net/core/drop_monitor.c

   1 /*
   2  * Monitoring code for network dropped packet alerts
   3  *
   4  * Copyright (C) 2009 Neil Horman <nhorman@tuxdriver.com>
   5  */
   6
   7 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   8
   9 #include <linux/netdevice.h>
  10 #include <linux/etherdevice.h>
  11 #include <linux/string.h>
  12 #include <linux/if_arp.h>
  13 #include <linux/inetdevice.h>
  14 #include <linux/inet.h>
  15 #include <linux/interrupt.h>
  16 #include <linux/netpoll.h>
  17 #include <linux/sched.h>
  18 #include <linux/delay.h>
  19 #include <linux/types.h>
  20 #include <linux/workqueue.h>
  21 #include <linux/netlink.h>
  22 #include <linux/net_dropmon.h>
  23 #include <linux/percpu.h>
  24 #include <linux/timer.h>
  25 #include <linux/bitops.h>
  26 #include <linux/slab.h>
  27 #include <linux/module.h>
  28 #include <net/genetlink.h>
  29 #include <net/netevent.h>
  30
  31 #include <trace/events/skb.h>
  32 #include <trace/events/napi.h>
  33
  34 #include <asm/unaligned.h>
  35
  36 #define TRACE_ON 1
  37 #define TRACE_OFF 0
  38
  39 /*
  40  * Globals, our netlink socket pointer
  41  * and the work handle that will send up
  42  * netlink alerts
  43  */
  44 static int trace_state = TRACE_OFF;
  45 static DEFINE_MUTEX(trace_state_mutex);
  46
  47 struct per_cpu_dm_data {
  48         spinlock_t              lock;
  49         struct sk_buff          *skb;
  50         struct work_struct      dm_alert_work;
  51         struct timer_list       send_timer;
  52 };
  53
  54 struct dm_hw_stat_delta {
  55         struct net_device *dev;
  56         unsigned long last_rx;
  57         struct list_head list;
  58         struct rcu_head rcu;
  59         unsigned long last_drop_val;
  60 };
  61
  62 static struct genl_family net_drop_monitor_family = {
  63         .id             = GENL_ID_GENERATE,
  64         .hdrsize        = 0,
  65         .name           = "NET_DM",
  66         .version        = 2,
  67 };
  68
  69 static DEFINE_PER_CPU(struct per_cpu_dm_data, dm_cpu_data);
  70
  71 static int dm_hit_limit = 64;
  72 static int dm_delay = 1;
  73 static unsigned long dm_hw_check_delta = 2*HZ;
  74 static LIST_HEAD(hw_stats_list);
  75
  76 static struct sk_buff *reset_per_cpu_data(struct per_cpu_dm_data *data)
  77 {
  78         size_t al;
  79         struct net_dm_alert_msg *msg;
  80         struct nlattr *nla;
  81         struct sk_buff *skb;
  82         unsigned long flags;
  83
  84         al = sizeof(struct net_dm_alert_msg);
  85         al += dm_hit_limit * sizeof(struct net_dm_drop_point);
  86         al += sizeof(struct nlattr);
  87
  88         skb = genlmsg_new(al, GFP_KERNEL);
  89
  90         if (skb) {
  91                 genlmsg_put(skb, 0, 0, &net_drop_monitor_family,
  92                                 0, NET_DM_CMD_ALERT);
  93                 nla = nla_reserve(skb, NLA_UNSPEC,
  94                                   sizeof(struct net_dm_alert_msg));
  95                 msg = nla_data(nla);
  96                 memset(msg, 0, al);
  97         } else {
  98                 mod_timer(&data->send_timer, jiffies + HZ / 10);
  99         }
 100
 101         spin_lock_irqsave(&data->lock, flags);
 102         swap(data->skb, skb);
 103         spin_unlock_irqrestore(&data->lock, flags);
 104
 105         return skb;
 106 }
 107
 108 static const struct genl_multicast_group dropmon_mcgrps[] = {
 109         { .name = "events", },
 110 };
 111
 112 static void send_dm_alert(struct work_struct *work)
 113 {
 114         struct sk_buff *skb;
 115         struct per_cpu_dm_data *data;
 116
 117         data = container_of(work, struct per_cpu_dm_data, dm_alert_work);
 118
 119         skb = reset_per_cpu_data(data);
 120
 121         if (skb)
 122                 genlmsg_multicast(&net_drop_monitor_family, skb, 0,
 123                                   0, GFP_KERNEL);
 124 }
 125
 126 /*
 127  * This is the timer function to delay the sending of an alert
 128  * in the event that more drops will arrive during the
 129  * hysteresis period.
