net/core/drop_monitor.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Monitoring code for network dropped packet alerts
   4  *
   5  * Copyright (C) 2009 Neil Horman <nhorman@tuxdriver.com>
   6  */
   7
   8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   9
  10 #include <linux/netdevice.h>
  11 #include <linux/etherdevice.h>
  12 #include <linux/string.h>
  13 #include <linux/if_arp.h>
  14 #include <linux/inetdevice.h>
  15 #include <linux/inet.h>
  16 #include <linux/interrupt.h>
  17 #include <linux/netpoll.h>
  18 #include <linux/sched.h>
  19 #include <linux/delay.h>
  20 #include <linux/types.h>
  21 #include <linux/workqueue.h>
  22 #include <linux/netlink.h>
  23 #include <linux/net_dropmon.h>
  24 #include <linux/percpu.h>
  25 #include <linux/timer.h>
  26 #include <linux/bitops.h>
  27 #include <linux/slab.h>
  28 #include <linux/module.h>
  29 #include <net/genetlink.h>
  30 #include <net/netevent.h>
  31
  32 #include <trace/events/skb.h>
  33 #include <trace/events/napi.h>
  34
  35 #include <asm/unaligned.h>
  36
  37 #define TRACE_ON 1
  38 #define TRACE_OFF 0
  39
  40 /*
  41  * Globals, our netlink socket pointer
  42  * and the work handle that will send up
  43  * netlink alerts
  44  */
  45 static int trace_state = TRACE_OFF;
  46 static DEFINE_MUTEX(trace_state_mutex);
  47
  48 struct per_cpu_dm_data {
  49         spinlock_t              lock;
  50         struct sk_buff          *skb;
  51         struct work_struct      dm_alert_work;
  52         struct timer_list       send_timer;
  53 };
  54
  55 struct dm_hw_stat_delta {
  56         struct net_device *dev;
  57         unsigned long last_rx;
  58         struct list_head list;
  59         struct rcu_head rcu;
  60         unsigned long last_drop_val;
  61 };
  62
  63 static struct genl_family net_drop_monitor_family;
  64
  65 static DEFINE_PER_CPU(struct per_cpu_dm_data, dm_cpu_data);
  66
  67 static int dm_hit_limit = 64;
  68 static int dm_delay = 1;
  69 static unsigned long dm_hw_check_delta = 2*HZ;
  70 static LIST_HEAD(hw_stats_list);
  71
  72 static struct sk_buff *reset_per_cpu_data(struct per_cpu_dm_data *data)
  73 {
  74         size_t al;
  75         struct net_dm_alert_msg *msg;
  76         struct nlattr *nla;
  77         struct sk_buff *skb;
  78         unsigned long flags;
  79         void *msg_header;
  80
  81         al = sizeof(struct net_dm_alert_msg);
  82         al += dm_hit_limit * sizeof(struct net_dm_drop_point);
  83         al += sizeof(struct nlattr);
  84
  85         skb = genlmsg_new(al, GFP_KERNEL);
  86
  87         if (!skb)
  88                 goto err;
  89
  90         msg_header = genlmsg_put(skb, 0, 0, &net_drop_monitor_family,
  91                                  0, NET_DM_CMD_ALERT);
  92         if (!msg_header) {
  93                 nlmsg_free(skb);
  94                 skb = NULL;
  95                 goto err;
  96         }
  97         nla = nla_reserve(skb, NLA_UNSPEC,
  98                           sizeof(struct net_dm_alert_msg));
  99         if (!nla) {
 100                 nlmsg_free(skb);
 101                 skb = NULL;
 102                 goto err;
 103         }
 104         msg = nla_data(nla);
 105         memset(msg, 0, al);
 106         goto out;
 107
 108 err:
 109         mod_timer(&data->send_timer, jiffies + HZ / 10);
 110 out:
 111         spin_lock_irqsave(&data->lock, flags);
 112         swap(data->skb, skb);
 113         spin_unlock_irqrestore(&data->lock, flags);
 114
 115         if (skb) {
 116                 struct nlmsghdr *nlh = (struct nlmsghdr *)skb->data;
 117                 struct genlmsghdr *gnlh = (struct genlmsghdr *)nlmsg_data(nlh);
 118
 119                 genlmsg_end(skb, genlmsg_data(gnlh));
 120         }
 121
 122         return skb;
 123 }
 124
 125 static const struct genl_multicast_group dropmon_mcgrps[] = {
 126         { .name = "events", },
 127 };
 128
 129 static void send_dm_alert(struct work_struct *work)
 130 {
 131         struct sk_buff *skb;
 132         struct per_cpu_dm_data *data;
 133
 134         data = container_of(work, struct per_cpu_dm_data, dm_alert_work);
 135
 136         skb = reset_per_cpu_data(data);
 137
 138         if (skb)
 139                 genlmsg_multicast(&net_drop_monitor_family, skb, 0,
 140                                   0, GFP_KERNEL);
 141 }
 142
 143 /*
 144  * This is the timer function to delay the sending of an alert
 145  * in the event that more drops will arrive during the
 146  * hysteresis period.
