[PATCH net-next v2] net: sysfs: also pass network device driver to uevent

[Til Kaiser <mail@tk154.de>]

Currently, for uevent, the interface name and
index are passed via shell variables.

This commit also passes the network device
driver as a shell variable to uevent.

One way to retrieve a network interface's driver
name is to resolve its sysfs device/driver symlink
and then substitute leading directory components.

You could implement this yourself (e.g., like udev from
systemd does) or with Linux tools by using a combination
of readlink and shell substitution or basename.

The advantages of passing the driver directly through uevent are:
 - Linux distributions don't need to implement additional code
   to retrieve the driver when, e.g., interface events happen.
 - There is no need to create additional process forks in shell
   scripts for readlink or basename.
 - If a user wants to check his network interface's driver on the
   command line, he can directly read it from the sysfs uevent file.

Signed-off-by: Til Kaiser <mail@tk154.de>
---
 net/core/net-sysfs.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 05cf5347f25e..67aad5ca82f8 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -2000,6 +2000,7 @@ EXPORT_SYMBOL_GPL(net_ns_type_operations);
 static int netdev_uevent(const struct device *d, struct kobj_uevent_env *env)
 {
 	const struct net_device *dev = to_net_dev(d);
+	const char *driver = netdev_drivername(dev);
 	int retval;
 
 	/* pass interface to uevent. */
@@ -2012,6 +2013,12 @@ static int netdev_uevent(const struct device *d, struct kobj_uevent_env *env)
 	 * and is what RtNetlink uses natively.
 	 */
 	retval = add_uevent_var(env, "IFINDEX=%d", dev->ifindex);
+	if (retval)
+		goto exit;
+
+	if (driver[0])
+		/* pass driver to uevent. */
+		retval = add_uevent_var(env, "DRIVER=%s", driver);
 
 exit:
 	return retval;
-- 
2.47.0