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