// SPDX-License-Identifier: GPL-2.0-only
/*
 * 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/drop_monitor.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 bool monitor_hw;

/* net_dm_mutex
 *
 * An overall lock guarding every operation coming from userspace.
 * It also guards the global 'hw_stats_list' list.
 */
static DEFINE_MUTEX(net_dm_mutex);

struct net_dm_stats {
        u64 dropped;
        struct u64_stats_sync syncp;
};

#define NET_DM_MAX_HW_TRAP_NAME_LEN 40

struct net_dm_hw_entry {
        char trap_name[NET_DM_MAX_HW_TRAP_NAME_LEN];
        u32 count;
};

struct net_dm_hw_entries {
        u32 num_entries;
        struct net_dm_hw_entry entries[0];
};

struct per_cpu_dm_data {
        spinlock_t              lock;   /* Protects 'skb', 'hw_entries' and
                                         * 'send_timer'
                                         */
        union {
                struct sk_buff                  *skb;
                struct net_dm_hw_entries        *hw_entries;
        };
        struct sk_buff_head     drop_queue;
        struct work_struct      dm_alert_work;
        struct timer_list       send_timer;
        struct net_dm_stats     stats;
};

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;

static DEFINE_PER_CPU(struct per_cpu_dm_data, dm_cpu_data);
static DEFINE_PER_CPU(struct per_cpu_dm_data, dm_hw_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 enum net_dm_alert_mode net_dm_alert_mode = NET_DM_ALERT_MODE_SUMMARY;
static u32 net_dm_trunc_len;
static u32 net_dm_queue_len = 1000;

struct net_dm_alert_ops {
        void (*kfree_skb_probe)(void *ignore, struct sk_buff *skb,
                                void *location);
        void (*napi_poll_probe)(void *ignore, struct napi_struct *napi,
                                int work, int budget);
        void (*work_item_func)(struct work_struct *work);
        void (*hw_work_item_func)(struct work_struct *work);
        void (*hw_probe)(struct sk_buff *skb,
                         const struct net_dm_hw_metadata *hw_metadata);
};

struct net_dm_skb_cb {
        union {
                struct net_dm_hw_metadata *hw_metadata;
                void *pc;
        };
};

#define NET_DM_SKB_CB(__skb) ((struct net_dm_skb_cb *)&((__skb)->cb[0]))

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;
        void *msg_header;

        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)
                goto err;

        msg_header = genlmsg_put(skb, 0, 0, &net_drop_monitor_family,
                                 0, NET_DM_CMD_ALERT);
        if (!msg_header) {
                nlmsg_free(skb);
                skb = NULL;
                goto err;
        }
        nla = nla_reserve(skb, NLA_UNSPEC,
                          sizeof(struct net_dm_alert_msg));
        if (!nla) {
                nlmsg_free(skb);
                skb = NULL;
                goto err;
        }
        msg = nla_data(nla);
        memset(msg, 0, al);
        goto out;

err:
        mod_timer(&data->send_timer, jiffies + HZ / 10);
out:
        spin_lock_irqsave(&data->lock, flags);
        swap(data->skb, skb);
        spin_unlock_irqrestore(&data->lock, flags);

        if (skb) {
                struct nlmsghdr *nlh = (struct nlmsghdr *)skb->data;
                struct genlmsghdr *gnlh = (struct genlmsghdr *)nlmsg_data(nlh);

                genlmsg_end(skb, genlmsg_data(gnlh));
        }

        return skb;
}

static const 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(struct timer_list *t)
{
        struct per_cpu_dm_data *data = from_timer(data, t, send_timer);

        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 = this_cpu_ptr(&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,
                                int work, int budget)
{
        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 struct net_dm_hw_entries *
net_dm_hw_reset_per_cpu_data(struct per_cpu_dm_data *hw_data)
{
        struct net_dm_hw_entries *hw_entries;
        unsigned long flags;

        hw_entries = kzalloc(struct_size(hw_entries, entries, dm_hit_limit),
                             GFP_KERNEL);
        if (!hw_entries) {
                /* If the memory allocation failed, we try to perform another
                 * allocation in 1/10 second. Otherwise, the probe function
                 * will constantly bail out.
                 */
                mod_timer(&hw_data->send_timer, jiffies + HZ / 10);
        }

        spin_lock_irqsave(&hw_data->lock, flags);
        swap(hw_data->hw_entries, hw_entries);
        spin_unlock_irqrestore(&hw_data->lock, flags);

        return hw_entries;
}

static int net_dm_hw_entry_put(struct sk_buff *msg,
                               const struct net_dm_hw_entry *hw_entry)
{
        struct nlattr *attr;

        attr = nla_nest_start(msg, NET_DM_ATTR_HW_ENTRY);
        if (!attr)
                return -EMSGSIZE;

        if (nla_put_string(msg, NET_DM_ATTR_HW_TRAP_NAME, hw_entry->trap_name))
                goto nla_put_failure;

        if (nla_put_u32(msg, NET_DM_ATTR_HW_TRAP_COUNT, hw_entry->count))
                goto nla_put_failure;

        nla_nest_end(msg, attr);

        return 0;

nla_put_failure:
        nla_nest_cancel(msg, attr);
        return -EMSGSIZE;
}

static int net_dm_hw_entries_put(struct sk_buff *msg,
                                 const struct net_dm_hw_entries *hw_entries)
{
        struct nlattr *attr;
        int i;

        attr = nla_nest_start(msg, NET_DM_ATTR_HW_ENTRIES);
        if (!attr)
                return -EMSGSIZE;

        for (i = 0; i < hw_entries->num_entries; i++) {
                int rc;

                rc = net_dm_hw_entry_put(msg, &hw_entries->entries[i]);
                if (rc)
                        goto nla_put_failure;
        }

        nla_nest_end(msg, attr);

        return 0;

nla_put_failure:
        nla_nest_cancel(msg, attr);
        return -EMSGSIZE;
}

static int
net_dm_hw_summary_report_fill(struct sk_buff *msg,
                              const struct net_dm_hw_entries *hw_entries)
{
        struct net_dm_alert_msg anc_hdr = { 0 };
        void *hdr;
        int rc;

        hdr = genlmsg_put(msg, 0, 0, &net_drop_monitor_family, 0,
                          NET_DM_CMD_ALERT);
        if (!hdr)
                return -EMSGSIZE;

