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

The only effect of this patch is to print a warning if IFLA_TXQLEN 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

@@ -1611,8 +1611,14 @@ static int do_setlink(const struct sk_buff *skb,
 		modified = 1;
 	}
 
-	if (tb[IFLA_TXQLEN])
-		dev->tx_queue_len = nla_get_u32(tb[IFLA_TXQLEN]);
+	if (tb[IFLA_TXQLEN]) {
+		unsigned long value = nla_get_u32(tb[IFLA_TXQLEN]);
+
+		if (dev->tx_queue_len ^ value)
+			modified = 1;
+
+		dev->tx_queue_len = value;
+	}
 
 	if (tb[IFLA_OPERSTATE])
 		set_operstate(dev, nla_get_u8(tb[IFLA_OPERSTATE]));