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/list.h>
  23 #include <linux/slab.h>
  24 #include <linux/workqueue.h>
  25 #include <linux/bitops.h>
  26 #include <asm/types.h>
  27
  28
  29 enum lw_bits {
  30         LW_RUNNING = 0,
  31         LW_SE_USED
  32 };
  33
  34 static unsigned long linkwatch_flags;
  35 static unsigned long linkwatch_nextevent;
  36
  37 static void linkwatch_event(struct work_struct *dummy);
  38 static DECLARE_DELAYED_WORK(linkwatch_work, linkwatch_event);
  39
  40 static LIST_HEAD(lweventlist);
  41 static DEFINE_SPINLOCK(lweventlist_lock);
  42
  43 struct lw_event {
  44         struct list_head list;
  45         struct net_device *dev;
  46 };
  47
  48 /* Avoid kmalloc() for most systems */
  49 static struct lw_event singleevent;
  50
  51 static unsigned char default_operstate(const struct net_device *dev)
  52 {
  53         if (!netif_carrier_ok(dev))
  54                 return (dev->ifindex != dev->iflink ?
  55                         IF_OPER_LOWERLAYERDOWN : IF_OPER_DOWN);
  56
  57         if (netif_dormant(dev))
  58                 return IF_OPER_DORMANT;
  59
  60         return IF_OPER_UP;
  61 }
  62
  63
  64 static void rfc2863_policy(struct net_device *dev)
  65 {
  66         unsigned char operstate = default_operstate(dev);
  67
  68         if (operstate == dev->operstate)
  69                 return;
  70
  71         write_lock_bh(&dev_base_lock);
  72
  73         switch(dev->link_mode) {
  74         case IF_LINK_MODE_DORMANT:
  75                 if (operstate == IF_OPER_UP)
  76                         operstate = IF_OPER_DORMANT;
  77                 break;
  78
  79         case IF_LINK_MODE_DEFAULT:
  80         default:
  81                 break;
  82         }
  83
  84         dev->operstate = operstate;
  85
  86         write_unlock_bh(&dev_base_lock);
  87 }
  88
  89
  90 /* Must be called with the rtnl semaphore held */
  91 void linkwatch_run_queue(void)
  92 {
  93         struct list_head head, *n, *next;
  94
  95         spin_lock_irq(&lweventlist_lock);
  96         list_replace_init(&lweventlist, &head);
  97         spin_unlock_irq(&lweventlist_lock);
  98
  99         list_for_each_safe(n, next, &head) {
 100                 struct lw_event *event = list_entry(n, struct lw_event, list);
 101                 struct net_device *dev = event->dev;
 102
 103                 if (event == &singleevent) {
 104                         clear_bit(LW_SE_USED, &linkwatch_flags);
 105                 } else {
 106                         kfree(event);
 107                 }
 108
 109                 /* We are about to handle this device,
 110                  * so new events can be accepted
 111                  */
 112                 clear_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state);
 113
 114                 rfc2863_policy(dev);
 115                 if (dev->flags & IFF_UP) {
 116                         if (netif_carrier_ok(dev)) {
 117                                 WARN_ON(dev->qdisc_sleeping == &noop_qdisc);
 118                                 dev_activate(dev);
 119                         } else
 120                                 dev_deactivate(dev);
 121
 122                         netdev_state_change(dev);
 123                 }
 124
 125                 dev_put(dev);
 126         }
 127 }
 128
 129
 130 static void linkwatch_event(struct work_struct *dummy)
 131 {
 132         /* Limit the number of linkwatch events to one
 133          * per second so that a runaway driver does not
 134          * cause a storm of messages on the netlink
 135          * socket
 136          */
 137         linkwatch_nextevent = jiffies + HZ;
 138         clear_bit(LW_RUNNING, &linkwatch_flags);
 139
 140         rtnl_lock();
 141         linkwatch_run_queue();
 142         rtnl_unlock();
 143 }
 144
 145
 146 void linkwatch_fire_event(struct net_device *dev)
 147 {
 148         if (!test_and_set_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state)) {
 149                 unsigned long flags;
 150                 struct lw_event *event;
 151
 152                 if (test_and_set_bit(LW_SE_USED, &linkwatch_flags)) {
 153                         event = kmalloc(sizeof(struct lw_event), GFP_ATOMIC);
 154
 155                         if (unlikely(event == NULL)) {
 156                                 clear_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state);
 157                                 return;
 158                         }
 159                 } else {
 160                         event = &singleevent;
 161                 }
 162
 163                 dev_hold(dev);
 164                 event->dev = dev;
 165
 166                 spin_lock_irqsave(&lweventlist_lock, flags);
 167                 list_add_tail(&event->list, &lweventlist);
 168                 spin_unlock_irqrestore(&lweventlist_lock, flags);
 169
 170                 if (!test_and_set_bit(LW_RUNNING, &linkwatch_flags)) {
 171                         unsigned long delay = linkwatch_nextevent - jiffies;
 172
 173                         /* If we wrap around we'll delay it by at most HZ. */
 174                         if (delay > HZ)
 175                                 delay = 0;
 176                         schedule_delayed_work(&linkwatch_work, delay);
 177                 }
 178         }
 179 }
 180
 181 EXPORT_SYMBOL(linkwatch_fire_event);