net: Disable NETIF_F_TSO_ECN when TSO is disabled

NETIF_F_TSO_ECN has no effect when TSO is disabled; this just means
that feature state will be accurately reported to user-space.
Signed-off-by: NBen Hutchings <bhutchings@solarflare.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -5208,6 +5208,10 @@ u32 netdev_fix_features(struct net_device *dev, u32 features)
 		features &= ~NETIF_F_ALL_TSO;
 	}
 
+	/* TSO ECN requires that TSO is present as well. */
+	if ((features & NETIF_F_ALL_TSO) == NETIF_F_TSO_ECN)
+		features &= ~NETIF_F_TSO_ECN;
+
 	/* Software GSO depends on SG. */
 	if ((features & NETIF_F_GSO) && !(features & NETIF_F_SG)) {
 		netdev_info(dev, "Dropping NETIF_F_GSO since no SG feature.\n");