dev: introduce dev_get_iflink()

The goal of this patch is to prepare the removal of the iflink field. It
introduces a new ndo function, which will be implemented by virtual interfaces.

There is no functional change into this patch. All readers of iflink field
now call dev_get_iflink().

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index cc5cf68..4238d6d 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -109,11 +109,19 @@
 NETDEVICE_SHOW_RO(dev_port, fmt_dec);
 NETDEVICE_SHOW_RO(addr_assign_type, fmt_dec);
 NETDEVICE_SHOW_RO(addr_len, fmt_dec);
-NETDEVICE_SHOW_RO(iflink, fmt_dec);
 NETDEVICE_SHOW_RO(ifindex, fmt_dec);
 NETDEVICE_SHOW_RO(type, fmt_dec);
 NETDEVICE_SHOW_RO(link_mode, fmt_dec);
 
+static ssize_t iflink_show(struct device *dev, struct device_attribute *attr,
+			   char *buf)
+{
+	struct net_device *ndev = to_net_dev(dev);
+
+	return sprintf(buf, fmt_dec, dev_get_iflink(ndev));
+}
+static DEVICE_ATTR_RO(iflink);
+
 static ssize_t format_name_assign_type(const struct net_device *dev, char *buf)
 {
 	return sprintf(buf, fmt_dec, dev->name_assign_type);