        /* We need to put the ancillary header in order not to break user
         * space.
         */
        if (nla_put(msg, NLA_UNSPEC, sizeof(anc_hdr), &anc_hdr))
                goto nla_put_failure;

        rc = net_dm_hw_entries_put(msg, hw_entries);
        if (rc)
                goto nla_put_failure;

        genlmsg_end(msg, hdr);

        return 0;

nla_put_failure:
        genlmsg_cancel(msg, hdr);
        return -EMSGSIZE;
}

static void net_dm_hw_summary_work(struct work_struct *work)
{
        struct net_dm_hw_entries *hw_entries;
        struct per_cpu_dm_data *hw_data;
        struct sk_buff *msg;
        int rc;

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

        hw_entries = net_dm_hw_reset_per_cpu_data(hw_data);
        if (!hw_entries)
                return;

        msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
        if (!msg)
                goto out;

        rc = net_dm_hw_summary_report_fill(msg, hw_entries);
        if (rc) {
                nlmsg_free(msg);
                goto out;
        }

        genlmsg_multicast(&net_drop_monitor_family, msg, 0, 0, GFP_KERNEL);

out:
        kfree(hw_entries);
}

static void
net_dm_hw_summary_probe(struct sk_buff *skb,
                        const struct net_dm_hw_metadata *hw_metadata)
{
        struct net_dm_hw_entries *hw_entries;
        struct net_dm_hw_entry *hw_entry;
        struct per_cpu_dm_data *hw_data;
        unsigned long flags;
        int i;

        hw_data = this_cpu_ptr(&dm_hw_cpu_data);
        spin_lock_irqsave(&hw_data->lock, flags);
        hw_entries = hw_data->hw_entries;

        if (!hw_entries)
                goto out;

        for (i = 0; i < hw_entries->num_entries; i++) {
                hw_entry = &hw_entries->entries[i];
                if (!strncmp(hw_entry->trap_name, hw_metadata->trap_name,
                             NET_DM_MAX_HW_TRAP_NAME_LEN - 1)) {
                        hw_entry->count++;
                        goto out;
                }
        }
        if (WARN_ON_ONCE(hw_entries->num_entries == dm_hit_limit))
                goto out;

        hw_entry = &hw_entries->entries[hw_entries->num_entries];
        strlcpy(hw_entry->trap_name, hw_metadata->trap_name,
                NET_DM_MAX_HW_TRAP_NAME_LEN - 1);
        hw_entry->count = 1;
        hw_entries->num_entries++;

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

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

static const struct net_dm_alert_ops net_dm_alert_summary_ops = {
        .kfree_skb_probe        = trace_kfree_skb_hit,
        .napi_poll_probe        = trace_napi_poll_hit,
        .work_item_func         = send_dm_alert,
        .hw_work_item_func      = net_dm_hw_summary_work,
        .hw_probe               = net_dm_hw_summary_probe,
};

static void net_dm_packet_trace_kfree_skb_hit(void *ignore,
                                              struct sk_buff *skb,
                                              void *location)
{
        ktime_t tstamp = ktime_get_real();
        struct per_cpu_dm_data *data;
        struct sk_buff *nskb;
        unsigned long flags;

        if (!skb_mac_header_was_set(skb))
                return;

        nskb = skb_clone(skb, GFP_ATOMIC);
        if (!nskb)
                return;

        NET_DM_SKB_CB(nskb)->pc = location;
        /* Override the timestamp because we care about the time when the
         * packet was dropped.
         */
        nskb->tstamp = tstamp;

        data = this_cpu_ptr(&dm_cpu_data);

        spin_lock_irqsave(&data->drop_queue.lock, flags);
        if (skb_queue_len(&data->drop_queue) < net_dm_queue_len)
                __skb_queue_tail(&data->drop_queue, nskb);
        else
                goto unlock_free;
        spin_unlock_irqrestore(&data->drop_queue.lock, flags);

        schedule_work(&data->dm_alert_work);

        return;

unlock_free:
        spin_unlock_irqrestore(&data->drop_queue.lock, flags);
        u64_stats_update_begin(&data->stats.syncp);
        data->stats.dropped++;
        u64_stats_update_end(&data->stats.syncp);
        consume_skb(nskb);
}

static void net_dm_packet_trace_napi_poll_hit(void *ignore,
                                              struct napi_struct *napi,
                                              int work, int budget)
{
}

static size_t net_dm_in_port_size(void)
{
               /* NET_DM_ATTR_IN_PORT nest */
        return nla_total_size(0) +
               /* NET_DM_ATTR_PORT_NETDEV_IFINDEX */
               nla_total_size(sizeof(u32)) +
               /* NET_DM_ATTR_PORT_NETDEV_NAME */
               nla_total_size(IFNAMSIZ + 1);
}

