6lowpan: introduce lowpan_fetch_skb function

This patch adds a helper function to parse the ipv6 header to a
6lowpan header in stream.

This function checks first if we can pull data with a specific
length from a skb. If this seems to be okay, we copy skb data to
a destination pointer and run skb_pull.

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

1 files changed, 12 insertions, 0 deletions

diff --git a/net/ieee802154/6lowpan.h b/net/ieee802154/6lowpan.h
index 4b8f917658b5..a636545d8dcf 100644
--- a/net/ieee802154/6lowpan.h
+++ b/net/ieee802154/6lowpan.h
@@ -230,4 +230,16 @@
                                         dest = 16 bit inline */
 #define LOWPAN_NHC_UDP_CS_P_11  0xF3 /* source & dest = 0xF0B + 4bit inline */
 
+static inline bool lowpan_fetch_skb(struct sk_buff *skb,
+                void *data, const unsigned int len)
+{
+        if (unlikely(!pskb_may_pull(skb, len)))
+                return true;
+
+        skb_copy_from_linear_data(skb, data, len);
+        skb_pull(skb, len);
+
+        return false;
+}
+
 #endif /* __6LOWPAN_H__ */