 130  */
 131 static void sched_send_work(unsigned long _data)
 132 {
 133         struct per_cpu_dm_data *data = (struct per_cpu_dm_data *)_data;
 134
 135         schedule_work(&data->dm_alert_work);
 136 }
 137
 138 static void trace_drop_common(struct sk_buff *skb, void *location)
 139 {
 140         struct net_dm_alert_msg *msg;
 141         struct nlmsghdr *nlh;
 142         struct nlattr *nla;
 143         int i;
 144         struct sk_buff *dskb;
 145         struct per_cpu_dm_data *data;
 146         unsigned long flags;
 147
 148         local_irq_save(flags);
 149         data = this_cpu_ptr(&dm_cpu_data);
 150         spin_lock(&data->lock);
 151         dskb = data->skb;
 152
 153         if (!dskb)
 154                 goto out;
 155
 156         nlh = (struct nlmsghdr *)dskb->data;
 157         nla = genlmsg_data(nlmsg_data(nlh));
 158         msg = nla_data(nla);
 159         for (i = 0; i < msg->entries; i++) {
 160                 if (!memcmp(&location, msg->points[i].pc, sizeof(void *))) {
 161                         msg->points[i].count++;
 162                         goto out;
 163                 }
 164         }
 165         if (msg->entries == dm_hit_limit)
 166                 goto out;
 167         /*
 168          * We need to create a new entry
 169          */
 170         __nla_reserve_nohdr(dskb, sizeof(struct net_dm_drop_point));
 171         nla->nla_len += NLA_ALIGN(sizeof(struct net_dm_drop_point));
 172         memcpy(msg->points[msg->entries].pc, &location, sizeof(void *));
 173         msg->points[msg->entries].count = 1;
 174         msg->entries++;
 175
 176         if (!timer_pending(&data->send_timer)) {
 177                 data->send_timer.expires = jiffies + dm_delay * HZ;
 178                 add_timer(&data->send_timer);
 179         }
 180
 181 out:
 182         spin_unlock_irqrestore(&data->lock, flags);
 183 }
 184
 185 static void trace_kfree_skb_hit(void *ignore, struct sk_buff *skb, void *location)
 186 {
 187         trace_drop_common(skb, location);
 188 }
 189
 190 static void trace_napi_poll_hit(void *ignore, struct napi_struct *napi,
 191                                 int work, int budget)
 192 {
 193         struct dm_hw_stat_delta *new_stat;
 194
 195         /*
 196          * Don't check napi structures with no associated device
 197          */
 198         if (!napi->dev)
 199                 return;
 200
 201         rcu_read_lock();
 202         list_for_each_entry_rcu(new_stat, &hw_stats_list, list) {
 203                 /*
 204                  * only add a note to our monitor buffer if:
 205                  * 1) this is the dev we received on
 206                  * 2) its after the last_rx delta
 207                  * 3) our rx_dropped count has gone up
 208                  */
 209                 if ((new_stat->dev == napi->dev)  &&
 210                     (time_after(jiffies, new_stat->last_rx + dm_hw_check_delta)) &&
 211                     (napi->dev->stats.rx_dropped != new_stat->last_drop_val)) {
 212                         trace_drop_common(NULL, NULL);
 213                         new_stat->last_drop_val = napi->dev->stats.rx_dropped;
 214                         new_stat->last_rx = jiffies;
 215                         break;
 216                 }
 217         }
 218         rcu_read_unlock();
 219 }
 220
 221 static int set_all_monitor_traces(int state)
 222 {
 223         int rc = 0;
 224         struct dm_hw_stat_delta *new_stat = NULL;
 225         struct dm_hw_stat_delta *temp;
 226
 227         mutex_lock(&trace_state_mutex);
 228
 229         if (state == trace_state) {
 230                 rc = -EAGAIN;
