loopback: packet drops accounting

We can in some situations drop packets in netif_rx()

loopback driver does not report these (unlikely) drops to its stats,
and incorrectly change packets/bytes counts.

After this patch applied, "ifconfig lo" can reports these drops as in :

# ifconfig lo
lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:692562900 errors:3228 dropped:3228 overruns:0 frame:0
          TX packets:692562900 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:2865674174 (2.6 GiB)  TX bytes:2865674174 (2.6 GiB)

I initialy chose to reflect those errors only in tx_dropped/tx_errors, but David
convinced me that it was really RX errors, as loopback_xmit() really starts
a RX process. (calling eth_type_trans() for example, that itself pulls the ethernet header)

These errors are accounted in rx_dropped/rx_errors.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 15 insertions, 6 deletions

diff --git a/drivers/net/loopback.c b/drivers/net/loopback.c
index b7d438a367f3..6f71157bea8e 100644
--- a/drivers/net/loopback.c
+++ b/drivers/net/loopback.c
@@ -62,6 +62,7 @@
 struct pcpu_lstats {
         unsigned long packets;
         unsigned long bytes;
+        unsigned long drops;
 };
 
 /*
@@ -71,18 +72,22 @@ struct pcpu_lstats {
 static int loopback_xmit(struct sk_buff *skb, struct net_device *dev)
 {
         struct pcpu_lstats *pcpu_lstats, *lb_stats;
+        int len;
 
         skb_orphan(skb);
 
-        skb->protocol = eth_type_trans(skb,dev);
+        skb->protocol = eth_type_trans(skb, dev);
 
         /* it's OK to use per_cpu_ptr() because BHs are off */
         pcpu_lstats = dev->ml_priv;
         lb_stats = per_cpu_ptr(pcpu_lstats, smp_processor_id());
-        lb_stats->bytes += skb->len;
-        lb_stats->packets++;
 
-        netif_rx(skb);
+        len = skb->len;
+        if (likely(netif_rx(skb) == NET_RX_SUCCESS)) {
+                lb_stats->bytes += len;
+                lb_stats->packets++;
+        } else
+                lb_stats->drops++;
 
         return 0;
 }
@@ -93,6 +98,7 @@ static struct net_device_stats *loopback_get_stats(struct net_device *dev)
         struct net_device_stats *stats = &dev->stats;
         unsigned long bytes = 0;
         unsigned long packets = 0;
+        unsigned long drops = 0;
         int i;
 
         pcpu_lstats = dev->ml_priv;
@@ -102,11 +108,14 @@ static struct net_device_stats *loopback_get_stats(struct net_device *dev)
                 lb_stats = per_cpu_ptr(pcpu_lstats, i);
                 bytes   += lb_stats->bytes;
                 packets += lb_stats->packets;
+                drops   += lb_stats->drops;
         }
         stats->rx_packets = packets;
         stats->tx_packets = packets;
-        stats->rx_bytes = bytes;
-        stats->tx_bytes = bytes;
+        stats->rx_dropped = drops;
+        stats->rx_errors  = drops;
+        stats->rx_bytes   = bytes;
+        stats->tx_bytes   = bytes;
         return stats;
 }