Subject: [PATCH net-next v2 5/6] net/lapb: support netdev events

From: Martin Schiller <[email-masked]>
Date: Mon, 16 Nov 2020 14:55:26 +0100

This makes it possible to handle carrier loss and detection.
In case of Carrier Loss, layer 2 is terminated
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 <[email-masked]>
---

Change from v1:
fix 'subject_prefix' and 'checkpatch' warnings

---
 net/lapb/lapb_iface.c | 83 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 83 insertions(+)

diff --git a/net/lapb/lapb_iface.c b/net/lapb/lapb_iface.c
index 3c03f6512c5f..63124cdf1926 100644
--- a/net/lapb/lapb_iface.c
+++ b/net/lapb/lapb_iface.c
@@ -418,14 +418,97 @@ 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 = ptr;
+	struct lapb_cb *lapb;
+
+	if (!net_eq(dev_net(dev), &init_net))
+		return NOTIFY_DONE;
+
+	if (dev->type == ARPHRD_X25) {
+		switch (event) {
+		case NETDEV_REGISTER:
+			lapb_dbg(0, "(%p): got event NETDEV_REGISTER for device: %s\n",
+				 dev, dev->name);
+			break;
+		case NETDEV_POST_TYPE_CHANGE:
+			lapb_dbg(0, "(%p): got event NETDEV_POST_TYPE_CHANGE for device: %s\n",
+				 dev, dev->name);
+			break;
+		case NETDEV_UP:
+			lapb_dbg(0, "(%p): got event NETDEV_UP for device: %s\n",
+				 dev, dev->name);
+			break;
+		case NETDEV_GOING_DOWN:
+			lapb_dbg(0, "(%p): got event NETDEV_GOING_DOWN for device: %s\n",
+				 dev, dev->name);
+			break;
+		case NETDEV_DOWN:
+			lapb_dbg(0, "(%p): got event NETDEV_DOWN for device: %s\n",
+				 dev, dev->name);
+			break;
+		case NETDEV_PRE_TYPE_CHANGE:
+			lapb_dbg(0, "(%p): got event NETDEV_PRE_TYPE_CHANGE for device: %s\n",
+				 dev, dev->name);
+			break;
+		case NETDEV_UNREGISTER:
+			lapb_dbg(0, "(%p): got event NETDEV_UNREGISTER for device: %s\n",
+				 dev, dev->name);
+			break;
+		case NETDEV_CHANGE:
+			lapb_dbg(0, "(%p): got event NETDEV_CHANGE for device: %s\n",
+				 dev, dev->name);
+			lapb = lapb_devtostruct(dev);
+			if (!lapb)
+				break;
+
+			if (!netif_carrier_ok(dev)) {
+				lapb_dbg(0, "(%p): Carrier lost -> Entering LAPB_STATE_0: %s\n",
+					 dev, dev->name);
+				lapb_disconnect_indication(lapb, LAPB_OK);
+				lapb_clear_queues(lapb);
+				lapb->state = LAPB_STATE_0;
+				lapb->n2count   = 0;
+				lapb_stop_t1timer(lapb);
+				lapb_stop_t2timer(lapb);
+			} else {
+				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);
+					}
+				}
+			}
+			break;
+		}
+	}
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block lapb_dev_notifier = {
+	.notifier_call = lapb_device_event,
+};
+
 static int __init lapb_init(void)
 {
+	register_netdevice_notifier(&lapb_dev_notifier);
+
 	return 0;
 }
 
 static void __exit lapb_exit(void)
 {
 	WARN_ON(!list_empty(&lapb_list));
+
+	unregister_netdevice_notifier(&lapb_dev_notifier);
 }
 
 MODULE_AUTHOR("Jonathan Naylor <[email-masked]>");
-- 
2.20.1