net/core/link_watch.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Linux network device link state notification
   4  *
   5  * Author:
   6  *     Stefan Rompf <sux@loplof.de>
   7  */
   8
   9 #include <linux/module.h>
  10 #include <linux/netdevice.h>
  11 #include <linux/if.h>
  12 #include <net/sock.h>
  13 #include <net/pkt_sched.h>
  14 #include <linux/rtnetlink.h>
  15 #include <linux/jiffies.h>
  16 #include <linux/spinlock.h>
  17 #include <linux/workqueue.h>
  18 #include <linux/bitops.h>
  19 #include <linux/types.h>
  20
  21
  22 enum lw_bits {
  23         LW_URGENT = 0,
  24 };
  25
  26 static unsigned long linkwatch_flags;
  27 static unsigned long linkwatch_nextevent;
  28
  29 static void linkwatch_event(struct work_struct *dummy);
  30 static DECLARE_DELAYED_WORK(linkwatch_work, linkwatch_event);
  31
  32 static LIST_HEAD(lweventlist);
  33 static DEFINE_SPINLOCK(lweventlist_lock);
  34
  35 static unsigned char default_operstate(const struct net_device *dev)
  36 {
  37         if (netif_testing(dev))
  38                 return IF_OPER_TESTING;
  39
  40         if (!netif_carrier_ok(dev))
  41                 return (dev->ifindex != dev_get_iflink(dev) ?
  42                         IF_OPER_LOWERLAYERDOWN : IF_OPER_DOWN);
  43
  44         if (netif_dormant(dev))
  45                 return IF_OPER_DORMANT;
  46
  47         return IF_OPER_UP;
  48 }
  49
  50
  51 static void rfc2863_policy(struct net_device *dev)
  52 {
  53         unsigned char operstate = default_operstate(dev);
  54
  55         if (operstate == dev->operstate)
  56                 return;
  57
  58         write_lock(&dev_base_lock);
  59
  60         switch(dev->link_mode) {
  61         case IF_LINK_MODE_TESTING:
  62                 if (operstate == IF_OPER_UP)
  63                         operstate = IF_OPER_TESTING;
  64                 break;
  65
  66         case IF_LINK_MODE_DORMANT:
  67                 if (operstate == IF_OPER_UP)
  68                         operstate = IF_OPER_DORMANT;
  69                 break;
  70         case IF_LINK_MODE_DEFAULT:
  71         default:
  72                 break;
  73         }
  74
  75         dev->operstate = operstate;
  76
  77         write_unlock(&dev_base_lock);
  78 }
  79
  80
  81 void linkwatch_init_dev(struct net_device *dev)
  82 {
  83         /* Handle pre-registration link state changes */
  84         if (!netif_carrier_ok(dev) || netif_dormant(dev) ||
  85             netif_testing(dev))
  86                 rfc2863_policy(dev);
  87 }
  88
  89
  90 static bool linkwatch_urgent_event(struct net_device *dev)
  91 {
  92         if (!netif_running(dev))
  93                 return false;
  94
  95         if (dev->ifindex != dev_get_iflink(dev))
  96                 return true;
  97
  98         if (netif_is_lag_port(dev) || netif_is_lag_master(dev))
  99                 return true;
 100
 101         return netif_carrier_ok(dev) && qdisc_tx_changing(dev);
 102 }
 103
 104
 105 static void linkwatch_add_event(struct net_device *dev)
 106 {
 107         unsigned long flags;
 108
 109         spin_lock_irqsave(&lweventlist_lock, flags);
 110         if (list_empty(&dev->link_watch_list)) {
 111                 list_add_tail(&dev->link_watch_list, &lweventlist);
 112                 dev_hold_track(dev, &dev->linkwatch_dev_tracker, GFP_ATOMIC);
 113         }
 114         spin_unlock_irqrestore(&lweventlist_lock, flags);
 115 }
 116
 117
 118 static void linkwatch_schedule_work(int urgent)
 119 {
 120         unsigned long delay = linkwatch_nextevent - jiffies;
 121
 122         if (test_bit(LW_URGENT, &linkwatch_flags))
 123                 return;
 124
 125         /* Minimise down-time: drop delay for up event. */
 126         if (urgent) {
 127                 if (test_and_set_bit(LW_URGENT, &linkwatch_flags))
 128                         return;
 129                 delay = 0;
 130         }
 131
 132         /* If we wrap around we'll delay it by at most HZ. */
 133         if (delay > HZ)
 134                 delay = 0;
 135
 136         /*
 137          * If urgent, schedule immediate execution; otherwise, don't
 138          * override the existing timer.
