drop_monitor.c

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/*
 * Monitoring code for network dropped packet alerts
 *
 * Copyright (C) 2009 Neil Horman <[email protected]>
 */

#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,
    .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 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 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(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.
 */
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 = 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 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(&net_drop_monitor_family,
                       dropmon_ops,
                       ARRAY_SIZE(dropmon_ops));
    if (rc) {
        pr_err("Could not create drop monitor netlink family\n");
        return rc;
    }

    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 <[email protected]>");
MODULE_ALIAS_GENL_FAMILY("NET_DM");