 147  */
 148 static void sched_send_work(struct timer_list *t)
 149 {
 150         struct per_cpu_dm_data *data = from_timer(data, t, send_timer);
 151
 152         schedule_work(&data->dm_alert_work);
 153 }
 154
 155 static void trace_drop_common(struct sk_buff *skb, void *location)
 156 {
 157         struct net_dm_alert_msg *msg;
 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         for (i = 0; i < msg->entries; i++) {
 177                 if (!memcmp(&location, msg->points[i].pc, sizeof(void *))) {
 178                         msg->points[i].count++;
 179                         goto out;
 180                 }
 181         }
 182         if (msg->entries == dm_hit_limit)
 183                 goto out;
 184         /*
 185          * We need to create a new entry
 186          */
 187         __nla_reserve_nohdr(dskb, sizeof(struct net_dm_drop_point));
 188         nla->nla_len += NLA_ALIGN(sizeof(struct net_dm_drop_point));
 189         memcpy(msg->points[msg->entries].pc, &location, sizeof(void *));
 190         msg->points[msg->entries].count = 1;
 191         msg->entries++;
 192
 193         if (!timer_pending(&data->send_timer)) {
 194                 data->send_timer.expires = jiffies + dm_delay * HZ;
 195                 add_timer(&data->send_timer);
 196         }
 197
 198 out:
 199         spin_unlock_irqrestore(&data->lock, flags);
 200 }
 201
 202 static void trace_kfree_skb_hit(void *ignore, struct sk_buff *skb, void *location)
 203 {
 204         trace_drop_common(skb, location);
 205 }
 206
 207 static void trace_napi_poll_hit(void *ignore, struct napi_struct *napi,
 208                                 int work, int budget)
 209 {
 210         struct dm_hw_stat_delta *new_stat;
 211
 212         /*
 213          * Don't check napi structures with no associated device
 214          */
 215         if (!napi->dev)
 216                 return;
 217
 218         rcu_read_lock();
 219         list_for_each_entry_rcu(new_stat, &hw_stats_list, list) {
 220                 /*
 221                  * only add a note to our monitor buffer if:
 222                  * 1) this is the dev we received on
 223                  * 2) its after the last_rx delta
 224                  * 3) our rx_dropped count has gone up
 225                  */
 226                 if ((new_stat->dev == napi->dev)  &&
 227                     (time_after(jiffies, new_stat->last_rx + dm_hw_check_delta)) &&
 228                     (napi->dev->stats.rx_dropped != new_stat->last_drop_val)) {
 229                         trace_drop_common(NULL, NULL);
 230                         new_stat->last_drop_val = napi->dev->stats.rx_dropped;
 231                         new_stat->last_rx = jiffies;
 232                         break;
 233                 }
 234         }
 235         rcu_read_unlock();
 236 }
 237
 238 static int set_all_monitor_traces(int state)
 239 {
 240         int rc = 0;
 241         struct dm_hw_stat_delta *new_stat = NULL;
 242         struct dm_hw_stat_delta *temp;
 243
 244         mutex_lock(&trace_state_mutex);
 245
 246         if (state == trace_state) {
 247                 rc = -EAGAIN;
 248                 goto out_unlock;
 249         }
 250
 251         switch (state) {
 252         case TRACE_ON:
 253                 if (!try_module_get(THIS_MODULE)) {
 254                         rc = -ENODEV;
 255                         break;
 256                 }
 257
 258                 rc |= register_trace_kfree_skb(trace_kfree_skb_hit, NULL);
 259                 rc |= register_trace_napi_poll(trace_napi_poll_hit, NULL);
 260                 break;
 261
 262         case TRACE_OFF:
