It is easier for some applications to deal with text based interfaces
like uevent, rather than using netlink to listen for events.

Note, this does not deal with network namespaces but that is a generic
problem that already exists with kobjects (see rename events).

Signed-off-by: Stephen Hemminger <redacted>

---
net/core/Makefile |    1
net/core/uevent.c |   61 ++++++++++++++++++++++++++++++++++++++++++++ 
++++++++++
2 files changed, 62 insertions(+)

--- a/net/core/Makefile	2008-11-24 12:07:18.000000000 -0800
+++ b/net/core/Makefile	2008-11-24 12:07:22.000000000 -0800

@@ -17,3 +17,4 @@ obj-$(CONFIG_NET_PKTGEN) += pktgen.o

obj-$(CONFIG_NETPOLL) += netpoll.o
obj-$(CONFIG_NET_DMA) += user_dma.o
obj-$(CONFIG_FIB_RULES) += fib_rules.o
+obj-$(CONFIG_HOTPLUG) += uevent.o

--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ b/net/core/uevent.c	2008-11-24 12:11:46.000000000 -0800

@@ -0,0 +1,55 @@
+/*
+ * Linux network device event notification
+ *
+ * Author:
+ *	Stephen Hemminger <shemminger@vyatta.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/netdevice.h>
+#include <linux/kobject.h>
+#include <linux/notifier.h>
+
+/*
+ * Generate uevent in response to network device state changes.
+ * Other events are already handled by device subsystem.
+ */
+static int netdev_event(struct notifier_block *this, unsigned long  

event, void *ptr)
+{
+	struct net_device *netdev = ptr;
+
+	switch (event) {
+	case NETDEV_UP:
+		kobject_uevent(&netdev->dev.kobj, KOBJ_ONLINE);
+		break;
+
+	case NETDEV_DOWN:
+		kobject_uevent(&netdev->dev.kobj, KOBJ_OFFLINE);
+		break;
+
+	case NETDEV_CHANGE: {
+		char str[64] = "DEVSTATE=UP";
+		char *envp[2] = { str, NULL };
+
+		if (netif_oper_up(netdev))
+			strcat(str, ",RUNNING");
+		if (netif_carrier_ok(netdev))
+			strcat(str, ",LOWER_UP");
+		if (netif_dormant(netdev))
+			strcat(str, ",DORMANT");
+		kobject_uevent_env(&netdev->dev.kobj, KOBJ_CHANGE, envp);
+		break;