i40e: report correct statistics when XDP is enabled

mainline inclusion
from mainline-4.20
commit cdec2141c24e
category: bugfix
bugzilla: 6128
CVE: NA

-------------------------------------------------

When XDP is enabled, the driver will report incorrect
statistics. Received frames will reported as transmitted frames.

This commits fixes the i40e implementation of ndo_get_stats64 (struct
net_device_ops), so that iproute2 will report correct statistics
(e.g. when running "ip -stats link show dev eth0") even when XDP is
enabled.
Reported-by: NJesper Dangaard Brouer <brouer@redhat.com>
Fixes: 74608d17 ("i40e: add support for XDP_TX action")
Signed-off-by: NBjörn Töpel <bjorn.topel@intel.com>
Tested-by: NAndrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: NZhiqiang Liu <liuzhiqiang26@huawei.com>
Signed-off-by: NMao Wenan <maowenan@huawei.com>
Reviewed-by: NWei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/net/ethernet/intel/i40e/i40e_main.c

@@ -424,9 +424,9 @@ static void i40e_get_netdev_stats_struct(struct net_device *netdev,
 				  struct rtnl_link_stats64 *stats)
 {
 	struct i40e_netdev_priv *np = netdev_priv(netdev);
-	struct i40e_ring *tx_ring, *rx_ring;
 	struct i40e_vsi *vsi = np->vsi;
 	struct rtnl_link_stats64 *vsi_stats = i40e_get_vsi_stats_struct(vsi);
+	struct i40e_ring *ring;
 	int i;
 
 	if (test_bit(__I40E_VSI_DOWN, vsi->state))
@@ -440,24 +440,26 @@ static void i40e_get_netdev_stats_struct(struct net_device *netdev,
 		u64 bytes, packets;
 		unsigned int start;
 
-		tx_ring = READ_ONCE(vsi->tx_rings[i]);
-		if (!tx_ring)
+		ring = READ_ONCE(vsi->tx_rings[i]);
+		if (!ring)
 			continue;
-		i40e_get_netdev_stats_struct_tx(tx_ring, stats);
+		i40e_get_netdev_stats_struct_tx(ring, stats);
 
-		rx_ring = &tx_ring[1];
+		if (i40e_enabled_xdp_vsi(vsi)) {
+			ring++;
+			i40e_get_netdev_stats_struct_tx(ring, stats);
+		}
 
+		ring++;
 		do {
-			start = u64_stats_fetch_begin_irq(&rx_ring->syncp);
-			packets = rx_ring->stats.packets;
-			bytes   = rx_ring->stats.bytes;
-		} while (u64_stats_fetch_retry_irq(&rx_ring->syncp, start));
+			start   = u64_stats_fetch_begin_irq(&ring->syncp);
+			packets = ring->stats.packets;
+			bytes   = ring->stats.bytes;
+		} while (u64_stats_fetch_retry_irq(&ring->syncp, start));
 
 		stats->rx_packets += packets;
 		stats->rx_bytes   += bytes;
 
-		if (i40e_enabled_xdp_vsi(vsi))
-			i40e_get_netdev_stats_struct_tx(&rx_ring[1], stats);
 	}
 	rcu_read_unlock();