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
  64 static DEFINE_PER_CPU(struct per_cpu_dm_data, dm_cpu_data);
  65
  66 static int dm_hit_limit = 64;
  67 static int dm_delay = 1;
  68 static unsigned long dm_hw_check_delta = 2*HZ;
  69 static LIST_HEAD(hw_stats_list);
  70
  71 static struct sk_buff *reset_per_cpu_data(struct per_cpu_dm_data *data)
  72 {
  73         size_t al;
  74         struct net_dm_alert_msg *msg;
  75         struct nlattr *nla;
  76         struct sk_buff *skb;
  77         unsigned long flags;
  78         void *msg_header;
  79
  80         al = sizeof(struct net_dm_alert_msg);
  81         al += dm_hit_limit * sizeof(struct net_dm_drop_point);
  82         al += sizeof(struct nlattr);
  83
  84         skb = genlmsg_new(al, GFP_KERNEL);
  85
  86         if (!skb)
  87                 goto err;
  88
  89         msg_header = genlmsg_put(skb, 0, 0, &net_drop_monitor_family,
  90                                  0, NET_DM_CMD_ALERT);
  91         if (!msg_header) {
  92                 nlmsg_free(skb);
  93                 skb = NULL;
  94                 goto err;
  95         }
  96         nla = nla_reserve(skb, NLA_UNSPEC,
  97                           sizeof(struct net_dm_alert_msg));
  98         if (!nla) {
  99                 nlmsg_free(skb);
 100                 skb = NULL;
 101                 goto err;
 102         }
 103         msg = nla_data(nla);
 104         memset(msg, 0, al);
 105         goto out;
 106
 107 err:
 108         mod_timer(&data->send_timer, jiffies + HZ / 10);
 109 out:
 110         spin_lock_irqsave(&data->lock, flags);
 111         swap(data->skb, skb);
 112         spin_unlock_irqrestore(&data->lock, flags);
 113
 114         if (skb) {
 115                 struct nlmsghdr *nlh = (struct nlmsghdr *)skb->data;
 116                 struct genlmsghdr *gnlh = (struct genlmsghdr *)nlmsg_data(nlh);
 117
 118                 genlmsg_end(skb, genlmsg_data(gnlh));
 119         }
 120
 121         return skb;
 122 }
 123
 124 static const struct genl_multicast_group dropmon_mcgrps[] = {
 125         { .name = "events", .cap_sys_admin = 1 },
 126 };
 127
 128 static void send_dm_alert(struct work_struct *work)
 129 {
 130         struct sk_buff *skb;
 131         struct per_cpu_dm_data *data;
 132
 133         data = container_of(work, struct per_cpu_dm_data, dm_alert_work);
 134
 135         skb = reset_per_cpu_data(data);
 136
 137         if (skb)
 138                 genlmsg_multicast(&net_drop_monitor_family, skb, 0,
 139                                   0, GFP_KERNEL);
 140 }
 141
 142 /*
 143  * This is the timer function to delay the sending of an alert
 144  * in the event that more drops will arrive during the
 145  * hysteresis period.
 146  */
 147 static void sched_send_work(struct timer_list *t)
 148 {
 149         struct per_cpu_dm_data *data = from_timer(data, t, send_timer);
 150
 151         schedule_work(&data->dm_alert_work);
 152 }
 153
 154 static void trace_drop_common(struct sk_buff *skb, void *location)
 155 {
 156         struct net_dm_alert_msg *msg;
 157         struct net_dm_drop_point *point;
 158         struct nlmsghdr *nlh;
 159         struct nlattr *nla;
 160         int i;
 161         struct sk_buff *dskb;
 162         struct per_cpu_dm_data *data;
 163         unsigned long flags;
 164
 165         local_irq_save(flags);
 166         data = this_cpu_ptr(&dm_cpu_data);
 167         spin_lock(&data->lock);
 168         dskb = data->skb;
 169
 170         if (!dskb)
 171                 goto out;
 172
 173         nlh = (struct nlmsghdr *)dskb->data;
 174         nla = genlmsg_data(nlmsg_data(nlh));
 175         msg = nla_data(nla);
 176         point = msg->points;
 177         for (i = 0; i < msg->entries; i++) {
 178                 if (!memcmp(&location, &point->pc, sizeof(void *))) {
 179                         point->count++;
 180                         goto out;
 181                 }
 182                 point++;
 183         }
 184         if (msg->entries == dm_hit_limit)
 185                 goto out;
 186         /*
 187          * We need to create a new entry
 188          */
 189         __nla_reserve_nohdr(dskb, sizeof(struct net_dm_drop_point));
 190         nla->nla_len += NLA_ALIGN(sizeof(struct net_dm_drop_point));
 191         memcpy(point->pc, &location, sizeof(void *));
 192         point->count = 1;
 193         msg->entries++;
 194
 195         if (!timer_pending(&data->send_timer)) {
 196                 data->send_timer.expires = jiffies + dm_delay * HZ;
 197                 add_timer(&data->send_timer);
 198         }
 199
 200 out:
 201         spin_unlock_irqrestore(&data->lock, flags);
 202 }
 203
 204 static void trace_kfree_skb_hit(void *ignore, struct sk_buff *skb, void *location)
 205 {
