ethtool: add FEATURES_NTF notification

Send ETHTOOL_MSG_FEATURES_NTF notification whenever network device features
are modified using ETHTOOL_MSG_FEATURES_SET netlink message, ethtool ioctl
request or any other way resulting in call to netdev_update_features() or
netdev_change_features()

Signed-off-by: Michal Kubecek <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

Documentation/networking/ethtool-netlink.rst

···
   ``ETHTOOL_MSG_WOL_NTF``               wake-on-lan settings notification
   ``ETHTOOL_MSG_FEATURES_GET_REPLY``    device features
   ``ETHTOOL_MSG_FEATURES_SET_REPLY``    optional reply to FEATURES_SET
+  ``ETHTOOL_MSG_FEATURES_NTF``          netdev features notification
   ===================================== =================================
 
 ``GET`` requests are sent by userspace applications to retrieve device
···
 reports the difference between old and new dev->features: mask consists of
 bits which have changed, values are their values in new dev->features (after
 the operation).
+
+``ETHTOOL_MSG_FEATURES_NTF`` notification is sent not only if device features
+are modified using ``ETHTOOL_MSG_FEATURES_SET`` request or on of ethtool ioctl
+request but also each time features are modified with netdev_update_features()
+or netdev_change_features().
 
 
 Request translation

include/uapi/linux/ethtool_netlink.h

···
 	ETHTOOL_MSG_WOL_NTF,
 	ETHTOOL_MSG_FEATURES_GET_REPLY,
 	ETHTOOL_MSG_FEATURES_SET_REPLY,
+	ETHTOOL_MSG_FEATURES_NTF,
 
 	/* add new constants above here */
 	__ETHTOOL_MSG_KERNEL_CNT,

net/ethtool/features.c

···
 	struct nlattr *tb[ETHTOOL_A_FEATURES_MAX + 1];
 	struct ethnl_req_info req_info = {};
 	struct net_device *dev;
+	bool mod;
 	int ret;
 
 	ret = nlmsg_parse(info->nlhdr, GENL_HDRLEN, tb,
···
 	dev->wanted_features = ethnl_bitmap_to_features(req_wanted);
 	__netdev_update_features(dev);
 	ethnl_features_to_bitmap(new_active, dev->features);
+	mod = !bitmap_equal(old_active, new_active, NETDEV_FEATURE_COUNT);
 
 	ret = 0;
 	if (!(req_info.flags & ETHTOOL_FLAG_OMIT_REPLY)) {
···
 					  wanted_diff_mask, new_active,
 					  active_diff_mask, compact);
 	}
+	if (mod)
+		ethtool_notify(dev, ETHTOOL_MSG_FEATURES_NTF, NULL);
 
 out_rtnl:
 	rtnl_unlock();

net/ethtool/netlink.c

···
 	[ETHTOOL_MSG_LINKMODES_NTF]	= &ethnl_linkmodes_request_ops,
 	[ETHTOOL_MSG_DEBUG_NTF]		= &ethnl_debug_request_ops,
 	[ETHTOOL_MSG_WOL_NTF]		= &ethnl_wol_request_ops,
+	[ETHTOOL_MSG_FEATURES_NTF]	= &ethnl_features_request_ops,
 };
 
 /* default notification handler */
···
 	[ETHTOOL_MSG_LINKMODES_NTF]	= ethnl_default_notify,
 	[ETHTOOL_MSG_DEBUG_NTF]		= ethnl_default_notify,
 	[ETHTOOL_MSG_WOL_NTF]		= ethnl_default_notify,
+	[ETHTOOL_MSG_FEATURES_NTF]	= ethnl_default_notify,
 };
 
 void ethtool_notify(struct net_device *dev, unsigned int cmd, const void *data)
···
 			  cmd, netdev_name(dev));
 }
 EXPORT_SYMBOL(ethtool_notify);
+
+static void ethnl_notify_features(struct netdev_notifier_info *info)
+{
+	struct net_device *dev = netdev_notifier_info_to_dev(info);
+
+	ethtool_notify(dev, ETHTOOL_MSG_FEATURES_NTF, NULL);
+}
+
+static int ethnl_netdev_event(struct notifier_block *this, unsigned long event,
+			      void *ptr)
+{
+	switch (event) {
+	case NETDEV_FEAT_CHANGE:
+		ethnl_notify_features(ptr);
+		break;
+	}
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block ethnl_netdev_notifier = {
+	.notifier_call = ethnl_netdev_event,
+};
 
 /* genetlink setup */
 
···
 		return ret;
 	ethnl_ok = true;
 
-	return 0;
+	ret = register_netdevice_notifier(&ethnl_netdev_notifier);
+	WARN(ret < 0, "ethtool: net device notifier registration failed");
+	return ret;
 }
 
 subsys_initcall(ethnl_init);