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         .maxattr        = NET_DM_CMD_MAX,
  68 };
  69
  70 static DEFINE_PER_CPU(struct per_cpu_dm_data, dm_cpu_data);
  71
  72 static int dm_hit_limit = 64;
  73 static int dm_delay = 1;
  74 static unsigned long dm_hw_check_delta = 2*HZ;
  75 static LIST_HEAD(hw_stats_list);
  76
  77 static struct sk_buff *reset_per_cpu_data(struct per_cpu_dm_data *data)
  78 {
  79         size_t al;
  80         struct net_dm_alert_msg *msg;
  81         struct nlattr *nla;
  82         struct sk_buff *skb;
  83         unsigned long flags;
  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                 genlmsg_put(skb, 0, 0, &net_drop_monitor_family,
  93                                 0, NET_DM_CMD_ALERT);
  94                 nla = nla_reserve(skb, NLA_UNSPEC,
  95                                   sizeof(struct net_dm_alert_msg));
  96                 msg = nla_data(nla);
  97                 memset(msg, 0, al);
  98         } else {
  99                 mod_timer(&data->send_timer, jiffies + HZ / 10);
 100         }
 101
 102         spin_lock_irqsave(&data->lock, flags);
 103         swap(data->skb, skb);
 104         spin_unlock_irqrestore(&data->lock, flags);
 105
 106         return skb;
 107 }
 108
 109 static struct genl_multicast_group dm_mcgrp = {
 110         .name = "events",
 111 };
 112
 113 static void send_dm_alert(struct work_struct *work)
 114 {
 115         struct sk_buff *skb;
 116         struct per_cpu_dm_data *data;
 117
 118         data = container_of(work, struct per_cpu_dm_data, dm_alert_work);
 119
 120         skb = reset_per_cpu_data(data);
 121
 122         if (skb)
 123                 genlmsg_multicast(&net_drop_monitor_family, skb, 0,
 124                                   dm_mcgrp.id, GFP_KERNEL);
 125 }
 126
 127 /*
 128  * This is the timer function to delay the sending of an alert
 129  * in the event that more drops will arrive during the
 130  * hysteresis period.
 131  */
 132 static void sched_send_work(unsigned long _data)
 133 {
 134         struct per_cpu_dm_data *data = (struct per_cpu_dm_data *)_data;
 135
 136         schedule_work(&data->dm_alert_work);
 137 }
 138
 139 static void trace_drop_common(struct sk_buff *skb, void *location)
 140 {
 141         struct net_dm_alert_msg *msg;
 142         struct nlmsghdr *nlh;
 143         struct nlattr *nla;
 144         int i;
 145         struct sk_buff *dskb;
 146         struct per_cpu_dm_data *data;
 147         unsigned long flags;
 148
 149         local_irq_save(flags);
 150         data = &__get_cpu_var(dm_cpu_data);
 151         spin_lock(&data->lock);
 152         dskb = data->skb;
 153
 154         if (!dskb)
 155                 goto out;
 156
 157         nlh = (struct nlmsghdr *)dskb->data;
 158         nla = genlmsg_data(nlmsg_data(nlh));
 159         msg = nla_data(nla);
 160         for (i = 0; i < msg->entries; i++) {
 161                 if (!memcmp(&location, msg->points[i].pc, sizeof(void *))) {
 162                         msg->points[i].count++;
 163                         goto out;
 164                 }
 165         }
 166         if (msg->entries == dm_hit_limit)
 167                 goto out;
 168         /*
 169          * We need to create a new entry
 170          */
 171         __nla_reserve_nohdr(dskb, sizeof(struct net_dm_drop_point));
 172         nla->nla_len += NLA_ALIGN(sizeof(struct net_dm_drop_point));
 173         memcpy(msg->points[msg->entries].pc, &location, sizeof(void *));
 174         msg->points[msg->entries].count = 1;
 175         msg->entries++;
 176
 177         if (!timer_pending(&data->send_timer)) {
 178                 data->send_timer.expires = jiffies + dm_delay * HZ;
 179                 add_timer(&data->send_timer);
 180         }
 181
 182 out:
 183         spin_unlock_irqrestore(&data->lock, flags);
 184 }
 185
 186 static void trace_kfree_skb_hit(void *ignore, struct sk_buff *skb, void *location)
 187 {
 188         trace_drop_common(skb, location);
 189 }
 190
 191 static void trace_napi_poll_hit(void *ignore, struct napi_struct *napi)
 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                 break;
 294         case NET_DM_CMD_STOP:
 295                 return set_all_monitor_traces(TRACE_OFF);
 296                 break;
 297         }
 298
 299         return -ENOTSUPP;
 300 }
 301
 302 static int dropmon_net_event(struct notifier_block *ev_block,
 303                              unsigned long event, void *ptr)
 304 {
 305         struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 306         struct dm_hw_stat_delta *new_stat = NULL;
 307         struct dm_hw_stat_delta *tmp;
 308
 309         switch (event) {
 310         case NETDEV_REGISTER:
 311                 new_stat = kzalloc(sizeof(struct dm_hw_stat_delta), GFP_KERNEL);
 312
 313                 if (!new_stat)
