net/core/link_watch.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Linux network device link state notification
   4  *
   5  * Author:
   6  *     Stefan Rompf <sux@loplof.de>
   7  */
   8
   9 #include <linux/module.h>
  10 #include <linux/netdevice.h>
  11 #include <linux/if.h>
  12 #include <net/sock.h>
  13 #include <net/pkt_sched.h>
  14 #include <linux/rtnetlink.h>
  15 #include <linux/jiffies.h>
  16 #include <linux/spinlock.h>
  17 #include <linux/workqueue.h>
  18 #include <linux/bitops.h>
  19 #include <linux/types.h>
  20
  21
  22 enum lw_bits {
  23         LW_URGENT = 0,
  24 };
  25
  26 static unsigned long linkwatch_flags;
  27 static unsigned long linkwatch_nextevent;
  28
  29 static void linkwatch_event(struct work_struct *dummy);
  30 static DECLARE_DELAYED_WORK(linkwatch_work, linkwatch_event);
  31
  32 static LIST_HEAD(lweventlist);
  33 static DEFINE_SPINLOCK(lweventlist_lock);
  34
  35 static unsigned char default_operstate(const struct net_device *dev)
  36 {
  37         if (netif_testing(dev))
  38                 return IF_OPER_TESTING;
  39
  40         if (!netif_carrier_ok(dev))
  41                 return (dev->ifindex != dev_get_iflink(dev) ?
  42                         IF_OPER_LOWERLAYERDOWN : IF_OPER_DOWN);
  43
  44         if (netif_dormant(dev))
  45                 return IF_OPER_DORMANT;
  46
  47         return IF_OPER_UP;
  48 }
  49
  50
  51 static void rfc2863_policy(struct net_device *dev)
  52 {
  53         unsigned char operstate = default_operstate(dev);
  54
  55         if (operstate == dev->operstate)
  56                 return;
  57
  58         write_lock_bh(&dev_base_lock);
  59
  60         switch(dev->link_mode) {
  61         case IF_LINK_MODE_TESTING:
  62                 if (operstate == IF_OPER_UP)
  63                         operstate = IF_OPER_TESTING;
  64                 break;
  65
  66         case IF_LINK_MODE_DORMANT:
  67                 if (operstate == IF_OPER_UP)
  68                         operstate = IF_OPER_DORMANT;
  69                 break;
  70         case IF_LINK_MODE_DEFAULT:
  71         default:
  72                 break;
  73         }
  74
  75         dev->operstate = operstate;
  76
  77         write_unlock_bh(&dev_base_lock);
  78 }
  79
  80
  81 void linkwatch_init_dev(struct net_device *dev)
  82 {
  83         /* Handle pre-registration link state changes */
  84         if (!netif_carrier_ok(dev) || netif_dormant(dev) ||
  85             netif_testing(dev))
  86                 rfc2863_policy(dev);
  87 }
  88
  89
  90 static bool linkwatch_urgent_event(struct net_device *dev)
  91 {
  92         if (!netif_running(dev))
  93                 return false;
  94
  95         if (dev->ifindex != dev_get_iflink(dev))
  96                 return true;
  97
  98         if (netif_is_lag_port(dev) || netif_is_lag_master(dev))
  99                 return true;
 100
 101         return netif_carrier_ok(dev) && qdisc_tx_changing(dev);
 102 }
 103
 104
 105 static void linkwatch_add_event(struct net_device *dev)
 106 {
 107         unsigned long flags;
 108
 109         spin_lock_irqsave(&lweventlist_lock, flags);
 110         if (list_empty(&dev->link_watch_list)) {
 111                 list_add_tail(&dev->link_watch_list, &lweventlist);
 112                 dev_hold(dev);
 113         }
 114         spin_unlock_irqrestore(&lweventlist_lock, flags);
 115 }
 116
 117
 118 static void linkwatch_schedule_work(int urgent)
 119 {
 120         unsigned long delay = linkwatch_nextevent - jiffies;
 121
 122         if (test_bit(LW_URGENT, &linkwatch_flags))
 123                 return;
 124
 125         /* Minimise down-time: drop delay for up event. */
 126         if (urgent) {
 127                 if (test_and_set_bit(LW_URGENT, &linkwatch_flags))
 128                         return;
 129                 delay = 0;
 130         }
 131
 132         /* If we wrap around we'll delay it by at most HZ. */
 133         if (delay > HZ)
 134                 delay = 0;
 135
 136         /*
 137          * If urgent, schedule immediate execution; otherwise, don't
 138          * override the existing timer.
