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