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_carrier_ok(dev))
  38                 return (dev->ifindex != dev_get_iflink(dev) ?
  39                         IF_OPER_LOWERLAYERDOWN : IF_OPER_DOWN);
  40
  41         if (netif_dormant(dev))
  42                 return IF_OPER_DORMANT;
  43
  44         return IF_OPER_UP;
  45 }
  46
  47
  48 static void rfc2863_policy(struct net_device *dev)
  49 {
  50         unsigned char operstate = default_operstate(dev);
  51
  52         if (operstate == dev->operstate)
  53                 return;
  54
  55         write_lock_bh(&dev_base_lock);
  56
  57         switch(dev->link_mode) {
  58         case IF_LINK_MODE_DORMANT:
  59                 if (operstate == IF_OPER_UP)
  60                         operstate = IF_OPER_DORMANT;
  61                 break;
  62
  63         case IF_LINK_MODE_DEFAULT:
  64         default:
  65                 break;
  66         }
  67
  68         dev->operstate = operstate;
  69
  70         write_unlock_bh(&dev_base_lock);
  71 }
  72
  73
  74 void linkwatch_init_dev(struct net_device *dev)
  75 {
  76         /* Handle pre-registration link state changes */
  77         if (!netif_carrier_ok(dev) || netif_dormant(dev))
  78                 rfc2863_policy(dev);
  79 }
  80
  81
  82 static bool linkwatch_urgent_event(struct net_device *dev)
  83 {
  84         if (!netif_running(dev))
  85                 return false;
  86
  87         if (dev->ifindex != dev_get_iflink(dev))
  88                 return true;
  89
  90         if (netif_is_lag_port(dev) || netif_is_lag_master(dev))
  91                 return true;
  92
  93         return netif_carrier_ok(dev) && qdisc_tx_changing(dev);
  94 }
  95
  96
  97 static void linkwatch_add_event(struct net_device *dev)
  98 {
  99         unsigned long flags;
 100
 101         spin_lock_irqsave(&lweventlist_lock, flags);
 102         if (list_empty(&dev->link_watch_list)) {
 103                 list_add_tail(&dev->link_watch_list, &lweventlist);
 104                 dev_hold(dev);
 105         }
 106         spin_unlock_irqrestore(&lweventlist_lock, flags);
 107 }
 108
 109
 110 static void linkwatch_schedule_work(int urgent)
 111 {
 112         unsigned long delay = linkwatch_nextevent - jiffies;
 113
 114         if (test_bit(LW_URGENT, &linkwatch_flags))
 115                 return;
 116
 117         /* Minimise down-time: drop delay for up event. */
 118         if (urgent) {
 119                 if (test_and_set_bit(LW_URGENT, &linkwatch_flags))
 120                         return;
 121                 delay = 0;
 122         }
 123
 124         /* If we wrap around we'll delay it by at most HZ. */
 125         if (delay > HZ)
 126                 delay = 0;
 127
 128         /*
 129          * If urgent, schedule immediate execution; otherwise, don't
 130          * override the existing timer.
 131          */
 132         if (test_bit(LW_URGENT, &linkwatch_flags))
 133                 mod_delayed_work(system_wq, &linkwatch_work, 0);
 134         else
 135                 schedule_delayed_work(&linkwatch_work, delay);
 136 }
 137
 138
 139 static void linkwatch_do_dev(struct net_device *dev)
 140 {
 141         /*
 142          * Make sure the above read is complete since it can be
 143          * rewritten as soon as we clear the bit below.
 144          */
 145         smp_mb__before_atomic();
 146
 147         /* We are about to handle this device,
 148          * so new events can be accepted
 149          */
 150         clear_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state);
 151
 152         rfc2863_policy(dev);
 153         if (dev->flags & IFF_UP && netif_device_present(dev)) {
 154                 if (netif_carrier_ok(dev))
 155                         dev_activate(dev);
 156                 else
 157                         dev_deactivate(dev);
 158
 159                 netdev_state_change(dev);
 160         }
 161         dev_put(dev);
 162 }
 163
 164 static void __linkwatch_run_queue(int urgent_only)
 165 {
 166         struct net_device *dev;
 167         LIST_HEAD(wrk);
 168
 169         /*
 170          * Limit the number of linkwatch events to one
 171          * per second so that a runaway driver does not
 172          * cause a storm of messages on the netlink
 173          * socket.  This limit does not apply to up events
 174          * while the device qdisc is down.
 175          */
 176         if (!urgent_only)
 177                 linkwatch_nextevent = jiffies + HZ;
 178         /* Limit wrap-around effect on delay. */
 179         else if (time_after(linkwatch_nextevent, jiffies + HZ))
 180                 linkwatch_nextevent = jiffies;
 181
 182         clear_bit(LW_URGENT, &linkwatch_flags);
 183
 184         spin_lock_irq(&lweventlist_lock);
 185         list_splice_init(&lweventlist, &wrk);
 186
 187         while (!list_empty(&wrk)) {
 188
 189                 dev = list_first_entry(&wrk, struct net_device, link_watch_list);
 190                 list_del_init(&dev->link_watch_list);
 191
 192                 if (urgent_only && !linkwatch_urgent_event(dev)) {
 193                         list_add_tail(&dev->link_watch_list, &lweventlist);
 194                         continue;
 195                 }
 196                 spin_unlock_irq(&lweventlist_lock);
 197                 linkwatch_do_dev(dev);
 198                 spin_lock_irq(&lweventlist_lock);
 199         }
 200
 201         if (!list_empty(&lweventlist))
 202                 linkwatch_schedule_work(0);
 203         spin_unlock_irq(&lweventlist_lock);
 204 }
 205
 206 void linkwatch_forget_dev(struct net_device *dev)
 207 {
 208         unsigned long flags;
 209         int clean = 0;
 210
 211         spin_lock_irqsave(&lweventlist_lock, flags);
 212         if (!list_empty(&dev->link_watch_list)) {
 213                 list_del_init(&dev->link_watch_list);
 214                 clean = 1;
 215         }
 216         spin_unlock_irqrestore(&lweventlist_lock, flags);
 217         if (clean)
 218                 linkwatch_do_dev(dev);
 219 }
 220
 221
 222 /* Must be called with the rtnl semaphore held */
 223 void linkwatch_run_queue(void)
 224 {
 225         __linkwatch_run_queue(0);
 226 }
 227
 228
 229 static void linkwatch_event(struct work_struct *dummy)
 230 {
 231         rtnl_lock();
 232         __linkwatch_run_queue(time_after(linkwatch_nextevent, jiffies));
 233         rtnl_unlock();
 234 }
 235
 236
 237 void linkwatch_fire_event(struct net_device *dev)
 238 {
 239         bool urgent = linkwatch_urgent_event(dev);
 240
 241         if (!test_and_set_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state)) {
 242                 linkwatch_add_event(dev);
 243         } else if (!urgent)
 244                 return;
 245
 246         linkwatch_schedule_work(urgent);
 247 }
 248 EXPORT_SYMBOL(linkwatch_fire_event);