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 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 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 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 99 100 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 } 113 114 115 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 } 126 127 128 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_unbound_wq, &linkwatch_work, 0); 152 else 153 queue_delayed_work(system_unbound_wq, &linkwatch_work, delay); 154 } 155 156 157 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 } 184 185 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 } 246 247 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 */ 268 void linkwatch_run_queue(void) 269 { 270 __linkwatch_run_queue(0); 271 } 272 273 274 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 } 280 281 282 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