#define NET_DM_MAX_SYMBOL_LEN 40

static size_t net_dm_packet_report_size(size_t payload_len)
{
        size_t size;

        size = nlmsg_msg_size(GENL_HDRLEN + net_drop_monitor_family.hdrsize);

        return NLMSG_ALIGN(size) +
               /* NET_DM_ATTR_ORIGIN */
               nla_total_size(sizeof(u16)) +
               /* NET_DM_ATTR_PC */
               nla_total_size(sizeof(u64)) +
               /* NET_DM_ATTR_SYMBOL */
               nla_total_size(NET_DM_MAX_SYMBOL_LEN + 1) +
               /* NET_DM_ATTR_IN_PORT */
               net_dm_in_port_size() +
               /* NET_DM_ATTR_TIMESTAMP */
               nla_total_size(sizeof(u64)) +
               /* NET_DM_ATTR_ORIG_LEN */
               nla_total_size(sizeof(u32)) +
               /* NET_DM_ATTR_PROTO */
               nla_total_size(sizeof(u16)) +
               /* NET_DM_ATTR_PAYLOAD */
               nla_total_size(payload_len);
}

static int net_dm_packet_report_in_port_put(struct sk_buff *msg, int ifindex,
                                            const char *name)
{
        struct nlattr *attr;

        attr = nla_nest_start(msg, NET_DM_ATTR_IN_PORT);
        if (!attr)
                return -EMSGSIZE;

        if (ifindex &&
            nla_put_u32(msg, NET_DM_ATTR_PORT_NETDEV_IFINDEX, ifindex))
                goto nla_put_failure;

        if (name && nla_put_string(msg, NET_DM_ATTR_PORT_NETDEV_NAME, name))
                goto nla_put_failure;

        nla_nest_end(msg, attr);

        return 0;

nla_put_failure:
        nla_nest_cancel(msg, attr);
        return -EMSGSIZE;
}

static int net_dm_packet_report_fill(struct sk_buff *msg, struct sk_buff *skb,
                                     size_t payload_len)
{
        u64 pc = (u64)(uintptr_t) NET_DM_SKB_CB(skb)->pc;
        char buf[NET_DM_MAX_SYMBOL_LEN];
        struct nlattr *attr;
        void *hdr;
        int rc;

        hdr = genlmsg_put(msg, 0, 0, &net_drop_monitor_family, 0,
                          NET_DM_CMD_PACKET_ALERT);
        if (!hdr)
                return -EMSGSIZE;

        if (nla_put_u16(msg, NET_DM_ATTR_ORIGIN, NET_DM_ORIGIN_SW))
                goto nla_put_failure;

        if (nla_put_u64_64bit(msg, NET_DM_ATTR_PC, pc, NET_DM_ATTR_PAD))
                goto nla_put_failure;

        snprintf(buf, sizeof(buf), "%pS", NET_DM_SKB_CB(skb)->pc);
        if (nla_put_string(msg, NET_DM_ATTR_SYMBOL, buf))
                goto nla_put_failure;

        rc = net_dm_packet_report_in_port_put(msg, skb->skb_iif, NULL);
        if (rc)
                goto nla_put_failure;

        if (nla_put_u64_64bit(msg, NET_DM_ATTR_TIMESTAMP,
                              ktime_to_ns(skb->tstamp), NET_DM_ATTR_PAD))
                goto nla_put_failure;

        if (nla_put_u32(msg, NET_DM_ATTR_ORIG_LEN, skb->len))
                goto nla_put_failure;

        if (!payload_len)
                goto out;

        if (nla_put_u16(msg, NET_DM_ATTR_PROTO, be16_to_cpu(skb->protocol)))
                goto nla_put_failure;

        attr = skb_put(msg, nla_total_size(payload_len));
        attr->nla_type = NET_DM_ATTR_PAYLOAD;
        attr->nla_len = nla_attr_size(payload_len);
        if (skb_copy_bits(skb, 0, nla_data(attr), payload_len))
                goto nla_put_failure;

out:
        genlmsg_end(msg, hdr);

        return 0;

nla_put_failure:
        genlmsg_cancel(msg, hdr);
        return -EMSGSIZE;
}

#define NET_DM_MAX_PACKET_SIZE (0xffff - NLA_HDRLEN - NLA_ALIGNTO)

static void net_dm_packet_report(struct sk_buff *skb)
{
        struct sk_buff *msg;
        size_t payload_len;
        int rc;

        /* Make sure we start copying the packet from the MAC header */
        if (skb->data > skb_mac_header(skb))
                skb_push(skb, skb->data - skb_mac_header(skb));
        else
                skb_pull(skb, skb_mac_header(skb) - skb->data);

        /* Ensure packet fits inside a single netlink attribute */
        payload_len = min_t(size_t, skb->len, NET_DM_MAX_PACKET_SIZE);
        if (net_dm_trunc_len)
                payload_len = min_t(size_t, net_dm_trunc_len, payload_len);

        msg = nlmsg_new(net_dm_packet_report_size(payload_len), GFP_KERNEL);
        if (!msg)
                goto out;

        rc = net_dm_packet_report_fill(msg, skb, payload_len);
        if (rc) {
                nlmsg_free(msg);
                goto out;
        }

        genlmsg_multicast(&net_drop_monitor_family, msg, 0, 0, GFP_KERNEL);

out:
        consume_skb(skb);
}

static void net_dm_packet_work(struct work_struct *work)
{
        struct per_cpu_dm_data *data;
        struct sk_buff_head list;
        struct sk_buff *skb;
        unsigned long flags;

