net: rx_dropped accounting

Under load, netif_rx() can drop incoming packets but administrators dont
have a chance to spot which device needs some tuning (RPS activation for
example)

This patch adds rx_dropped accounting in vlans and tunnels.
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/8021q/vlan.h

@@ -25,6 +25,7 @@ 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;
@@ -32,6 +33,7 @@ struct vlan_rx_stats {
 	u64			rx_multicast;
 	struct u64_stats_sync	syncp;
 	unsigned long		rx_errors;
+	unsigned long		rx_dropped;
 };
 
 /**

net/8021q/vlan_dev.c

@@ -225,7 +225,10 @@ int vlan_skb_recv(struct sk_buff *skb, struct net_device *dev,
 		}
 	}
 
-	netif_rx(skb);
+	if (unlikely(netif_rx(skb) == NET_RX_DROP)) {
+		if (rx_stats)
+			rx_stats->rx_dropped++;
+	}
 	rcu_read_unlock();
 	return NET_RX_SUCCESS;
 
@@ -843,13 +846,15 @@ 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 is an ulong, not protected by syncp */
+			/* rx_errors, rx_dropped are 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;
 }

net/ipv4/ip_gre.c

@@ -647,9 +647,11 @@ static int ipgre_rcv(struct sk_buff *skb)
 		skb_reset_network_header(skb);
 		ipgre_ecn_decapsulate(iph, skb);
 
-		netif_rx(skb);
+		if (netif_rx(skb) == NET_RX_DROP)
+			stats->rx_dropped++;
+
 		rcu_read_unlock();
-		return(0);
+		return 0;
 	}
 	icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
 

net/ipv4/ipip.c

@@ -377,7 +377,10 @@ static int ipip_rcv(struct sk_buff *skb)
 		skb_tunnel_rx(skb, tunnel->dev);
 
 		ipip_ecn_decapsulate(iph, skb);
-		netif_rx(skb);
+
+		if (netif_rx(skb) == NET_RX_DROP)
+			tunnel->dev->stats.rx_dropped++;
+
 		rcu_read_unlock();
 		return 0;
 	}

net/ipv6/ip6_tunnel.c

@@ -725,7 +725,10 @@ static int ip6_tnl_rcv(struct sk_buff *skb, __u16 protocol,
 		skb_tunnel_rx(skb, t->dev);
 
 		dscp_ecn_decapsulate(t, ipv6h, skb);
-		netif_rx(skb);
+
+		if (netif_rx(skb) == NET_RX_DROP)
+			t->dev->stats.rx_dropped++;
+
 		rcu_read_unlock();
 		return 0;
 	}

net/ipv6/ip6mr.c

@@ -666,7 +666,9 @@ static int pim6_rcv(struct sk_buff *skb)
 
 	skb_tunnel_rx(skb, reg_dev);
 
-	netif_rx(skb);
+	if (netif_rx(skb) == NET_RX_DROP)
+		reg_dev->stats.rx_dropped++;
+
 	dev_put(reg_dev);
 	return 0;
  drop:

net/ipv6/sit.c

@@ -564,7 +564,10 @@ static int ipip6_rcv(struct sk_buff *skb)
 		skb_tunnel_rx(skb, tunnel->dev);
 
 		ipip6_ecn_decapsulate(iph, skb);
-		netif_rx(skb);
+
+		if (netif_rx(skb) == NET_RX_DROP)
+			tunnel->dev->stats.rx_dropped++;
+
 		rcu_read_unlock();
 		return 0;
 	}