_buff skb, void location)
	{
	struct net_dm_alert_msg *msg;
	struct nlmsghdr *nlh;
	struct nlattr *nla;
	int i;
	struct sk_buff *dskb;
	struct per_cpu_dm_data *data;
	unsigned long flags;

	local_irq_save(flags);
	data = &__get_cpu_var(dm_cpu_data);
	spin_lock(&data->lock);
	dskb = data->skb;

	if (!dskb)
	goto out;

	nlh = (struct nlmsghdr *)dskb->data;
	nla = genlmsg_data(nlmsg_data(nlh));
	msg = nla_data(nla);
	for (i = 0; i < msg->entries; i++) {
	if (!memcmp(&location, msg->points[i].pc, sizeof(void *))) {
	msg->points[i].count++;
	goto out;
	}
	}
	if (msg->entries == dm_hit_limit)
	goto out;
	/*
	* We need to create a new entry
	*/
	__nla_reserve_nohdr(dskb, sizeof(struct net_dm_drop_point));
	nla->nla_len += NLA_ALIGN(sizeof(struct net_dm_drop_point));
	memcpy(msg->points[msg->entries].pc, &location, sizeof(void *));
	msg->points[msg->entries].count = 1;
	msg->entries++;

	if (!timer_pending(&data->send_timer)) {
	data->send_timer.expires = jiffies + dm_delay * HZ;
	add_timer(&data->send_timer);
	}

	out:
	spin_unlock_irqrestore(&data->lock, flags);
	}

	static void trace_kfree_skb_hit(void ignore, struct sk_buff skb, void *location)
	{
	trace_drop_common(skb, location);
	}

	static void trace_napi_poll_hit(void ignore, struct napi_struct napi)
	{
	struct dm_hw_stat_delta *new_stat;

	/*
	* Don't check napi structures with no associated device
	*/
	if (!napi->dev)
	return;

	rcu_read_lock();
	list_for_each_entry_rcu(new_stat, &hw_stats_list, list) {
	/*
	* only add a note to our monitor buffer if:
	* 1) this is the dev we received on
	* 2) its after the last_rx delta
	* 3) our rx_dropped count has gone up
	*/
	if ((new_stat->dev == napi->dev) &&
	(time_after(jiffies, new_stat->last_rx + dm_hw_check_delta)) &&
	(napi->dev->stats.rx_dropped != new_stat->last_drop_val)) {
	trace_drop_common(NULL, NULL);
	new_stat->last_drop_val = napi->dev->stats.rx_dropped;
	new_stat->last_rx = jiffies;
	break;
	}
	}
	rcu_read_unlock();
	}

	static int set_all_monitor_traces(int state)
	{
	int rc = 0;
	struct dm_hw_stat_delta *new_stat = NULL;
	struct dm_hw_stat_delta *temp;

	mutex_lock(&trace_state_mutex);

	if (state == trace_state) {
	rc = -EAGAIN;
	goto out_unlock;
	}

	switch (state) {
	case TRACE_ON:
	if (!try_module_get(THIS_MODULE)) {
	rc = -ENODEV;
	break;
	}

	rc \|= register_trace_kfree_skb(trace_kfree_skb_hit, NULL);
	rc \|= register_trace_napi_poll(trace_napi_poll_hit, NULL);
	break;

	case TRACE_OFF:
	rc \|= unregister_trace_kfree_skb(trace_kfree_skb_hit, NULL);
	rc \|= unregister_trace_napi_poll(trace_napi_poll_hit, NULL);

	tracepoint_synchronize_unregister();

	/*
	* Clean the device list
	*/
	list_for_each_entry_safe(new_stat, temp, &hw_stats_list, list) {
	if (new_stat->dev == NULL) {
	list_del_rcu(&new_stat->list);
	kfree_rcu(new_stat, rcu);
	}
	}

	module_put(THIS_MODULE);

	break;
	default:
	rc = 1;
	break;
	}

	if (!rc)
	trace_state = state;
	else
	rc = -EINPROGRESS;

	out_unlock:
	mutex_unlock(&trace_state_mutex);

	return rc;
	}


	static int net_dm_cmd_config(struct sk_buff *skb,
	struct genl_info *info)
	{
	return -ENOTSUPP;
	}

	static int net_dm_cmd_trace(struct sk_buff *skb,
	struct genl_info *info)
	{
	switch (info->genlhdr->cmd) {
	case NET_DM_CMD_START:
	return set_all_monitor_traces(TRACE_ON);
	break;
	case NET_DM_CMD_STOP:
	return set_all_monitor_traces(TRACE_OFF);
	break;
	}