 139          */
 140         if (test_bit(LW_URGENT, &linkwatch_flags))
 141                 mod_delayed_work(system_wq, &linkwatch_work, 0);
 142         else
 143                 schedule_delayed_work(&linkwatch_work, delay);
 144 }
 145
 146
 147 static void linkwatch_do_dev(struct net_device *dev)
 148 {
 149         /*
 150          * Make sure the above read is complete since it can be
 151          * rewritten as soon as we clear the bit below.
 152          */
 153         smp_mb__before_atomic();
 154
 155         /* We are about to handle this device,
 156          * so new events can be accepted
 157          */
 158         clear_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state);
 159
 160         rfc2863_policy(dev);
 161         if (dev->flags & IFF_UP) {
 162                 if (netif_carrier_ok(dev))
 163                         dev_activate(dev);
 164                 else
 165                         dev_deactivate(dev);
 166
 167                 netdev_state_change(dev);
 168         }
 169         dev_put(dev);
 170 }
 171
 172 static void __linkwatch_run_queue(int urgent_only)
 173 {
 174 #define MAX_DO_DEV_PER_LOOP     100
 175
 176         int do_dev = MAX_DO_DEV_PER_LOOP;
 177         struct net_device *dev;
 178         LIST_HEAD(wrk);
 179
 180         /* Give urgent case more budget */
 181         if (urgent_only)
 182                 do_dev += MAX_DO_DEV_PER_LOOP;
 183
 184         /*
 185          * Limit the number of linkwatch events to one
 186          * per second so that a runaway driver does not
 187          * cause a storm of messages on the netlink
 188          * socket.  This limit does not apply to up events
 189          * while the device qdisc is down.
 190          */
 191         if (!urgent_only)
 192                 linkwatch_nextevent = jiffies + HZ;
 193         /* Limit wrap-around effect on delay. */
 194         else if (time_after(linkwatch_nextevent, jiffies + HZ))
 195                 linkwatch_nextevent = jiffies;
 196
 197         clear_bit(LW_URGENT, &linkwatch_flags);
 198
 199         spin_lock_irq(&lweventlist_lock);
 200         list_splice_init(&lweventlist, &wrk);
 201
 202         while (!list_empty(&wrk) && do_dev > 0) {
 203
 204                 dev = list_first_entry(&wrk, struct net_device, link_watch_list);
 205                 list_del_init(&dev->link_watch_list);
 206
 207                 if (!netif_device_present(dev) ||
 208                     (urgent_only && !linkwatch_urgent_event(dev))) {
 209                         list_add_tail(&dev->link_watch_list, &lweventlist);
 210                         continue;
 211                 }
 212                 spin_unlock_irq(&lweventlist_lock);
 213                 linkwatch_do_dev(dev);
 214                 do_dev--;
 215                 spin_lock_irq(&lweventlist_lock);
 216         }
 217
 218         /* Add the remaining work back to lweventlist */
 219         list_splice_init(&wrk, &lweventlist);
 220
 221         if (!list_empty(&lweventlist))
 222                 linkwatch_schedule_work(0);
 223         spin_unlock_irq(&lweventlist_lock);
 224 }
 225
 226 void linkwatch_forget_dev(struct net_device *dev)
 227 {
 228         unsigned long flags;
 229         int clean = 0;
 230
 231         spin_lock_irqsave(&lweventlist_lock, flags);
 232         if (!list_empty(&dev->link_watch_list)) {
 233                 list_del_init(&dev->link_watch_list);
 234                 clean = 1;
 235         }
 236         spin_unlock_irqrestore(&lweventlist_lock, flags);
 237         if (clean)
 238                 linkwatch_do_dev(dev);
 239 }
 240
 241
 242 /* Must be called with the rtnl semaphore held */
 243 void linkwatch_run_queue(void)
 244 {
 245         __linkwatch_run_queue(0);
 246 }
 247
 248
 249 static void linkwatch_event(struct work_struct *dummy)
 250 {
 251         rtnl_lock();
 252         __linkwatch_run_queue(time_after(linkwatch_nextevent, jiffies));
 253         rtnl_unlock();
 254 }
 255
 256
 257 void linkwatch_fire_event(struct net_device *dev)
 258 {
 259         bool urgent = linkwatch_urgent_event(dev);
 260
 261         if (!test_and_set_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state)) {
 262                 linkwatch_add_event(dev);
 263         } else if (!urgent)
 264                 return;
 265
 266         linkwatch_schedule_work(urgent);
 267 }
 268 EXPORT_SYMBOL(linkwatch_fire_event);