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
23enum lw_bits {
24 LW_URGENT = 0,
25};
26
27static unsigned long linkwatch_flags;
28static unsigned long linkwatch_nextevent;
29
30static void linkwatch_event(struct work_struct *dummy);
31static DECLARE_DELAYED_WORK(linkwatch_work, linkwatch_event);
32
33static LIST_HEAD(lweventlist);
34static DEFINE_SPINLOCK(lweventlist_lock);
35
36static 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 struct net_device *peer;
46 int iflink;
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_REGISTERED)
52 iflink = dev_get_iflink(dev);
53 else
54 iflink = dev->ifindex;
55
56 if (iflink == dev->ifindex)
57 return IF_OPER_DOWN;
58
59 ASSERT_RTNL();
60 peer = __dev_get_by_index(net: dev_net(dev), ifindex: iflink);
61 if (!peer)
62 return IF_OPER_DOWN;
63
64 return netif_carrier_ok(dev: peer) ? IF_OPER_DOWN :
65 IF_OPER_LOWERLAYERDOWN;
66 }
67
68 if (netif_dormant(dev))
69 return IF_OPER_DORMANT;
70
71 return IF_OPER_UP;
72}
73
74static void rfc2863_policy(struct net_device *dev)
75{
76 unsigned int operstate = default_operstate(dev);
77
78 if (operstate == READ_ONCE(dev->operstate))
79 return;
80
81 switch(dev->link_mode) {
82 case IF_LINK_MODE_TESTING:
83 if (operstate == IF_OPER_UP)
84 operstate = IF_OPER_TESTING;
85 break;
86
87 case IF_LINK_MODE_DORMANT:
88 if (operstate == IF_OPER_UP)
89 operstate = IF_OPER_DORMANT;
90 break;
91 case IF_LINK_MODE_DEFAULT:
92 default:
93 break;
94 }
95
96 WRITE_ONCE(dev->operstate, operstate);
97}
98
99
100void linkwatch_init_dev(struct net_device *dev)
101{
102 /* Handle pre-registration link state changes */
103 if (!netif_carrier_ok(dev) || netif_dormant(dev) ||
104 netif_testing(dev))
105 rfc2863_policy(dev);
106}
107
108
109static bool linkwatch_urgent_event(struct net_device *dev)
110{
111 if (!netif_running(dev))
112 return false;
113
114 if (dev->ifindex != dev_get_iflink(dev))
115 return true;
116
117 if (netif_is_lag_port(dev) || netif_is_lag_master(dev))
118 return true;
119
120 return netif_carrier_ok(dev) && qdisc_tx_changing(dev);
121}
122
123
124static void linkwatch_add_event(struct net_device *dev)
125{
126 unsigned long flags;
127
128 spin_lock_irqsave(&lweventlist_lock, flags);
129 if (list_empty(head: &dev->link_watch_list)) {
130 list_add_tail(new: &dev->link_watch_list, head: &lweventlist);
131 netdev_hold(dev, tracker: &dev->linkwatch_dev_tracker, GFP_ATOMIC);
132 }
133 spin_unlock_irqrestore(lock: &lweventlist_lock, flags);
134}
135
136
137static void linkwatch_schedule_work(int urgent)
138{
139 unsigned long delay = linkwatch_nextevent - jiffies;
140
141 if (test_bit(LW_URGENT, &linkwatch_flags))
142 return;
143
144 /* Minimise down-time: drop delay for up event. */
145 if (urgent) {
146 if (test_and_set_bit(nr: LW_URGENT, addr: &linkwatch_flags))
147 return;
148 delay = 0;
149 }
150
151 /* If we wrap around we'll delay it by at most HZ. */
152 if (delay > HZ)
153 delay = 0;
154
155 /*
156 * If urgent, schedule immediate execution; otherwise, don't
157 * override the existing timer.
158 */
159 if (test_bit(LW_URGENT, &linkwatch_flags))
160 mod_delayed_work(wq: system_dfl_wq, dwork: &linkwatch_work, delay: 0);
161 else
162 queue_delayed_work(wq: system_dfl_wq, dwork: &linkwatch_work, delay);
163}
164
165
166static void linkwatch_do_dev(struct net_device *dev)
167{
168 /*
169 * Make sure the above read is complete since it can be
170 * rewritten as soon as we clear the bit below.
171 */
172 smp_mb__before_atomic();
173
174 /* We are about to handle this device,
175 * so new events can be accepted
176 */
177 clear_bit(nr: __LINK_STATE_LINKWATCH_PENDING, addr: &dev->state);
178
179 rfc2863_policy(dev);
180 if (dev->flags & IFF_UP) {
181 if (netif_carrier_ok(dev))
182 dev_activate(dev);
183 else
184 dev_deactivate(dev);
185
186 netif_state_change(dev);
187 }
188}
189
190static void __linkwatch_run_queue(int urgent_only)
191{
192#define MAX_DO_DEV_PER_LOOP 100
193
194 int do_dev = MAX_DO_DEV_PER_LOOP;
195 /* Use a local list here since we add non-urgent
196 * events back to the global one when called with
197 * urgent_only=1.