	return -ENOTSUPP;
	}

	static int dropmon_net_event(struct notifier_block *ev_block,
	unsigned long event, void *ptr)
	{
	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
	struct dm_hw_stat_delta *new_stat = NULL;
	struct dm_hw_stat_delta *tmp;

	switch (event) {
	case NETDEV_REGISTER:
	new_stat = kzalloc(sizeof(struct dm_hw_stat_delta), GFP_KERNEL);

	if (!new_stat)
	goto out;

	new_stat->dev = dev;
	new_stat->last_rx = jiffies;
	mutex_lock(&trace_state_mutex);
	list_add_rcu(&new_stat->list, &hw_stats_list);
	mutex_unlock(&trace_state_mutex);
	break;
	case NETDEV_UNREGISTER:
	mutex_lock(&trace_state_mutex);
	list_for_each_entry_safe(new_stat, tmp, &hw_stats_list, list) {
	if (new_stat->dev == dev) {
	new_stat->dev = NULL;
	if (trace_state == TRACE_OFF) {
	list_del_rcu(&new_stat->list);
	kfree_rcu(new_stat, rcu);
	break;
	}
	}
	}
	mutex_unlock(&trace_state_mutex);
	break;
	}
	out:
	return NOTIFY_DONE;
	}

	static const struct genl_ops dropmon_ops[] = {
	{
	.cmd = NET_DM_CMD_CONFIG,
	.doit = net_dm_cmd_config,
	},
	{
	.cmd = NET_DM_CMD_START,
	.doit = net_dm_cmd_trace,
	},
	{
	.cmd = NET_DM_CMD_STOP,
	.doit = net_dm_cmd_trace,
	},
	};

	static struct notifier_block dropmon_net_notifier = {
	.notifier_call = dropmon_net_event
	};

	static int __init init_net_drop_monitor(void)
	{
	struct per_cpu_dm_data *data;
	int cpu, rc;

	pr_info("Initializing network drop monitor service\n");

	if (sizeof(void *) > 8) {
	pr_err("Unable to store program counters on this arch, Drop monitor failed\n");
	return -ENOSPC;
	}

	rc = genl_register_family_with_ops_groups(&net_drop_monitor_family,
	dropmon_ops, dropmon_mcgrps);
	if (rc) {
	pr_err("Could not create drop monitor netlink family\n");
	return rc;
	}
	WARN_ON(net_drop_monitor_family.mcgrp_offset != NET_DM_GRP_ALERT);

	rc = register_netdevice_notifier(&dropmon_net_notifier);
	if (rc < 0) {
	pr_crit("Failed to register netdevice notifier\n");
	goto out_unreg;
	}

	rc = 0;

	for_each_possible_cpu(cpu) {
	data = &per_cpu(dm_cpu_data, cpu);
	INIT_WORK(&data->dm_alert_work, send_dm_alert);
	init_timer(&data->send_timer);
	data->send_timer.data = (unsigned long)data;
	data->send_timer.function = sched_send_work;
	spin_lock_init(&data->lock);
	reset_per_cpu_data(data);
	}


	goto out;

	out_unreg:
	genl_unregister_family(&net_drop_monitor_family);
	out:
	return rc;
	}

	static void exit_net_drop_monitor(void)
	{
	struct per_cpu_dm_data *data;
	int cpu;

	BUG_ON(unregister_netdevice_notifier(&dropmon_net_notifier));

	/*
	* Because of the module_get/put we do in the trace state change path
	* we are guarnateed not to have any current users when we get here
	* all we need to do is make sure that we don't have any running timers
	* or pending schedule calls
	*/

	for_each_possible_cpu(cpu) {
	data = &per_cpu(dm_cpu_data, cpu);
	del_timer_sync(&data->send_timer);
	cancel_work_sync(&data->dm_alert_work);
	/*
	* At this point, we should have exclusive access
	* to this struct and can free the skb inside it
	*/
	kfree_skb(data->skb);
	}

	BUG_ON(genl_unregister_family(&net_drop_monitor_family));
	}

	module_init(init_net_drop_monitor);
	module_exit(exit_net_drop_monitor);

	MODULE_LICENSE("GPL v2");
	MODULE_AUTHOR("Neil Horman <nhorman@tuxdriver.com>");
	MODULE_ALIAS_GENL_FAMILY("NET_DM");