datapath: Backport "openvswitch: Fix mask generation for nested attributes."

datapath: Backport "openvswitch: Fix mask generation for nested attributes."

Upstream commit:
    openvswitch: Fix mask generation for nested attributes.

    Masks were added to OVS flows in a way that was backwards compatible
    with userspace programs that did not generate masks. As a result, it is
    possible that we may receive flows that do not have a mask and we need
    to synthesize one.

    Generating a mask requires iterating over attributes and descending into
    nested attributes. For each level we need to know the size to generate the
    correct mask. We do this with a linked table of attribute types.

    Although the logic to handle these nested attributes was there in concept,
    there are a number of bugs in practice. Examples include incomplete links
    between tables, variable length attributes being treated as nested and
    missing sanity checks.

    Signed-off-by: Jesse Gross <jesse@nicira.com>
    Acked-by: Pravin B Shelar <pshelar@nicira.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
Upstream: 982b5270 ("openvswitch: Fix mask generation for nested attributes.")
Signed-off-by: Jesse Gross <jesse@nicira.com>
Acked-by: Pravin B Shelar <pshelar@nicira.com>