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

        __skb_queue_head_init(&list);

        spin_lock_irqsave(&data->drop_queue.lock, flags);
        skb_queue_splice_tail_init(&data->drop_queue, &list);
        spin_unlock_irqrestore(&data->drop_queue.lock, flags);

        while ((skb = __skb_dequeue(&list)))
                net_dm_packet_report(skb);
}

static size_t
net_dm_hw_packet_report_size(size_t payload_len,
                             const struct net_dm_hw_metadata *hw_metadata)
{
        size_t size;

        size = nlmsg_msg_size(GENL_HDRLEN + net_drop_monitor_family.hdrsize);

        return NLMSG_ALIGN(size) +
               /* NET_DM_ATTR_ORIGIN */
               nla_total_size(sizeof(u16)) +
               /* NET_DM_ATTR_HW_TRAP_GROUP_NAME */
               nla_total_size(strlen(hw_metadata->trap_group_name) + 1) +
               /* NET_DM_ATTR_HW_TRAP_NAME */
               nla_total_size(strlen(hw_metadata->trap_name) + 1) +
               /* NET_DM_ATTR_IN_PORT */
               net_dm_in_port_size() +
               /* NET_DM_ATTR_TIMESTAMP */
               nla_total_size(sizeof(u64)) +
               /* NET_DM_ATTR_ORIG_LEN */
               nla_total_size(sizeof(u32)) +
               /* NET_DM_ATTR_PROTO */
               nla_total_size(sizeof(u16)) +
               /* NET_DM_ATTR_PAYLOAD */
               nla_total_size(payload_len);
}

static int net_dm_hw_packet_report_fill(struct sk_buff *msg,
                                        struct sk_buff *skb, size_t payload_len)
{
        struct net_dm_hw_metadata *hw_metadata;
        struct nlattr *attr;
        void *hdr;

        hw_metadata = NET_DM_SKB_CB(skb)->hw_metadata;

        hdr = genlmsg_put(msg, 0, 0, &net_drop_monitor_family, 0,
                          NET_DM_CMD_PACKET_ALERT);
        if (!hdr)
                return -EMSGSIZE;

        if (nla_put_u16(msg, NET_DM_ATTR_ORIGIN, NET_DM_ORIGIN_HW))
                goto nla_put_failure;

        if (nla_put_string(msg, NET_DM_ATTR_HW_TRAP_GROUP_NAME,
                           hw_metadata->trap_group_name))
                goto nla_put_failure;

        if (nla_put_string(msg, NET_DM_ATTR_HW_TRAP_NAME,
                           hw_metadata->trap_name))
                goto nla_put_failure;

        if (hw_metadata->input_dev) {
                struct net_device *dev = hw_metadata->input_dev;
                int rc;

                rc = net_dm_packet_report_in_port_put(msg, dev->ifindex,
                                                      dev->name);
                if (rc)
                        goto nla_put_failure;
        }

        if (nla_put_u64_64bit(msg, NET_DM_ATTR_TIMESTAMP,
                              ktime_to_ns(skb->tstamp), NET_DM_ATTR_PAD))
                goto nla_put_failure;

        if (nla_put_u32(msg, NET_DM_ATTR_ORIG_LEN, skb->len))
                goto nla_put_failure;

        if (!payload_len)
                goto out;

        if (nla_put_u16(msg, NET_DM_ATTR_PROTO, be16_to_cpu(skb->protocol)))
                goto nla_put_failure;

        attr = skb_put(msg, nla_total_size(payload_len));
        attr->nla_type = NET_DM_ATTR_PAYLOAD;
        attr->nla_len = nla_attr_size(payload_len);
        if (skb_copy_bits(skb, 0, nla_data(attr), payload_len))
                goto nla_put_failure;

out:
        genlmsg_end(msg, hdr);

        return 0;

nla_put_failure:
        genlmsg_cancel(msg, hdr);
        return -EMSGSIZE;
}

static struct net_dm_hw_metadata *
net_dm_hw_metadata_clone(const struct net_dm_hw_metadata *hw_metadata)
{
        struct net_dm_hw_metadata *n_hw_metadata;
        const char *trap_group_name;
        const char *trap_name;

        n_hw_metadata = kmalloc(sizeof(*hw_metadata), GFP_ATOMIC);
        if (!n_hw_metadata)
                return NULL;

        trap_group_name = kmemdup(hw_metadata->trap_group_name,
                                  strlen(hw_metadata->trap_group_name) + 1,
                                  GFP_ATOMIC | __GFP_ZERO);
        if (!trap_group_name)
                goto free_hw_metadata;
        n_hw_metadata->trap_group_name = trap_group_name;

        trap_name = kmemdup(hw_metadata->trap_name,
                            strlen(hw_metadata->trap_name) + 1,
                            GFP_ATOMIC | __GFP_ZERO);
        if (!trap_name)
                goto free_trap_group;
        n_hw_metadata->trap_name = trap_name;

        n_hw_metadata->input_dev = hw_metadata->input_dev;
        if (n_hw_metadata->input_dev)
                dev_hold(n_hw_metadata->input_dev);

        return n_hw_metadata;

free_trap_group:
        kfree(trap_group_name);
free_hw_metadata:
        kfree(n_hw_metadata);
        return NULL;
}

static void
net_dm_hw_metadata_free(const struct net_dm_hw_metadata *hw_metadata)
{
        if (hw_metadata->input_dev)
                dev_put(hw_metadata->input_dev);
        kfree(hw_metadata->trap_name);
        kfree(hw_metadata->trap_group_name);
        kfree(hw_metadata);
}

static void net_dm_hw_packet_report(struct sk_buff *skb)
{
        struct net_dm_hw_metadata *hw_metadata;
        struct sk_buff *msg;
        size_t payload_len;
        int rc;

        if (skb->data > skb_mac_header(skb))
                skb_push(skb, skb->data - skb_mac_header(skb));
        else
                skb_pull(skb, skb_mac_header(skb) - skb->data);

        payload_len = min_t(size_t, skb->len, NET_DM_MAX_PACKET_SIZE);
        if (net_dm_trunc_len)
                payload_len = min_t(size_t, net_dm_trunc_len, payload_len);

        hw_metadata = NET_DM_SKB_CB(skb)->hw_metadata;
        msg = nlmsg_new(net_dm_hw_packet_report_size(payload_len, hw_metadata),
                        GFP_KERNEL);
        if (!msg)
                goto out;

        rc = net_dm_hw_packet_report_fill(msg, skb, payload_len);
        if (rc) {
                nlmsg_free(msg);
                goto out;
        }

        genlmsg_multicast(&net_drop_monitor_family, msg, 0, 0, GFP_KERNEL);

out:
        net_dm_hw_metadata_free(NET_DM_SKB_CB(skb)->hw_metadata);
        consume_skb(skb);
}

static void net_dm_hw_packet_work(struct work_struct *work)
{
        struct per_cpu_dm_data *hw_data;
        struct sk_buff_head list;
        struct sk_buff *skb;
        unsigned long flags;

