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Linux/net/core/link_watch.c

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  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         if (dev->priv_flags & IFF_TEAM_PORT)
 96                 return true;
 97 
 98         return netif_carrier_ok(dev) && qdisc_tx_changing(dev);
 99 }
100 
101 
102 static void linkwatch_add_event(struct net_device *dev)
103 {
104         unsigned long flags;
105 
106         spin_lock_irqsave(&lweventlist_lock, flags);
107         if (list_empty(&dev->link_watch_list)) {
108                 list_add_tail(&dev->link_watch_list, &lweventlist);
109                 dev_hold(dev);
110         }
111         spin_unlock_irqrestore(&lweventlist_lock, flags);
112 }
113 
114 
115 static void linkwatch_schedule_work(int urgent)
116 {
117         unsigned long delay = linkwatch_nextevent - jiffies;
118 
119         if (test_bit(LW_URGENT, &linkwatch_flags))
120                 return;
121 
122         /* Minimise down-time: drop delay for up event. */
123         if (urgent) {
124                 if (test_and_set_bit(LW_URGENT, &linkwatch_flags))
125                         return;
126                 delay = 0;
127         }
128 
129         /* If we wrap around we'll delay it by at most HZ. */
130         if (delay > HZ)
131                 delay = 0;
132 
133         /*
134          * If urgent, schedule immediate execution; otherwise, don't
135          * override the existing timer.
136          */
137         if (test_bit(LW_URGENT, &linkwatch_flags))
138                 mod_delayed_work(system_wq, &linkwatch_work, 0);
139         else
140                 schedule_delayed_work(&linkwatch_work, delay);
141 }
142 
143 
144 static void linkwatch_do_dev(struct net_device *dev)
145 {
146         /*
147          * Make sure the above read is complete since it can be
148          * rewritten as soon as we clear the bit below.
149          */
150         smp_mb__before_clear_bit();
151 
152         /* We are about to handle this device,
153          * so new events can be accepted
154          */
155         clear_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state);
156 
157         rfc2863_policy(dev);
158         if (dev->flags & IFF_UP) {
159                 if (netif_carrier_ok(dev))
160                         dev_activate(dev);
161                 else
162                         dev_deactivate(dev);
163 
164                 netdev_state_change(dev);
165         }
166         dev_put(dev);
167 }
168 
169 static void __linkwatch_run_queue(int urgent_only)
170 {
171         struct net_device *dev;
172         LIST_HEAD(wrk);
173 
174         /*
175          * Limit the number of linkwatch events to one
176          * per second so that a runaway driver does not
177          * cause a storm of messages on the netlink
178          * socket.  This limit does not apply to up events
179          * while the device qdisc is down.
180          */
181         if (!urgent_only)
182                 linkwatch_nextevent = jiffies + HZ;
183         /* Limit wrap-around effect on delay. */
184         else if (time_after(linkwatch_nextevent, jiffies + HZ))
185                 linkwatch_nextevent = jiffies;
186 
187         clear_bit(LW_URGENT, &linkwatch_flags);
188 
189         spin_lock_irq(&lweventlist_lock);
190         list_splice_init(&lweventlist, &wrk);
191 
192         while (!list_empty(&wrk)) {
193 
194                 dev = list_first_entry(&wrk, struct net_device, link_watch_list);
195                 list_del_init(&dev->link_watch_list);
196 
197                 if (urgent_only && !linkwatch_urgent_event(dev)) {
198                         list_add_tail(&dev->link_watch_list, &lweventlist);
199                         continue;
200                 }
201                 spin_unlock_irq(&lweventlist_lock);
202                 linkwatch_do_dev(dev);
203                 spin_lock_irq(&lweventlist_lock);
204         }
205 
206         if (!list_empty(&lweventlist))
207                 linkwatch_schedule_work(0);
208         spin_unlock_irq(&lweventlist_lock);
209 }
210 
211 void linkwatch_forget_dev(struct net_device *dev)
212 {
213         unsigned long flags;
214         int clean = 0;
215 
216         spin_lock_irqsave(&lweventlist_lock, flags);
217         if (!list_empty(&dev->link_watch_list)) {
218                 list_del_init(&dev->link_watch_list);
219                 clean = 1;
220         }
221         spin_unlock_irqrestore(&lweventlist_lock, flags);
222         if (clean)
223                 linkwatch_do_dev(dev);
224 }
225 
226 
227 /* Must be called with the rtnl semaphore held */
228 void linkwatch_run_queue(void)
229 {
230         __linkwatch_run_queue(0);
231 }
232 
233 
234 static void linkwatch_event(struct work_struct *dummy)
235 {
236         rtnl_lock();
237         __linkwatch_run_queue(time_after(linkwatch_nextevent, jiffies));
238         rtnl_unlock();
239 }
240 
241 
242 void linkwatch_fire_event(struct net_device *dev)
243 {
244         bool urgent = linkwatch_urgent_event(dev);
245 
246         if (!test_and_set_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state)) {
247                 linkwatch_add_event(dev);
248         } else if (!urgent)
249                 return;
250 
251         linkwatch_schedule_work(urgent);
252 }
253 EXPORT_SYMBOL(linkwatch_fire_event);
254 

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