 231                 goto out_unlock;
 232         }
 233
 234         switch (state) {
 235         case TRACE_ON:
 236                 if (!try_module_get(THIS_MODULE)) {
 237                         rc = -ENODEV;
 238                         break;
 239                 }
 240
 241                 rc |= register_trace_kfree_skb(trace_kfree_skb_hit, NULL);
 242                 rc |= register_trace_napi_poll(trace_napi_poll_hit, NULL);
 243                 break;
 244
 245         case TRACE_OFF:
 246                 rc |= unregister_trace_kfree_skb(trace_kfree_skb_hit, NULL);
 247                 rc |= unregister_trace_napi_poll(trace_napi_poll_hit, NULL);
 248
 249                 tracepoint_synchronize_unregister();
 250
 251                 /*
 252                  * Clean the device list
 253                  */
 254                 list_for_each_entry_safe(new_stat, temp, &hw_stats_list, list) {
 255                         if (new_stat->dev == NULL) {
 256                                 list_del_rcu(&new_stat->list);
 257                                 kfree_rcu(new_stat, rcu);
 258                         }
 259                 }
 260
 261                 module_put(THIS_MODULE);
 262
 263                 break;
 264         default:
 265                 rc = 1;
 266                 break;
 267         }
 268
 269         if (!rc)
 270                 trace_state = state;
 271         else
 272                 rc = -EINPROGRESS;
 273
 274 out_unlock:
 275         mutex_unlock(&trace_state_mutex);
 276
 277         return rc;
 278 }
 279
 280
 281 static int net_dm_cmd_config(struct sk_buff *skb,
 282                         struct genl_info *info)
 283 {
 284         return -ENOTSUPP;
 285 }
 286
 287 static int net_dm_cmd_trace(struct sk_buff *skb,
 288                         struct genl_info *info)
 289 {
 290         switch (info->genlhdr->cmd) {
 291         case NET_DM_CMD_START:
 292                 return set_all_monitor_traces(TRACE_ON);
 293         case NET_DM_CMD_STOP:
 294                 return set_all_monitor_traces(TRACE_OFF);
 295         }
 296
 297         return -ENOTSUPP;
 298 }
 299
 300 static int dropmon_net_event(struct notifier_block *ev_block,
 301                              unsigned long event, void *ptr)
 302 {
 303         struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 304         struct dm_hw_stat_delta *new_stat = NULL;
 305         struct dm_hw_stat_delta *tmp;
 306
 307         switch (event) {
 308         case NETDEV_REGISTER:
 309                 new_stat = kzalloc(sizeof(struct dm_hw_stat_delta), GFP_KERNEL);
 310
 311                 if (!new_stat)
 312                         goto out;
 313
 314                 new_stat->dev = dev;
 315                 new_stat->last_rx = jiffies;
 316                 mutex_lock(&trace_state_mutex);
 317                 list_add_rcu(&new_stat->list, &hw_stats_list);
 318                 mutex_unlock(&trace_state_mutex);
 319                 break;
 320         case NETDEV_UNREGISTER:
 321                 mutex_lock(&trace_state_mutex);
 322                 list_for_each_entry_safe(new_stat, tmp, &hw_stats_list, list) {
 323                         if (new_stat->dev == dev) {
 324                                 new_stat->dev = NULL;
 325                                 if (trace_state == TRACE_OFF) {
 326                                         list_del_rcu(&new_stat->list);
 327                                         kfree_rcu(new_stat, rcu);
 328                                         break;
 329                                 }
 330                         }
 331                 }
