net: RPS: Make hardware-accelerated RFS conditional on NETIF_F_NTUPLE

For testing and debugging purposes it is useful to be able to disable
hardware acceleration of RFS without disabling RFS altogether.  Since
this is a similar feature to 'n-tuple' flow steering through the
ethtool API, test the same feature flag that controls that.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

net/core/dev.c

@@ -2607,7 +2607,8 @@ set_rps_cpu(struct net_device *dev, struct sk_buff *skb,
 		int rc;
 
 		/* Should we steer this flow to a different hardware queue? */
-		if (!skb_rx_queue_recorded(skb) || !dev->rx_cpu_rmap)
+		if (!skb_rx_queue_recorded(skb) || !dev->rx_cpu_rmap ||
+		    !(dev->features & NETIF_F_NTUPLE))
 			goto out;
 		rxq_index = cpu_rmap_lookup_index(dev->rx_cpu_rmap, next_cpu);
 		if (rxq_index == skb_get_rx_queue(skb))