 139          */
 140         if (test_bit(LW_URGENT, &linkwatch_flags))
 141                 mod_delayed_work(system_wq, &linkwatch_work, 0);
 142         else
 143                 schedule_delayed_work(&linkwatch_work, delay);
 144 }
 145
 146
 147 static void linkwatch_do_dev(struct net_device *dev)
 148 {
 149         /*
 150          * Make sure the above read is complete since it can be
 151          * rewritten as soon as we clear the bit below.
 152          */
 153         smp_mb__before_atomic();
 154
 155         /* We are about to handle this device,
 156          * so new events can be accepted
 157          */
 158         clear_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state);
 159
 160         rfc2863_policy(dev);
 161         if (dev->flags & IFF_UP) {
 162                 if (netif_carrier_ok(dev))
 163                         dev_activate(dev);
 164                 else
 165                         dev_deactivate(dev);
 166
 167                 netdev_state_change(dev);
 168         }
 169         /* Note: our callers are responsible for
 170          * calling netdev_tracker_free().
 171          */
 172         dev_put(dev);
 173 }
 174
 175 static void __linkwatch_run_queue(int urgent_only)
 176 {
 177 #define MAX_DO_DEV_PER_LOOP     100
 178
 179         int do_dev = MAX_DO_DEV_PER_LOOP;
 180         struct net_device *dev;
 181         LIST_HEAD(wrk);
 182
 183         /* Give urgent case more budget */
 184         if (urgent_only)
 185                 do_dev += MAX_DO_DEV_PER_LOOP;
 186
 187         /*
 188          * Limit the number of linkwatch events to one
 189          * per second so that a runaway driver does not
 190          * cause a storm of messages on the netlink
 191          * socket.  This limit does not apply to up events
 192          * while the device qdisc is down.
 193          */
 194         if (!urgent_only)
 195                 linkwatch_nextevent = jiffies + HZ;
 196         /* Limit wrap-around effect on delay. */
 197         else if (time_after(linkwatch_nextevent, jiffies + HZ))
 198                 linkwatch_nextevent = jiffies;
 199
 200         clear_bit(LW_URGENT, &linkwatch_flags);
 201
 202         spin_lock_irq(&lweventlist_lock);
 203         list_splice_init(&lweventlist, &wrk);
 204
 205         while (!list_empty(&wrk) && do_dev > 0) {
 206
 207                 dev = list_first_entry(&wrk, struct net_device, link_watch_list);
 208                 list_del_init(&dev->link_watch_list);
 209
 210                 if (!netif_device_present(dev) ||
 211                     (urgent_only && !linkwatch_urgent_event(dev))) {
 212                         list_add_tail(&dev->link_watch_list, &lweventlist);
 213                         continue;
 214                 }
 215                 /* We must free netdev tracker under
 216                  * the spinlock protection.
 217                  */
 218                 netdev_tracker_free(dev, &dev->linkwatch_dev_tracker);
 219                 spin_unlock_irq(&lweventlist_lock);
 220                 linkwatch_do_dev(dev);
 221                 do_dev--;
 222                 spin_lock_irq(&lweventlist_lock);
 223         }
 224
 225         /* Add the remaining work back to lweventlist */
 226         list_splice_init(&wrk, &lweventlist);
 227
 228         if (!list_empty(&lweventlist))
 229                 linkwatch_schedule_work(0);
 230         spin_unlock_irq(&lweventlist_lock);
 231 }
 232
 233 void linkwatch_forget_dev(struct net_device *dev)
 234 {
 235         unsigned long flags;
 236         int clean = 0;
 237
 238         spin_lock_irqsave(&lweventlist_lock, flags);
 239         if (!list_empty(&dev->link_watch_list)) {
 240                 list_del_init(&dev->link_watch_list);
 241                 clean = 1;
 242                 /* We must release netdev tracker under
 243                  * the spinlock protection.
 244                  */
 245                 netdev_tracker_free(dev, &dev->linkwatch_dev_tracker);
 246         }
 247         spin_unlock_irqrestore(&lweventlist_lock, flags);
 248         if (clean)
 249                 linkwatch_do_dev(dev);
 250 }
 251
 252
 253 /* Must be called with the rtnl semaphore held */
 254 void linkwatch_run_queue(void)
 255 {
 256         __linkwatch_run_queue(0);
 257 }
 258
 259
 260 static void linkwatch_event(struct work_struct *dummy)
 261 {
 262         rtnl_lock();
 263         __linkwatch_run_queue(time_after(linkwatch_nextevent, jiffies));
 264         rtnl_unlock();
 265 }
 266
 267
 268 void linkwatch_fire_event(struct net_device *dev)
 269 {
 270         bool urgent = linkwatch_urgent_event(dev);
 271
 272         if (!test_and_set_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state)) {
 273                 linkwatch_add_event(dev);
 274         } else if (!urgent)
 275                 return;
 276
 277         linkwatch_schedule_work(urgent);
 278 }
 279 EXPORT_SYMBOL(linkwatch_fire_event);