net/core/link_watch.c

   1 /*
   2  * Linux network device link state notification
   3  *
   4  * Author:
   5  *     Stefan Rompf <sux@loplof.de>
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License
   9  * as published by the Free Software Foundation; either version
  10  * 2 of the License, or (at your option) any later version.
  11  *
  12  */
  13
  14 #include <linux/module.h>
  15 #include <linux/netdevice.h>
  16 #include <linux/if.h>
  17 #include <net/sock.h>
  18 #include <net/pkt_sched.h>
  19 #include <linux/rtnetlink.h>
  20 #include <linux/jiffies.h>
  21 #include <linux/spinlock.h>
  22 #include <linux/slab.h>
  23 #include <linux/workqueue.h>
  24 #include <linux/bitops.h>
  25 #include <asm/types.h>
  26
  27
  28 enum lw_bits {
  29         LW_URGENT = 0,
  30 };
  31
  32 static unsigned long linkwatch_flags;
  33 static unsigned long linkwatch_nextevent;
  34
  35 static void linkwatch_event(struct work_struct *dummy);
  36 static DECLARE_DELAYED_WORK(linkwatch_work, linkwatch_event);
  37
  38 static struct net_device *lweventlist;
  39 static DEFINE_SPINLOCK(lweventlist_lock);
  40
  41 static unsigned char default_operstate(const struct net_device *dev)
  42 {
  43         if (!netif_carrier_ok(dev))
  44                 return (dev->ifindex != dev->iflink ?
  45                         IF_OPER_LOWERLAYERDOWN : IF_OPER_DOWN);
  46
  47         if (netif_dormant(dev))
  48                 return IF_OPER_DORMANT;
  49
  50         return IF_OPER_UP;
  51 }
  52
  53
  54 static void rfc2863_policy(struct net_device *dev)
  55 {
  56         unsigned char operstate = default_operstate(dev);
  57
  58         if (operstate == dev->operstate)
  59                 return;
  60
  61         write_lock_bh(&dev_base_lock);
  62
  63         switch(dev->link_mode) {
  64         case IF_LINK_MODE_DORMANT:
  65                 if (operstate == IF_OPER_UP)
  66                         operstate = IF_OPER_DORMANT;
  67                 break;
  68
  69         case IF_LINK_MODE_DEFAULT:
  70         default:
  71                 break;
  72         }
  73
  74         dev->operstate = operstate;
  75
  76         write_unlock_bh(&dev_base_lock);
  77 }
  78
  79
  80 static bool linkwatch_urgent_event(struct net_device *dev)
  81 {
  82         return netif_running(dev) && netif_carrier_ok(dev) &&
  83                 qdisc_tx_changing(dev);
  84 }
  85
  86
  87 static void linkwatch_add_event(struct net_device *dev)
  88 {
  89         unsigned long flags;
  90
  91         spin_lock_irqsave(&lweventlist_lock, flags);
  92         dev->link_watch_next = lweventlist;
  93         lweventlist = dev;
  94         spin_unlock_irqrestore(&lweventlist_lock, flags);
  95 }
  96
  97
  98 static void linkwatch_schedule_work(int urgent)
  99 {
 100         unsigned long delay = linkwatch_nextevent - jiffies;
 101
 102         if (test_bit(LW_URGENT, &linkwatch_flags))
 103                 return;
 104
 105         /* Minimise down-time: drop delay for up event. */
 106         if (urgent) {
 107                 if (test_and_set_bit(LW_URGENT, &linkwatch_flags))
 108                         return;
 109                 delay = 0;
 110         }
 111
 112         /* If we wrap around we'll delay it by at most HZ. */
 113         if (delay > HZ)
 114                 delay = 0;
 115
 116         /*
 117          * This is true if we've scheduled it immeditately or if we don't
 118          * need an immediate execution and it's already pending.
 119          */
 120         if (schedule_delayed_work(&linkwatch_work, delay) == !delay)
 121                 return;
 122
 123         /* Don't bother if there is nothing urgent. */
 124         if (!test_bit(LW_URGENT, &linkwatch_flags))
 125                 return;
 126
 127         /* It's already running which is good enough. */
 128         if (!cancel_delayed_work(&linkwatch_work))
 129                 return;
 130
 131         /* Otherwise we reschedule it again for immediate exection. */
 132         schedule_delayed_work(&linkwatch_work, 0);
 133 }
 134
 135
 136 static void __linkwatch_run_queue(int urgent_only)
 137 {
 138         struct net_device *next;
 139
 140         /*
 141          * Limit the number of linkwatch events to one
 142          * per second so that a runaway driver does not
 143          * cause a storm of messages on the netlink
 144          * socket.  This limit does not apply to up events
 145          * while the device qdisc is down.
 146          */
 147         if (!urgent_only)
 148                 linkwatch_nextevent = jiffies + HZ;
 149         /* Limit wrap-around effect on delay. */
 150         else if (time_after(linkwatch_nextevent, jiffies + HZ))
 151                 linkwatch_nextevent = jiffies;
 152
 153         clear_bit(LW_URGENT, &linkwatch_flags);
 154
 155         spin_lock_irq(&lweventlist_lock);
 156         next = lweventlist;
 157         lweventlist = NULL;
 158         spin_unlock_irq(&lweventlist_lock);
 159
 160         while (next) {
 161                 struct net_device *dev = next;
 162
 163                 next = dev->link_watch_next;
 164
 165                 if (urgent_only && !linkwatch_urgent_event(dev)) {
 166                         linkwatch_add_event(dev);
 167                         continue;
 168                 }
 169
 170                 /*
 171                  * Make sure the above read is complete since it can be
 172                  * rewritten as soon as we clear the bit below.
 173                  */
 174                 smp_mb__before_clear_bit();
 175
 176                 /* We are about to handle this device,
 177                  * so new events can be accepted
 178                  */
 179                 clear_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state);
 180
 181                 rfc2863_policy(dev);
 182                 if (dev->flags & IFF_UP) {
 183                         if (netif_carrier_ok(dev))
 184                                 dev_activate(dev);
 185                         else
 186                                 dev_deactivate(dev);
 187
 188                         netdev_state_change(dev);
 189                 }
 190
 191                 dev_put(dev);
 192         }
 193
 194         if (lweventlist)
 195                 linkwatch_schedule_work(0);
 196 }
 197
 198
 199 /* Must be called with the rtnl semaphore held */
 200 void linkwatch_run_queue(void)
 201 {
 202         __linkwatch_run_queue(0);
 203 }
 204
 205
 206 static void linkwatch_event(struct work_struct *dummy)
 207 {
 208         rtnl_lock();
 209         __linkwatch_run_queue(time_after(linkwatch_nextevent, jiffies));
 210         rtnl_unlock();
 211 }
 212
 213
 214 void linkwatch_fire_event(struct net_device *dev)
 215 {
 216         bool urgent = linkwatch_urgent_event(dev);
 217
 218         if (!test_and_set_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state)) {
 219                 dev_hold(dev);
 220
 221                 linkwatch_add_event(dev);
 222         } else if (!urgent)
 223                 return;
 224
 225         linkwatch_schedule_work(urgent);
 226 }
 227
 228 EXPORT_SYMBOL(linkwatch_fire_event);