net: add and use skb_gso_transport_seglen()

commit de960aa9ab4decc3304959f69533eef64d05d8e8 upstream.

[ no skb_gso_seglen helper in 3.4, leave tbf alone ]

This moves part of Eric Dumazets skb_gso_seglen helper from tbf sched to
skbuff core so it may be reused by upcoming ip forwarding path patch.

Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 42b919c..9cfc1ff 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2159,6 +2159,8 @@
 extern struct sk_buff *skb_segment(struct sk_buff *skb,
 				   netdev_features_t features);
 
+unsigned int skb_gso_transport_seglen(const struct sk_buff *skb);
+
 static inline void *skb_header_pointer(const struct sk_buff *skb, int offset,
 				       int len, void *buffer)
 {