Commit 7eebb0b2 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

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:  Mask:
          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: default avatarEric Dumazet <>
Signed-off-by: default avatarDavid S. Miller <>
parent eb62efd2
......@@ -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->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;
len = skb->len;
if (likely(netif_rx(skb) == NET_RX_SUCCESS)) {
lb_stats->bytes += len;
} else
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;
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