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

        __skb_queue_head_init(&list);

        spin_lock_irqsave(&hw_data->drop_queue.lock, flags);
        skb_queue_splice_tail_init(&hw_data->drop_queue, &list);
        spin_unlock_irqrestore(&hw_data->drop_queue.lock, flags);

        while ((skb = __skb_dequeue(&list)))
                net_dm_hw_packet_report(skb);
}

static void
net_dm_hw_packet_probe(struct sk_buff *skb,
                       const struct net_dm_hw_metadata *hw_metadata)
{
        struct net_dm_hw_metadata *n_hw_metadata;
        ktime_t tstamp = ktime_get_real();
        struct per_cpu_dm_data *hw_data;
        struct sk_buff *nskb;
        unsigned long flags;

        if (!skb_mac_header_was_set(skb))
                return;

        nskb = skb_clone(skb, GFP_ATOMIC);
        if (!nskb)
                return;

        n_hw_metadata = net_dm_hw_metadata_clone(hw_metadata);
        if (!n_hw_metadata)
                goto free;

        NET_DM_SKB_CB(nskb)->hw_metadata = n_hw_metadata;
        nskb->tstamp = tstamp;

        hw_data = this_cpu_ptr(&dm_hw_cpu_data);

        spin_lock_irqsave(&hw_data->drop_queue.lock, flags);
        if (skb_queue_len(&hw_data->drop_queue) < net_dm_queue_len)
                __skb_queue_tail(&hw_data->drop_queue, nskb);
        else
                goto unlock_free;
        spin_unlock_irqrestore(&hw_data->drop_queue.lock, flags);

        schedule_work(&hw_data->dm_alert_work);

        return;

unlock_free:
        spin_unlock_irqrestore(&hw_data->drop_queue.lock, flags);
        u64_stats_update_begin(&hw_data->stats.syncp);
        hw_data->stats.dropped++;
        u64_stats_update_end(&hw_data->stats.syncp);
        net_dm_hw_metadata_free(n_hw_metadata);
free:
        consume_skb(nskb);
}

static const struct net_dm_alert_ops net_dm_alert_packet_ops = {
        .kfree_skb_probe        = net_dm_packet_trace_kfree_skb_hit,
        .napi_poll_probe        = net_dm_packet_trace_napi_poll_hit,
        .work_item_func         = net_dm_packet_work,
        .hw_work_item_func      = net_dm_hw_packet_work,
        .hw_probe               = net_dm_hw_packet_probe,
};

static const struct net_dm_alert_ops *net_dm_alert_ops_arr[] = {
        [NET_DM_ALERT_MODE_SUMMARY]     = &net_dm_alert_summary_ops,
        [NET_DM_ALERT_MODE_PACKET]      = &net_dm_alert_packet_ops,
};

void net_dm_hw_report(struct sk_buff *skb,
                      const struct net_dm_hw_metadata *hw_metadata)
{
        rcu_read_lock();

        if (!monitor_hw)
                goto out;

        net_dm_alert_ops_arr[net_dm_alert_mode]->hw_probe(skb, hw_metadata);

out:
        rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(net_dm_hw_report);

static int net_dm_hw_monitor_start(struct netlink_ext_ack *extack)
{
        const struct net_dm_alert_ops *ops;
        int cpu;

        if (monitor_hw) {
                NL_SET_ERR_MSG_MOD(extack, "Hardware monitoring already enabled");
                return -EAGAIN;
        }

        ops = net_dm_alert_ops_arr[net_dm_alert_mode];

        if (!try_module_get(THIS_MODULE)) {
                NL_SET_ERR_MSG_MOD(extack, "Failed to take reference on module");
                return -ENODEV;
        }

        for_each_possible_cpu(cpu) {
                struct per_cpu_dm_data *hw_data = &per_cpu(dm_hw_cpu_data, cpu);
                struct net_dm_hw_entries *hw_entries;

                INIT_WORK(&hw_data->dm_alert_work, ops->hw_work_item_func);
                timer_setup(&hw_data->send_timer, sched_send_work, 0);
                hw_entries = net_dm_hw_reset_per_cpu_data(hw_data);
                kfree(hw_entries);
        }

        monitor_hw = true;

        return 0;

}

static void net_dm_hw_monitor_stop(struct netlink_ext_ack *extack)
{
        int cpu;

        if (!monitor_hw)
                NL_SET_ERR_MSG_MOD(extack, "Hardware monitoring already disabled");

        monitor_hw = false;

        /* After this call returns we are guaranteed that no CPU is processing
         * any hardware drops.
         */
        synchronize_rcu();

        for_each_possible_cpu(cpu) {
                struct per_cpu_dm_data *hw_data = &per_cpu(dm_hw_cpu_data, cpu);
                struct sk_buff *skb;

                del_timer_sync(&hw_data->send_timer);
                cancel_work_sync(&hw_data->dm_alert_work);
                while ((skb = __skb_dequeue(&hw_data->drop_queue))) {
                        struct net_dm_hw_metadata *hw_metadata;

