rtnl/do_setlink(): set modified when IFLA_LINKMODE is updated

The only effect of this patch is to print a warning if IFLA_LINKMODE is updated
and a following change fails.
Signed-off-by: NNicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/rtnetlink.c

@@ -1624,8 +1624,12 @@ static int do_setlink(const struct sk_buff *skb,
 		set_operstate(dev, nla_get_u8(tb[IFLA_OPERSTATE]));
 
 	if (tb[IFLA_LINKMODE]) {
+		unsigned char value = nla_get_u8(tb[IFLA_LINKMODE]);
+
 		write_lock_bh(&dev_base_lock);
-		dev->link_mode = nla_get_u8(tb[IFLA_LINKMODE]);
+		if (dev->link_mode ^ value)
+			modified = 1;
+		dev->link_mode = value;
 		write_unlock_bh(&dev_base_lock);
 	}