ieee802154: 6lowpan: add tx/rx stats

This patch adds support for increment transmit and receive stats. The
meaning of these stats are IPv6 based, which shows the stats after
running the 6lowpan adaptation layer (uncompression/compression,
fragmentation handling) on receive and before the adaptation layer
when transmit.
Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/ieee802154/6lowpan/rx.c

@@ -29,6 +29,8 @@
 static int lowpan_give_skb_to_device(struct sk_buff *skb)
 {
 	skb->protocol = htons(ETH_P_IPV6);
+	skb->dev->stats.rx_packets++;
+	skb->dev->stats.rx_bytes += skb->len;
 
 	return netif_rx(skb);
 }

net/ieee802154/6lowpan/tx.c

@@ -192,6 +192,8 @@ lowpan_xmit_fragmented(struct sk_buff *skb, struct net_device *ldev,
 		}
 	} while (skb_unprocessed > frag_cap);
 
+	ldev->stats.tx_packets++;
+	ldev->stats.tx_bytes += dgram_size;
 	consume_skb(skb);
 	return NET_XMIT_SUCCESS;
 
@@ -277,6 +279,8 @@ netdev_tx_t lowpan_xmit(struct sk_buff *skb, struct net_device *ldev)
 
 	if (skb_tail_pointer(skb) - skb_network_header(skb) <= max_single) {
 		skb->dev = lowpan_dev_info(ldev)->wdev;
+		ldev->stats.tx_packets++;
+		ldev->stats.tx_bytes += dgram_size;
 		return dev_queue_xmit(skb);
 	} else {
 		netdev_tx_t rc;