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 #include "dev.h"
22
23 enum lw_bits {
24 LW_URGENT = 0,
25 };
26
27 static unsigned long linkwatch_flags;
28 static unsigned long linkwatch_nextevent;
29
30 static void linkwatch_event(struct work_struct *dummy);
31 static DECLARE_DELAYED_WORK(linkwatch_work, linkwatch_event);
32
33 static LIST_HEAD(lweventlist);
34 static DEFINE_SPINLOCK(lweventlist_lock);
35
default_operstate(const struct net_device * dev)36 static unsigned char default_operstate(const struct net_device *dev)
37 {
38 if (netif_testing(dev))
39 return IF_OPER_TESTING;
40
41 /* Some uppers (DSA) have additional sources for being down, so
42 * first check whether lower is indeed the source of its down state.
43 */
44 if (!netif_carrier_ok(dev)) {
45 int iflink = dev_get_iflink(dev);
46 struct net_device *peer;
47
48 /* If called from netdev_run_todo()/linkwatch_sync_dev(),
49 * dev_net(dev) can be already freed, and RTNL is not held.
50 */
51 if (dev->reg_state == NETREG_UNREGISTERED ||
52 iflink == dev->ifindex)
53 return IF_OPER_DOWN;
54
55 ASSERT_RTNL();
56 peer = __dev_get_by_index(dev_net(dev), iflink);
57 if (!peer)
58 return IF_OPER_DOWN;
59
60 return netif_carrier_ok(peer) ? IF_OPER_DOWN :
61 IF_OPER_LOWERLAYERDOWN;
62 }
63
64 if (netif_dormant(dev))
65 return IF_OPER_DORMANT;
66
67 return IF_OPER_UP;
68 }
69
70
rfc2863_policy(struct net_device * dev)71 static void rfc2863_policy(struct net_device *dev)
72 {
73 unsigned char operstate = default_operstate(dev);
74
75 if (operstate == READ_ONCE(dev->operstate))
76 return;
77
78 write_lock(&dev_base_lock);
79
80 switch(dev->link_mode) {
81 case IF_LINK_MODE_TESTING:
82 if (operstate == IF_OPER_UP)
83 operstate = IF_OPER_TESTING;
84 break;
85
86 case IF_LINK_MODE_DORMANT:
87 if (operstate == IF_OPER_UP)
88 operstate = IF_OPER_DORMANT;
89 break;
90 case IF_LINK_MODE_DEFAULT:
91 default:
92 break;
93 }
94
95 WRITE_ONCE(dev->operstate, operstate);
96
97 write_unlock(&dev_base_lock);
98 }
99
100
linkwatch_init_dev(struct net_device * dev)101 void linkwatch_init_dev(struct net_device *dev)
102 {
103 /* Handle pre-registration link state changes */
104 if (!netif_carrier_ok(dev) || netif_dormant(dev) ||
105 netif_testing(dev))
106 rfc2863_policy(dev);
107 }
108
109
linkwatch_urgent_event(struct net_device * dev)110 static bool linkwatch_urgent_event(struct net_device *dev)
111 {
112 if (!netif_running(dev))
113 return false;
114
115 if (dev->ifindex != dev_get_iflink(dev))
116 return true;
117
118 if (netif_is_lag_port(dev) || netif_is_lag_master(dev))
119 return true;
120
121 return netif_carrier_ok(dev) && qdisc_tx_changing(dev);
122 }
123
124
linkwatch_add_event(struct net_device * dev)125 static void linkwatch_add_event(struct net_device *dev)
126 {
127 unsigned long flags;
128
129 spin_lock_irqsave(&lweventlist_lock, flags);
130 if (list_empty(&dev->link_watch_list)) {
131 list_add_tail(&dev->link_watch_list, &lweventlist);
132 netdev_hold(dev, &dev->linkwatch_dev_tracker, GFP_ATOMIC);
133 }
134 spin_unlock_irqrestore(&lweventlist_lock, flags);
135 }
136
137
linkwatch_schedule_work(int urgent)138 static void linkwatch_schedule_work(int urgent)
139 {
140 unsigned long delay = linkwatch_nextevent - jiffies;
141
142 if (test_bit(LW_URGENT, &linkwatch_flags))
143 return;
144
145 /* Minimise down-time: drop delay for up event. */
146 if (urgent) {
147 if (test_and_set_bit(LW_URGENT, &linkwatch_flags))
148 return;
149 delay = 0;
150 }
151
152 /* If we wrap around we'll delay it by at most HZ. */
153 if (delay > HZ)
154 delay = 0;
155
156 /*
157 * If urgent, schedule immediate execution; otherwise, don't
158 * override the existing timer.
