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 void linkwatch_init_dev(struct net_device *dev)
  80 {
  81         /* Handle pre-registration link state changes */
  82         if (!netif_carrier_ok(dev) || netif_dormant(dev))
  83                 rfc2863_policy(dev);
  84 }
  85
  86
  87 static bool linkwatch_urgent_event(struct net_device *dev)
  88 {
  89         if (!netif_running(dev))
  90                 return false;
  91
  92         if (dev->ifindex != dev->iflink)
  93                 return true;
  94
  95         return netif_carrier_ok(dev) && qdisc_tx_changing(dev);
  96 }
  97
  98
  99 static void linkwatch_add_event(struct net_device *dev)
 100 {
 101         unsigned long flags;
 102
 103         spin_lock_irqsave(&lweventlist_lock, flags);
 104         if (list_empty(&dev->link_watch_list)) {
 105                 list_add_tail(&dev->link_watch_list, &lweventlist);
 106                 dev_hold(dev);
 107         }
 108         spin_unlock_irqrestore(&lweventlist_lock, flags);
 109 }
 110
 111
 112 static void linkwatch_schedule_work(int urgent)
 113 {
 114         unsigned long delay = linkwatch_nextevent - jiffies;
 115
 116         if (test_bit(LW_URGENT, &linkwatch_flags))
 117                 return;
 118
 119         /* Minimise down-time: drop delay for up event. */
 120         if (urgent) {
 121                 if (test_and_set_bit(LW_URGENT, &linkwatch_flags))
 122                         return;
 123                 delay = 0;
 124         }
 125
 126         /* If we wrap around we'll delay it by at most HZ. */
 127         if (delay > HZ)
 128                 delay = 0;
 129
 130         /*
 131          * If urgent, schedule immediate execution; otherwise, don't
 132          * override the existing timer.
 133          */
 134         if (test_bit(LW_URGENT, &linkwatch_flags))
 135                 mod_delayed_work(system_wq, &linkwatch_work, 0);
 136         else
 137                 schedule_delayed_work(&linkwatch_work, delay);
 138 }
 139
 140
 141 static void linkwatch_do_dev(struct net_device *dev)
 142 {
 143         /*
 144          * Make sure the above read is complete since it can be
 145          * rewritten as soon as we clear the bit below.
 146          */
 147         smp_mb__before_clear_bit();
 148
 149         /* We are about to handle this device,
 150          * so new events can be accepted
 151          */
 152         clear_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state);
 153
 154         rfc2863_policy(dev);
 155         if (dev->flags & IFF_UP) {
 156                 if (netif_carrier_ok(dev))
 157                         dev_activate(dev);
 158                 else
 159                         dev_deactivate(dev);
 160
 161                 netdev_state_change(dev);
 162         }
 163         dev_put(dev);
 164 }
 165
 166 static void __linkwatch_run_queue(int urgent_only)
 167 {
 168         struct net_device *dev;
 169         LIST_HEAD(wrk);
 170
 171         /*
 172          * Limit the number of linkwatch events to one
 173          * per second so that a runaway driver does not
 174          * cause a storm of messages on the netlink
 175          * socket.  This limit does not apply to up events
 176          * while the device qdisc is down.
 177          */
 178         if (!urgent_only)
 179                 linkwatch_nextevent = jiffies + HZ;
 180         /* Limit wrap-around effect on delay. */
 181         else if (time_after(linkwatch_nextevent, jiffies + HZ))
 182                 linkwatch_nextevent = jiffies;
 183
 184         clear_bit(LW_URGENT, &linkwatch_flags);
 185
 186         spin_lock_irq(&lweventlist_lock);
 187         list_splice_init(&lweventlist, &wrk);
 188
 189         while (!list_empty(&wrk)) {
 190
 191                 dev = list_first_entry(&wrk, struct net_device, link_watch_list);
 192                 list_del_init(&dev->link_watch_list);
 193
 194                 if (urgent_only && !linkwatch_urgent_event(dev)) {
 195                         list_add_tail(&dev->link_watch_list, &lweventlist);
 196                         continue;
 197                 }
 198                 spin_unlock_irq(&lweventlist_lock);
 199                 linkwatch_do_dev(dev);
 200                 spin_lock_irq(&lweventlist_lock);
 201         }
 202
 203         if (!list_empty(&lweventlist))
 204                 linkwatch_schedule_work(0);
 205         spin_unlock_irq(&lweventlist_lock);
 206 }
 207
 208 void linkwatch_forget_dev(struct net_device *dev)
 209 {
 210         unsigned long flags;
 211         int clean = 0;
 212
 213         spin_lock_irqsave(&lweventlist_lock, flags);
 214         if (!list_empty(&dev->link_watch_list)) {
 215                 list_del_init(&dev->link_watch_list);
 216                 clean = 1;
 217         }
 218         spin_unlock_irqrestore(&lweventlist_lock, flags);
 219         if (clean)
 220                 linkwatch_do_dev(dev);
 221 }
 222
 223
 224 /* Must be called with the rtnl semaphore held */
 225 void linkwatch_run_queue(void)
 226 {
 227         __linkwatch_run_queue(0);
 228 }
 229
 230
 231 static void linkwatch_event(struct work_struct *dummy)
 232 {
 233         rtnl_lock();
 234         __linkwatch_run_queue(time_after(linkwatch_nextevent, jiffies));
 235         rtnl_unlock();
 236 }
 237
 238
 239 void linkwatch_fire_event(struct net_device *dev)
 240 {
 241         bool urgent = linkwatch_urgent_event(dev);
 242
 243         if (!test_and_set_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state)) {
 244                 linkwatch_add_event(dev);
 245         } else if (!urgent)
 246                 return;
 247
 248         linkwatch_schedule_work(urgent);
 249 }
 250 EXPORT_SYMBOL(linkwatch_fire_event);