                        hw_metadata = NET_DM_SKB_CB(skb)->hw_metadata;
                        net_dm_hw_metadata_free(hw_metadata);
                        consume_skb(skb);
                }
        }

        module_put(THIS_MODULE);
}

static int net_dm_trace_on_set(struct netlink_ext_ack *extack)
{
        const struct net_dm_alert_ops *ops;
        int cpu, rc;

        ops = net_dm_alert_ops_arr[net_dm_alert_mode];

        if (!try_module_get(THIS_MODULE)) {
                NL_SET_ERR_MSG_MOD(extack, "Failed to take reference on module");
                return -ENODEV;
        }

        for_each_possible_cpu(cpu) {
                struct per_cpu_dm_data *data = &per_cpu(dm_cpu_data, cpu);
                struct sk_buff *skb;

                INIT_WORK(&data->dm_alert_work, ops->work_item_func);
                timer_setup(&data->send_timer, sched_send_work, 0);
                /* Allocate a new per-CPU skb for the summary alert message and
                 * free the old one which might contain stale data from
                 * previous tracing.
                 */
                skb = reset_per_cpu_data(data);
                consume_skb(skb);
        }

        rc = register_trace_kfree_skb(ops->kfree_skb_probe, NULL);
        if (rc) {
                NL_SET_ERR_MSG_MOD(extack, "Failed to connect probe to kfree_skb() tracepoint");
                goto err_module_put;
        }

        rc = register_trace_napi_poll(ops->napi_poll_probe, NULL);
        if (rc) {
                NL_SET_ERR_MSG_MOD(extack, "Failed to connect probe to napi_poll() tracepoint");
                goto err_unregister_trace;
        }

        return 0;

err_unregister_trace:
        unregister_trace_kfree_skb(ops->kfree_skb_probe, NULL);
err_module_put:
        module_put(THIS_MODULE);
        return rc;
}

static void net_dm_trace_off_set(void)
{
        struct dm_hw_stat_delta *new_stat, *temp;
        const struct net_dm_alert_ops *ops;
        int cpu;

        ops = net_dm_alert_ops_arr[net_dm_alert_mode];

        unregister_trace_napi_poll(ops->napi_poll_probe, NULL);
        unregister_trace_kfree_skb(ops->kfree_skb_probe, NULL);

        tracepoint_synchronize_unregister();

        /* Make sure we do not send notifications to user space after request
         * to stop tracing returns.
         */
        for_each_possible_cpu(cpu) {
                struct per_cpu_dm_data *data = &per_cpu(dm_cpu_data, cpu);
                struct sk_buff *skb;

                del_timer_sync(&data->send_timer);
                cancel_work_sync(&data->dm_alert_work);
                while ((skb = __skb_dequeue(&data->drop_queue)))
                        consume_skb(skb);
        }

        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);
}

static int set_all_monitor_traces(int state, struct netlink_ext_ack *extack)
{
        int rc = 0;

        if (state == trace_state) {
                NL_SET_ERR_MSG_MOD(extack, "Trace state already set to requested state");
                return -EAGAIN;
        }

        switch (state) {
        case TRACE_ON:
                rc = net_dm_trace_on_set(extack);
                break;
        case TRACE_OFF:
                net_dm_trace_off_set();
                break;
        default:
                rc = 1;
                break;
        }

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

        return rc;
}

static bool net_dm_is_monitoring(void)
{
        return trace_state == TRACE_ON || monitor_hw;
}

static int net_dm_alert_mode_get_from_info(struct genl_info *info,
                                           enum net_dm_alert_mode *p_alert_mode)
{
        u8 val;

        val = nla_get_u8(info->attrs[NET_DM_ATTR_ALERT_MODE]);

        switch (val) {
        case NET_DM_ALERT_MODE_SUMMARY: /* fall-through */
        case NET_DM_ALERT_MODE_PACKET:
                *p_alert_mode = val;
                break;
        default:
                return -EINVAL;
        }

        return 0;
}

static int net_dm_alert_mode_set(struct genl_info *info)
{
        struct netlink_ext_ack *extack = info->extack;
        enum net_dm_alert_mode alert_mode;
        int rc;

        if (!info->attrs[NET_DM_ATTR_ALERT_MODE])
                return 0;

        rc = net_dm_alert_mode_get_from_info(info, &alert_mode);
        if (rc) {
                NL_SET_ERR_MSG_MOD(extack, "Invalid alert mode");
                return -EINVAL;
        }

        net_dm_alert_mode = alert_mode;

        return 0;
}

static void net_dm_trunc_len_set(struct genl_info *info)
{
        if (!info->attrs[NET_DM_ATTR_TRUNC_LEN])
                return;

        net_dm_trunc_len = nla_get_u32(info->attrs[NET_DM_ATTR_TRUNC_LEN]);
}

static void net_dm_queue_len_set(struct genl_info *info)
{
        if (!info->attrs[NET_DM_ATTR_QUEUE_LEN])
                return;

        net_dm_queue_len = nla_get_u32(info->attrs[NET_DM_ATTR_QUEUE_LEN]);
}

static int net_dm_cmd_config(struct sk_buff *skb,
                        struct genl_info *info)
{
        struct netlink_ext_ack *extack = info->extack;
        int rc;

        if (net_dm_is_monitoring()) {
                NL_SET_ERR_MSG_MOD(extack, "Cannot configure drop monitor during monitoring");
                return -EBUSY;
        }

        rc = net_dm_alert_mode_set(info);
        if (rc)
                return rc;

        net_dm_trunc_len_set(info);

        net_dm_queue_len_set(info);

