veth: check for NAPI instead of xdp_prog before xmit of XDP frame

The recent patch that tied enabling of veth NAPI to the GRO flag also has
the nice side effect that a veth device can be the target of an
XDP_REDIRECT without an XDP program needing to be loaded on the peer
device. However, the patch adding this extra NAPI mode didn't actually
change the check in veth_xdp_xmit() to also look at the new NAPI pointer,
so let's fix that.

Fixes: 6788fa154546 ("veth: allow enabling NAPI even without XDP")
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/veth.c

@@ -486,11 +486,10 @@ static int veth_xdp_xmit(struct net_device *dev, int n,
 
 	rcv_priv = netdev_priv(rcv);
 	rq = &rcv_priv->rq[veth_select_rxq(rcv)];
-	/* Non-NULL xdp_prog ensures that xdp_ring is initialized on receive
-	 * side. This means an XDP program is loaded on the peer and the peer
-	 * device is up.
+	/* The napi pointer is set if NAPI is enabled, which ensures that
+	 * xdp_ring is initialized on receive side and the peer device is up.
 	 */
-	if (!rcu_access_pointer(rq->xdp_prog))
+	if (!rcu_access_pointer(rq->napi))
 		goto out;
 
 	max_len = rcv->mtu + rcv->hard_header_len + VLAN_HLEN;