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/slab.h>
23 #include <linux/workqueue.h>
24 #include <linux/bitops.h>
25 #include <asm/types.h>
26
27
28 enum lw_bits {
29 LW_URGENT = 0,
30 };
31
32 static unsigned long linkwatch_flags;
33 static unsigned long linkwatch_nextevent;
34
35 static void linkwatch_event(struct work_struct *dummy);
36 static DECLARE_DELAYED_WORK(linkwatch_work, linkwatch_event);
37
38 static struct net_device *lweventlist;
39 static DEFINE_SPINLOCK(lweventlist_lock);
40
default_operstate(const struct net_device * dev)41 static unsigned char default_operstate(const struct net_device *dev)
42 {
43 if (!netif_carrier_ok(dev))
44 return (dev->ifindex != dev->iflink ?
45 IF_OPER_LOWERLAYERDOWN : IF_OPER_DOWN);
46
47 if (netif_dormant(dev))
48 return IF_OPER_DORMANT;
49
50 return IF_OPER_UP;
51 }
52
53
rfc2863_policy(struct net_device * dev)54 static void rfc2863_policy(struct net_device *dev)
55 {
56 unsigned char operstate = default_operstate(dev);
57
58 if (operstate == dev->operstate)
59 return;
60
61 write_lock_bh(&dev_base_lock);
62
63 switch(dev->link_mode) {
64 case IF_LINK_MODE_DORMANT:
65 if (operstate == IF_OPER_UP)
66 operstate = IF_OPER_DORMANT;
67 break;
68
69 case IF_LINK_MODE_DEFAULT:
70 default:
71 break;
72 }
73
74 dev->operstate = operstate;
75
76 write_unlock_bh(&dev_base_lock);
77 }
78
79
linkwatch_urgent_event(struct net_device * dev)80 static bool linkwatch_urgent_event(struct net_device *dev)
81 {
82 return netif_running(dev) && netif_carrier_ok(dev) &&
83 qdisc_tx_changing(dev);
84 }
85
86
linkwatch_add_event(struct net_device * dev)87 static void linkwatch_add_event(struct net_device *dev)
88 {
89 unsigned long flags;
90
91 spin_lock_irqsave(&lweventlist_lock, flags);
92 dev->link_watch_next = lweventlist;
93 lweventlist = dev;
94 spin_unlock_irqrestore(&lweventlist_lock, flags);
95 }
96
97
linkwatch_schedule_work(int urgent)98 static void linkwatch_schedule_work(int urgent)
99 {
100 unsigned long delay = linkwatch_nextevent - jiffies;
101
102 if (test_bit(LW_URGENT, &linkwatch_flags))
103 return;
104
105 /* Minimise down-time: drop delay for up event. */
106 if (urgent) {
107 if (test_and_set_bit(LW_URGENT, &linkwatch_flags))
108 return;
109 delay = 0;
110 }
111
112 /* If we wrap around we'll delay it by at most HZ. */
113 if (delay > HZ)
114 delay = 0;
115
116 /*
117 * This is true if we've scheduled it immeditately or if we don't
118 * need an immediate execution and it's already pending.
119 */
120 if (schedule_delayed_work(&linkwatch_work, delay) == !delay)
121 return;
122
123 /* Don't bother if there is nothing urgent. */
124 if (!test_bit(LW_URGENT, &linkwatch_flags))
125 return;
126
127 /* It's already running which is good enough. */
128 if (!cancel_delayed_work(&linkwatch_work))
129 return;
130
131 /* Otherwise we reschedule it again for immediate exection. */
132 schedule_delayed_work(&linkwatch_work, 0);
133 }
134
135
__linkwatch_run_queue(int urgent_only)136 static void __linkwatch_run_queue(int urgent_only)
137 {
138 struct net_device *next;
139
140 /*
141 * Limit the number of linkwatch events to one
142 * per second so that a runaway driver does not
143 * cause a storm of messages on the netlink
144 * socket. This limit does not apply to up events
145 * while the device qdisc is down.
146 */
147 if (!urgent_only)
148 linkwatch_nextevent = jiffies + HZ;
149 /* Limit wrap-around effect on delay. */
150 else if (time_after(linkwatch_nextevent, jiffies + HZ))
151 linkwatch_nextevent = jiffies;
152
153 clear_bit(LW_URGENT, &linkwatch_flags);
154
155 spin_lock_irq(&lweventlist_lock);
156 next = lweventlist;
157 lweventlist = NULL;
158 spin_unlock_irq(&lweventlist_lock);
159
160 while (next) {
161 struct net_device *dev = next;
162
163 next = dev->link_watch_next;
164
165 if (urgent_only && !linkwatch_urgent_event(dev)) {
166 linkwatch_add_event(dev);
167 continue;
168 }
169
170 /*
171 * Make sure the above read is complete since it can be
172 * rewritten as soon as we clear the bit below.
173 */
174 smp_mb__before_clear_bit();
175
176 /* We are about to handle this device,
177 * so new events can be accepted
178 */
179 clear_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state);
180
181 rfc2863_policy(dev);
182 if (dev->flags & IFF_UP) {
183 if (netif_carrier_ok(dev))
184 dev_activate(dev);
185 else
186 dev_deactivate(dev);
187
188 netdev_state_change(dev);
189 }
190
191 dev_put(dev);
192 }
193
194 if (lweventlist)
195 linkwatch_schedule_work(0);
196 }
197
198
199 /* Must be called with the rtnl semaphore held */
linkwatch_run_queue(void)200 void linkwatch_run_queue(void)
201 {
202 __linkwatch_run_queue(0);
203 }
204
205
linkwatch_event(struct work_struct * dummy)206 static void linkwatch_event(struct work_struct *dummy)
207 {
208 rtnl_lock();
209 __linkwatch_run_queue(time_after(linkwatch_nextevent, jiffies));
210 rtnl_unlock();
211 }
212
213
linkwatch_fire_event(struct net_device * dev)214 void linkwatch_fire_event(struct net_device *dev)
215 {
216 bool urgent = linkwatch_urgent_event(dev);
217
218 if (!test_and_set_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state)) {
219 dev_hold(dev);
220
221 linkwatch_add_event(dev);
222 } else if (!urgent)
223 return;
224
225 linkwatch_schedule_work(urgent);
226 }
227
228 EXPORT_SYMBOL(linkwatch_fire_event);
229