Merge branch 'skb-helpers'

Eric Dumazet says:

====================
net: better use of skb helpers

First patch is a pure cleanup.

Second patch adds a DEBUG_NET_WARN_ON_ONCE() in skb_network_header_len(),
this could help to discover old bugs.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>