        return 0;
}

static int net_dm_monitor_start(bool set_sw, bool set_hw,
                                struct netlink_ext_ack *extack)
{
        bool sw_set = false;
        int rc;

        if (set_sw) {
                rc = set_all_monitor_traces(TRACE_ON, extack);
                if (rc)
                        return rc;
                sw_set = true;
        }

        if (set_hw) {
                rc = net_dm_hw_monitor_start(extack);
                if (rc)
                        goto err_monitor_hw;
        }

        return 0;

err_monitor_hw:
        if (sw_set)
                set_all_monitor_traces(TRACE_OFF, extack);
        return rc;
}

static void net_dm_monitor_stop(bool set_sw, bool set_hw,
                                struct netlink_ext_ack *extack)
{
        if (set_hw)
                net_dm_hw_monitor_stop(extack);
        if (set_sw)
                set_all_monitor_traces(TRACE_OFF, extack);
}

static int net_dm_cmd_trace(struct sk_buff *skb,
                        struct genl_info *info)
{
        bool set_sw = !!info->attrs[NET_DM_ATTR_SW_DROPS];
        bool set_hw = !!info->attrs[NET_DM_ATTR_HW_DROPS];
        struct netlink_ext_ack *extack = info->extack;

        /* To maintain backward compatibility, we start / stop monitoring of
         * software drops if no flag is specified.
         */
        if (!set_sw && !set_hw)
                set_sw = true;

        switch (info->genlhdr->cmd) {
        case NET_DM_CMD_START:
                return net_dm_monitor_start(set_sw, set_hw, extack);
        case NET_DM_CMD_STOP:
                net_dm_monitor_stop(set_sw, set_hw, extack);
                return 0;
        }

        return -EOPNOTSUPP;
}

static int net_dm_config_fill(struct sk_buff *msg, struct genl_info *info)
{
        void *hdr;

        hdr = genlmsg_put(msg, info->snd_portid, info->snd_seq,
                          &net_drop_monitor_family, 0, NET_DM_CMD_CONFIG_NEW);
        if (!hdr)
                return -EMSGSIZE;

        if (nla_put_u8(msg, NET_DM_ATTR_ALERT_MODE, net_dm_alert_mode))
                goto nla_put_failure;

        if (nla_put_u32(msg, NET_DM_ATTR_TRUNC_LEN, net_dm_trunc_len))
                goto nla_put_failure;

        if (nla_put_u32(msg, NET_DM_ATTR_QUEUE_LEN, net_dm_queue_len))
                goto nla_put_failure;

        genlmsg_end(msg, hdr);

        return 0;

nla_put_failure:
        genlmsg_cancel(msg, hdr);
        return -EMSGSIZE;
}

static int net_dm_cmd_config_get(struct sk_buff *skb, struct genl_info *info)
{
        struct sk_buff *msg;
        int rc;

        msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
        if (!msg)
                return -ENOMEM;

        rc = net_dm_config_fill(msg, info);
        if (rc)
                goto free_msg;

        return genlmsg_reply(msg, info);

free_msg:
        nlmsg_free(msg);
        return rc;
}

static void net_dm_stats_read(struct net_dm_stats *stats)
{
        int cpu;

        memset(stats, 0, sizeof(*stats));
        for_each_possible_cpu(cpu) {
                struct per_cpu_dm_data *data = &per_cpu(dm_cpu_data, cpu);
                struct net_dm_stats *cpu_stats = &data->stats;
                unsigned int start;
                u64 dropped;

                do {
                        start = u64_stats_fetch_begin_irq(&cpu_stats->syncp);
                        dropped = cpu_stats->dropped;
                } while (u64_stats_fetch_retry_irq(&cpu_stats->syncp, start));

                stats->dropped += dropped;
        }
}

static int net_dm_stats_put(struct sk_buff *msg)
{
        struct net_dm_stats stats;
        struct nlattr *attr;

        net_dm_stats_read(&stats);

        attr = nla_nest_start(msg, NET_DM_ATTR_STATS);
        if (!attr)
                return -EMSGSIZE;

        if (nla_put_u64_64bit(msg, NET_DM_ATTR_STATS_DROPPED,
                              stats.dropped, NET_DM_ATTR_PAD))
                goto nla_put_failure;

        nla_nest_end(msg, attr);

        return 0;

nla_put_failure:
        nla_nest_cancel(msg, attr);
        return -EMSGSIZE;
}

static void net_dm_hw_stats_read(struct net_dm_stats *stats)
{
        int cpu;

        memset(stats, 0, sizeof(*stats));
        for_each_possible_cpu(cpu) {
                struct per_cpu_dm_data *hw_data = &per_cpu(dm_hw_cpu_data, cpu);
                struct net_dm_stats *cpu_stats = &hw_data->stats;
                unsigned int start;
                u64 dropped;

                do {
                        start = u64_stats_fetch_begin_irq(&cpu_stats->syncp);
                        dropped = cpu_stats->dropped;
                } while (u64_stats_fetch_retry_irq(&cpu_stats->syncp, start));

                stats->dropped += dropped;
        }
}

static int net_dm_hw_stats_put(struct sk_buff *msg)
{
        struct net_dm_stats stats;
        struct nlattr *attr;

        net_dm_hw_stats_read(&stats);

        attr = nla_nest_start(msg, NET_DM_ATTR_HW_STATS);
        if (!attr)
                return -EMSGSIZE;

        if (nla_put_u64_64bit(msg, NET_DM_ATTR_STATS_DROPPED,
                              stats.dropped, NET_DM_ATTR_PAD))
                goto nla_put_failure;

        nla_nest_end(msg, attr);

        return 0;