198 */
199 LIST_HEAD(wrk);
200
201 /* Give urgent case more budget */
202 if (urgent_only)
203 do_dev += MAX_DO_DEV_PER_LOOP;
204
205 /*
206 * Limit the number of linkwatch events to one
207 * per second so that a runaway driver does not
208 * cause a storm of messages on the netlink
209 * socket. This limit does not apply to up events
210 * while the device qdisc is down.
211 */
212 if (!urgent_only)
213 linkwatch_nextevent = jiffies + HZ;
214 /* Limit wrap-around effect on delay. */
215 else if (time_after(linkwatch_nextevent, jiffies + HZ))
216 linkwatch_nextevent = jiffies;
217
218 clear_bit(nr: LW_URGENT, addr: &linkwatch_flags);
219
220 spin_lock_irq(lock: &lweventlist_lock);
221 list_splice_init(list: &lweventlist, head: &wrk);
222
223 while (!list_empty(head: &wrk) && do_dev > 0) {
224 struct net_device *dev;
225
226 dev = list_first_entry(&wrk, struct net_device, link_watch_list);
227 list_del_init(entry: &dev->link_watch_list);
228
229 if (!netif_device_present(dev) ||
230 (urgent_only && !linkwatch_urgent_event(dev))) {
231 list_add_tail(new: &dev->link_watch_list, head: &lweventlist);
232 continue;
233 }
234 /* We must free netdev tracker under
235 * the spinlock protection.
236 */
237 netdev_tracker_free(dev, tracker: &dev->linkwatch_dev_tracker);
238 spin_unlock_irq(lock: &lweventlist_lock);
239 netdev_lock_ops(dev);
240 linkwatch_do_dev(dev);
241 netdev_unlock_ops(dev);
242 /* Use __dev_put() because netdev_tracker_free() was already
243 * called above. Must be after netdev_unlock_ops() to prevent
244 * netdev_run_todo() from freeing the device while still in use.
245 */
246 __dev_put(dev);
247 do_dev--;
248 spin_lock_irq(lock: &lweventlist_lock);
249 }
250
251 /* Add the remaining work back to lweventlist */
252 list_splice_init(list: &wrk, head: &lweventlist);
253
254 if (!list_empty(head: &lweventlist))
255 linkwatch_schedule_work(urgent: 0);
256 spin_unlock_irq(lock: &lweventlist_lock);
257}
258
259static bool linkwatch_clean_dev(struct net_device *dev)
260{
261 unsigned long flags;
262 bool clean = false;
263
264 spin_lock_irqsave(&lweventlist_lock, flags);
265 if (!list_empty(head: &dev->link_watch_list)) {
266 list_del_init(entry: &dev->link_watch_list);
267 clean = true;
268 /* We must release netdev tracker under
269 * the spinlock protection.
270 */
271 netdev_tracker_free(dev, tracker: &dev->linkwatch_dev_tracker);
272 }
273 spin_unlock_irqrestore(lock: &lweventlist_lock, flags);
274
275 return clean;
276}
277
278void __linkwatch_sync_dev(struct net_device *dev)
279{
280 netdev_ops_assert_locked(dev);
281
282 if (linkwatch_clean_dev(dev)) {
283 linkwatch_do_dev(dev);
284 /* Use __dev_put() because netdev_tracker_free() was already
285 * called inside linkwatch_clean_dev().
286 */
287 __dev_put(dev);
288 }
289}
290
291void linkwatch_sync_dev(struct net_device *dev)
292{
293 if (linkwatch_clean_dev(dev)) {
294 netdev_lock_ops(dev);
295 linkwatch_do_dev(dev);
296 netdev_unlock_ops(dev);
297 /* Use __dev_put() because netdev_tracker_free() was already
298 * called inside linkwatch_clean_dev().
299 */
300 __dev_put(dev);
301 }
302}
303
304/* Must be called with the rtnl semaphore held */
305void linkwatch_run_queue(void)
306{
307 __linkwatch_run_queue(urgent_only: 0);
308}
309
310
311static void linkwatch_event(struct work_struct *dummy)
312{
313 rtnl_lock();
314 __linkwatch_run_queue(time_after(linkwatch_nextevent, jiffies));
315 rtnl_unlock();
316}
317
318
319void linkwatch_fire_event(struct net_device *dev)
320{
321 bool urgent = linkwatch_urgent_event(dev);
322
323 if (!test_and_set_bit(nr: __LINK_STATE_LINKWATCH_PENDING, addr: &dev->state)) {
324 linkwatch_add_event(dev);
325 } else if (!urgent)
326 return;
327
328 linkwatch_schedule_work(urgent);
329}
330EXPORT_SYMBOL(linkwatch_fire_event);
331

source code of linux/net/core/link_watch.c