 206         trace_drop_common(skb, location);
 207 }
 208
 209 static void trace_napi_poll_hit(void *ignore, struct napi_struct *napi,
 210                                 int work, int budget)
 211 {
 212         struct dm_hw_stat_delta *new_stat;
 213
 214         /*
 215          * Don't check napi structures with no associated device
 216          */
 217         if (!napi->dev)
 218                 return;
 219
 220         rcu_read_lock();
 221         list_for_each_entry_rcu(new_stat, &hw_stats_list, list) {
 222                 struct net_device *dev;
 223
 224                 /*
 225                  * only add a note to our monitor buffer if:
 226                  * 1) this is the dev we received on
 227                  * 2) its after the last_rx delta
 228                  * 3) our rx_dropped count has gone up
 229                  */
 230                 /* Paired with WRITE_ONCE() in dropmon_net_event() */
 231                 dev = READ_ONCE(new_stat->dev);
 232                 if ((dev == napi->dev)  &&
 233                     (time_after(jiffies, new_stat->last_rx + dm_hw_check_delta)) &&
 234                     (napi->dev->stats.rx_dropped != new_stat->last_drop_val)) {
 235                         trace_drop_common(NULL, NULL);
 236                         new_stat->last_drop_val = napi->dev->stats.rx_dropped;
 237                         new_stat->last_rx = jiffies;
 238                         break;
 239                 }
 240         }
 241         rcu_read_unlock();
 242 }
 243
 244 static int set_all_monitor_traces(int state)
 245 {
 246         int rc = 0;
 247         struct dm_hw_stat_delta *new_stat = NULL;
 248         struct dm_hw_stat_delta *temp;
 249
 250         mutex_lock(&trace_state_mutex);
 251
 252         if (state == trace_state) {
 253                 rc = -EAGAIN;
 254                 goto out_unlock;
 255         }
 256
 257         switch (state) {
 258         case TRACE_ON:
 259                 if (!try_module_get(THIS_MODULE)) {
 260                         rc = -ENODEV;
 261                         break;
 262                 }
 263
 264                 rc |= register_trace_kfree_skb(trace_kfree_skb_hit, NULL);
 265                 rc |= register_trace_napi_poll(trace_napi_poll_hit, NULL);
 266                 break;
 267
 268         case TRACE_OFF:
 269                 rc |= unregister_trace_kfree_skb(trace_kfree_skb_hit, NULL);
 270                 rc |= unregister_trace_napi_poll(trace_napi_poll_hit, NULL);
 271
 272                 tracepoint_synchronize_unregister();
 273
 274                 /*
 275                  * Clean the device list
 276                  */
 277                 list_for_each_entry_safe(new_stat, temp, &hw_stats_list, list) {
 278                         if (new_stat->dev == NULL) {
 279                                 list_del_rcu(&new_stat->list);
 280                                 kfree_rcu(new_stat, rcu);
 281                         }
 282                 }
 283
 284                 module_put(THIS_MODULE);
 285
 286                 break;
 287         default:
 288                 rc = 1;
 289                 break;
 290         }
 291
 292         if (!rc)
 293                 trace_state = state;
 294         else
 295                 rc = -EINPROGRESS;
 296
 297 out_unlock:
 298         mutex_unlock(&trace_state_mutex);
 299
 300         return rc;
 301 }
 302
 303
 304 static int net_dm_cmd_config(struct sk_buff *skb,
 305                         struct genl_info *info)
 306 {
 307         return -ENOTSUPP;
 308 }
 309
 310 static int net_dm_cmd_trace(struct sk_buff *skb,
 311                         struct genl_info *info)
 312 {
 313         switch (info->genlhdr->cmd) {
 314         case NET_DM_CMD_START:
 315                 return set_all_monitor_traces(TRACE_ON);
 316         case NET_DM_CMD_STOP:
 317                 return set_all_monitor_traces(TRACE_OFF);
 318         }
 319
 320         return -ENOTSUPP;
 321 }
 322
 323 static int dropmon_net_event(struct notifier_block *ev_block,
 324                              unsigned long event, void *ptr)
 325 {
 326         struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 327         struct dm_hw_stat_delta *new_stat = NULL;
 328         struct dm_hw_stat_delta *tmp;
 329
 330         switch (event) {
 331         case NETDEV_REGISTER:
 332                 new_stat = kzalloc(sizeof(struct dm_hw_stat_delta), GFP_KERNEL);
 333
 334                 if (!new_stat)
 335                         goto out;
 336
 337                 new_stat->dev = dev;
 338                 new_stat->last_rx = jiffies;
 339                 mutex_lock(&trace_state_mutex);
 340                 list_add_rcu(&new_stat->list, &hw_stats_list);
 341                 mutex_unlock(&trace_state_mutex);
