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