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