nla_put_failure:
        nla_nest_cancel(msg, attr);
        return -EMSGSIZE;
}

static int net_dm_stats_fill(struct sk_buff *msg, struct genl_info *info)
{
        void *hdr;
        int rc;

        hdr = genlmsg_put(msg, info->snd_portid, info->snd_seq,
                          &net_drop_monitor_family, 0, NET_DM_CMD_STATS_NEW);
        if (!hdr)
                return -EMSGSIZE;

        rc = net_dm_stats_put(msg);
        if (rc)
                goto nla_put_failure;

        rc = net_dm_hw_stats_put(msg);
        if (rc)
                goto nla_put_failure;

        genlmsg_end(msg, hdr);

        return 0;

nla_put_failure:
        genlmsg_cancel(msg, hdr);
        return -EMSGSIZE;
}

static int net_dm_cmd_stats_get(struct sk_buff *skb, struct genl_info *info)
{
        struct sk_buff *msg;
        int rc;

        msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
        if (!msg)
                return -ENOMEM;

        rc = net_dm_stats_fill(msg, info);
        if (rc)
                goto free_msg;

        return genlmsg_reply(msg, info);

free_msg:
        nlmsg_free(msg);
        return rc;
}

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(&net_dm_mutex);
                list_add_rcu(&new_stat->list, &hw_stats_list);
                mutex_unlock(&net_dm_mutex);
                break;
        case NETDEV_UNREGISTER:
                mutex_lock(&net_dm_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(&net_dm_mutex);
                break;
        }
out:
        return NOTIFY_DONE;
}

static const struct nla_policy net_dm_nl_policy[NET_DM_ATTR_MAX + 1] = {
        [NET_DM_ATTR_UNSPEC] = { .strict_start_type = NET_DM_ATTR_UNSPEC + 1 },
        [NET_DM_ATTR_ALERT_MODE] = { .type = NLA_U8 },
        [NET_DM_ATTR_TRUNC_LEN] = { .type = NLA_U32 },
        [NET_DM_ATTR_QUEUE_LEN] = { .type = NLA_U32 },
        [NET_DM_ATTR_SW_DROPS]  = {. type = NLA_FLAG },
        [NET_DM_ATTR_HW_DROPS]  = {. type = NLA_FLAG },
};

static const struct genl_ops dropmon_ops[] = {
        {
                .cmd = NET_DM_CMD_CONFIG,
                .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
                .doit = net_dm_cmd_config,
                .flags = GENL_ADMIN_PERM,
        },
        {
                .cmd = NET_DM_CMD_START,
                .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
                .doit = net_dm_cmd_trace,
        },
        {
                .cmd = NET_DM_CMD_STOP,
                .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
                .doit = net_dm_cmd_trace,
        },
        {
                .cmd = NET_DM_CMD_CONFIG_GET,
                .doit = net_dm_cmd_config_get,
        },
        {
                .cmd = NET_DM_CMD_STATS_GET,
                .doit = net_dm_cmd_stats_get,
        },
};

static int net_dm_nl_pre_doit(const struct genl_ops *ops,
                              struct sk_buff *skb, struct genl_info *info)
{
        mutex_lock(&net_dm_mutex);

        return 0;
}

static void net_dm_nl_post_doit(const struct genl_ops *ops,
                                struct sk_buff *skb, struct genl_info *info)
{
        mutex_unlock(&net_dm_mutex);
}

static struct genl_family net_drop_monitor_family __ro_after_init = {
        .hdrsize        = 0,
        .name           = "NET_DM",
        .version        = 2,
        .maxattr        = NET_DM_ATTR_MAX,
        .policy         = net_dm_nl_policy,
        .pre_doit       = net_dm_nl_pre_doit,
        .post_doit      = net_dm_nl_post_doit,
        .module         = THIS_MODULE,
        .ops            = dropmon_ops,
        .n_ops          = ARRAY_SIZE(dropmon_ops),
        .mcgrps         = dropmon_mcgrps,
        .n_mcgrps       = ARRAY_SIZE(dropmon_mcgrps),
};

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

static void __net_dm_cpu_data_init(struct per_cpu_dm_data *data)
{
        spin_lock_init(&data->lock);
        skb_queue_head_init(&data->drop_queue);
        u64_stats_init(&data->stats.syncp);
}

static void __net_dm_cpu_data_fini(struct per_cpu_dm_data *data)
{
        WARN_ON(!skb_queue_empty(&data->drop_queue));
}

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

        data = &per_cpu(dm_cpu_data, cpu);
        __net_dm_cpu_data_init(data);
}

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

        data = &per_cpu(dm_cpu_data, cpu);
        /* At this point, we should have exclusive access
         * to this struct and can free the skb inside it.
         */
        consume_skb(data->skb);
        __net_dm_cpu_data_fini(data);
}

static void net_dm_hw_cpu_data_init(int cpu)
{
        struct per_cpu_dm_data *hw_data;

        hw_data = &per_cpu(dm_hw_cpu_data, cpu);
        __net_dm_cpu_data_init(hw_data);
}

static void net_dm_hw_cpu_data_fini(int cpu)
{
        struct per_cpu_dm_data *hw_data;

        hw_data = &per_cpu(dm_hw_cpu_data, cpu);
        kfree(hw_data->hw_entries);
        __net_dm_cpu_data_fini(hw_data);
}

static int __init init_net_drop_monitor(void)
{
        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(&net_drop_monitor_family);
        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) {
                net_dm_cpu_data_init(cpu);
                net_dm_hw_cpu_data_init(cpu);
        }

        goto out;

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

static void exit_net_drop_monitor(void)
{
        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
         */

        for_each_possible_cpu(cpu) {
                net_dm_hw_cpu_data_fini(cpu);
                net_dm_cpu_data_fini(cpu);
        }

        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");