 263                 rc |= unregister_trace_kfree_skb(trace_kfree_skb_hit, NULL);
 264                 rc |= unregister_trace_napi_poll(trace_napi_poll_hit, NULL);
 265
 266                 tracepoint_synchronize_unregister();
 267
 268                 /*
 269                  * Clean the device list
 270                  */
 271                 list_for_each_entry_safe(new_stat, temp, &hw_stats_list, list) {
 272                         if (new_stat->dev == NULL) {
 273                                 list_del_rcu(&new_stat->list);
 274                                 kfree_rcu(new_stat, rcu);
 275                         }
 276                 }
 277
 278                 module_put(THIS_MODULE);
 279
 280                 break;
 281         default:
 282                 rc = 1;
 283                 break;
 284         }
 285
 286         if (!rc)
 287                 trace_state = state;
 288         else
 289                 rc = -EINPROGRESS;
 290
 291 out_unlock:
 292         mutex_unlock(&trace_state_mutex);
 293
 294         return rc;
 295 }
 296
 297
 298 static int net_dm_cmd_config(struct sk_buff *skb,
 299                         struct genl_info *info)
 300 {
 301         return -ENOTSUPP;
 302 }
 303
 304 static int net_dm_cmd_trace(struct sk_buff *skb,
 305                         struct genl_info *info)
 306 {
 307         switch (info->genlhdr->cmd) {
 308         case NET_DM_CMD_START:
 309                 return set_all_monitor_traces(TRACE_ON);
 310         case NET_DM_CMD_STOP:
 311                 return set_all_monitor_traces(TRACE_OFF);
 312         }
 313
 314         return -ENOTSUPP;
 315 }
 316
 317 static int dropmon_net_event(struct notifier_block *ev_block,
 318                              unsigned long event, void *ptr)
 319 {
 320         struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 321         struct dm_hw_stat_delta *new_stat = NULL;
 322         struct dm_hw_stat_delta *tmp;
 323
 324         switch (event) {
 325         case NETDEV_REGISTER:
 326                 new_stat = kzalloc(sizeof(struct dm_hw_stat_delta), GFP_KERNEL);
 327
 328                 if (!new_stat)
 329                         goto out;
 330
 331                 new_stat->dev = dev;
 332                 new_stat->last_rx = jiffies;
 333                 mutex_lock(&trace_state_mutex);
 334                 list_add_rcu(&new_stat->list, &hw_stats_list);
 335                 mutex_unlock(&trace_state_mutex);
 336                 break;
 337         case NETDEV_UNREGISTER:
 338                 mutex_lock(&trace_state_mutex);
 339                 list_for_each_entry_safe(new_stat, tmp, &hw_stats_list, list) {
 340                         if (new_stat->dev == dev) {
 341                                 new_stat->dev = NULL;
 342                                 if (trace_state == TRACE_OFF) {
 343                                         list_del_rcu(&new_stat->list);
 344                                         kfree_rcu(new_stat, rcu);
 345                                         break;
 346                                 }
 347                         }
 348                 }
 349                 mutex_unlock(&trace_state_mutex);
 350                 break;
 351         }
 352 out:
 353         return NOTIFY_DONE;
 354 }
 355
 356 static const struct genl_ops dropmon_ops[] = {
 357         {
 358                 .cmd = NET_DM_CMD_CONFIG,
 359                 .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
 360                 .doit = net_dm_cmd_config,
 361         },
 362         {
 363                 .cmd = NET_DM_CMD_START,
