1 /* 2 * Linux network device link state notification 3 * 4 * Author: 5 * Stefan Rompf <sux@loplof.de> 6 * 7 * This program is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU General Public License 9 * as published by the Free Software Foundation; either version 10 * 2 of the License, or (at your option) any later version. 11 * 12 */ 13 14 #include <linux/module.h> 15 #include <linux/netdevice.h> 16 #include <linux/if.h> 17 #include <net/sock.h> 18 #include <net/pkt_sched.h> 19 #include <linux/rtnetlink.h> 20 #include <linux/jiffies.h> 21 #include <linux/spinlock.h> 22 #include <linux/slab.h> 23 #include <linux/workqueue.h> 24 #include <linux/bitops.h> 25 #include <asm/types.h> 26 27 28 enum lw_bits { 29 LW_URGENT = 0, 30 }; 31 32 static unsigned long linkwatch_flags; 33 static unsigned long linkwatch_nextevent; 34 35 static void linkwatch_event(struct work_struct *dummy); 36 static DECLARE_DELAYED_WORK(linkwatch_work, linkwatch_event); 37 38 static struct net_device *lweventlist; 39 static DEFINE_SPINLOCK(lweventlist_lock); 40 41 static unsigned char default_operstate(const struct net_device *dev) 42 { 43 if (!netif_carrier_ok(dev)) 44 return (dev->ifindex != dev->iflink ? 45 IF_OPER_LOWERLAYERDOWN : IF_OPER_DOWN); 46 47 if (netif_dormant(dev)) 48 return IF_OPER_DORMANT; 49 50 return IF_OPER_UP; 51 } 52 53 54 static void rfc2863_policy(struct net_device *dev) 55 { 56 unsigned char operstate = default_operstate(dev); 57 58 if (operstate == dev->operstate) 59 return; 60 61 write_lock_bh(&dev_base_lock); 62 63 switch(dev->link_mode) { 64 case IF_LINK_MODE_DORMANT: 65 if (operstate == IF_OPER_UP) 66 operstate = IF_OPER_DORMANT; 67 break; 68 69 case IF_LINK_MODE_DEFAULT: 70 default: 71 break; 72 } 73 74 dev->operstate = operstate; 75 76 write_unlock_bh(&dev_base_lock); 77 } 78 79 80 static bool linkwatch_urgent_event(struct net_device *dev) 81 { 82 return netif_running(dev) && netif_carrier_ok(dev) && 83 qdisc_tx_changing(dev); 84 } 85 86 87 static void linkwatch_add_event(struct net_device *dev) 88 { 89 unsigned long flags; 90 91 spin_lock_irqsave(&lweventlist_lock, flags); 92 dev->link_watch_next = lweventlist; 93 lweventlist = dev; 94 spin_unlock_irqrestore(&lweventlist_lock, flags); 95 } 96 97 98 static void linkwatch_schedule_work(int urgent) 99 { 100 unsigned long delay = linkwatch_nextevent - jiffies; 101 102 if (test_bit(LW_URGENT, &linkwatch_flags)) 103 return; 104 105 /* Minimise down-time: drop delay for up event. */ 106 if (urgent) { 107 if (test_and_set_bit(LW_URGENT, &linkwatch_flags)) 108 return; 109 delay = 0; 110 } 111 112 /* If we wrap around we'll delay it by at most HZ. */ 113 if (delay > HZ) 114 delay = 0; 115 116 /* 117 * This is true if we've scheduled it immeditately or if we don't 118 * need an immediate execution and it's already pending. 119 */ 120 if (schedule_delayed_work(&linkwatch_work, delay) == !delay) 121 return; 122 123 /* Don't bother if there is nothing urgent. */ 124 if (!test_bit(LW_URGENT, &linkwatch_flags)) 125 return; 126 127 /* It's already running which is good enough. */ 128 if (!cancel_delayed_work(&linkwatch_work)) 129 return; 130 131 /* Otherwise we reschedule it again for immediate exection. */ 132 schedule_delayed_work(&linkwatch_work, 0); 133 } 134 135 136 static void __linkwatch_run_queue(int urgent_only) 137 { 138 struct net_device *next; 139 140 /* 141 * Limit the number of linkwatch events to one 142 * per second so that a runaway driver does not 143 * cause a storm of messages on the netlink 144 * socket. This limit does not apply to up events 145 * while the device qdisc is down. 146 */ 147 if (!urgent_only) 148 linkwatch_nextevent = jiffies + HZ; 149 /* Limit wrap-around effect on delay. */ 150 else if (time_after(linkwatch_nextevent, jiffies + HZ)) 151 linkwatch_nextevent = jiffies; 152 153 clear_bit(LW_URGENT, &linkwatch_flags); 154 155 spin_lock_irq(&lweventlist_lock); 156 next = lweventlist; 157 lweventlist = NULL; 158 spin_unlock_irq(&lweventlist_lock); 159 160 while (next) { 161 struct net_device *dev = next; 162 163 next = dev->link_watch_next; 164 165 if (urgent_only && !linkwatch_urgent_event(dev)) { 166 linkwatch_add_event(dev); 167 continue; 168 } 169 170 /* 171 * Make sure the above read is complete since it can be 172 * rewritten as soon as we clear the bit below. 173 */ 174 smp_mb__before_clear_bit(); 175 176 /* We are about to handle this device, 177 * so new events can be accepted 178 */ 179 clear_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state); 180 181 rfc2863_policy(dev); 182 if (dev->flags & IFF_UP) { 183 if (netif_carrier_ok(dev)) 184 dev_activate(dev); 185 else 186 dev_deactivate(dev); 187 188 netdev_state_change(dev); 189 } 190 191 dev_put(dev); 192 } 193 194 if (lweventlist) 195 linkwatch_schedule_work(0); 196 } 197 198 199 /* Must be called with the rtnl semaphore held */ 200 void linkwatch_run_queue(void) 201 { 202 __linkwatch_run_queue(0); 203 } 204 205 206 static void linkwatch_event(struct work_struct *dummy) 207 { 208 rtnl_lock(); 209 __linkwatch_run_queue(time_after(linkwatch_nextevent, jiffies)); 210 rtnl_unlock(); 211 } 212 213 214 void linkwatch_fire_event(struct net_device *dev) 215 { 216 bool urgent = linkwatch_urgent_event(dev); 217 218 if (!test_and_set_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state)) { 219 dev_hold(dev); 220 221 linkwatch_add_event(dev); 222 } else if (!urgent) 223 return; 224 225 linkwatch_schedule_work(urgent); 226 } 227 228 EXPORT_SYMBOL(linkwatch_fire_event); 229