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>

11 files changed, 26 insertions, 34 deletions

diff --git a/drivers/net/loopback.c b/drivers/net/loopback.c
index 4b0e30b564e5..2d9663a1c54d 100644
--- a/drivers/net/loopback.c
+++ b/drivers/net/loopback.c
@@ -64,7 +64,6 @@ struct pcpu_lstats {
         u64                     packets;
         u64                     bytes;
         struct u64_stats_sync   syncp;
-        unsigned long           drops;
 };
 
 /*
@@ -90,8 +89,7 @@ static netdev_tx_t loopback_xmit(struct sk_buff *skb,
                 lb_stats->bytes += len;
                 lb_stats->packets++;
                 u64_stats_update_end(&lb_stats->syncp);
-        } else
-                lb_stats->drops++;
+        }
 
         return NETDEV_TX_OK;
 }
@@ -101,7 +99,6 @@ static struct rtnl_link_stats64 *loopback_get_stats64(struct net_device *dev,
 {
         u64 bytes = 0;
         u64 packets = 0;
-        u64 drops = 0;
         int i;
 
         for_each_possible_cpu(i) {
@@ -115,14 +112,11 @@ static struct rtnl_link_stats64 *loopback_get_stats64(struct net_device *dev,
                         tbytes = lb_stats->bytes;
                         tpackets = lb_stats->packets;
                 } while (u64_stats_fetch_retry(&lb_stats->syncp, start));
-                drops   += lb_stats->drops;
                 bytes   += tbytes;
                 packets += tpackets;
         }
         stats->rx_packets = packets;
         stats->tx_packets = packets;
-        stats->rx_dropped = drops;
-        stats->rx_errors  = drops;
         stats->rx_bytes   = bytes;
         stats->tx_bytes   = bytes;
         return stats;
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 92d81edd5808..6abcef67b178 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -884,6 +884,9 @@ struct net_device {
         int                     iflink;
 
         struct net_device_stats stats;
+        atomic_long_t           rx_dropped; /* dropped packets by core network
+                                             * Do not use this in drivers.
+                                             */
 
 #ifdef CONFIG_WIRELESS_EXT
         /* List of functions to handle Wireless Extensions (instead of ioctl).
diff --git a/net/8021q/vlan.h b/net/8021q/vlan.h
index b26ce343072c..8d9503ad01da 100644
--- a/net/8021q/vlan.h
+++ b/net/8021q/vlan.h
@@ -25,7 +25,6 @@ struct vlan_priority_tci_mapping {
  *      @rx_multicast: number of received multicast packets
  *      @syncp: synchronization point for 64bit counters
  *      @rx_errors: number of errors
- *      @rx_dropped: number of dropped packets
  */
 struct vlan_rx_stats {
         u64                     rx_packets;
@@ -33,7 +32,6 @@ struct vlan_rx_stats {
         u64                     rx_multicast;
         struct u64_stats_sync   syncp;
         unsigned long           rx_errors;
-        unsigned long           rx_dropped;
 };
 
 /**
diff --git a/net/8021q/vlan_core.c b/net/8021q/vlan_core.c
index b6d55a9304f2..dee727ce0291 100644
--- a/net/8021q/vlan_core.c
+++ b/net/8021q/vlan_core.c
@@ -33,6 +33,7 @@ int __vlan_hwaccel_rx(struct sk_buff *skb, struct vlan_group *grp,
         return polling ? netif_receive_skb(skb) : netif_rx(skb);
 
 drop:
+        atomic_long_inc(&skb->dev->rx_dropped);
         dev_kfree_skb_any(skb);
         return NET_RX_DROP;
 }
@@ -123,6 +124,7 @@ vlan_gro_common(struct napi_struct *napi, struct vlan_group *grp,
         return dev_gro_receive(napi, skb);
 
 drop:
+        atomic_long_inc(&skb->dev->rx_dropped);
         return GRO_DROP;
 }
 
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;
 }
diff --git a/net/core/dev.c b/net/core/dev.c
index ce6ad88c980b..7d149550e8d6 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1483,8 +1483,9 @@ int dev_forward_skb(struct net_device *dev, struct sk_buff *skb)
         skb_orphan(skb);
         nf_reset(skb);
 
