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net/lapb: support netdev events

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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>
This commit is contained in:
Martin Schiller 2020-11-26 07:35:54 +01:00 committed by Jakub Kicinski
parent 7eed751b3b
commit a4989fa911
1 changed files with 81 additions and 1 deletions
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82
net/lapb/lapb_iface.c
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@ -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>");