net: add a core netdev->rx_dropped counter

In various situations, a device provides a packet to our stack and we
drop it before it enters protocol stack :
- softnet backlog full (accounted in /proc/net/softnet_stat)
- bad vlan tag (not accounted)
- unknown/unregistered protocol (not accounted)

We can handle a per-device counter of such dropped frames at core level,
and automatically adds it to the device provided stats (rx_dropped), so
that standard tools can be used (ifconfig, ip link, cat /proc/net/dev)

This is a generalization of commit 8990f468a (net: rx_dropped
accounting), thus reverting it.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 7 deletions

diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
index f6fbcc0f1af9..f54251edd40d 100644
--- a/net/8021q/vlan_dev.c
+++ b/net/8021q/vlan_dev.c
@@ -225,16 +225,15 @@ int vlan_skb_recv(struct sk_buff *skb, struct net_device *dev,
                 }
         }
 
-        if (unlikely(netif_rx(skb) == NET_RX_DROP)) {
-                if (rx_stats)
-                        rx_stats->rx_dropped++;
-        }
+        netif_rx(skb);
+
         rcu_read_unlock();
         return NET_RX_SUCCESS;
 
 err_unlock:
         rcu_read_unlock();
 err_free:
+        atomic_long_inc(&dev->rx_dropped);
         kfree_skb(skb);
         return NET_RX_DROP;
 }
@@ -846,15 +845,13 @@ static struct rtnl_link_stats64 *vlan_dev_get_stats64(struct net_device *dev, st
                         accum.rx_packets += rxpackets;
                         accum.rx_bytes   += rxbytes;
                         accum.rx_multicast += rxmulticast;
-                        /* rx_errors, rx_dropped are ulong, not protected by syncp */
+                        /* rx_errors is ulong, not protected by syncp */
                         accum.rx_errors  += p->rx_errors;
-                        accum.rx_dropped += p->rx_dropped;
                 }
                 stats->rx_packets = accum.rx_packets;
                 stats->rx_bytes   = accum.rx_bytes;
                 stats->rx_errors  = accum.rx_errors;
                 stats->multicast  = accum.rx_multicast;
-                stats->rx_dropped = accum.rx_dropped;
         }
         return stats;
 }