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