ieee802154: 6lowpan: set ackreq when needed

This patch sets the acknowledge request bit inside the 802.15.4 mac
header when frame retries is 0 or above. The other frame retries value
which is -1 indicates that the transmitter doesn't care about an
acknowledge frame which will be ignored after transmitting if the node
sends anyway an ack frame after receiving. This is currently unnecessary
traffic if the max frame retries parameter is -1.
Signed-off-by: NAlexander Aring <alex.aring@gmail.com>
Reviewed-by: NStefan Schmidt <stefan@osg.samsung.com>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

net/ieee802154/6lowpan/tx.c

@@ -190,6 +190,7 @@ lowpan_xmit_fragmented(struct sk_buff *skb, struct net_device *dev,
 
 static int lowpan_header(struct sk_buff *skb, struct net_device *dev)
 {
+	struct wpan_dev *wpan_dev = lowpan_dev_info(dev)->real_dev->ieee802154_ptr;
 	struct ieee802154_addr sa, da;
 	struct ieee802154_mac_cb *cb = mac_cb_init(skb);
 	struct lowpan_addr_info info;
@@ -207,7 +208,7 @@ static int lowpan_header(struct sk_buff *skb, struct net_device *dev)
 
 	/* prepare wpan address data */
 	sa.mode = IEEE802154_ADDR_LONG;
-	sa.pan_id = lowpan_dev_info(dev)->real_dev->ieee802154_ptr->pan_id;
+	sa.pan_id = wpan_dev->pan_id;
 	sa.extended_addr = ieee802154_devaddr_from_raw(saddr);
 
 	/* intra-PAN communications */
@@ -223,7 +224,7 @@ static int lowpan_header(struct sk_buff *skb, struct net_device *dev)
 	} else {
 		da.mode = IEEE802154_ADDR_LONG;
 		da.extended_addr = ieee802154_devaddr_from_raw(daddr);
-		cb->ackreq = true;
+		cb->ackreq = wpan_dev->frame_retries >= 0;
 	}
 
 	return dev_hard_header(skb, lowpan_dev_info(dev)->real_dev,