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/config.h>
  15 #include <linux/module.h>
  16 #include <linux/netdevice.h>
  17 #include <linux/if.h>
  18 #include <net/sock.h>
  19 #include <net/pkt_sched.h>
  20 #include <linux/rtnetlink.h>
  21 #include <linux/jiffies.h>
  22 #include <linux/spinlock.h>
  23 #include <linux/list.h>
  24 #include <linux/slab.h>
  25 #include <linux/workqueue.h>
  26 #include <linux/bitops.h>
  27 #include <asm/types.h>
  28
  29
  30 enum lw_bits {
  31         LW_RUNNING = 0,
  32         LW_SE_USED
  33 };
  34
  35 static unsigned long linkwatch_flags;
  36 static unsigned long linkwatch_nextevent;
  37
  38 static void linkwatch_event(void *dummy);
  39 static DECLARE_WORK(linkwatch_work, linkwatch_event, NULL);
  40
  41 static LIST_HEAD(lweventlist);
  42 static DEFINE_SPINLOCK(lweventlist_lock);
  43
  44 struct lw_event {
  45         struct list_head list;
  46         struct net_device *dev;
  47 };
  48
  49 /* Avoid kmalloc() for most systems */
  50 static struct lw_event singleevent;
  51
  52 static unsigned char default_operstate(const struct net_device *dev)
  53 {
  54         if (!netif_carrier_ok(dev))
  55                 return (dev->ifindex != dev->iflink ?
  56                         IF_OPER_LOWERLAYERDOWN : IF_OPER_DOWN);
  57
  58         if (netif_dormant(dev))
  59                 return IF_OPER_DORMANT;
  60
  61         return IF_OPER_UP;
  62 }
  63
  64
  65 static void rfc2863_policy(struct net_device *dev)
  66 {
  67         unsigned char operstate = default_operstate(dev);
  68
  69         if (operstate == dev->operstate)
  70                 return;
  71
  72         write_lock_bh(&dev_base_lock);
  73
  74         switch(dev->link_mode) {
  75         case IF_LINK_MODE_DORMANT:
  76                 if (operstate == IF_OPER_UP)
  77                         operstate = IF_OPER_DORMANT;
  78                 break;
  79
  80         case IF_LINK_MODE_DEFAULT:
  81         default:
  82                 break;
  83         };
  84
  85         dev->operstate = operstate;
  86
  87         write_unlock_bh(&dev_base_lock);
  88 }
  89
  90
  91 /* Must be called with the rtnl semaphore held */
  92 void linkwatch_run_queue(void)
  93 {
  94         LIST_HEAD(head);
  95         struct list_head *n, *next;
  96
  97         spin_lock_irq(&lweventlist_lock);
  98         list_splice_init(&lweventlist, &head);
  99         spin_unlock_irq(&lweventlist_lock);
 100
 101         list_for_each_safe(n, next, &head) {
 102                 struct lw_event *event = list_entry(n, struct lw_event, list);
 103                 struct net_device *dev = event->dev;
 104
 105                 if (event == &singleevent) {
 106                         clear_bit(LW_SE_USED, &linkwatch_flags);
 107                 } else {
 108                         kfree(event);
 109                 }
 110
 111                 /* We are about to handle this device,
 112                  * so new events can be accepted
 113                  */
 114                 clear_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state);
 115
 116                 rfc2863_policy(dev);
 117                 if (dev->flags & IFF_UP) {
 118                         if (netif_carrier_ok(dev)) {
 119                                 WARN_ON(dev->qdisc_sleeping == &noop_qdisc);
 120                                 dev_activate(dev);
 121                         } else
 122                                 dev_deactivate(dev);
 123
 124                         netdev_state_change(dev);
 125                 }
 126
 127                 dev_put(dev);
 128         }
 129 }
 130
 131
 132 static void linkwatch_event(void *dummy)
 133 {
 134         /* Limit the number of linkwatch events to one
 135          * per second so that a runaway driver does not
 136          * cause a storm of messages on the netlink
 137          * socket
 138          */
 139         linkwatch_nextevent = jiffies + HZ;
 140         clear_bit(LW_RUNNING, &linkwatch_flags);
 141
 142         rtnl_lock();
 143         linkwatch_run_queue();
 144         rtnl_unlock();
 145 }
 146
 147
 148 void linkwatch_fire_event(struct net_device *dev)
 149 {
 150         if (!test_and_set_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state)) {
 151                 unsigned long flags;
 152                 struct lw_event *event;
 153
 154                 if (test_and_set_bit(LW_SE_USED, &linkwatch_flags)) {
 155                         event = kmalloc(sizeof(struct lw_event), GFP_ATOMIC);
 156
 157                         if (unlikely(event == NULL)) {
 158                                 clear_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state);
 159                                 return;
 160                         }
 161                 } else {
 162                         event = &singleevent;
 163                 }
 164
 165                 dev_hold(dev);
 166                 event->dev = dev;
 167
 168                 spin_lock_irqsave(&lweventlist_lock, flags);
 169                 list_add_tail(&event->list, &lweventlist);
 170                 spin_unlock_irqrestore(&lweventlist_lock, flags);
 171
 172                 if (!test_and_set_bit(LW_RUNNING, &linkwatch_flags)) {
 173                         unsigned long delay = linkwatch_nextevent - jiffies;
 174
 175                         /* If we wrap around we'll delay it by at most HZ. */
 176                         if (!delay || delay > HZ)
 177                                 schedule_work(&linkwatch_work);
 178                         else
 179                                 schedule_delayed_work(&linkwatch_work, delay);
 180                 }
 181         }
 182 }
 183
 184 EXPORT_SYMBOL(linkwatch_fire_event);