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/workqueue.h>
  23 #include <linux/bitops.h>
  24 #include <asm/types.h>
  25
  26
  27 enum lw_bits {
  28         LW_URGENT = 0,
  29 };
  30
  31 static unsigned long linkwatch_flags;
  32 static unsigned long linkwatch_nextevent;
  33
  34 static void linkwatch_event(struct work_struct *dummy);
  35 static DECLARE_DELAYED_WORK(linkwatch_work, linkwatch_event);
  36
  37 static LIST_HEAD(lweventlist);
  38 static DEFINE_SPINLOCK(lweventlist_lock);
  39
  40 static unsigned char default_operstate(const struct net_device *dev)
  41 {
  42         if (!netif_carrier_ok(dev))
  43                 return (dev->ifindex != dev->iflink ?
  44                         IF_OPER_LOWERLAYERDOWN : IF_OPER_DOWN);
  45
  46         if (netif_dormant(dev))
  47                 return IF_OPER_DORMANT;
  48
  49         return IF_OPER_UP;
  50 }
  51
  52
  53 static void rfc2863_policy(struct net_device *dev)
  54 {
  55         unsigned char operstate = default_operstate(dev);
  56
  57         if (operstate == dev->operstate)
  58                 return;
  59
  60         write_lock_bh(&dev_base_lock);
  61
  62         switch(dev->link_mode) {
  63         case IF_LINK_MODE_DORMANT:
  64                 if (operstate == IF_OPER_UP)
  65                         operstate = IF_OPER_DORMANT;
  66                 break;
  67
  68         case IF_LINK_MODE_DEFAULT:
  69         default:
  70                 break;
  71         }
  72
  73         dev->operstate = operstate;
  74
  75         write_unlock_bh(&dev_base_lock);
  76 }
  77
  78
  79 static bool linkwatch_urgent_event(struct net_device *dev)
  80 {
  81         return netif_running(dev) && netif_carrier_ok(dev) &&
  82                 qdisc_tx_changing(dev);
  83 }
  84
  85
  86 static void linkwatch_add_event(struct net_device *dev)
  87 {
  88         unsigned long flags;
  89
  90         spin_lock_irqsave(&lweventlist_lock, flags);
  91         if (list_empty(&dev->link_watch_list)) {
  92                 list_add_tail(&dev->link_watch_list, &lweventlist);
  93                 dev_hold(dev);
  94         }
  95         spin_unlock_irqrestore(&lweventlist_lock, flags);
  96 }
  97
  98
  99 static void linkwatch_schedule_work(int urgent)
 100 {
 101         unsigned long delay = linkwatch_nextevent - jiffies;
 102
 103         if (test_bit(LW_URGENT, &linkwatch_flags))
 104                 return;
 105
 106         /* Minimise down-time: drop delay for up event. */
 107         if (urgent) {
 108                 if (test_and_set_bit(LW_URGENT, &linkwatch_flags))
 109                         return;
 110                 delay = 0;
 111         }
 112
 113         /* If we wrap around we'll delay it by at most HZ. */
 114         if (delay > HZ)
 115                 delay = 0;
 116
 117         /*
 118          * This is true if we've scheduled it immeditately or if we don't
 119          * need an immediate execution and it's already pending.
 120          */
 121         if (schedule_delayed_work(&linkwatch_work, delay) == !delay)
 122                 return;
 123
 124         /* Don't bother if there is nothing urgent. */
 125         if (!test_bit(LW_URGENT, &linkwatch_flags))
 126                 return;
 127
 128         /* It's already running which is good enough. */
 129         if (!cancel_delayed_work(&linkwatch_work))
 130                 return;
 131
 132         /* Otherwise we reschedule it again for immediate execution. */
 133         schedule_delayed_work(&linkwatch_work, 0);
 134 }
 135
 136
 137 static void linkwatch_do_dev(struct net_device *dev)
 138 {
 139         /*
 140          * Make sure the above read is complete since it can be
 141          * rewritten as soon as we clear the bit below.
 142          */
 143         smp_mb__before_clear_bit();
 144
 145         /* We are about to handle this device,
 146          * so new events can be accepted
 147          */
 148         clear_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state);
 149
 150         rfc2863_policy(dev);
 151         if (dev->flags & IFF_UP) {
 152                 if (netif_carrier_ok(dev))
 153                         dev_activate(dev);
 154                 else
 155                         dev_deactivate(dev);
 156
 157                 netdev_state_change(dev);
 158         }
 159         dev_put(dev);
 160 }
 161
 162 static void __linkwatch_run_queue(int urgent_only)
 163 {
 164         struct net_device *dev;
 165         LIST_HEAD(wrk);
 166
 167         /*
 168          * Limit the number of linkwatch events to one
 169          * per second so that a runaway driver does not
 170          * cause a storm of messages on the netlink
 171          * socket.  This limit does not apply to up events
 172          * while the device qdisc is down.
 173          */
 174         if (!urgent_only)
 175                 linkwatch_nextevent = jiffies + HZ;
 176         /* Limit wrap-around effect on delay. */
 177         else if (time_after(linkwatch_nextevent, jiffies + HZ))
 178                 linkwatch_nextevent = jiffies;
 179
 180         clear_bit(LW_URGENT, &linkwatch_flags);
 181
 182         spin_lock_irq(&lweventlist_lock);
 183         list_splice_init(&lweventlist, &wrk);
 184
 185         while (!list_empty(&wrk)) {
 186
 187                 dev = list_first_entry(&wrk, struct net_device, link_watch_list);
 188                 list_del_init(&dev->link_watch_list);
 189
 190                 if (urgent_only && !linkwatch_urgent_event(dev)) {
 191                         list_add_tail(&dev->link_watch_list, &lweventlist);
 192                         continue;
 193                 }
 194                 spin_unlock_irq(&lweventlist_lock);
 195                 linkwatch_do_dev(dev);
 196                 spin_lock_irq(&lweventlist_lock);
 197         }
 198
 199         if (!list_empty(&lweventlist))
 200                 linkwatch_schedule_work(0);
 201         spin_unlock_irq(&lweventlist_lock);
 202 }
 203
 204 void linkwatch_forget_dev(struct net_device *dev)
 205 {
 206         unsigned long flags;
 207         int clean = 0;
 208
 209         spin_lock_irqsave(&lweventlist_lock, flags);
 210         if (!list_empty(&dev->link_watch_list)) {
 211                 list_del_init(&dev->link_watch_list);
 212                 clean = 1;
 213         }
 214         spin_unlock_irqrestore(&lweventlist_lock, flags);
 215         if (clean)
 216                 linkwatch_do_dev(dev);
 217 }
 218
 219
 220 /* Must be called with the rtnl semaphore held */
 221 void linkwatch_run_queue(void)
 222 {
 223         __linkwatch_run_queue(0);
 224 }
 225
 226
 227 static void linkwatch_event(struct work_struct *dummy)
 228 {
 229         rtnl_lock();
 230         __linkwatch_run_queue(time_after(linkwatch_nextevent, jiffies));
 231         rtnl_unlock();
 232 }
 233
 234
 235 void linkwatch_fire_event(struct net_device *dev)
 236 {
 237         bool urgent = linkwatch_urgent_event(dev);
 238
 239         if (!test_and_set_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state)) {
 240                 linkwatch_add_event(dev);
 241         } else if (!urgent)
 242                 return;
 243
 244         linkwatch_schedule_work(urgent);
 245 }
 246 EXPORT_SYMBOL(linkwatch_fire_event);