 342                 break;
 343         case NETDEV_UNREGISTER:
 344                 mutex_lock(&trace_state_mutex);
 345                 list_for_each_entry_safe(new_stat, tmp, &hw_stats_list, list) {
 346                         if (new_stat->dev == dev) {
 347
 348                                 /* Paired with READ_ONCE() in trace_napi_poll_hit() */
 349                                 WRITE_ONCE(new_stat->dev, NULL);
 350
 351                                 if (trace_state == TRACE_OFF) {
 352                                         list_del_rcu(&new_stat->list);
 353                                         kfree_rcu(new_stat, rcu);
 354                                         break;
 355                                 }
 356                         }
 357                 }
 358                 mutex_unlock(&trace_state_mutex);
 359                 break;
 360         }
 361 out:
 362         return NOTIFY_DONE;
 363 }
 364
 365 static const struct genl_ops dropmon_ops[] = {
 366         {
 367                 .cmd = NET_DM_CMD_CONFIG,
 368                 .doit = net_dm_cmd_config,
 369         },
 370         {
 371                 .cmd = NET_DM_CMD_START,
 372                 .doit = net_dm_cmd_trace,
 373                 .flags = GENL_ADMIN_PERM,
 374         },
 375         {
 376                 .cmd = NET_DM_CMD_STOP,
 377                 .doit = net_dm_cmd_trace,
 378                 .flags = GENL_ADMIN_PERM,
 379         },
 380 };
 381
 382 static struct genl_family net_drop_monitor_family __ro_after_init = {
 383         .hdrsize        = 0,
 384         .name           = "NET_DM",
 385         .version        = 2,
 386         .module         = THIS_MODULE,
 387         .ops            = dropmon_ops,
 388         .n_ops          = ARRAY_SIZE(dropmon_ops),
 389         .mcgrps         = dropmon_mcgrps,
 390         .n_mcgrps       = ARRAY_SIZE(dropmon_mcgrps),
 391 };
 392
 393 static struct notifier_block dropmon_net_notifier = {
 394         .notifier_call = dropmon_net_event
 395 };
 396
 397 static int __init init_net_drop_monitor(void)
 398 {
 399         struct per_cpu_dm_data *data;
 400         int cpu, rc;
 401
 402         pr_info("Initializing network drop monitor service\n");
 403
 404         if (sizeof(void *) > 8) {
 405                 pr_err("Unable to store program counters on this arch, Drop monitor failed\n");
 406                 return -ENOSPC;
 407         }
 408
 409         rc = genl_register_family(&net_drop_monitor_family);
 410         if (rc) {
 411                 pr_err("Could not create drop monitor netlink family\n");
 412                 return rc;
 413         }
 414         WARN_ON(net_drop_monitor_family.mcgrp_offset != NET_DM_GRP_ALERT);
 415
 416         rc = register_netdevice_notifier(&dropmon_net_notifier);
 417         if (rc < 0) {
 418                 pr_crit("Failed to register netdevice notifier\n");
 419                 goto out_unreg;
 420         }
 421
 422         rc = 0;
 423
 424         for_each_possible_cpu(cpu) {
 425                 data = &per_cpu(dm_cpu_data, cpu);
 426                 INIT_WORK(&data->dm_alert_work, send_dm_alert);
 427                 timer_setup(&data->send_timer, sched_send_work, 0);
 428                 spin_lock_init(&data->lock);
 429                 reset_per_cpu_data(data);
 430         }
 431
 432
 433         goto out;
 434
 435 out_unreg:
 436         genl_unregister_family(&net_drop_monitor_family);
 437 out:
 438         return rc;
 439 }
 440
 441 static void exit_net_drop_monitor(void)
 442 {
 443         struct per_cpu_dm_data *data;
 444         int cpu;
 445
 446         BUG_ON(unregister_netdevice_notifier(&dropmon_net_notifier));
 447
 448         /*
 449          * Because of the module_get/put we do in the trace state change path
 450          * we are guarnateed not to have any current users when we get here
 451          * all we need to do is make sure that we don't have any running timers
 452          * or pending schedule calls
 453          */
 454
 455         for_each_possible_cpu(cpu) {
 456                 data = &per_cpu(dm_cpu_data, cpu);
 457                 del_timer_sync(&data->send_timer);
 458                 cancel_work_sync(&data->dm_alert_work);
 459                 /*
 460                  * At this point, we should have exclusive access
 461                  * to this struct and can free the skb inside it
 462                  */
 463                 kfree_skb(data->skb);
 464         }
 465
 466         BUG_ON(genl_unregister_family(&net_drop_monitor_family));
 467 }
 468
 469 module_init(init_net_drop_monitor);
 470 module_exit(exit_net_drop_monitor);
 471
 472 MODULE_LICENSE("GPL v2");
 473 MODULE_AUTHOR("Neil Horman <nhorman@tuxdriver.com>");
 474 MODULE_ALIAS_GENL_FAMILY("NET_DM");