loopback: packet drops accounting (7eebb0b2) · Commits · 戴 / test

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>

drivers/net/loopback.c

+15 −6

Original line number	Diff line number	Diff line
		@@ -62,6 +62,7 @@
		struct pcpu_lstats {
		unsigned long packets;
		unsigned long bytes;
		unsigned long drops;
		};

		/*
		@@ -71,6 +72,7 @@ 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);

		@@ -79,10 +81,13 @@ static int loopback_xmit(struct sk_buff skb, struct net_device 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;
		@@ -102,9 +108,12 @@ 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_dropped = drops;
		stats->rx_errors = drops;
		stats->rx_bytes = bytes;
		stats->tx_bytes = bytes;
		return stats;

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