 314                         goto out;
 315
 316                 new_stat->dev = dev;
 317                 new_stat->last_rx = jiffies;
 318                 mutex_lock(&trace_state_mutex);
 319                 list_add_rcu(&new_stat->list, &hw_stats_list);
 320                 mutex_unlock(&trace_state_mutex);
 321                 break;
 322         case NETDEV_UNREGISTER:
 323                 mutex_lock(&trace_state_mutex);
 324                 list_for_each_entry_safe(new_stat, tmp, &hw_stats_list, list) {
 325                         if (new_stat->dev == dev) {
 326                                 new_stat->dev = NULL;
 327                                 if (trace_state == TRACE_OFF) {
 328                                         list_del_rcu(&new_stat->list);
 329                                         kfree_rcu(new_stat, rcu);
 330                                         break;
 331                                 }
 332                         }
 333                 }
 334                 mutex_unlock(&trace_state_mutex);
 335                 break;
 336         }
 337 out:
 338         return NOTIFY_DONE;
 339 }
 340
 341 static const struct genl_ops dropmon_ops[] = {
 342         {
 343                 .cmd = NET_DM_CMD_CONFIG,
 344                 .doit = net_dm_cmd_config,
 345         },
 346         {
 347                 .cmd = NET_DM_CMD_START,
 348                 .doit = net_dm_cmd_trace,
 349         },
 350         {
 351                 .cmd = NET_DM_CMD_STOP,
 352                 .doit = net_dm_cmd_trace,
 353         },
 354 };
 355
 356 static struct notifier_block dropmon_net_notifier = {
 357         .notifier_call = dropmon_net_event
 358 };
 359
 360 static int __init init_net_drop_monitor(void)
 361 {
 362         struct per_cpu_dm_data *data;
 363         int cpu, rc;
 364
 365         pr_info("Initializing network drop monitor service\n");
 366
 367         if (sizeof(void *) > 8) {
 368                 pr_err("Unable to store program counters on this arch, Drop monitor failed\n");
 369                 return -ENOSPC;
 370         }
 371
 372         rc = genl_register_family_with_ops(&net_drop_monitor_family,
 373                                            dropmon_ops);
 374         if (rc) {
 375                 pr_err("Could not create drop monitor netlink family\n");
 376                 return rc;
 377         }
 378
 379         rc = genl_register_mc_group(&net_drop_monitor_family, &dm_mcgrp);
 380         if (rc) {
 381                 pr_err("Failed to register drop monitor mcast group\n");
 382                 goto out_unreg;
 383         }
 384         WARN_ON(dm_mcgrp.id != NET_DM_GRP_ALERT);
 385
 386         rc = register_netdevice_notifier(&dropmon_net_notifier);
 387         if (rc < 0) {
 388                 pr_crit("Failed to register netdevice notifier\n");
 389                 goto out_unreg;
 390         }
 391
 392         rc = 0;
 393
 394         for_each_possible_cpu(cpu) {
 395                 data = &per_cpu(dm_cpu_data, cpu);
 396                 INIT_WORK(&data->dm_alert_work, send_dm_alert);
 397                 init_timer(&data->send_timer);
 398                 data->send_timer.data = (unsigned long)data;
 399                 data->send_timer.function = sched_send_work;
 400                 spin_lock_init(&data->lock);
 401                 reset_per_cpu_data(data);
 402         }
 403
 404
 405         goto out;
 406
 407 out_unreg:
 408         genl_unregister_family(&net_drop_monitor_family);
 409 out:
 410         return rc;
 411 }
 412
 413 static void exit_net_drop_monitor(void)
 414 {
 415         struct per_cpu_dm_data *data;
 416         int cpu;
 417
 418         BUG_ON(unregister_netdevice_notifier(&dropmon_net_notifier));
 419
 420         /*
 421          * Because of the module_get/put we do in the trace state change path
 422          * we are guarnateed not to have any current users when we get here
 423          * all we need to do is make sure that we don't have any running timers
 424          * or pending schedule calls
 425          */
 426
 427         for_each_possible_cpu(cpu) {
 428                 data = &per_cpu(dm_cpu_data, cpu);
 429                 del_timer_sync(&data->send_timer);
 430                 cancel_work_sync(&data->dm_alert_work);
 431                 /*
 432                  * At this point, we should have exclusive access
 433                  * to this struct and can free the skb inside it
 434                  */
 435                 kfree_skb(data->skb);
 436         }
 437
 438         BUG_ON(genl_unregister_family(&net_drop_monitor_family));
 439 }
 440
 441 module_init(init_net_drop_monitor);
 442 module_exit(exit_net_drop_monitor);
 443
 444 MODULE_LICENSE("GPL v2");
 445 MODULE_AUTHOR("Neil Horman <nhorman@tuxdriver.com>");
 446 MODULE_ALIAS_GENL_FAMILY("NET_DM");