 332                 mutex_unlock(&trace_state_mutex);
 333                 break;
 334         }
 335 out:
 336         return NOTIFY_DONE;
 337 }
 338
 339 static const struct genl_ops dropmon_ops[] = {
 340         {
 341                 .cmd = NET_DM_CMD_CONFIG,
 342                 .doit = net_dm_cmd_config,
 343         },
 344         {
 345                 .cmd = NET_DM_CMD_START,
 346                 .doit = net_dm_cmd_trace,
 347         },
 348         {
 349                 .cmd = NET_DM_CMD_STOP,
 350                 .doit = net_dm_cmd_trace,
 351         },
 352 };
 353
 354 static struct notifier_block dropmon_net_notifier = {
 355         .notifier_call = dropmon_net_event
 356 };
 357
 358 static int __init init_net_drop_monitor(void)
 359 {
 360         struct per_cpu_dm_data *data;
 361         int cpu, rc;
 362
 363         pr_info("Initializing network drop monitor service\n");
 364
 365         if (sizeof(void *) > 8) {
 366                 pr_err("Unable to store program counters on this arch, Drop monitor failed\n");
 367                 return -ENOSPC;
 368         }
 369
 370         rc = genl_register_family_with_ops_groups(&net_drop_monitor_family,
 371                                                   dropmon_ops, dropmon_mcgrps);
 372         if (rc) {
 373                 pr_err("Could not create drop monitor netlink family\n");
 374                 return rc;
 375         }
 376         WARN_ON(net_drop_monitor_family.mcgrp_offset != NET_DM_GRP_ALERT);
 377
 378         rc = register_netdevice_notifier(&dropmon_net_notifier);
 379         if (rc < 0) {
 380                 pr_crit("Failed to register netdevice notifier\n");
 381                 goto out_unreg;
 382         }
 383
 384         rc = 0;
 385
 386         for_each_possible_cpu(cpu) {
 387                 data = &per_cpu(dm_cpu_data, cpu);
 388                 INIT_WORK(&data->dm_alert_work, send_dm_alert);
 389                 init_timer(&data->send_timer);
 390                 data->send_timer.data = (unsigned long)data;
 391                 data->send_timer.function = sched_send_work;
 392                 spin_lock_init(&data->lock);
 393                 reset_per_cpu_data(data);
 394         }
 395
 396
 397         goto out;
 398
 399 out_unreg:
 400         genl_unregister_family(&net_drop_monitor_family);
 401 out:
 402         return rc;
 403 }
 404
 405 static void exit_net_drop_monitor(void)
 406 {
 407         struct per_cpu_dm_data *data;
 408         int cpu;
 409
 410         BUG_ON(unregister_netdevice_notifier(&dropmon_net_notifier));
 411
 412         /*
 413          * Because of the module_get/put we do in the trace state change path
 414          * we are guarnateed not to have any current users when we get here
 415          * all we need to do is make sure that we don't have any running timers
 416          * or pending schedule calls
 417          */
 418
 419         for_each_possible_cpu(cpu) {
 420                 data = &per_cpu(dm_cpu_data, cpu);
 421                 del_timer_sync(&data->send_timer);
 422                 cancel_work_sync(&data->dm_alert_work);
 423                 /*
 424                  * At this point, we should have exclusive access
 425                  * to this struct and can free the skb inside it
 426                  */
 427                 kfree_skb(data->skb);
 428         }
 429
 430         BUG_ON(genl_unregister_family(&net_drop_monitor_family));
 431 }
 432
 433 module_init(init_net_drop_monitor);
 434 module_exit(exit_net_drop_monitor);
 435
 436 MODULE_LICENSE("GPL v2");
 437 MODULE_AUTHOR("Neil Horman <nhorman@tuxdriver.com>");
 438 MODULE_ALIAS_GENL_FAMILY("NET_DM");