6lowpan_rtnl: fix fragmentation with two fragments

This patch fix the 6LoWPAN fragmentation for the case if we have exactly
two fragments. The problem is that the (skb_unprocessed >= frag_cap)
condition is always false on the second fragment after sending the first
fragment. A fragmentation with only one fragment doesn't make any sense.
The solution is that we use a do while loop here, that ensures we sending
always a minimum of two fragments if we need a fragmentation.

This issue was introduced by commit d4b2816d67d6e07b2f27037f282d8db03a5829d7
("6lowpan: fix fragmentation").

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 2 deletions

diff --git a/net/ieee802154/6lowpan_rtnl.c b/net/ieee802154/6lowpan_rtnl.c
index 1ae8a5628fb5..9d57026fd9d5 100644
--- a/net/ieee802154/6lowpan_rtnl.c
+++ b/net/ieee802154/6lowpan_rtnl.c
@@ -312,7 +312,7 @@ lowpan_xmit_fragmented(struct sk_buff *skb, struct net_device *dev,
         frag_hdr[0] |= LOWPAN_DISPATCH_FRAGN;
         frag_cap = round_down(payload_cap - LOWPAN_FRAGN_HEAD_SIZE, 8);
 
-        while (skb_unprocessed >= frag_cap) {
+        do {
                 dgram_offset += frag_len;
                 skb_offset += frag_len;
                 skb_unprocessed -= frag_len;
@@ -328,7 +328,7 @@ lowpan_xmit_fragmented(struct sk_buff *skb, struct net_device *dev,
                                  __func__, frag_tag, skb_offset);
                         goto err;
                 }
-        }
+        } while (skb_unprocessed >= frag_cap);
 
         consume_skb(skb);
         return NET_XMIT_SUCCESS;