Depending on how a packet is vlan tagged (i.e. hardware accelerated or
not), the encapsulated protocol is stored in different locations.  This
provides a consistent method of accessing that protocol, which is needed
by drivers, security checks, etc.
Signed-off-by: NHao Zheng <hzheng@nicira.com>
Signed-off-by: NJesse Gross <jesse@nicira.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>