159 */
160 if (test_bit(LW_URGENT, &linkwatch_flags))
161 mod_delayed_work(system_unbound_wq, &linkwatch_work, 0);
162 else
163 queue_delayed_work(system_unbound_wq, &linkwatch_work, delay);
164 }
165
166
linkwatch_do_dev(struct net_device * dev)167 static void linkwatch_do_dev(struct net_device *dev)
168 {
169 /*
170 * Make sure the above read is complete since it can be
171 * rewritten as soon as we clear the bit below.
172 */
173 smp_mb__before_atomic();
174
175 /* We are about to handle this device,
176 * so new events can be accepted
177 */
178 clear_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state);
179
180 rfc2863_policy(dev);
181 if (dev->flags & IFF_UP) {
182 if (netif_carrier_ok(dev))
183 dev_activate(dev);
184 else
185 dev_deactivate(dev);
186
187 netdev_state_change(dev);
188 }
189 /* Note: our callers are responsible for calling netdev_tracker_free().
190 * This is the reason we use __dev_put() instead of dev_put().
191 */
192 __dev_put(dev);
193 }
194
__linkwatch_run_queue(int urgent_only)195 static void __linkwatch_run_queue(int urgent_only)
196 {
197 #define MAX_DO_DEV_PER_LOOP 100
198
199 int do_dev = MAX_DO_DEV_PER_LOOP;
200 struct net_device *dev;
201 LIST_HEAD(wrk);
202
203 /* Give urgent case more budget */
204 if (urgent_only)
205 do_dev += MAX_DO_DEV_PER_LOOP;
206
207 /*
208 * Limit the number of linkwatch events to one
209 * per second so that a runaway driver does not
210 * cause a storm of messages on the netlink
211 * socket. This limit does not apply to up events
212 * while the device qdisc is down.
213 */
214 if (!urgent_only)
215 linkwatch_nextevent = jiffies + HZ;
216 /* Limit wrap-around effect on delay. */
217 else if (time_after(linkwatch_nextevent, jiffies + HZ))
218 linkwatch_nextevent = jiffies;
219
220 clear_bit(LW_URGENT, &linkwatch_flags);
221
222 spin_lock_irq(&lweventlist_lock);
223 list_splice_init(&lweventlist, &wrk);
224
225 while (!list_empty(&wrk) && do_dev > 0) {
226
227 dev = list_first_entry(&wrk, struct net_device, link_watch_list);
228 list_del_init(&dev->link_watch_list);
229
230 if (!netif_device_present(dev) ||
231 (urgent_only && !linkwatch_urgent_event(dev))) {
232 list_add_tail(&dev->link_watch_list, &lweventlist);
233 continue;
234 }
235 /* We must free netdev tracker under
236 * the spinlock protection.
237 */
238 netdev_tracker_free(dev, &dev->linkwatch_dev_tracker);
239 spin_unlock_irq(&lweventlist_lock);
240 linkwatch_do_dev(dev);
241 do_dev--;
242 spin_lock_irq(&lweventlist_lock);
243 }
244
245 /* Add the remaining work back to lweventlist */
246 list_splice_init(&wrk, &lweventlist);
247
248 if (!list_empty(&lweventlist))
249 linkwatch_schedule_work(0);
250 spin_unlock_irq(&lweventlist_lock);
251 }
252
linkwatch_forget_dev(struct net_device * dev)253 void linkwatch_forget_dev(struct net_device *dev)
254 {
255 unsigned long flags;
256 int clean = 0;
257
258 spin_lock_irqsave(&lweventlist_lock, flags);
259 if (!list_empty(&dev->link_watch_list)) {
260 list_del_init(&dev->link_watch_list);
261 clean = 1;
262 /* We must release netdev tracker under
263 * the spinlock protection.
264 */
265 netdev_tracker_free(dev, &dev->linkwatch_dev_tracker);
266 }
267 spin_unlock_irqrestore(&lweventlist_lock, flags);
268 if (clean)
269 linkwatch_do_dev(dev);
270 }
271
272
273 /* Must be called with the rtnl semaphore held */
linkwatch_run_queue(void)274 void linkwatch_run_queue(void)
275 {
276 __linkwatch_run_queue(0);
277 }
278
279
linkwatch_event(struct work_struct * dummy)280 static void linkwatch_event(struct work_struct *dummy)
281 {
282 rtnl_lock();
283 __linkwatch_run_queue(time_after(linkwatch_nextevent, jiffies));
284 rtnl_unlock();
285 }
286
287
linkwatch_fire_event(struct net_device * dev)288 void linkwatch_fire_event(struct net_device *dev)
289 {
290 bool urgent = linkwatch_urgent_event(dev);
291
292 if (!test_and_set_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state)) {
293 linkwatch_add_event(dev);
294 } else if (!urgent)
295 return;
296
297 linkwatch_schedule_work(urgent);
298 }
299 EXPORT_SYMBOL(linkwatch_fire_event);
300