 364                 .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
 365                 .doit = net_dm_cmd_trace,
 366         },
 367         {
 368                 .cmd = NET_DM_CMD_STOP,
 369                 .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
 370                 .doit = net_dm_cmd_trace,
 371         },
 372 };
 373
 374 static struct genl_family net_drop_monitor_family __ro_after_init = {
 375         .hdrsize        = 0,
 376         .name           = "NET_DM",
 377         .version        = 2,
 378         .module         = THIS_MODULE,
 379         .ops            = dropmon_ops,
 380         .n_ops          = ARRAY_SIZE(dropmon_ops),
 381         .mcgrps         = dropmon_mcgrps,
 382         .n_mcgrps       = ARRAY_SIZE(dropmon_mcgrps),
 383 };
 384
 385 static struct notifier_block dropmon_net_notifier = {
 386         .notifier_call = dropmon_net_event
 387 };
 388
 389 static int __init init_net_drop_monitor(void)
 390 {
 391         struct per_cpu_dm_data *data;
 392         int cpu, rc;
 393
 394         pr_info("Initializing network drop monitor service\n");
 395
 396         if (sizeof(void *) > 8) {
 397                 pr_err("Unable to store program counters on this arch, Drop monitor failed\n");
 398                 return -ENOSPC;
 399         }
 400
 401         rc = genl_register_family(&net_drop_monitor_family);
 402         if (rc) {
 403                 pr_err("Could not create drop monitor netlink family\n");
 404                 return rc;
 405         }
 406         WARN_ON(net_drop_monitor_family.mcgrp_offset != NET_DM_GRP_ALERT);
 407
 408         rc = register_netdevice_notifier(&dropmon_net_notifier);
 409         if (rc < 0) {
 410                 pr_crit("Failed to register netdevice notifier\n");
 411                 goto out_unreg;
 412         }
 413
 414         rc = 0;
 415
 416         for_each_possible_cpu(cpu) {
 417                 data = &per_cpu(dm_cpu_data, cpu);
 418                 INIT_WORK(&data->dm_alert_work, send_dm_alert);
 419                 timer_setup(&data->send_timer, sched_send_work, 0);
 420                 spin_lock_init(&data->lock);
 421                 reset_per_cpu_data(data);
 422         }
 423
 424
 425         goto out;
 426
 427 out_unreg:
 428         genl_unregister_family(&net_drop_monitor_family);
 429 out:
 430         return rc;
 431 }
 432
 433 static void exit_net_drop_monitor(void)
 434 {
 435         struct per_cpu_dm_data *data;
 436         int cpu;
 437
 438         BUG_ON(unregister_netdevice_notifier(&dropmon_net_notifier));
 439
 440         /*
 441          * Because of the module_get/put we do in the trace state change path
 442          * we are guarnateed not to have any current users when we get here
 443          * all we need to do is make sure that we don't have any running timers
 444          * or pending schedule calls
 445          */
 446
 447         for_each_possible_cpu(cpu) {
 448                 data = &per_cpu(dm_cpu_data, cpu);
 449                 del_timer_sync(&data->send_timer);
 450                 cancel_work_sync(&data->dm_alert_work);
 451                 /*
 452                  * At this point, we should have exclusive access
 453                  * to this struct and can free the skb inside it
 454                  */
 455                 kfree_skb(data->skb);
 456         }
 457
 458         BUG_ON(genl_unregister_family(&net_drop_monitor_family));
 459 }
 460
 461 module_init(init_net_drop_monitor);
 462 module_exit(exit_net_drop_monitor);
 463
 464 MODULE_LICENSE("GPL v2");
 465 MODULE_AUTHOR("Neil Horman <nhorman@tuxdriver.com>");
 466 MODULE_ALIAS_GENL_FAMILY("NET_DM");