/*
   * Monitoring code for network dropped packet alerts
   *
   * Copyright (C) 2009 Neil Horman <nhorman@tuxdriver.com>
   */
  
  #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 <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
  
  static void send_dm_alert(struct work_struct *unused);
  
  
  /*
   * Globals, our netlink socket pointer
   * and the work handle that will send up
   * netlink alerts
   */

  static int trace_state = TRACE_OFF;

  static DEFINE_SPINLOCK(trace_state_lock);

  
  struct per_cpu_dm_data {
  	struct work_struct dm_alert_work;
  	struct sk_buff *skb;
  	atomic_t dm_hit_count;
  	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,

  	.maxattr        = NET_DM_CMD_MAX,
  };
  
  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 void reset_per_cpu_data(struct per_cpu_dm_data *data)
  {
  	size_t al;
  	struct net_dm_alert_msg *msg;

  	struct nlattr *nla;

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

  	al += sizeof(struct nlattr);

  	data->skb = genlmsg_new(al, GFP_KERNEL);
  	genlmsg_put(data->skb, 0, 0, &net_drop_monitor_family,
  			0, NET_DM_CMD_ALERT);

  	nla = nla_reserve(data->skb, NLA_UNSPEC, sizeof(struct net_dm_alert_msg));
  	msg = nla_data(nla);

  	memset(msg, 0, al);
  	atomic_set(&data->dm_hit_count, dm_hit_limit);
  }
  
  static void send_dm_alert(struct work_struct *unused)
  {
  	struct sk_buff *skb;
  	struct per_cpu_dm_data *data = &__get_cpu_var(dm_cpu_data);
  
  	/*
  	 * Grab the skb we're about to send
  	 */
  	skb = data->skb;
  
  	/*
  	 * Replace it with a new one
  	 */
  	reset_per_cpu_data(data);
  
  	/*
  	 * Ship it!
  	 */
  	genlmsg_multicast(skb, 0, NET_DM_GRP_ALERT, 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.  Note that it operates under the timer interrupt
   * so we don't need to disable preemption here
   */
  static void sched_send_work(unsigned long unused)
  {
  	struct per_cpu_dm_data *data =  &__get_cpu_var(dm_cpu_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 per_cpu_dm_data *data = &__get_cpu_var(dm_cpu_data);
  
  
  	if (!atomic_add_unless(&data->dm_hit_count, -1, 0)) {
  		/*
  		 * we're already at zero, discard this hit
  		 */
  		goto out;
  	}
  
  	nlh = (struct nlmsghdr *)data->skb->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;
  		}
  	}
  
  	/*
  	 * We need to create a new entry
  	 */
  	__nla_reserve_nohdr(data->skb, 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_on(&data->send_timer, smp_processor_id());
  	}
  
  out:
  	return;
  }

  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;
  
  	spin_lock(&trace_state_lock);

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

  	switch (state) {
  	case TRACE_ON:

  		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);

  			}
  		}

  		break;
  	default:
  		rc = 1;
  		break;
  	}

  	if (!rc)
  		trace_state = state;

  	else
  		rc = -EINPROGRESS;

  out_unlock:

  	spin_unlock(&trace_state_lock);

  	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 = 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;

  		spin_lock(&trace_state_lock);
  		list_add_rcu(&new_stat->list, &hw_stats_list);
  		spin_unlock(&trace_state_lock);
  		break;
  	case NETDEV_UNREGISTER:
  		spin_lock(&trace_state_lock);
  		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;
  				}
  			}
  		}
  		spin_unlock(&trace_state_lock);
  		break;
  	}
  out:
  	return NOTIFY_DONE;
  }

  
  static 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;

  	printk(KERN_INFO "Initializing network drop monitor service
  ");

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

  	rc = genl_register_family_with_ops(&net_drop_monitor_family,
  					   dropmon_ops,
  					   ARRAY_SIZE(dropmon_ops));
  	if (rc) {

  		printk(KERN_ERR "Could not create drop monitor netlink family
  ");

  		return rc;

  	}

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

  	rc = 0;
  
  	for_each_present_cpu(cpu) {
  		data = &per_cpu(dm_cpu_data, cpu);
  		reset_per_cpu_data(data);
  		INIT_WORK(&data->dm_alert_work, send_dm_alert);
  		init_timer(&data->send_timer);
  		data->send_timer.data = cpu;
  		data->send_timer.function = sched_send_work;
  	}

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