-        if (!(dev->flags & IFF_UP) ||
-            (skb->len > (dev->mtu + dev->hard_header_len))) {
+        if (unlikely(!(dev->flags & IFF_UP) ||
+                     (skb->len > (dev->mtu + dev->hard_header_len)))) {
+                atomic_long_inc(&dev->rx_dropped);
                 kfree_skb(skb);
                 return NET_RX_DROP;
         }
@@ -2548,6 +2549,7 @@ enqueue:
 
         local_irq_restore(flags);
 
+        atomic_long_inc(&skb->dev->rx_dropped);
         kfree_skb(skb);
         return NET_RX_DROP;
 }
@@ -2995,6 +2997,7 @@ ncls:
         if (pt_prev) {
                 ret = pt_prev->func(skb, skb->dev, pt_prev, orig_dev);
         } else {
+                atomic_long_inc(&skb->dev->rx_dropped);
                 kfree_skb(skb);
                 /* Jamal, now you will not able to escape explaining
                  * me how you were going to use this. :-)
@@ -5429,14 +5432,14 @@ struct rtnl_link_stats64 *dev_get_stats(struct net_device *dev,
 
         if (ops->ndo_get_stats64) {
                 memset(storage, 0, sizeof(*storage));
-                return ops->ndo_get_stats64(dev, storage);
-        }
-        if (ops->ndo_get_stats) {
+                ops->ndo_get_stats64(dev, storage);
+        } else if (ops->ndo_get_stats) {
                 netdev_stats_to_stats64(storage, ops->ndo_get_stats(dev));
-                return storage;
+        } else {
+                netdev_stats_to_stats64(storage, &dev->stats);
+                dev_txq_stats_fold(dev, storage);
         }
-        netdev_stats_to_stats64(storage, &dev->stats);
-        dev_txq_stats_fold(dev, storage);
+        storage->rx_dropped += atomic_long_read(&dev->rx_dropped);
         return storage;
 }
 EXPORT_SYMBOL(dev_get_stats);
diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index fbe2c473a06a..9d421f4cf3ef 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -679,8 +679,7 @@ static int ipgre_rcv(struct sk_buff *skb)
                 skb_reset_network_header(skb);
                 ipgre_ecn_decapsulate(iph, skb);
 
-                if (netif_rx(skb) == NET_RX_DROP)
-                        tunnel->dev->stats.rx_dropped++;
+                netif_rx(skb);
 
                 rcu_read_unlock();
                 return 0;
diff --git a/net/ipv4/ipip.c b/net/ipv4/ipip.c
index 6ad46c28ede2..e9b816e6cd73 100644
--- a/net/ipv4/ipip.c
+++ b/net/ipv4/ipip.c
@@ -414,8 +414,7 @@ static int ipip_rcv(struct sk_buff *skb)
 
                 ipip_ecn_decapsulate(iph, skb);
 
-                if (netif_rx(skb) == NET_RX_DROP)
-                        tunnel->dev->stats.rx_dropped++;
+                netif_rx(skb);
 
                 rcu_read_unlock();
                 return 0;
diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index 8be3c452af90..c2c0f89397b1 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -768,8 +768,7 @@ static int ip6_tnl_rcv(struct sk_buff *skb, __u16 protocol,
 
                 dscp_ecn_decapsulate(t, ipv6h, skb);
 
-                if (netif_rx(skb) == NET_RX_DROP)
-                        t->dev->stats.rx_dropped++;
+                netif_rx(skb);
 
                 rcu_read_unlock();
                 return 0;
diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index 2640c9be589d..6f32ffce7022 100644
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -666,8 +666,7 @@ static int pim6_rcv(struct sk_buff *skb)
 
         skb_tunnel_rx(skb, reg_dev);
 
-        if (netif_rx(skb) == NET_RX_DROP)
-                reg_dev->stats.rx_dropped++;
+        netif_rx(skb);
 
         dev_put(reg_dev);
         return 0;
diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index d7701782b639..367a6cc584cc 100644
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -600,8 +600,7 @@ static int ipip6_rcv(struct sk_buff *skb)
 
                 ipip6_ecn_decapsulate(iph, skb);
 
-                if (netif_rx(skb) == NET_RX_DROP)
-                        tunnel->dev->stats.rx_dropped++;
+                netif_rx(skb);
 
                 rcu_read_unlock();
                 return 0;