net/lapb: support netdev events

This patch allows layer2 (LAPB) to react to netdev events itself and
avoids the detour via layer3 (X.25).

1. Establish layer2 on NETDEV_UP events, if the carrier is already up.

2. Call lapb_disconnect_request() on NETDEV_GOING_DOWN events to signal
   the peer that the connection will go down.
   (Only when the carrier is up.)

3. When a NETDEV_DOWN event occur, clear all queues, enter state
   LAPB_STATE_0 and stop all timers.

4. The NETDEV_CHANGE event makes it possible to handle carrier loss and
   detection.

   In case of Carrier Loss, clear all queues, enter state LAPB_STATE_0
   and stop all timers.

   In case of Carrier Detection, we start timer t1 on a DCE interface,
   and on a DTE interface we change to state LAPB_STATE_1 and start
   sending SABM(E).

Signed-off-by: Martin Schiller <ms@dev.tdt.de>
Acked-by: Xie He <xie.he.0141@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/lapb/lapb_iface.c b/net/lapb/lapb_iface.c
index 3c03f65..213ea7a 100644 (file)
--- a/net/lapb/lapb_iface.c
+++ b/net/lapb/lapb_iface.c
@@ -418,14 +418,94 @@ int lapb_data_transmit(struct lapb_cb *lapb, struct sk_buff *skb)
        return used;
 }
 
+/* Handle device status changes. */
+static int lapb_device_event(struct notifier_block *this, unsigned long event,
+                            void *ptr)
+{
+       struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+       struct lapb_cb *lapb;
+
+       if (!net_eq(dev_net(dev), &init_net))
+               return NOTIFY_DONE;
+
+       if (dev->type != ARPHRD_X25)
+               return NOTIFY_DONE;
+
+       lapb = lapb_devtostruct(dev);
+       if (!lapb)
+               return NOTIFY_DONE;
+
+       switch (event) {
+       case NETDEV_UP:
+               lapb_dbg(0, "(%p) Interface up: %s\n", dev, dev->name);
+
+               if (netif_carrier_ok(dev)) {
+                       lapb_dbg(0, "(%p): Carrier is already up: %s\n", dev,
+                                dev->name);
+                       if (lapb->mode & LAPB_DCE) {
+                               lapb_start_t1timer(lapb);
+                       } else {
+                               if (lapb->state == LAPB_STATE_0) {
+                                       lapb->state = LAPB_STATE_1;
+                                       lapb_establish_data_link(lapb);
+                               }
+                       }
+               }
+               break;
+       case NETDEV_GOING_DOWN:
+               if (netif_carrier_ok(dev))
+                       lapb_disconnect_request(dev);
+               break;
+       case NETDEV_DOWN:
+               lapb_dbg(0, "(%p) Interface down: %s\n", dev, dev->name);
+               lapb_dbg(0, "(%p) S%d -> S0\n", dev, lapb->state);
+               lapb_clear_queues(lapb);
+               lapb->state = LAPB_STATE_0;
+               lapb->n2count   = 0;
+               lapb_stop_t1timer(lapb);
+               lapb_stop_t2timer(lapb);
+               break;
+       case NETDEV_CHANGE:
+               if (netif_carrier_ok(dev)) {
+                       lapb_dbg(0, "(%p): Carrier detected: %s\n", dev,
+                                dev->name);
+                       if (lapb->mode & LAPB_DCE) {
+                               lapb_start_t1timer(lapb);
+                       } else {
+                               if (lapb->state == LAPB_STATE_0) {
+                                       lapb->state = LAPB_STATE_1;
+                                       lapb_establish_data_link(lapb);
+                               }
+                       }
+               } else {
+                       lapb_dbg(0, "(%p) Carrier lost: %s\n", dev, dev->name);
+                       lapb_dbg(0, "(%p) S%d -> S0\n", dev, lapb->state);
+                       lapb_clear_queues(lapb);
+                       lapb->state = LAPB_STATE_0;
+                       lapb->n2count   = 0;
+                       lapb_stop_t1timer(lapb);
+                       lapb_stop_t2timer(lapb);
+               }
+               break;
+       }
+
+       return NOTIFY_DONE;
+}
+
+static struct notifier_block lapb_dev_notifier = {
+       .notifier_call = lapb_device_event,
+};
+
 static int __init lapb_init(void)
 {
-       return 0;
+       return register_netdevice_notifier(&lapb_dev_notifier);
 }
 
 static void __exit lapb_exit(void)
 {
        WARN_ON(!list_empty(&lapb_list));
+
+       unregister_netdevice_notifier(&lapb_dev_notifier);
 }
 
 MODULE_AUTHOR("Jonathan Naylor <g4klx@g4klx.demon.co.uk>");